Puerto Rico Weather Apr 12, 2017 4:40:16 GMT -6
Post by cycloneye on Apr 12, 2017 4:40:16 GMT -6
Area Forecast Discussion
National Weather Service San Juan PR
506 AM AST Wed Apr 12 2017
.SYNOPSIS....Lingering sfc trough will have an associated sfc low
developing to the north of the local islands today. This will
cause the local winds to remain fairly light today with the
western part of the forecast area observing light northerly winds
and the eastern part of the forecast area observing light
southeasterly winds. Another round of showers and thunderstorms
are expected this afternoon across the interior and western
portions of Puerto Rico.
.SHORT TERM...Lingering induced surface trough and an associated
area of low pressure expected to develop north of the region, will
combine with the fairly moist south to southeast low level wind
flow to maintain an unstable airmass across the region through
the end of the week. In addition, the slowly weakening upper trough
and proximity of the jet max just north of the region will continue
to provide good ventilation and instability for showers and thunderstorm
development across the coastal waters and parts of the islands
today through Thursday with a gradual improvement expected by late
Friday and into the weekend.
This aforementioned instability will support early morning shower
development across the coastal waters and portions of the east coastal
sections of mainly Puerto Rico and the adjacent islands of Culebra
and Vieques. Isolated thunderstorms will also remain possible
mainly over the offshore Atlantic waters in the vicinity of the
upper level jet maxima. Local and diurnal effect will lead to
convective development initially across parts of the interior
sections of PR, but the prevailing wind flow should steer most of
the activity across the northern half of Puerto rico as well as in
the vicinity of the San Juan metro area. Portions of the U.S.
Virgin islands can also expect isolated shower activity during
the afternoon. This overall weather pattern is to persist at
least until Friday, however the overall pattern and model guidance
still suggest a shift in the steering flow as the low to mid level
winds are to become more south to southwest. This will therefore
focus afternoon convection across parts of the central interior and
northeast sections of Puerto Rico including the San Juan metro area.
.LONG TERM...The long range models are now starting to indicate
that the bulk of the moisture and shower activity for this weekend
will be much closer to the local islands compared to what they
were suggesting a few days ago. They still insist that the bulk of
the moisture will be just to the south of the local islands, over
the Caribbean waters but they are now hinting for deeper moisture
over the USVI and PR and not just over the Caribbean waters.
Because of the recent change in the model forecast, the
confidence is fairly low as a slight change north or south of
this moisture boundary would mean a big difference in weather
expected. However, the models keep insisting in very deep moisture
over the local islands by the middle of next week, even though
that is very far into the forecast period, the models have been
consistent with that.
.AVIATION...Mostly VFR at local TAF sites. Passing SHRA ovr offshore
ATL and Caribbean waters and en route btw PR and the Nrn Leewards.
Psbl VCSH at TJSJ/TJNR/TISX/TIST TIL 12/14Z with brief Mtn Top obscr
ovr Ern PR in low clds and -SHRA. SCT-BKN lyrs nr FL025... FL060...
FL100. few tops btw FL200-FL250. Sfc Wnds calm to lgt/vrb bcmg fm E-
SE aft 12/14z except for sea breeze variations.
.MARINE...Seas are generally 2-4 feet today with gentle winds.
Seas will gradually increase tonight and Thursday. Because of the
tranquil seas and light winds, the risk of rip currents is low
today, but will be moderate across some beaches tonight and
.PRELIMINARY POINT TEMPS/POPS...
SJU 88 76 87 76 / 40 30 40 20
STT 84 74 84 75 / 50 40 40 30