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
Development 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.
Strong Azores High inhibits hurricanes
Strong El Niño suppresses hurricanes
Wet springs inhibit hurricanes
Strong stratospheric easterlies suppress hurricanes
Low SST’s inhibits hurricanes
Storm surge (5-6m common)
High winds (see Saffir-Simpson)
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?
Increasing population at risk (80% of residents of Florida =8M people live within 8 km of coast; 3M within storm surge zone)
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).
12 - 7 - 3
12 NAMED STORMS
3 MAJOR STORMS
79 NAMED STORMS
24 MAJOR STORMS
Lost, Hurricane JANET - 1955
SST 26.5C OR MORE
TO A LEAST 46 METERS
155 MPH = 100 lbs per SQUARE FOOT.
CUBIC YARD SALT WATER = 3/4 TON.