Convective Nocturnal Thunderstorms
Convective nocturnal thunderstorm
activity over water occurs over the Gulf from May through September. They
most often occur 25-50 nm south of the coast during July and August.
Activity begins to develop after 2200 local. Cumulus humulus
gradually develop into thunderstorm activity by 0400 local.
Thunderstorm activity begins to dissipate at 0900 local. By 1100 local
most thunderstorm activity has dissipated and skies are generally clear
skies over the Gulf by 1200 local. The normal movement of nocturnal
thunderstorm activity is a slow drift to the north.
Early in the season, dissipation of the thunderstorm activity
usually begins before the thunderstorm activity reaches land. When this
is the case, only light rain and mid-level cloudiness reach the coast.
As the season progresses, the water adjacent to the coast
becomes warmer. Thunderstorm activity reaches the immediate coastline before
dissipation, but rarely moves more than 5 miles inland. KNPA experiences
brief periods of ceilings below 1,000' and visibility below 5 miles. Surface
wind gusts are minimal with a maximum of less than 30 knots.
When 500 mb or 700 mb troughs move over the local area,
thunderstorm activity increases, prevails longer, and on occasion produces
funnel clouds and waterspouts along the immediate coast.
Perdido Bay Nocturnal Thunderstorms are a local and seasonal
type of convective nocturnal thunderstorm. Nocturnal thunderstorm activity
occurs over Perdido Bay (west of KNPA) from May through October. This activity
begins about 0300 local and reaches its maximum intensity shortly after
sunrise. Movement of the storm (if any) takes the storm over land. Dissipation
of storm activity begins as soon as landfall is reached.