A trough or cyclonic curvature
maximum in the trade-wind easterlies. The wave may reach maximum amplitude in the lower middle
TROUGH: An elongated area of relatively low
atmospheric pressure, usually not associated with a closed circulation, and thus used to distinguish from a
closed low. The opposite of ridge.
Transport of warm air into an area
by horizontal winds.
Variation in wind speed (speed
shear) and/or direction (directional shear) over a short distance. Shear usually refers to vertical wind
shear, i.e., the change in wind with height,
Clouds And Rainfall
BRIEF SHOWERS: Occurring for less than 20
CLOUDY: Cloudy most of the time, with relatively high
probability of rainfall.
Less than 5 miles (8km) from the
sea and below 500ft.
FAIR AND SUNNY:
Little clouds for most of the time
with relatively low probability of rainfall.
FINE: Few clouds, no rain
More than five miles (8km) from the
Occurring over less than 10% of the
All areas above
LOW LYING AREAS:
Occurring over 80%__95% of the
Occurring at least three
Cloudy all the time, with
relatively high probability of rainfall.
Varying at times between fair and
mainly cloudy with relatively low probability of rainfall.
Occurring for more than 2
RAIN: Continuous rainfall from mainly stratified
cloud (sheet clouds), with intensity from light to moderate or moderate to
Occurring over 30%__60% of the