Advisory FFA Flood Watch — Tue Feb 6, 2024 4:06 AM

FFASJU) is in effect for
all of Puerto Rico and the U.S. Virgin Islands. Hazardous seas and life-
threatening rip currents due to increasing winds and a northerly swell
will affect the local waters and most northwest to northeastern coastal
areas of the islands through the rest of the week.

Variably cloudy skies prevailed through the overnight hours as showers
and isolated thunderstorms developed under southerly steering winds
across portions of the interior and eastern Puerto Rico. The doppler
radar estimated near 1 inch of rain in Orocovis and Cayey after
midnight. Minimum temperatures were from the mid 60s across the higher
elevations to the mid 70s and low 80s across the lower elevations. Wind
gusts were between 16-22 mph across coastal areas. Breezy conditions
are expected to prevail across the islands today as low-level wind
speed convergence continues over the region.

A deep layered polar trough and associated surface low will continue to
amplify over the southwestern Atlantic during the next few days. This
will promote a deep southerly wind flow and pooling of tropical
moisture from South America into the northeastern Caribbean and the
Atlantic waters through at least late Wednesday night. Therefore, an
unsettled weather pattern is expected with numerous showers and
thunderstorm development across the local area. The wettest period is
expected from this morning over southern PR, stretching eastward into
the Virgin Islands later today, with a second round of flooding rains
on Wednesday. The highest accumulations should be for the south,
interior, and eastern PR, as well as the U.S. Virgin Islands. The most
likely scenario calls for 3 to 6 inches of rainfall for
southern/eastern PR and 2-4 for the USVI. Isolated higher amounts are
possible through the event. The main impacts are flash flooding and
mudslides, but thunderstorms with strong gusty winds are expected as
well.

By Thursday, a strong surface high pressure over Southeastern USA, and
the surface low now over the north central Atlantic will promote a long
northerly wind fetch across the western Atlantic into the northeastern
Caribbean. This will cause the local winds to turn from the north-
northwest and push the plume of moisture further east and away of the
local area. The precipitable water content is expected to decrease
below normal levels by early Thursday afternoon. However, the upper-
level trough axis is expected to cross the local area earlier in the
day and the 500 mb temperatures are forecast to drop to around -10C.
Therefore, the threat for additional shower and isolated thunderstorm
development could last into Thursday morning.


.LONG TERM...Friday through Tuesday...

A drier and more stable trend is forecasted for the beginning of
the long term. Model guidance indicates a more stable pattern at
the upper levels as the divergent side of the polar trough moves
eastward out of the forecast area, leaving subsidence over the
islands and being replaced by ridging. A similar trend is expected
at the mid-levels, with the GFS suggesting a broad building mid-
level ridge extending from the western Atlantic into the
Caribbean. The presence of the mid-level ridge will begin on
Friday afternoon and persist for the rest of the period as it
stretches into the central Atlantic.

The last part of the long-term global model guidance shows some
discrepancies between the two solutions, one stable and drier and
another stable but with more moisture. According to the GFS, from
Friday onwards and for the rest of the forecast period, the
islands are expected to be mostly dominated by a building surface
high-pressure system extending from the western Atlantic into the
Central Atlantic, resulting in northerly winds for Friday and
veering winds for the rest of the forecast period. Conversely, the
ECMWF solution shows a similar trend with a surface high-pressure
system located over the western Atlantic, but from Sunday into
Monday, the guide suggests a decent increase in humidity at 850 MB
and a weak short-wave trough over the area. As we are still far
away in the forecast, the forecast for the last part of the long
term reflects a combination of both solutions, resulting in a
variable weather pattern, given the presence of the mid-level
ridge causing a strong trade wind cap inversion and drier air
aloft.

&&

.AVIATION...
(06Z TAFS)

SCT SHRA/Isold TSRA will develop over PR today, and
across portions of the southern and eastern waters of the islands,
affecting the USVI terminals at times through the forecast
period. Tempo MVFR to brief IFR conditions are possible across all
local terminals. Mtn top obscd and BKN/OVC layers through FL100
expected. Low level winds will continue from the south-southwest
between 15 to 25 kt with higher gusts near SHRA/TSRA.

&&

.MARINE...

The interaction of a deep-layer trough and the broad Atlantic
ridge extending into the eastern Caribbean will result in
southerly fresh to locally strong winds. This wind-driven sea will
create hazardous marine conditions for the Atlantic offshore
waters. By midweek, the arrival of a northerly swell will
aggravate the situation, resulting in building seas and large
breaking waves. The local waters will experience squally marine
weather from today through Thursday, resulting in localized
hazardous marine conditions.

For beachgoers, there is a moderate rip current risk across all
the northern coastal areas of Puerto Rico and the local islands.
An increase in breaking waves is forecast from late tomorrow into
the rest of the workweek.

&&

.SJU WATCHES/WARNINGS/ADVISORIES...
PR...Flood Watch through late Wednesday night for PRZ001>013.

VI...Flood Watch through late Wednesday night for VIZ001-002.

AM...Small Craft Advisory from 2 PM this afternoon to 8 AM AST Monday
     for AMZ711.

     Small Craft Advisory from 2 PM this afternoon to 3 AM AST
     Wednesday for AMZ716-723.

     Small Craft Advisory from 2 PM this afternoon to 8 PM AST this
     evening for AMZ726.

     Small Craft Advisory from 8 PM this evening to 2 AM AST Thursday
     for AMZ741.

&&

$$