Post on 15-Jan-2016
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