Tropical Meteorology and Equatorial Weather Hazards
Tropical atmosphere
The tropics have a weak Coriolis force, a high tropopause, abundant moisture and strong insolation. The intertropical convergence zone is a belt of convergence and deep convection that migrates with the sun, lying near Brunei in the northern summer. Easterly waves move westward and trigger organised convection. Tropical cyclones require sea-surface temperatures above about 26.5°C, low vertical wind shear and sufficient distance from the equator (about 5°), and they do not form exactly on the equator.
Equatorial hazards
Convective storms are frequent, with heavy rain, lightning, hail, downbursts and microbursts. Orographic uplift along Borneo's interior produces afternoon and evening cloud. Fog and low stratus form in moist calm conditions overnight. Haze and smoke reduce visibility seasonally. Thunderstorm cells can produce wind shear and runway water hazards.
Traps
A common trap is assuming tropical cyclones cross the equator; they do not. Another is expecting a strong diurnal temperature range; the humid tropical day–night range is modest. Do not confuse the ITCZ with the subtropical ridge. Squall lines in the tropics can be very intense and move quickly.
Worked example
An easterly wave approaches with a falling surface pressure, backing wind and increasing cumulus. Expect intensifying showers, possible thunder and gusty outflow winds, so plan for a wind shear check and a possible diversion.