Hurricanes

Storm surge

- a storm surge is a dome of water 65-80 km across - It occurs near where the eye make landfall - Water is piled up from surface winds

A tropical cyclonic storm having minimum winds of 119 kph (74 mph) is known as a hurricane in the Atlantic basin (Typhoon in the western pacific and Cyclone in the Indian ocean)

-From between latitudes of 5 and 20 degrees over all tropical waters except South Atlantic and eastern South Pacific - Northern Pacific has the most activity averaging 20 per year - Most often in the late summer when ocean waters have reached 29 degrees c (80 f) or higher

Hurricane profile

-very strong pressure gradient causes the rapid, inward spiraling winds - As the inward rush of warm, moist surface air reaches the center, it turns upward and ascends in a ring of cumulonimbus towers. The center is where the most intense convection is found called the *eyewall* -The *eye* of the storm is an area of subsidence where there's less wind and precipitation -Hurricanes are different than mid-latitude cyclones in that they are warm core cyclones

VORTRAC

A new hurricane tracking technique Vortex Objective Radar Tracking and Circulation is intended to help improve short-term warnings It constantly monitors all Doppler radars on cost lines It combines data for a better picture of the hurricane

Naming Hurricanes

Before names were given, meteorologist kept records by latitude and longitude. It was easier for meteorologists, researchers, emergency response workers, ship captains and citizens to communicate about specific hurricanes and be clearly understood. Earlier sailors would give them female names For that reason (since 1979) the World Meteorological Organization develops a list of names that are assigned in alphabetical order to tropical storms as they are discovered in each hurricane season. Names can be repeated after an interval of six years, but the names of especially severe storms are permanently retired from use

Hurricane formation

Great amounts of heat are needed to fuel hurricanes, and the primary source of this energy is the release of latent heat supplied by evaporation from the ocean surface Because of high evaporation, hurricanes only form where the ocean has a deep surface layer with temperatures above 81 f

Hurricane Destruction

Hurricanes cause major damage 4 ways -Storm Surge -Wind Damage -Flooding -loss of life

Hurricane Decay

Hurricanes lose their punch whenever -they move over cool or cold water -move over land -wind shear aloft -upwelling

Tropical Storm

Once cyclones each reach sustained winds between 37 and 74 mph, they are given a name ( the name stays the same once the storm reaches hurricane status)

Roll of satellites

Satellites make it easy to detect the development of hurricanes and monitor its movements They are remote sensors, however, and cannot measure wind speeds accurately

Aircraft reconnaissance

Specially instrumented aircraft fly through and around a hurricane. They provide "snapshot" Because range is a problem, measurements cannot be taken until a hurricane is relatively close to shore

Tropical Depression

Spin development sustained winds 37 mph (it's a cyclone at this point)

Estimating the intensity of a Hurricane

The accurate observations needed are sometimes difficult to obtain. Wind aloft are stronger than those at the surface

More than 21 storms

There are normally fewer than 21 named tropical storms in any calendar year. In the rare years when there are more than 21 storms are named are named the additional storms are given names from the Greek Alphabet: Alpha, Beta, Gama, Delta are used for their names

Retired names

The only change that is made to the list of Atlantic hurricane names is the occasional retirement of a name. This is done when a hurricane causes so much death and destruction that reuse of the same name would be insensitive to the people who suffered losses.

Flooding

The torrential rains often cause flooding flash floods and mudflows often result

In 1997, the GPS dropwindsonde was developed

This instrument measures pressure, wind speed, and direction as it falls through a hurricane

Radar

When a hurricane is near land (approximately 320 km from the cost), it is monitored by Doppler weather radar These systems measure winds speed and direction. They can also measure precipitation

Data Buoys

are another method of data gathering They are remote, floating instrument packages Data Buoys are in fixed locations along the Gulf and Atlantic Coasts of the United States

Wind damage

high winds turn objects into missiles High winds can also spawn tornadoes

Hurricane Watch

is an announcement that conditions are possible It is issued 48 hours before winds are intended to reach tropical storm force

Hurricane Warning

is issued 36 hours in advance of the anticipated onset of tropical storm force winds It indicates that conditions are expected It can remain in effect when dangerously high water and waves continue

Hurricane warning

is issued when sustained winds of 74 mph or higher are expected within 24 hours or less

Hurricane watch

is the announcement aimed at specific coastal area that a hurricane poses a threat, generally within 36 hours

Hurricanes are measured by

the sustained wind speeds and categorized by the potential damage Saffir-Simpson Scale

Tropical wave

thunderstorm that forms along a trough (front)

Track Forecasts

try to determine where the hurricane is going

Tropical disturbance

unorganized array of thunderstorms. Most dissipate, but some grow larger and develop strong rotation