National Weather Service San Juan PR
522 AM AST Mon Oct 1 2018
.SYNOPSIS...Mid to upper level ridge will settle across the region
today, as the Tutt low and associated trough lifts farther north
and west of the region. High level cloudiness and moisture associated
with tropical wave now south of Hispaniola will continue to diminish
and pull away today, as drier and more stable weather pattern will
filter and prevail for the next few days. By the latter part of the
week and into the following weekend, another round of deep tropical
moisture originating from an approaching tropical wave and an evolving
trough across the Central Caribbean, will lift northwards over the
area. This will interact with an elongated upper-level low to result
in a wet and unstable weather pattern once again.during this period.
&&
.SHORT TERM...Today through Wednesday...
Mid to upper level ridge will hold through Tuesday. This ridge
aloft will erode some of the moisture across the local area,
reaching a minimum of 1.5 inches of precipitable water tonight.
Although, atmospheric conditions are not favorable for widespread
showers and thunderstorms, the weak steering flow will allow
diurnal cycle to dominate. As a result, local effects will induce
the development of showers and a couple of thunderstorms over the
Cordillera Central this afternoon. Across the U.S. Virgin Islands
minimal shower activity is forecast for today, however high level
clouds will maintain the skies mostly cloudy.
For Tuesday and Wednesday, a similar pattern is expected with
showers and thunderstorms developing mainly in the afternoon across
the interior sections of Puerto Rico. However, the coverage and
intensity of the afternoon thunderstorms may increase as moisture
are forecast to increase and mid-level temperature will decrease
somewhat as a mid-level trough forms over the Central Caribbean late
Tuesday into Wednesday.
.LONG TERM...Thursday through Tuesday...
Model guidance continued to suggest a drier airmass with stable
weather pattern through at least early Thursday. However upper level
support is forecast to become more favorable and unstable by the
end of the week as the upper ridge is expected to erode. This along
with available tropical moisture will be sufficient to combine with
local effects and diurnal heating resulting in afternoon convection
across portions of the islands each day.
Another tropical wave is forecast to reach the northeast Caribbean
Sea by Thursday. In addition, a polar trough is forecast to amplify
and spread across the region increasing upper level instability
through at least Saturday. In addition,recent model guidance continued
to suggest an evolving surface low pressure system which is forecast
to develop across the Caribbean and lift northward just west of
the region by the upcoming weekend. However there remains discrepancies
as far as location and timing of the expected unsettled weather
conditions and confidence is still low to moderate at this time.
Regardless, a fairly moist and unstable weather patterns will
remain possible by the latter part of the work week and into the
following weekend. By Sunday, a mid to upper level ridge is
forecast to build over the northeast Caribbean and help to erode
moisture pooling resulting in a gradual improvement in the
weather conditions. Another tropical wave is forecast to approach
the region by Tuesday.
&&
.AVIATION...VFR conds will continue across the terminals thru at
least 01/18Z. However, VCTS are possible at the TJSJ,TJMZ,TJSJ and
TJPS between 18Z-22Z as most of the TSRA will concentrate over the
Cordillera Central. A weak easterly flow will prevail below FL150.
&&
.MARINE...Seas at buoy 41043/41044 continue to gradually subside
as well as the near shore buoy 41053, which suggest subsiding and
diminishing seas between 6 to 7 feet and breaking waves between 8
to 10 feet respectively. Therefore small craft advisory will remain
in effect for the offshore Atlantic waters and the Mona passage. A
high risk of rip current will continue for the northern beaches
of Puerto Rico, Culebra and Saint Croix. Please refer to the
latest Coastal Waters Forecast (CWFSJU), Marine Weather Message
(MWWSJU) and the Coastal Hazard Messages (CFWSJU) for the latest
and additional information and updates. Expect another hazardous
northeast swell to return by Wednesday.
&&
.PRELIMINARY POINT TEMPS/POPS...
SJU 88 77 89 78 / 20 20 30 30
STT 88 77 88 77 / 20 20 30 40