hurricanes final
How does vertical wind shear influence the initial development of a mesocyclonic tornado in a supercell
It generates horizontal vortex lines, which are tilted upward by the updraft and create the initial vertical rotation for the tornado
Almost all severe tornadoes (those rated EF-3 or higher) occur as a result of:
a supercell
What kind of alert issued by the NWS means that severe weather conditions will soon occur in your area
a warning
The Enhanced Fujita scale rates the intensity of tornadoes using ____. The Saffir-Simpson scale rates the intensity of hurricanes using _____.
damage; measured wind speeds
Nargis (killed)
138,000
Labor Day 1935 surge
15' to 20' storm surge
New Orlean Adaptation
- Elevated Living Quarters - Closed the Mississippi River Gulf Outlet - Surge Gates: Intracoastal Waterway
Cat 5 winds exceed
157 mph
Tropical cyclones don't occur very near the equator because the Coriolis force is not strong enough to organize them. A. True B. False
A
3 Major Approaches to Forecasting
1. Dynamical models 2. Statistical Models 3. Statistical-Dynamical hybrids
Most intense Landfall US hurricanes
1. Labor Day 2. Camille 3. Katrina 4. Andrew
Strongest US landfalling hurricanes
1. Labor Day (185 mph) 2. Camille 3. Andrew
Cyclone Mala, 2006 (killed)
37
The first media reports about Hurricane Katrina's impact on New Orleans were: A. Very misleading. B. Mostly accurate but with exaggerations about the flooding. C. Very accurate.
A
Which of the following statements correctly describes the relationship between the size and intensity (in terms of wind speed) of hurricanes? A. Size and intensity are unrelated; storms of very different sizes may produce equally strong winds. B. The smaller the diameter of the hurricane, the stronger its winds. C. The larger the diameter of the hurricane, the stronger its winds. D. Both unusually large and unusually small hurricanes tend to be weaker than average-sized storms.
A
Which was better forecast for Katrina? A. track B. intensity
A. The Track
10 Costliest Hurricanes: No inflation adjustment -----
All but one occur after 2003 (hurricane Andrew)
Katrina: many evacuees were moved to the ___
Astrodome
Tropical Storm Emily
August 2, 2011
NOAA 2015 Atlantic Hurricane Season Outlook
Average is 12 named storms, 6 hurricanes, 3 are major
2011 Atlantic Tracks 7th most costly 56 killed
Hurricane/ Tropical Storm Irene
Idealized Atmosphere in Equilibrium
Balanced when surface temperature is 303 K (86° F) SOLAR incoming = IR emitted Cloud emits more IR SOLAR + IR incoming = IR emitted Surface now emits twice the IR
Katrina Land Lost near
Burras
t or f: Most intense tropical cyclone activity is in the Western Pacific
t
t or f: No hurricanes very close to the equator.
t
t or f: Only 2 feet of flood water is enough to carry away most vehicles
t
Major Hurricane is
Cat 3 or greater
Which of the following statements correctly describes the forecasts made 24 hours before Hurricane Katrina made landfall? (a) The predicted track of the hurricane was very accurate. (b) The National Hurricane Center issued hurricane warnings that emphasized that the strength of the storm was unprecedented and would cause catastrophic damage. (c) Hurricane Katrina was poorly forecast; the deadly flooding in New Orleans was completely unexpected. Choices (a) and (b)
Choices (a) and (b)
Which of the following will cause a tropical cyclone to weaken or dissipate? (a) Moving over land (b) Moving over a region of warmer sea-surface temperatures (c) Strong vertical wind shear Choices (a) and (c) only Choices (a), (b), and (c)
Choices (a) and (c) only
t or f: There are storms in all tropical basins except the SE Pacific and SE Atlantic
t
Unsaturated air parcels cool at the dry adiabatic lapse rate. Saturated air parcels cool at the moist adiabatic lapse rate. Why is the moist adiabatic lapse rate less than the dry adiabatic lapse rate?
Condensation occurs as a saturated parcel rises; this releases latent heat and prevents the saturated air from cooling as rapidly as an unsaturated parcel
Why do hurricanes rotate?
Coriolis Force
Tropical Depression 20
December 4, 2013
January Anomalies show ___
El Nino
Which state in the US is notable for having the highest annual frequency of lightning strikes within a 50 by 50 mile square area?
Florida
Katrina Press coverage
GROSS EXAGGERATION ● Reports of 200 dead at the Superdome ● Truth: 6 died ● (4 of natural causes, 1 over-dose, 1 suicide) ●Four died at the Convention Center ● (1 homicide) ● Bad journalism, but it was also the Mayor and the Police Chief
____ occurs if the equilibrium temperature increases due to the presence of more greenhouse gases Water vapor, CO2, Methane (O2, N2, do not absorb IR)
Global warming
Katrina Storm Surge
Gulfport, Mississippi
Katrina Monday, Aug. 29, 2005
Hit Louisiana- Mississippi Coast
Tropical Disturbance 16
July 6, 2010
Hurricane season in the Atlantic Basin
June 1 - December 1
Why did Katrina (Cat 3 at landfall) create a stronger surge than Camille (Cat 5)?
Katrina was larger
Compare Katrina and Camille: Storm surge observations at Pass Christian
Katrina: 27.8 ft Camille: 22.6 ft
(Hurricane Wilma) ____ hit hardest by the backside
Keys
Hurricane Season Forecast Ingredients
Largely based on ● Sea surface temperatures (SST) in the tropical north Atlantic - Local effect of SST beneath the hurricanes ● Presence of El Niño or La Niña - Remote influence of SST in the equatorial Pacific Ocean
Why can cloud droplets remain liquid at sub-freezing temperatures of -10 C?
Liquid water requires an ice nucleus or a preexisting ice crystal to freeze onto unless the temperature is well below freezing
Ike Aftermath
Many Houston residents without power for 2-3 weeks. Bolivar Pennisula
Sandy Rainfall
Oct 24-31, 2012 4227 sites maximum of 12.83"
Tide Gauge at Southern Tip of Manhattan
Maximum storm surge about high tide. Predictions are only for the astronomical tides.
Tropical Cyclone Nargis (date)
May 1, 2008
Hurricane season in the Eastern N. Pacific
May 15 - December 1
Nargis Near Landfall
May 2, 2008; JTWC wind estimate 135 mph (Cat 4)
2015 Western Pacific summary through the middle of last May
Maysak, Noul, and Dolphin reached super typhoon strength (winds > 150 mph).
Single Member with Warmest DJF North America
Ontario area?
____ in Nicaragua
Mudslides
which country were the most lives lost to a single tropical cyclone after 2000?
Myanmar
How have recent Atlantic hurricane season forecasts performed?
NOAA May 2015 Outlook: Below Normal Long-term average ● 12 named storms ● 6 hurricanes ● 3 major hurricanes
Recurving
Once westward moving storms in the deep tropics drift far enough north, they recurve back to toward the east as they feel the westerly (eastward) winds in mid-latitudes.
NHC product introduced in 2014
Potential Storm Surge Flooding
- Typically most severe when the storm encounters mountains. - Often this is after the storm has come ashore and weakened.
Rainfall and Flooding
Tropical Storm Lee
September 3, 2011
Katrina high water marks
Ship Island
Hurricanes stir up the ocean beneath them, _______ the surface of the ocean, which tends to _______ the hurricane.
cooling; weaken
Why don't hurricanes form along the equator?
The Coriolis force is too weak at the equator.
Failure to order a timely evacuation of their encampment led to the death of over 250 WWI veterans when an intense hurricane in 1935 struck
The Florida Keys
what US region is a future hurricane death toll mostly likely to exceed that from Katrina?
The Florida Keys
Which of the following is a reason why tropical storms do not form over the southeastern Pacific Ocean?
The sea surface temperatures are too low to sustain tropical cyclones.
Which of the following is a feature associated with tropical cyclones?
Their winds are strongest near the surface and weaken near the top of the storm
Hurricanes never impact Washington State.
They sort of do: - Hurricanes never come ashore in Washington as a tropical cyclone. - But hurricanes can be reborn as very intense extra- tropical cyclones (mid-latitude low pressure systems). - These intense systems occasionally have great impact on the Pacific Northwest.
Why are radars usually incapable of detecting a tornado?
Tornadoes are usually smaller than the width of the radar beam
Irene Visits ______
Vermont
Shallow Bottom Prevents _______ from Reaching Surface
cold water
Which of the following causes the most thunderstorm-related deaths in the US?
floods
Storm Surge produced primarily by
primarily by wind blowing water against a shore
Influence of Sea Surface Temperature:
● Too much vertical wind shear ● Too few triggers
Hurricane Asymmetries : Ground Relative
●Important influence on hazards due to ● Waves ● Storm surge
Once a tropical cyclone moves inland and into mountains, the greatest threat to life comes from A. flying debris. B. flooding. C. lightning. D. strong winds.
B
Over the past 20 years in the north Atlantic basin, tropical cyclone track forecasting has improved _______ and tropical cyclone intensity forecasting has improved _______. A. little; significantly B. significantly; little C. little; little D. significantly; significantly
B
Prior to Katrina there had been few studies suggesting hurricane impacts on New Orleans could become that severe. A. True B. False
B
Regardless of the effects of global warming, destruction in the United States resulting from tropical cyclones will likely increase in the future because A. a higher number of tropical cyclones will hit land. B. coastal development continues and is even subsidized by government flood insurance. C. forecasts of tropical cyclones will not continue to improve. D. none of the above.
B
The flood waters in New Orleans A. Receded rapidly after the storm B. Where laced with chemicals and sewage C. Provided welcome fishing opportunities for those stranded by the high water.
B
Tokyo reports 10-minute averaged winds for tropical cyclones. Miami reports 1-minute averages. For the same storm, which center will report the higher winds speed? A. Tokyo B. Miami
B
When are tropical systems named in the Atlantic basin? a. when they become tropical depressions (when they have organized rotation) b. when they reach tropical storm strength (sustained winds >39 mph) c. when they reach hurricane strength (sustained winds >74 mph)
B
Which aspect of a hurricane is NOT a direct contributor to the strength of the hurricane's storm surge? a. The slope of the ocean floor b. The amount of rain that falls on the coast c. The speed of the hurricane's winds d. The low pressure in the storm's eye
B
Which of the following scenarios will most likely result in locally enhanced precipitation from a tropical cyclone? a. The tropical cyclone moves over colder sea surface temperatures. b. The tropical cyclone makes landfall in a mountainous region. c. The tropical cyclone makes landfall on small, low-lying islands.
B
Which tropical-cyclone quadrant is most dangerous in the southern hemisphere? A. Right front B. Left front C. Right rear D. Left rear
B
If we want the IR images to look similar to black and white visible images, hotter areas should appear ____ than cool areas. A. lighter B. Darker
B The clouds, which are aloft where it is cooler, should appear white against a dark background.
Vertical wind shear___ the formation of strong tornadoes and ___ the formation of hurricanes A. inhibits, helps B. helps, inhibits C. inhibits, inhibits D. helps, helps
B Vertical wind shear helps make strong tornadoes by providing a source of initial rotation around a horizontal axis that gets tilted into the vertical.
El Nino tends to increase the vertical wind shear in the Tropical Atlantic. This will favor the development of Atlantic hurricanes. A. True B. False
B Vertical wind shear tends to tear tropical cyclones apart.
(Atlantic Basin) Track Forecasts are Getting _____
Better
Sandy aftermath
Bridgehampton, NY Some areas are built up as the sand is moved.
Katrina 2nd landfall
Buras-Triumph Monday, September 29, 5:10 AM CDT
How did Hurricane Andrew affect the US insurance industry? A. The industry boomed as residents of South Florida clamored to buy insurance in the wake of Andrew. B. Insurers were not impacted by Hurricane Andrew; business continued as usual. C. Many insurers went out of business because they could not afford to pay out all of the claims from storm damage.
C
Hurricane Mitch (1998) is the second-deadliest Atlantic hurricane ever on record (after the Great Hurricane of 1780). What made Hurricane Mitch so deadly? a. An extraordinarily large storm surge inundated vast stretches of coastline. b. Mitch transitioned into a midlatitude low upon interacting with the mountains of Central America. c. Intense rains led to extreme flooding and mudslides. d. Extreme Category-5 winds destroyed numerous shantytowns in Honduras.
C
Over the preceding decades, scientific studies of the possibility hurricane-induced flooding in New Orleans A. Had minimized the possible impacts (similar to Galveston) B. Had been noted, but did not suggest anything this extreme C. Suggested flooding at least as bad as what occurred would develop in worst- case scenarios
C
The 1962 Columbus Day Storm in the Pacific Northwest was caused by a. The landfall of a tropical cyclone on the Oregon coast. b. The polar vortex bringing in an extremely cold air mass from Canada. c. An extra-tropical cyclone that originally was a western Pacific typhoon.
C
The Atlantic seasonal hurricane forecast issued by the National Hurricane Center predicts all of the following except a. The number of named tropical storms. b. The number of hurricanes. c. The number of hurricanes that will make landfall in the United States. d. The number of major (Category 3 or higher) hurricanes.
C
The Greenhouse Effect: Day after day, the Earth absorbs the sun's rays. In response, the Earth A. Keeps gradually heating up. B. Is cooled by an equal amount as winds carry the heat upward all the way out into space. C. Is cooled by an equal amount as the Earth and the atmosphere emit IR radiation to space.
C
The deadliest tropical cyclone on record killed between 300,000 and 500,000 people in East Pakistan (modern-day Bangladesh) in 1970. In 1997 another strong tropical cyclone struck the same region, but only 100 people were killed. Why were there fewer deaths in 1997 than in 1970? a. In 1997, the government was able to evacuate most of the coastal population to areas well inland. b. After the 1970 cyclone, the government enforced stronger building codes and required that all buildings be able to withstand 120 mph winds. c. By 1997, cyclone shelters had been constructed that provided nearly 1 million people with protection from the storm surge.
C
The record likely shows fewer tropical cyclones prior to the early 1960's because A. There simply were fewer then. B. After the early 1960s, more ships started encountering tropical cyclones and reporting them. C. After the early 1960s, satellites were monitoring all the world's oceans, recording images of almost all tropical cyclones.
C
Which of the following is an effect of global warming that could possibly increase the intensity of future tropical cyclones? A. Increased upper-level winds in the tropics B. Inceased global average sea levels C. Inceased tropical sea surface temperatures D. Increased ocean acidity
C
Which of the following statements about changes in a warming climate is most certain? A. Tropical cyclones will become more frequent. B. Tropical cyclones will become more intense. C. Global sea levels will continue to rise. D. Global precipitation will, on average, decrease.
C
hurricane is making landfall in the northern hemisphere, heading directly perpendicular to the coast. The most damage will tend to occur A. Just outside the eye on the le; side of the track. B. Right where the center of the eye hits land. C. Just outside the eye on the right side of the track.
C
What besides intensity changes might have a major influence on hurricane-induced destruction? A. Changes in sea level B. Changes in coastal land use C. Both of the above
C Sea level rise is far more certain than the possible changes in tropical cyclone frequency or intensity!
How did a category 2 storm do so much damage? A. Ike was a very deep storm with cloud tops extending higher than usual. B. Ike came ashore at the Eme of low "astronomical" Ede. C. Ike was a very large storm, covering a broad area.
C size matters, not just wind speeds.
_____ deflects converging air heading into the eye's low pressure.
Coriolis force
In the aftermath of Hurricane Katrina, the government and people of New Orleans have A. developed housing more suitable for withstanding flooding. B. blocked the Mississippi River Gulf Outlet to prevent storm surge waters from finding an easy route to the city. C. increased property taxes to fund improved levee maintenance. D. choices (a) and (b). E. choices (a), (b), and (c).
D
Prior to 1960, we did not realize that there were more Eastern Pacific hurricanes each year on average than in the Atlantic. Why? a. The Eastern Pacific is not a region with many shipping lanes, removing potential witnesses to the storm. b. The tracks of most Eastern Pacific hurricanes take them away from land. c. No weather satellites were monitoring the region. d. All of the above
D
Which of the following affects the motion of tropical cyclones? a. The change in the strength of the Coriolis force with latitude b. The trade winds in the tropics c. The westerlies in the midlatitudes d. All of the above
D
Which of the following are necessary for hurricane formation? A. Weak vertical wind shear B. Some Coriolis force C. Sea-surface temperatures greater than 80°F D. All of the above
D
Labor Day Hurricane of 1935 made landfall in A. New England B. New Orleans C. Miami D. The Florida Keys
D -At least 438 dead -Storm surge of 15 to 20' washed over the upper keys.
Visible images
Black and white photo of the clouds and surface. Not useful at night - can't loop images for long periods.
Record Hurricane Rainfall
La Réunion Is. January 1966 45" in 12 hours 72" in 24 hours April 1958 97" in 48 hours January 1980 18.5 feet in 10 days Storm looped around
Hurricane John 1994
Record for: Longest lived: 31 days Longest track: 7,165 miles No deaths, only minor damage
IR images
Satellite senses the temperature of the clouds and surface. Images available night and day.
Hurricane Mitch Oct 29, 1998
Second deadliest Atlantic Hurricane 18,974 killed; $6.1 billion dollars in damage Damage to Honduras: 70-80% of transportation network was destroyed, Widespread power outages 70% of the country lost access to fresh water after the storm. 70% of crops destroyed Destruction and damage left 1.5 million people homeless - about 20% of the total population. Nicaragua was also hit very hard.
2016 Atlantic Hurricane Season Forecast Ingredients
"Near Normal" in Atlantic ● El Niño gives way to near neutral or weak La Niña ● Current sea surface temperatures near normal ● Toward the end of the active cycle in the Atlantic Multi-Decadal Oscillation
Ike storm surge
- 19 feet near Galveston - 22 feet near Port Arthur (highest ever recorded there) - Bolivar Peninsula covered by at least 5 ft of water with 15 ft in most areas (not counting wave action).
Hurricane Ike
- 195 killed; US share 112 plus 23 missing - 4th costliest hurricane in US history (inflation adjusted) +Katrina, Sandy and Andrew were worse - Strong category 2 storm!
Factors Determining the Storm Tide
- Astronomical tide (2 high tides, 2 low tides per day) - Storm surge (generated by the hurricane) - (High waves ride on top of the storm tide.)
How do we estimate the winds in tropical cyclones?
- Atlantic storms that threaten the US are observed by aircraft. + NOAA and Air Force units - Some East Pacific hurricanes are also sampled. - Others are only observed by satellite + Wind speed estimated by variant of Dvorak scale - Shape and evolution of the storm - Difference in IR temperatures between the eye and eyewall. + Nominal RMS error is 11 knots when compared with
Ike: Evacuations
- Authorities in Louisiana and Texas ordered major evacuations for Hurricane Ike. Roughly 1 million people left their homes, but more than 100,000 people did not. - The special needs population was effectively managed during the evacuation of Hurricane Ike. - "Despite dire warnings of storm surge and certain death from forecasters, an estimated forty percent of Galveston's residents did not evacuate in response to the mandatory order." - It was the local indifference to the storm surge hazard that reduced evacuation compliance and ultimately led to a significant loss of life in the Galveston area.
Galveston 1900 Aftermath
- Galveston was finished as "The New York of the Gulf", but not abandoned. - 17' high sea wall was built and the city raised as much as 17' within the wall - A similar storm in 1915 caused much less damage and 53 deaths.
Rebirth as a Mid-latitude Low
- Hurricanes die when they move + Over land or cold water + Into a region of strong vertical wind shear - Hurricanes that recurve over the ocean can become intense mid-latitude lows. + John became a low that influenced Alaska
Visible and IR, which is which?
- Low clouds look darker in IR: their temperatures are close to those of the surface. - IR is lower resolution than visible. - Space is white in IR (cold) and black in visible.
Gentle Bottom Slope Actually Makes Things Worse
- Shallow slope is more favorable for storm surge. - Shallow slope prevents cold water from mixing upward to the surface while the hurricane is approaching + Cold surface waters weakens the storm
Fantome Last Voyage
- The Fantome departed the harbor of Omoa in Honduras for a planned 6 day cruise. - Mitch was initially perceived as threat to Jamaica, but changed course. - Passengers and non-essential personnel were put ashore in Belize City. - Ship last radioed it was in 40 foot waves with 100 mph winds. + It was 40 miles south of the 155 mph winds in Mitch's eyewall. - All 31 crew members were lost.
Storm Surge Influenced by
- Wind speed (major factor) - Drop in atmospheric pressure (minor factor) - Shape of the sea floor / beach slope - Path of the hurricane relative to the coast. + Is the storm approaching head-on or almost parallel to the coast?
Stages in Hurricane Development
1. Tropical disturbance ● Cluster of thunderstorms with weak winds ● Average of about 80(?) per season in the Atlantic Basin 2. Tropical depression ● Cyclonic circulation evident; winds up to 38 mph 3. Tropical storm ● Winds between 39 and 73 mph ● Storms gets name ● Average of 11 per season in the Atlantic 4. Hurricane ● Winds greater than 74 mph ● Average of 6 per season in the Atlantic Evolution from a tropical disturbance to a hurricane is not inevitable. (Wind values are 1 min sustained speeds 33 feet above ground)
Super typhoon winds exceed
150 mph
Atlantic Hurricane Low Activity
1970-1994
Simplified Storm Surge Product Introduced in
2015
Non-uniform Sea Level Rise: 1950-2009
2mm per year x 59 years = 4.5" of rise East Coast - New york Hurricane Sandy - $65 billion
Katrina : Oil and gas industry admits causing ____ of the damage.
36%
Pressure contribution typically just ___ of total surge.
5%
Sea-surface temperatures greater than ______ required for tropical cyclones
80°F
Approximately what percentage of New Orleans' car- less population was the Superdome supplied to accommodate? A. 10% B. 25% C. 50% D. 75%
A
Classroom experiment: The drain swirl reverses direction because each time I: A. Spun the water around a different way. B. Sloshed the water straight back and forth across the drain a different way. C. The equator really is running through our classroom.
A
How did the extremely small size of Cyclone Tracy impact the ability of the Darwin Tropical Cyclone Warning Center to forecast the path and intensity of the storm? A. The small size made it very hard to determine the current strength of the storm since no measurements happened to be taken near its center. B. The small size made it very easy to measure the environment around the storm, leading to more accurate forecasts of strength and track. C. Neither of the above.
A
If you want to observe clouds at nighttime, which of the following satellite images will be useful? a. Infrared (IR) only b. Visible only c. Both are useful d. Neither are useful
A
The longest tropical cyclone season in the world is in the a. Northwest Pacific Ocean. b. Northeast Pacific Ocean. c. Southern Indian Ocean. d. North Atlantic Ocean.
A
Why were many houses built after 1980 more severely damaged by Hurricane Andrew than those built earlier? A. Because of inadequate building inspections during construction. B. Because the Dade County building codes were unusually lax. C. Because homes built after 1980 were more likely to be sheltered from the winds by large, sturdy trees.
A
What would the temperature of the single-level atmosphere be? A. 0° F (same as the ground in the no-atmosphere equilibrium case) B. 60°F(observedaverage surface temperature) C. 86°F(surface temperature in this idealization)
A The temperature required to produce IR emissions that balance the incoming solar from our idealized atmospheric layer is again 0° F. (The idealized layer is emitting upward like the ground in the no-atmosphere case.)
Unfreeze the Hurricane
Account for hurricane motion as well a wave propagation. (Suppose it moves at the same speed as the waves.)
Why do raindrops not grow larger than about 8 millimeters in diameter?
Aerodynamic drag causes larger drops to break up
Which of the following data are NOT used in short-term (5 days or less) forecasts of hurricanes? A. Satellite imagery B. Aircraft measurements C. Ocean buoy measurements D. Weather radar E. All of the above are used in forecasting hurricanes
E
All the following seasons nominally had 19 tropical storms in the Atlantic. In reality, which one probably had the most? A. 2012 B. 2011 C. 2010 D. 1995 E. 1887
E No satellites in 1887, several storms probably went undetected. 2nd place for most active Atlantic Season, 1933, likely also had undetected storms
Tropical Cyclone Names ***
Every 6 years, alternate M and F, separate lists for each ocean, only named when it gets to tropical storm status, name is retired if a storm causes lots of damage or loss of life
Coriolis Force summary 1
Ex: throwing balls on a rotating platform ● Arises because we are looking at motions in a rotating frame of reference. ● Turns winds to the right/left in the northern/ southern hemisphere.
Right hand side gets higher winds why?
Example: environmental winds are 50 kph (31 mph); hurricane induced circular wind is 175 kph (109 mph). LEFT: Environmental and storm generated winds subtract RIGHT: Environmental and storm generated winds add
True or False: In the last 20 years, hurricane intensity forecasts have improved just as much as hurricane track forecasts
F
How do regions of separate positive and negative charge develop in a thunderstorm?
Falling hail collides with rising ice crystals, causing the falling hail to become negatively charged and the rising ice crystals to become positively charged
True or False: The Atlantic hurricane season tends to be more active when there is an El Nino in the equatorial Pacific Ocean.
False
Hurricane Freda: Columbus Day Storm 1962 IMPACTS
HEAVY RAIN -> flooding In one day, the average hurricane at sea dumps about 3 times the fresh water consumed in the US in 1995. (Divine Wind)
Smaller Atlantic Hurricanes had similar 190 mph winds
Hurricane Camille Hurricane Andrew
Hurricane Asymmetries - Storm Relative (visible in the distribution of the spiral bands)
Hurricane Daniel: August 27, 2010
Columbus Day Storm 1962
Hurricane Freda Catches the Westerlies The Low Comes Ashore: Oct 13, 1962 Peak Wind Gusts
Contrast with Annular Tropical Cyclones
Hurricane Isabel: September 13, 2003
Waves propagate away from region of generation =
Hurricane motion is frozen
Stimulated Depth of Layer Mixed by a Traveling Hurricane (in meters)
Hurricane moves right to left along black line
The Superdome
Mayor Ray Nagin of New Orleans: it's a "refuge of last resort," only limited food, water, and supplies would be provided. Residents who evacuated to the Superdome were warned to bring their own supplies. Municipal buses carried some to the Superdome
Which city slid into an economic depression three years before the 1929 stock market crash because it was struck by an intense hurricane?
Miami, Florida
Streamlines Showing ------ over the Atlantic
Mid-level winds
Katrina: Water invaded the ____
Mississippi Delta
Single Member with Coldest DJF North America
Montana
Hurricane Wilma (2005)
Most intense Atlantic Hurricane on record Winds 185 mph Central pressure 882 hPa Eye shrank to 2.3 miles during intensification (smallest on record)
(Atlantic Basic and Eastern North Pacific Basin) One-Day Intensity Forecasts are ___
NOT improving
NOAA 2016 Seasonal Forecast:
Near Normal Named storms: 10-16 Hurricanes: 4-8 Major Hurricanes: 1-4
In what region did 680 people die due to a poorly-forecast 1938 hurricane that moved northward very quickly?
New England
Sandy Snowfall
Oct 28-31, 2012 178 sites Max: 36" Richwood, WV & Wolf Laurel Mt., NC
Which of the following describes the dissipating stage of a single-cell thunderstorm?
Only downdrafts are present; all the warm, moist air has been cut off from the storm due to the spreading cold pool
Myanmar Deadly Track
Retained intensity because it stayed close to the sea. Storm surge penetrated 25 miles inland
_____ transitions to extratropical just before landfall
Sandy
Number of Storms on Each Date: Atlantic Basin
Strongly peaked around September 1st Minimum around Februrary 1st
Tip and Tracy
Super Typhoon Tip (1979) killed 99, mostly in Japan and out at sea. 1200 mi diameter Tropical Cyclone Tracy (Dec 24-25, 1974) destroyed much of Darwin Australia, killing 71 (Cat 3). 60 mi diameter
What is unique about supercells compared to single-cell and multi-cell thunderstorms?
Supercells have a rotating updraft called a mesocyclone
Idealized Atmosphere: Imbalance
Temperature of the surface must increase due to the imbalance. Emitted IR increases very rapidly with temperature. SOLAR incoming > IR emitted Atmosphere assumed to absorb and emit IR at one level SOLAR + IR incoming > IR emitted Surface emitting as if there was no atmosphere.
The image below depicts an enhanced infrared (IR) image of a tropical cyclone with the color-temperature scale located at the bottom of the image. In which region are the cloud tops the highest?
The blackest area
Once over land, hurricanes weaken rapidly. The biggest reason for this is
The drastic reduction in the water vapor evaporated from the surface beneath the storm. Increasing rainfall releases more latent heat, which might (other things being equal) strengthen the storm. Extra drag on the surface winds over land, does tend to weaken the storm, but not nearly as much as the loss of its fuel supply: water vapor evaporated off a warm sea-surface.
In the US, why are cyclonically- (counterclockwise) rotating supercell thunderstorms produced much more frequently than anticyclonically - (clockwise) rotating ones?
The environmental vertical wind shear leads to an upward pressure force favoring the cyclonically-rotating storm
Which of the following potential hurricane tracks would likely produce the largest storm surge in Charleston Harbor?
The first arrow on the left
Strength of tropical storms from weakest to strongest
Tropical Depression Tropical Storm Cat 1 Hurricane Cat 2 Hurricane Cat 3 Hurricane Cat 4 Hurricane Cat 5 Hurricane
Most "intense" hurricane
Typhoon Tip in the Northwest Pacific Ocean on 12 October 1979 - Measured central pressure of 870 mb - Estimated sustained winds of 190 mph
Sandy direct fatalities
US 73, Haiti 54, Cuba 11 $65 billion in damage
_________ has the warmest SST's
Western North Pacific
What is the advantage of having an underground storm cellar in your garage in comparison to having an underground storm cellar outside of your house?
You do not have to leave your house to access the shelter
Water Temperature in the Equatorial Pacific
Zone of rapid temperature decrease connects the warm upper ocean to the cold deep ocean
All of the following contributed to the disaster in New Orleans caused by Hurricane Katrina except a. poorly regulated building codes made homes very susceptible to strong winds. b. the large size of the hurricane caused very large storm surges that led to flooding. c. the levees, which were intended to protect the city from flooding, were not effective at holding back flood waters. d. the city lies, on average, below sea level, making it prone to flooding.
a
Since the satellite age, the number of tropical cyclones per year worldwide has been relatively constant. However, individual basins like the north Atlantic can have widely varying numbers of tropical cyclones in different years. Why? a. In a given year, natural variations in global climate such as El Nino can create more or less favorable conditions for tropical cyclones in different regions of the world. b. Average sea surface temperatures have risen in the north Atlantic but not in any other tropical cyclone basin. c. High or low numbers of tropical cyclones occur completely randomly and unpredictably in individual basins. d. None of the above.
a
The image below shows radial velocity obtained from a radar. Red shading indicated winds away from the radar while green indicated winds towards the radar. What phenomenon is the radar observing?
a mesocyclone (green and red swirl together)
Most clouds are formed when
air is lifted and cools to its dew point
The image below shows radar reflectivity of a thunderstorm. The highest reflectivities are dark red and purple. The low reflectivity inside the white circle, within the "hook," occurs because
air is rising too fast in the updraft to allow precipitation to fall into this region
For a parcel of air at a given pressure, which of the following is the best indicator of the total number of water vapor molecules in the parcel? a. temperature b. dew point c. relative humidity d. saturation vapor pressure
b
The radar image below was taken from a reconnaissance flight through Hurricane Hugo on September 15, 1989 when the storm was near its peak intensity. Which enclosed region in the image is a spiral rainband?
b
Which is not a reason clouds stop growing vertically? a. they encounter an inversion b. they encounter cold air aloft c. they entrain dry air d. they reach the stratosphere
b
Which of the following statements accurately describes water vapor? a. Water vapor is what you see when you "see your breath" on a cold day b. Water vapor is an invisible gas; the individual molecules in water vapor are only very rarely bonded together c. All of the individual water molecules in water vapor are bonded together with weak, flexible bonds d. The only place where water vapor is found in the atmosphere is inside clouds
b
Which of the following statements describes what may happen to a tropical cyclone after it recurves and remains over the ocean? a. All tropical cyclones weaken and completely disappear shortly after recurving. b. The tropical cyclone can transition into an intense midlatitude low. c. The tropical cyclone often intensifies and accelerates toward the west. d. None of the above.
b
The Earth and atmosphere emit IR radiation to space that on-average just ____ the heat from the sun.
balances
In connection with Hurricane Katrina, the Superdome was a. to be completely evacuated before Hurricane Katrina made landfall. b. the single location where all the residents of New Orleans took shelter during the storm. Residents were told to go to the Superdome instead of evacuating the city. c. the designated place of refuge for residents who could not evacuate. d. stocked with enough food, cots, and emergency medical supplies to accommodate about half of the city's population that had no access to cars.
c
Which of the following is NOT true for an unsaturated air parcel? a. its relative humidity is below 100% b. it will cool at the dry adiabatic lapse rate if lifted adiabatically c. its vapor pressure is grater than its saturation vapor pressure d. its dew point is lower than its temperature
c
Why is the front-right quadrant of a hurricane (colored pink in the diagram below), as shown below, the most hazardous for ships? (Note the heavy black arrow should be labelled "track" not "tack".) a. The storm surge is at its lowest point in that quadrant. b. There are more tornadoes there than in the other quadrants. c. The high winds on the right side create large waves just forward of the storm. d. The winds and waves are most amplified by the Coriolis force in that quadrant.
c
_______ are models that solve mathematical equations to predict the future state of the atmosphere without explicitly considering data from similar past events. a. Statistical models b. Dynamical-Statistical hybrid models c. Dynamical models
c
New Orleans Elevations
city below sea level--Former cypress swamps and marshes settled up to 9 feet over last 100 years People in New Orleans live at the bottom of an empty swimming pool
In the image below, the atmospheric environment between level A (just above the cloud base) and level B (the top of the cloud) is ______ and the environment above level B is _____
conditionally unstable; stable
The atmosphere is conditionally unstable, unsaturated and with a relatively uniform wind throughout the lower few kilometers of the atmosphere. The possibility of a thunderstorm developing is increased if a. a gust front passes, lifting the low-level air b. the surface dew point is increased c. the surface temperature is increased d. all of the above
d
Which of the following has the fastest rotational wind speeds? a. tropical disturbance b. tropical depression c. tropical storm d. hurricane
d
Which of the following statements about the levees in New Orleans is correct? a. The Army Corps of Engineers was largely blamed for the failure of the levees. b. The levees started to fail a few hours after Katrina made landfall and continued to fail over the next several days. c. The levees were essential to the safety of New Orleans since a large portion of the city lies below sea level. d. All of the above are correct.
d
During the passage of a strong gust front, it is not uncommon for the temperature to significantly _____ and the relative humidity to ______.
decrease; increase
In the northern plains of the US, around Minnesota, tornadoes are most frequent during
early summer
In the satellite image below, the region located at the center of the tropical cyclone, devoid of cloudiness, is called the _______ and air within this region is _______.
eye; sinking
Levee Breach with Barge: t or f: flood water here is about 3' deep in a lightly developed section of New Orleans
f
t or f: It is safe to cross fast moving flood waters as long as they are no deeper than mid-calf.
f
t or f: When the valve further restricts the outflow, so the water starts backing up, water will eventually start overflowing at the top.
f
About half of the deaths associated with Hurricane Camille occurred as a result of hurricane's landfall in southern Mississippi. The other half mostly occurred in Virginia as a result of
flash flooding from heavy rains.
The image before shows radar reflectivity of a thunderstorm. The highest reflectivity's are dark red and purple. The radar return from the (red and purple) region inside the white circle is produced by
flying debris
Which of the following is the greatest danger of a tornado?
flying debris
You should avoid lying flat on the ground if caught outside in the midst of lightning strikes to avoid injury or death due to
ground currents
On a conditionally unstable day a series of cumulus clouds occurring at the same location gradually grow to a height of 2 km before dissipating. Another cloud starts growing (rising) in the same location. This last cloud will likely rise
higher than 2 km because previous clouds added moisture to the environment
Sandy Ceases to Be a ______
hurricane
As the winds in a tropical cyclone circle the eye, the winds near the surface are also moving _______ the eyewall and winds aloft are also moving _______ the eyewall.
in towards; out away from
Which of the following would help enhance a downdraft in a single cell thunderstorm?
increasing the amount of falling precipitation
The advent of _______ made airborne reconnaissance of hurricanes feasible
instrument flying
Hurricane Camille became so intense in part because
it passed over an extremely warm current in the Gulf of Mexico.
How does low-level wind shear help extend the lifetime of a thunderstorm?
it prevents the storm's gust front from cutting off the supply of warm updraft air
Microbursts are most dangerous to
large jet aircraft attempting landings
Tropical cyclone activity in the North Atlantic basin usually peaks in _______ when _______ are the warmest.
late summer and early fall; sea surface temperatures
Katrina flooding from ____
levee breach
Which of the following is one of the ingredients necessary to produce all types of thunderstorms?
low-level moisture
Most rain in Seattle is formed by
melting snow formed by the ice crystal process
Hurricanes help balance the global heat budget. They cool the tropics by
moving heat upward from the ocean surface and radiating it out to space
The tornadoes in the following image are best described as
non-mesocyclones
Tropical Cyclone rotation northern hemisphere: southern hemisphere:
north: counterclockwise south: clockwise
Which measure of atmospheric moisture indicates how close an air parcel is to saturation?
relative humidity
Latent heat is ____ when water vapor condenses into liquid water because the bonds between molecules are ______.
released, forming
The dry adiabatic lapse rate is 10 C per kilometer and the moist adiabatic lapse rate is 6 C per kilometer. Suppose the environmental lapse rate is 7 C per kilometer. If lifted a short distance adiabatically, a dry air parcel will ____ and a saturated parcel will ______.
return to its original position; continue to rise
Coriolis force deflection - northern hemisphere: winds turn to the ____ southern hemisphere: winds turn to the ____
right left
Each set of waves is exposed to high winds longer on the ___ side of the storm than on the ____ side. These larger waves propagate into the ______ quadrant.
right; left right-front
Storm Surge produced secondarily by
secondarily by the local drop in pressure near the eye.
In which of the following types of thunderstorms can hail be produced?
single-cell, multi-cell, and supercell thunderstorms
Older right-side waves continue to be exposed to strong winds; they ______. __________ waves are generated on the left side.
strengthen New weaker
The most intense damage resulting from large, severe tornadoes (those rated EF-3 or higher) is often caused by
suction vortices within the tornado
t of f: Color can be added to IR images to highlight the coldest (highest) clouds.
t
t or f: Conditions become favorable for severe tornadoes more often in the US than in any other country in the world
t
t or f: If caught outside when there is a tornado, you should lie flat in a low spot on the ground rather than shelter under an overpass
t
t or f: In the tropics, thunderstorms are more likely over land than over ocean.
t
t or f: Waves move faster than the hurricane, so worst quadrant is the right front
t
t or f: US government policies encourage development of land vulnerable to hurricane storm surges.
t National Flood Insurance Program (created in 1968)
t or f: Hurricane Camille killed more people in the mountains of Virginia than on the gulf coast.
t 259 killed; 153 died in floods in Virginia mountains
t or f: No- Atmosphere Radiative Equilibrium
t Emitted IR increases very rapidly with temperature. Balance when surface temperature is 255K (0°F)
t or f: Evacuation is a big issue for the Florida Keys
t BIG
What was the deadliest hurricane in US history?
the Galveston Hurricane of 1900
When an unsaturated parcel of air is lifted from the ground, it cools because
the atmospheric pressure decreases with height so the air parcel expands and the air molecules within the parcel lose energy during the expansion
If a saturated air parcel containing a cloud is forced to descend,
the cloud will tend to disappear because the air in the parcel is compressed and its temperature rises
What feature of a thunderstorm is sometimes accompanied by a "shelf" cloud as seen in the image below?
the gust front
The winds are strongest in the right-hand half (northern half if the storm is moving to the west) of a northern-hemisphere hurricane because in the right-hand half,
the hurricane's rotating winds add to the winds in the larger environment that are carrying it forward.
What important formation mechanism do all tornadoes have in common?
the intensification of rotation about a vertical axis by an updraft
Mississippi River Gulf Outlet enhanced _____
the storm surge flooding
In the spring, baseball-size hail might infrequently occur in Dallas, Texas, but never in Seattle, because
the updrafts in Dallas thunderstorms are stronger than those in Seattle thunderstorms
Which of the following options is true about single air mass thunderstorms?
they are relatively short-lived
The image below depicts a ____ cyclone that is occurring in the ____ hemisphere
tropical; northern
Hurricane Seasons are ___ approximate
very
A Doppler weather radar detects all of the following except
water vapor
Hurricane Floyd stimulated ____
wave height
Hurricane Winds generate ____
waves
Because of the prevailing winds in the atmosphere, hurricanes generally move ______ near the equator and ______ when they move to the mid-latitudes.
westward; eastward
The original source of rotation in tornadoes is _____ and the original source of rotation in hurricanes is _____
wind shear; the earth's rotation
Does the Coriolis force also regulate the direction of the swirl in a drain?
yes, down at the equator
El Niño
• Is the absence of typical cold conditions in the eastern equatorial Pacific • Warm anomaly (difference from average conditions) • Influences the atmosphere by shifting thunderstorm activity eastward along the equator
Hurricane Isabel: September 13, 2003
• Much more circular symmetry than the typical hurricane. • 4% of all hurricanes • Relatively intense storms • Their intensity is more constant over time.
Global Mean Sea-Level Change
• Thermal expansion of the warming oceans • Melting of ice on land
The Biggert-Waters Flood Insurance Reform Act of 2012
● "Designed to allow premiums to rise to reflect the true risk of living in high-flood areas" ● Supposed to deal with the insolvency of the National Flood Insurance Program ●Result was ● 10 fold increase in some premiums ● Intense lobbying by affected property owners ● Two examples (Forbes) ● Longtime Greenwich, CT, family's premium rises from $458 to $5,500. ● Rhode Island resident's premium on a recently purchased second home rises from $5000 to $66,000.
Katrina: Civil Government
● 1/6 of the police deserted. 2 months after Katrina 240 of the officers in the 1,450 member force unaccounted for. ● Plenty of looting ● Mayor Nagan remained holed up in on the 27th floor of the Westin Hotel
Superdome: Aftermath
● 15,000 - 20,000 eventually in the dome ● Escaping the flooding ● Dropped off by rescuers ● August 30th Governor Blanco orders New Orleans completely evacuted ● 475 buses complete the evacuation by September 4th ● Includes another large group at the Convention Center
New Orleans Hurricane Planning
● 1998: Hurricane George triggers first evacuation in 20 years ● Traffic is a mess ● Storm misses New Orleans ● 2004: Hurricane Ivan tests improvements ● Monumental highway congestion ● Storm misses New Orleans ● 2005: Improved contra-flow planning (all lanes head out of town): auto-centric evacuation for Katrina goes better than expected. ● Clears in "just" 36 hours ● 112,000 people did not have access to vehicles ● Total population 484,000
Other Extreme Storm Surges
● 40-44' Great Backerganj Cyclone of 1876. ● 34.8' Great Bhola Cyclone of 1970, during one of the highest high tides of the year ● Bangladesh is particularly susceptible to strong storm surges - Shallow sloping sea floor - At the top of a funnel-shaped bay
Record High Storm Surge
● 43-48' Bathurst Bay Cyclone (Australia) March 5, 1899 ● Constable J. M. Kenny camped on a ridge 40 feet above sea level and 1/2 mile inland. A wave left him waist- deep in water. ● On nearby Flinders Island, fish and dolphins were found on top of 49 foot cliffs. ● Nevertheless, this was probably mostly due to storm waves, not the surge (or storm tide) per se. - Sea floor slopes steeply away from the coast. - Great Barrier Reef roughly 20 miles from the shore.
Complete Description of the Balance
● Accounts for absorption and emission from each level of the atmosphere. ● Accounts for heat transported by atmospheric motions ● Including thunderstorms and hurricanes ● Includes "dry" heat and latent heat ● Accounts for clouds
Relation to Climate Change: Dealing with the hurricane threat
● Adaption and mitigation involved spending significant resources on ● An event that might not occur for decades ● An even that would preferentially impact poor communities with little political voice. ● There were no "hurricane skeptics".
All Calculations Predict
● Adding CO2, methane, .... increases the average equilibrium surface temperature of the Earth ● Water vapor concentrations are determined as part of the atmospheric/oceanic response. ● The ocean heats up too (and becomes more acidic).
Coriolis Force summary 2
● Arises because we are looking at motions in a rotating frame of reference. ● Turns winds to the right/left in the northern/ southern hemisphere. ● Most important for motions that take place over time periods comparable to one rotation of the Earth.
Sandy Transition to Extratropical Caused
● Confusion about NOAA forecasts ● NHC or local offices to issue the warnings? ● June 1, 2013: hurricane and tropical storm watches and warnings broadened to allow them to be issued or remain in effect after a tropical cyclone becomes post- tropical. ● Watches and Warnings ● Confusion about insurance
Superdome supplies
● Enough to supply 15,000 people for three days. ● No water purification equipment on site, no chemical toilets ● No antibiotics and no anti- diarrheals stored for a crisis. ● No designated medical staff. ● Almost no cots
Wilma Hits Key West as Cat 3
● Estimated 80% of population does not evacuate. ● Up to 8 foot storm surge from back side of storm ● Winds during back-side surge less than 40 mph ● Many homes flooded with 1 - 2 feet of water ● Tens of thousands of cars destroyed ● Highest areas (12 - 16 feet) do not flood. (35 deaths throughout Florida)
Galveston, TX: 1900
● Galveston was booming as a center of trade. ● Biggest city in Texas (population 36,000). ● In 1875 nearby Indianola was second to Galveston among Texas port cities, but was destroyed by a hurricane, rebuilt and destroyed again 1886.
Depth of the Warm Water Matters
● Hurricanes stir the water ● Waves and strong winds create turbulence in the water below the surface that mix the water through a deep layer. ● Often brings much colder water to the surface
Hurricane Motion
● Hurricanes tend to move with the flow in their surrounding environment, which are ● Easterlies (winds from the east) in the deep tropics ● Westerlies (winds from the west) in mid-latitudes ● (Naming convention for winds uses the region from which the winds are blowing.) ● Nevertheless, hurricanes also influence their own track. ● When moving from the east in the deep tropics they tend to angle to the north (due to the northward increase in the Coriolis force)
Some El Niño Impacts
● Increases the environmental vertical wind shear in the Tropical Atlantic ● Decreases the environmental vertical wind shear in the Eastern Pacific ● Tends to make the winters warmer and drier in the Pacific Northwest
Katrina: FEMA Response
● Like the city and the state, slow to get resources prepositioned and mobilized. ● No buses for superdome evacuation. ● Michael Brown resigns as head of FEMA (Federal Emergency Management Agency) on September 12, 2005. ● Michael Chertoff (Homeland Security Secretary, Brown's boss) ultimately assigned principal blame by the Government Accountability Office
Hurricanes in a Warmer Climate
● Need to know the changes in ● Sea surface temperatures (will rise) ● Vertical wind shear (???) ● Triggers (???) ● Much uncertainty, but some indication tropical cyclones will be ● Bigger rain makers ● More frequently intense (> Cat 3) ● Less common overall
Superdome: In the Beginning
● Night of August 28/29th ● 9,000 residents and 550 National Guardsmen ride out the approaching storm ● Two 15' holes open in the ceiling letting in rain, but otherwise it holds up ● Morning August 29th: Governor Kathleen Blanco calls the Superdome shelter strategy an "experiment" on ABC news when asked if it could hold the storm or the flood. ● Flooding on August 30th brings the water up to field level
(Global warming) What's Certain?
● No doubt about the sign and qualitative values of global temperature changes at equilibrium in response to added greenhouse gases. ● No doubt that sea levels will be rising due to ● Thermal expansion as the ocean warms ● Melting of glaciers
National Flood Insurance Program (created in 1968)
● Property owners in participating communities can purchase flood insurance from the US government. ● About 5.5 million properties are currently covered by the program. ● 20% (?) receive discount rates of less than half what a private insurance company would charge. ● Sandy focused Congressional attention on its substantial losses.
Homeowner Flood Insurance Affordability Act of 2014
● Repeals many provisions of BW-2012 ● "Close to 80 percent of NFIP policyholders paid a full-risk rate prior to either BW-12 or HFIAA, and are minimally impacted by either law." ● For policies below full-risk rate ●Annual increases generally limited to between 5% and 18% (a few can increase by 25%) ● 18%-a-year increases compounds to a factor of 10 in 14 years (meanwhile real estate values increase at what rate?) ● For all policies ● Additional surcharges of $25 for primary residences, $250 for all others. ● Highly regressive.
The Mariner's Viewpoint
● Right-hand side gets higher winds. Example: environmental winds are 50 kph (31 mph); hurricane induced circular wind is 175 kph (109 mph). LEFT: Environmental and storm generated winds subtract RIGHT: Environmental and storm generated winds add ● Higher Waves in the Right Front Quadrant
Galveston, TX: 1900
● Sea wall for Galveston was proposed, but there was not sufficient support for construction. ● No serious problems with hurricanes in the previous 50 years. ● Scientists had published papers arguing severe storm surges were impossible in Galveston because of the gently sloping sea bottom. - Destruction of Indianola by storm surge in 1875 and 1886 was ignored
Katrina's #1 Records
● Storm surge: 27.8' at Pass Christian ● High water mark: 34.1' ● 22' surge + 11' waves + 1' tide ● Beau Rivage Lighthouse, Biloxi
Time Scales
● The Coriolis force only has a major impact on motions that take place over times comparable or longer than the period of the Earth's rotation (many hours). ● Most tornadoes last less than 10 minutes. ● We get the occasional anticyclonic (clockwise in NH) tornado. ● We never get anticyclonic hurricanes.
SST's are too cold to support tropical cyclones in
● The Eastern South Pacific ● The Eastern South Atlantic ● Off California
(Global Warming) What's Uncertain?
● The rate at which changes will occur ● Particularly in comparison to natural variability ● Particularly if we switch focus from the global average to smaller regions ● Nicely illustrated by a paper published in 2012: ● 40 member ensemble of state-of-the-art climate model simulations with almost identical initial conditions beginning in 2000. ● Trend in Dec-Jan-Feb (DJF) temperatures compared for the 55-year period 2005 - 2060.
Katrina: Ernest Morial Convention Center
● Thousands were directed to the Convention Center as an unofficial evacuation center. ● By police and word of mouth ● Not a designated refuge. ● No supplies, food or water ● September 1: Homeland Security Secretary Michael Chertoff on NPR: ● "I have not heard a report of thousands of people in the Convention Center who don't have food and water."
Dynamical Models
● Use computers to solve equations predicting how the atmosphere should evolve from its current state. ● In theory the most general and flexible approach, particularly as computers become increasingly powerful. ● Errors arise from ● Inaccurate specification of the current state ● Approximations used to formulate and solve the models ● Require lots of computer time in their most accurate formulations.
Statistical Models
● Use relationships between storm-specific information (location, time of year, ...) and the behavior of historical storms. ● Provided key forecast guidance in past decades, ● Now mostly benchmarks against which modern dynamical and statistical-dynamical models are compared. ● They require little computer power and therefore produce forecasts very quickly.
Statistical-Dynamical Hybrids
● Use statistical relationships between storm behavior and environmental conditions estimated from both ● Dynamical model forecasts ● The behavior of historical storms ● "Has historically outperformed most of the dynamical models"
Higher Waves in the Right Front Quadrant - Why?
● Waves are generated by wind blowing across the sea surface. 1. The stronger the winds, the bigger the waves. 2. The more time the waves are exposed to the wind, the larger they get. (Why more time?)
Katrina Levee Breaches
●Breaches occurred in the Industrial Canal a few hours after Katrina's landfall. ●28 levee failures in the first 24 hours ●A total of more than 50 in the next several days, left 75% of the city underwater ●Largely attributed to design flaws by the Corps of Engineers
Atlantic Basin Impact of El Niño
●Hurricane development is inhibited by ● Enhanced vertical wind shear ● Fewer triggers ● Fewer easterly waves moving off the African coast ● Increased sinking motion dries out mid-level air
Tropical Cyclones and Climate Change: Decadal Variations
●More Atlantic tropical storms and major hurricanes in 1995 - 2013 than 1970 - 1994. ● But 1950-1970 was another active period. ● Natural variability? ● Sea surface temperatures: Atlantic Multi-Decadal Oscillation ● Vertical shear: El Niño ● Try looking worldwide because ● Increases in activity in one region often accompany decreases in another.
Hurricanes need:
●Very warm water ● Sea surface temperatures (SST) greater than 26.5° C (80° F) ● Weak vertical wind shear ● Some Coriolis force (storm needs to be 5° or more away from the equator)
