Tropical storms•Classification

•Development

•Trajectories

•Forecasting

•Hazards

•Future prospects

Tropical disturbances, etc.

Saffir-Simpson scale

Spawning areas for tropical storms (SST >27°C)

Tropical storm genesis:convergence behind an easterly wave

In a typical hurricane season some 60 easterly waves develop in the North Atlantic. Only about 1 wave in 5 becomes a tropical depression. Strong upper level troughs and westerly winds commonly suppress hurricane formation

Mature hurricaneDevelopment fostered by release of heat from condensed water in bands of clouds around the tropical storm centre more rapid convergence and updrafts. This +ve feedback leads to intensification and hurricane formation.

Structure of Hurricane Gilbert(Doppler radar cross-section )

The Atlantic hurricane season(Dr. William Gray @ Colorado State U.)

Strong El Niño suppresses hurricanes(but 1998?)

Wet springs inhibit

hurricanes

Strong Azores High

inhibits hurricanes

Strong stratospheric easterlies suppress

hurricanes

Low SST’s inhibits

hurricanes

Atlantic hurricanes(1995 season)

Tracks of typhoons

affecting the China Sea

region

Tracks of cyclones in the northern Indian Ocean

Effects of travelling high and low pressure systems on hurricane pathsTypical pathActual pathHL

Hurricane Andrew (1992)

Hurricanes - examples of unpredictability

Laurie(Oct, 1969)Inga(Sep-Oct, 1969)

Forecasting• NHC (Miami) uses nine tracking and intensity models to forecast

hurricane movement.

• Seven models based on global climate forecasts; two (NHC90/91 and CLIPER) based on statistical analyses of past hurricane trajectories.

• Forecasts are for 12h, 24h, 36h, 48h and 72h ahead and are updated at 4h intervals.

• Some models are used for ‘early’ stages; others for ‘late’ (i.e. close to landfall).

• Average errors vary from ocean to ocean, depending on typical recurvature (Atlantic errors are large)

Mean error (nm) for Atlantic hurricanes (1996-97 seasons)

0

50

100

150

200

250

300

350

400

CLIPER LBAR UKMET GFDL

24h48h72h

Forecast model

The geography of forecasting error

72 h

48 h

24 h

Estimated annual deaths from hurricanes in the USA

0

500

1000

1500

2000

2500

1920's 1930's 1940's 1950's 1960's 1970's 1980's 1990's

Damages from hurricanes in the USA ($ billions)

0

5

10

15

20

25

30

35

1920's 1930's 1940's 1950's 1960's 1970's 1980's 1990's

Hurricane hazards

Storm surge (5-6m common)High winds (see Saffir-Simpson)

Intense rainfall

Increasing population at risk (80% of residents of Florida =8M people live within 8 km of coast; 3M within storm surge zone)

X

New Orleans (-2m elev.)~72h to evacuate 1.6M residents. Old and poor (~100 000) who rely on public transport present a major problem. Solution: move them to high floors of skyscrapers?

El Niño events and tropical storm activity(e.g. 1998 El Niño)

• PACIFIC OCEAN - 14 tropical storms in E. Pacific ; 9 developed into hurricanes.

• ATLANTIC OCEAN - 14 tropical storms; 10 developed into hurricanes.H. George: most powerful storm in ~200 yrs; hit Puerto Rico, Virgin Is., Domincan Rep., Florida and US Gulf coast - 300 deaths, $5G in damage.H. Mitch: most destructive storm in ~200 yrs; hit Nicaragua - Guatemala - >13 000 dead or missing, $5G in damage.

Global warming and tropical storm activity

Emanual (MIT) forecasts:

1. that the hurricane season will be extended by 2 months or more in the North Atlantic and Caribbean.

2. that hurricane intensity will increase by more than 50% - attaining maximum wind speeds of >300 km/h (cf. >200 km/h at present).

HURRICANE SEASON 2001

12 - 7 - 312 NAMED STORMS

7 HURRICANES

3 MAJOR STORMS

1995-2000 MOST ACTIVE 6 YEARS ON RECORD

79 NAMED STORMS

49 HURRICANES

24 MAJOR STORMS

Gilbert 1988 (5) 26.22 in. 888 mbFlorida Keys 1935 (5) 26.35 in. 892 mbAllen 1980 (5) 26.55 in. 899 mbCamille 1969 (5) 26.61 in. 901mbMitch 1998 (5) 26.73 in. 905 mbJanet 1955 (5) 27.00 in. 914 mbAndrew 1992 (4) 27.23 in. 922 mbFlorida Keys/Tex 1919 (4) 27.37 in. 927 mb

Opal* 1995 (4) 27.40 in. 929 mbOkeechobee 1928 (4) 27.43 in. 930 mbDonna 1960 (4) 27.46 in. 930 mbGalveston 1900 (4) 27.49 in. 931 mbGrand Isle 1909 (4) 27.49 in. 931 mbNew Orleans 1915 (4) 27.49 in. 931 mbCarla 1961 (4) 27.49 in. 931 mbHugo 1989 (4) 27.58 in. 934 mbMiami 1926 (4) 27.61 in. 935 mbGeorges 1998 (4) 27.70 in. 938 mbHazel 1954 (4) 27.70 in. 938 mbFlorida, S.E. 1947 (4) 27.76 in. 940 mb

Most Intense

SAFFIR -- SIMPSON SCALECategory Surge

mb in kts MPH ftTD na na <34 <39 na

TS na na 34-63 39-73 na1 980 28.93 64-82 74-95 4-5

2 965-980 28.48-28.93 83-95 96-110 6-83 945-965 27.88-28.48 96-112 111-130 9-12

4 920-945 27.13-27.88 113-134 131-155 13-185 <920 <27.13 >134 >155 >18

Pressure Winds

PB4Y-2 PRIVATEER(Hurricane Hunter)Lost, Hurricane JANET - 1955

COSMOSPHERE-HURRICANE

SUN PROVIDES HEAT

ATMOSPHERE-HURRICANE

WHAT’S REQUIRED ???1. INFLOW - OUTFLOW2. WARM, MOIST AIR - SST 80 TO

3. EXISTING DISTURBANCE

4. LOW WIND SHEAR

5. CORIOLIS

150 FT.

SST 26.5C OR MORE

DEEPTO A LEAST 46 METERS

TEMPERATURE

INFLOW-OUTFLOW

WARM/MOIST

CORIOLIS

SHEAR

155 MPH = 100 lbs per SQUARE FOOT.

CUBIC YARD SALT WATER = 3/4 TON.

SURGE

WINDS

HYDROSPHERE-HURRICANE

OCEAN PROVIDES MOISTURE

BIOSPHERE-HURRICANE

HABITAT DAMAGE

Board “Growing” in a TreeHurricane Andrew, 1992

ANTHROPOSPHERE/GEOSPHERE-HURRICANE“A-SPHERE”

DEATH & DISTRUCTION

1935

FLORIDA KEYS

FLORIDA KEYS 1935

CAMILLE

1969

RICHELIEU APTS. PASS CHRISTIAN

HURRICANE CAMILLE

AFTER CAMILLE

HURRICANE CAMILLE

American Legion Post, Bay St. Louis

CAMILLE

Hurricane Andrew, 1992

ERIN1995

OCEANOGRAPHY 101 by ERIN

FLOYD ANDREW1999 1992

WC-130 USAF(RES) HURRICANE HUNTER

AIRCRAFT RADAR

Andrew 1992 (4) $30.5 billionHugo 1989 (4) $8.5 billionAgnes 1972 (1) $7.5 billionBetsy 1965 (3) $7.4 billionCamille 1969 (5) $6.1 billionDiane 1955 (1) $4.8 billionFrederic 1979 (3) $4.3 billionNew England 1938 (3) $4.1 billionFran 1996 (3) $3.2 billionOpal 1995 (4) $3.1 billionAlicia 1983 (3) $2.9 billionCarol 1954 (3) $2.7 billionCarla 1961 (4) $2.2 billionJuan 1985 (1) $2.1 billionDonna 1960 (4) $2.1 billionCelia 1970 (3) $1.8 billionElena 1985 (3) $1.7 billionBob 1991 (2) $1.7 billionHazel 1954 (4) $1.6 billionMiami * 1926 (4) $1.5 billion

Adjusted to 1996 dollars

Costliest

Mitch 1998 (5) >13000Galveston 1900 (4) >6000

Okeechobee 1928 (4) 1836*Georges 1998 (4) 602

Florida/Texas 1919 (4) 600New England 1938 (3) 600Florida Keys 1935 (5) 408

Audrey 1957 (4) 390N.E. U. S. 1944 (3) 390

Grand Isle, La. 1909 (4) 350New Orleans 1915 (4) 275

Galveston 1915 (4) 275Camille 1969 (5) 256Miami 1926 (4) 243Diane 1955 (1) 184

Deadliest

THE BIG ONE IS STILL OUT

THERE