Tropical Cyclone - CEES at TAMIU

							    WHAT YOU NEED TO KNOW
     ABOUT HURRICANES &
      TROPICAL CYCLONES




AUG 19, 2009
 TROPICAL CYCLONES
Marvin Bennett and Ken Tobin
       (CEES/TAMIU)
              OVERVIEW

   DEFINITIONS, CLIMATOLOGY, & HISTORY


   HURRICANE HAZARDS


   FORECAST PROCESS


   HURRICANE PREPAREDNESS
Tropical Cyclone Definitions

Tropical Cyclone is a generic term
for a warm-core low pressure
system that forms in the tropics or
subtropics.


Tropical Systems are further
categorized by a difference in their
wind speed.
       Tropical Cyclogenesis (Formation)
To become a tropical cyclone several ingredients are
needed:


     Tropical Disturbance with thunderstorms
     Distance of at least 300 miles from the equator
     Ocean temperatures at 80ºF or warmer
     Abundant moisture - low and middle part of
      atmosphere
     Weak vertical wind shear
          TROPICAL CYCLONES
BIRTH :       Nearly all tropical storms/hurricanes start out as a
tropical disturbance - an area of unsettled weather in the tropics.
   Tropical Storm Cyclogenesis (Formation)

The conditions on the previous slide only occur close to
the tropics (generally within 25o latitude) & during
specific times of year!


Hence hurricane season in the Atlantic Basin is defined
between June 1 and November 30.


The peak in hurricane season is around September
10th, which corresponds to the time when ocean water
in the tropics reaches its maximum temperature.
    Tropical Cyclone Definitions
Once a distributed area becomes organized this
system becomes a Tropical Cyclone.
Tropical Cyclones are categorized by difference in their
wind speed:

   Tropical Depression = < 39 mph
   Tropical Storm = 39 mph – 73 mph
   Hurricane = > 74 mph
   Major Hurricane = > 110 mph (Cat 3 or greater)
Tropical Cyclone Evolution
  Tropical Depression = < 39 mph
Tropical Cyclone Evolution
Tropical Storm = 39 mph - 74 mph
        Tropical Cyclone Evolution
                       Hurricane = > 74 mph




Hurricane Isabel’s power initially focused attention on the storm, but its size, not power,
ensured it would be destructive. Surfers loved the big waves rolling into Ocean City, N.J.,
on Monday, but when Isabel hit on Thursday, much larger waves were hitting much of the
East Coast.
           Tropical Cyclone Structure
• Doppler radar showing
  hurricane main parts:

   – Eye

   – Eyewall

   – Rainbands.


• Counter-clockwise rotation.

• In very center of the storm,
  air sinks, forming an "eye"
  that is mostly cloud-free.
         FAMILY OF TROPICAL CYCLONES
INFRARED SATELLITE PHOTOGRAPH … AUGUST 28, 1996
         Tropical Climatology




                          Points of Origin -- June




• Storms favor the Gulf of Mexico & Western Caribbean
    Tropical Climatology



                  Points of Origin -- September




• Most active month of the hurricane season.
         Texas Hurricanes - Galveston
                                                             LOUISIANA
•   Sep 8-9, 1900                             TEXAS

•   8000+ killed
•   $30M damage                                       * Galveston
•   20 ft. surge
•   Max 135 mph
•   Cat 4

                                     MEXICO
         Points of Origin -- September
      Tropical Cyclone Hazards
• Storm Surge

• High Winds

• Inland Flooding

• Tornados
 Tropical Storm/ Hurricane Impacts




• Storm Surge - simply water that is pushed toward the shore by the force of
  the winds swirling around the storm.
• Advancing surge combines with normal tides to create the hurricane storm
  tide - can increase the average water level 15 feet or more.
Tropical Cyclone
Impacts
Cameron County

Storm Surge
From SLOSH
Model
Tropical Storm/ Hurricane Impacts




Heavy rains create inland flooding that results in fatalities and/or loss of
property. An example is Hurricane Carla where in Jefferson County, 180
miles from the land falling storm, $17.5 million in damage occurred, with $14
million of it water damage. Rain totaled up to 19". Three to four feet of water
flooded Port Arthur. Total damages from Carla estimated near $400 million.
 Tropical Storm/ Hurricane Impacts
• Tornadoes

  – Hurricane Carla had its greatest
    impact in Texas.

  – Twenty-six tornadoes were
    spawned

  – one tore apart 120 buildings
    and killed 6 in Galveston

   Hurricane Beulah spawned over
    100 tornadoes
               Forecast Process

NWS Internet Site
www.srh.noaa.gov
• Forecasts obtained by
  either postal zip code,
  city/state search, or by
  point & click maps
• Weather Information in
  clear, concise format
• Emphasizes local
  weather expertise
           Forecast Process
• TROPICAL STORM WATCH - A tropical storm
  watch is issued when tropical storm conditions,
  including winds from 39 to 73 miles per hour
  (mph), pose a possible threat to a specified
  coastal area within 36 hours.

• TROPICAL STORM WARNING - A tropical storm
  warning is issued when tropical storm
  conditions, including winds from 39 to 73 mph,
  are expected in a specified coastal area within
  24 hours or less.
              Forecast Process
• HURRICANE WATCH - A hurricane watch is issued
  for a specified coastal area for which a hurricane
  or a hurricane-related hazard is a possible threat
  within 36 hours.

•    HURRICANE WARNING - A hurricane warning is
    issued when a hurricane with sustained winds of
    74 mph or higher is expected in a specified coastal
    area in 24 hours or less. A hurricane warning can
    remain in effect when dangerously high water or a
    combination of dangerously high water and
    exceptionally high waves continues, even though
    the winds may have subsided below hurricane
    intensity.
  Forecast Process - Graphic Product
Note that the
center line
indicates the
“average” of the
forecast track.

Storm can end
up any where in
the cone & affect
areas outside of
the cone

The size of the cone
increases as the
forecast period
becomes greater
Tropical Cyclone Preparedness




      Hypothetical
    Hurricane “Carly”
                          Source: UT Space Science Center
   Brownsville Landfall
Tropical Cyclone Preparedness




          .


                Source: UT Space Science Center
         Brownsville




                               Source: UT Space Science
                                        Center
Brownsville / South Padre I.
     Mean Sea Level
       Brownsville




                     Source: UT Space Science
 Hurricane Carly              Center
 9/11 at 1500 CDT
MEOW NW at 8 MPH
 Surge: 17.3 Feet