Advisory FFA Flood Watch — Mon Feb 5, 2024 8:51 PM

FFASJU) remains in effect from 6 AM AST
Tuesday through 6AM AST Thursday.

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/FROM PREVIOUS DISCUSSION ISSUED AT 502 PM AST Mon Feb 5 2024/

.SYNOPSIS...

An unstable weather pattern is expected starting tomorrow through
Thursday, with rain activity possible across the entire forecast
area. Due to this, a flood watch is out for all of the local
islands until at least Thursday. For more details on the rainfall
event, please refer to the Hydrologic Outlook (ESFSJU). A small
northerly swell and fresh northerly winds will aid buildings seas
from tomorrow through the weekend, resulting in hazardous and
choppy seas. Please refer to the Marine Weather Message (MWWSJU)
for more information.

&&

.SHORT TERM...Tonight through Wednesday

Today`s sounding detected low-level winds between 10 and 25 knots
out from the south with normal to above-normal Total Precipitable
Water (TPW). The islands had a mix of sunshine and clouds. Light to
moderate rains developed across the interior and southern PR from
noon onward. Rainfall amounts were minimal, but ponding of water
developed with the isolated periods of heavy rain. Temperatures were
in the low 90s along the coast and the low or mid-80s in the
mountains.

We expect a short break in the rain activity early this evening
today. Under a light and variable southerly wind flow, most of this
evening`s rain activity will occasionally affect the southern
windward areas of mainland PR and the USVI. The rain activity will
slowly increase from the Southern Caribbean into south-PR before the
onset of an unsettled weather pattern early Tuesday morning through
early Thursday morning with the arrival of the deep-layer trough and
a frontal boundary, pooling above normal moisture.

The wettest period will be early Tuesday for southern PR, stretching
eastward into the Virgin Islands later that day, 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 3-6" for
southern/eastern PR and 2-4" for the USVI. The reasonable worst-case
scenario calls for 5-8" across southern/eastern PR and 3-5" for the
USVI. The main impact of this event is the flooding, including flash
flooding, but also we expect strong thunderstorms and windy
conditions. We could also experience rapid river rises and
mudslides. Therefore, we issued a Flash Flood Watch for the
territories from early Tuesday to early Thursday.

&&

.LONG TERM...Thursday through Monday...
/from previous discussion/

A transition in the weather pattern is expected for Thursday as
the tropical moisture and instability associated with a deep layer
trough slowly exit from the forecast area. According to the
global guidances (GFS & ECMWF), the highest probability of showers
is anticipated across sectors of the eastern part of the island
and the U.S. Virgin Islands, resulting in additional rainfall.
Although the intensity and duration of showers during the day are
not expected to be very significant, additional rain on already
saturated soils could exacerbate flooding issues in sectors of
eastern Puerto Rico. Therefore, for Thursday, there is a limited
flood threat for the southeastern sections of Puerto Rico.

As the day progresses, all the tropical moisture is expected to
shift east of the island, pushed by a mass of dry air with
precipitable water values below climatological normals.
Additionally, a broad mid-level range will replace the divergent
side of the trough, eroding the available moisture and resulting
in more stable conditions. From Friday onwards, the island will
mostly be dominated by high pressure in the western Atlantic,
resulting in a northwest wind flow by early Friday. From Saturday
into Monday, winds are forecasted to veer as the surface high
pressure moves farther eastward into the Central Atlantic,
becoming northeast by Sunday.

&&

.AVIATION...
(00Z)
South-southwesterly low level winds between 10 to 20 kt will
persist overnight, increasing at 15 to 25 kt with higher gusts aft
06/06Z. SCT SHRA/ Isold TSRA will move from the Southern
Caribbean into PR/USVI after 06/06z, creating squally weather
across the local flying area with prevailing VFR but occasional
MVFR or IFR conditions psbl especially between 06/10z-06/22Z.

&&

.MARINE...
The interaction of two surface lows, one over the Northwest
Atlantic and another near the Gulf of Mexico, and an approaching
frontal boundary will promote fresh southerly winds overnight
through Tuesday. The interaction of a deep- layer trough and the
broad Atlantic ridge extending into the eastern Caribbean, will
result in fresh to locally strong winds, hazardous seas and
squally weather across the regional waters and passages from early
tomorrow morning through early Thursday morning. The arrival of a
northerly swell will aggravate the situation through the second
part of the work-week.


&&

.SJU WATCHES/WARNINGS/ADVISORIES...
PR...Flood Watch from 6 AM AST Tuesday through late Wednesday night
     for PRZ001>013.

VI...Flood Watch from 6 AM AST Tuesday through late Wednesday night
     for VIZ001-002.

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

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

     Small Craft Advisory from 2 PM to 8 PM AST Tuesday for AMZ726.

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

&&

$$