Scientific Forecaster Discussion
Area forecast discussion
National Weather Service San Juan PR
258 PM AST Friday may 22 2015
aloft...the islands lies between a trough to the north and a ridge
to the south. By Tuesday...an upper level trough will build off
to the northeast of the local area. A middle level ridge will move
across eastern Caribbean through Sunday...followed by a middle level
trough. A Saharan air layer will continue moving across the
eastern Caribbean throughout the weekend.
latest model forecast and observations along with recent tjsj radiosonde observation
data continue to suggest the spreading of a Saharan air layer
across eastern Caribbean. Additionally...a sub tropical jet aloft
will continue to push high clouds into the region this afternoon
and tonight. Therefore...limited convective shower activity is
expected during that period...most of the activity...if any will
be across the interior and western sections of the islands.
Moderate trade winds and hazy conditions are expected to prevail
across the local area today. A similar pattern is expected
throughout the weekend across the local area...with nocturnal trade
wind passing showers across the eastern sections of PR...the USVI
and their surrounding waters...and afternoon convection across
western Puerto Rico each day.
For early next week...moisture is expected to increase and typical
trade wind pattern and afternoon convection with T-storms across
western PR will establish once again across the islands. The
operational models continue to suggest increasing tropical
moisture by the latter portions of the upcoming week.
Aviation...VFR conds for PR/USVI xcpt brief local MVFR in rain showers/isolated
thunderstorms and rain by the way 18z-22z today and Sat mainly over western PR... few obscure mountain top
over due to rain showers/possible -tsra. Scattered-broken low cloud layers by the way fl020- fl050.
Wind from southeast 10-15 kts below fl200...becoming from west above and increase west/heat maximum wind
65-70 kts near fl450. No sig weather forecast en Route by the way islands excpt for
slight haze aloft.
Marine...Ponce buoy is indicating wind driving waves up to five
feet...among that...the local buoy network continues to indicate
fairly tranquil seas of 5 feet or less and winds at 15 to 20
Preliminary point temps/pops...
sju 76 91 76 88 / 10 20 20 20
stt 78 89 77 87 / 20 20 20 20