SYNOPSIS...Brisk trade winds will continue to push a few clouds
and light showers across the local islands through midweek. Moisture
is below normal therefore little or no rainfall accumulation are
expected with the morning showers. Measurable rainfall is likely
each afternoon across western Puerto Rico. A wetter and more
unstable pattern is forecast the second half of the week as a deep
upper level trough develops over Puerto Rico and the U.S. Virgin
Islands. Marine and coastal conditions will remain hazardous over
the next couple of days.
SHORT TERM...Tonight through Tuesday...
Intervals of dry and humid patches of air will continue affecting
the islands through the short term forecast period. Current
satellite precipitable water (PWAT) indicate a patch of moisture
with values up to around 1.3 inches moving across the region with
other dry or less humid patches behind it. At the upper-levels, a
trough is moving across the islands, gradually exiting the area.
Impacts from this feature however, will continue to be minimal due
to ridging at around 700 mb. Any available moisture will be mostly
restricted to below 700 mb to start the workweek. At surface level,
a high pressure system over the Atlantic continues to spread
eastward and promoting breezy conditions with for most of the
period. Breezy conditions will also aid in limiting rainfall
accumulations over the islands as showers will be fast moving. Most
shower activity during the short term period will depend on those
patches of moisture embedded in the trade winds reaching our area
and bringing associated passing showers. PWAT values should overall
reach near or below normal levels today, promoting more variable
conditions; current model guidance indicates a decrease in PWAT to
below normal levels tomorrow morning, making it possibly the
driest day in the short term period, and a gradual increase in
PWAT on Tuesday. Shower activity, including isolated to scattered
showers over windward sectors during the morning and evening and
afternoon convection over western Puerto Rico due to local effects
and diurnal heating, will increase when those patches of
moisture, fragments of old frontal boundaries, are affecting the
area and decrease to cease when drier air filters in.
LONG TERM...Wednesday through Sunday...
Unstable weather conditions are forecast for the second part of
next week as a deep layer low develops over the northeast Caribbean
region. Both models, GFS and ECMWF, have been consistent with the
location and intensity of the upper trough near the local area
late in the week. Also, 500 mb temperature and geopotential height
anomalies are significantly lower for our area if it's compared
with our sounding climatology. Therefore, high instability and
enhanced risk of heavy rain will be associated with this potent
mid-upper level low. Very cold temperatures at mid- levels will
enhance the potential of thunderstorms across the region,
especially Thursday and Friday. The peak of instability and
organized convection should occur between Thursday and Friday when
the trough/low deepens over Puerto Rico and the U.S. Virgin
Islands. The ECMWF EFI continues to suggest organized convection
associated with this trough/low. The highest signal is over the
U.S. Virgin Islands and the Caribbean waters south of Puerto Rico.
If the model verifies, the U.S. Virgin Islands, Culebra, Vieques
and eastern Puerto Rico will likely experience the brunt of the
shower and thunderstorm activity. During the weekend, operational
models are showing that the trough will weaken as it lifts
northward into the western Atlantic. As a result, conditions will
likely improve Saturday and Sunday as moisture and instability
will gradually decrease across the local islands.
AVIATION...Overall VFR conditions will continue across the
terminals, brief MVFR conditions possible due to passing shower
activity across mainly TJSJ/TISX/TIST during the early morning
hours. Wind flow will be generally easterly to ESE at around 15-25
kts, with higher gusts and sea breeze variations. Afternoon
convective activity could also promote brief MVFR conditions at TJBQ
during the afternoon afternoon hours.
MARINE...Fresh trade winds continue across the regional waters
resulting in choppy conditions. Wind-driven seas and a small
north-northeast swell are producing hazardous seas of 5-7 feet
across the local Atlantic waters and Caribbean Passages. These
hazardous marine conditions will continue over the next couple of
days. Small Craft Advisories are in effect for most of the local
waters though the morning hours, however some of the zones such as
the offshore Atlantic waters and Anegada Passage continues
through at least Monday afternoon. The high risk of rip currents
will continue for the Atlantic beaches of most the islands.
FIRE WEATHER...Breezy conditions and a relatively dry air mass
will lead to elevated fire weather conditions across portions of
the islands once again today. As a result, a Fire Danger Statement
was issued for the southern coastal plains of Puerto Rico. For
more information, please refer to the Fire Danger Statement
(RFDSJU) and Fire Weather Planning Forecast (FWFSJU) products.
&&
.SJU WATCHES/WARNINGS/ADVISORIES...
PR...High Rip Current Risk through Monday afternoon for PRZ001-002-
005-008-012.
High Rip Current Risk through late tonight for PRZ010-013.
VI...High Rip Current Risk through Monday afternoon for VIZ001.
High Rip Current Risk through late tonight for VIZ002.
AM...Small Craft Advisory until 2 PM AST Monday for AMZ711-723.
&&
$$
DSR/GRS