Scientific Forecaster Discussion
Area forecast discussion
National Weather Service San Juan PR
403 am AST Thursday Nov 27 2014
Synopsis...upper low NE of the area will lift away from the
region tonight. Upper ridge will build tonight through Friday then
flatten during the weekend as southern stream trough moves across the SW Atlantic.
Discussion...subsidence inversion will strengthen rapidly later
today leading to rapid erosion of low-level moisture. Thus...expecting
current showers to dissipate rapidly after 12z. Subsidence
inversion holds through 12z Sat keeping rather tranquil conditions
next 48 hours. Upper level ridge begins to flatten Friday night and Sat
with subsidence inversion weakening on Sat leading to steepening
lapse rates and promoting moisture transport. Expect scattered showers
and possible T-storms Sat afternoon over inland areas. Moisture
deepens through sun with scattered rain shower/thunderstorms and rain expected. Shortwave ridge
builds Monday-Monday night behind departing southern stream trough leading
to middle-level drying. A second middle-level trough over the greater Mexico will
move into SW Atlantic and northwest Caribbean Tuesday and Wednesday and promote significant
moisture transport into the region Wednesday on with the risk of heavy
rainfall developing toward the end of next week.
Aviation...VFR conditions will prevail for the next 24 hours at all
terminals. East northeast surface winds at 10-15 knots. No sig operational
weather impact expected at this time.
Marine...winds will subside rapidly today through Friday afternoon
leading to significant improvement in seas. Will undercut ww3
guidance next 72 hours as wave model looks too pessimistic. Winds
strengthen again Sat through early next week with seas building
5-7 feet. A northwest swell group is also expected to arrive sun increasing
the risk of rip currents.
Preliminary point temps/pops...
sju 84 74 84 76 / 0 0 0 30
stt 86 77 86 78 / 0 0 20 20
Coastal waters...Small Craft Advisory until 6 am AST early this morning for
Anegada Passage southward to 17n-Atlantic waters of Puerto Rico
and USVI from 10nm to 19.5n-Caribbean waters of Puerto Rico
from 10 nm to 17n-coastal waters of northern USVI and
Culebra out 10 nm-coastal waters of southern USVI Vieques
and eastern Puerto Rico out 10 nm.