Rip Current in Puerto Rico, April 16, 2021

Area Forecast Discussion
National Weather Service San Juan PR
1039 AM AST Fri Apr 16 2021

.UPDATE...

No significant changes made to forecast, which is tracking well.
Showers have been observed on radar to the east and southeast of
Puerto Rico, with activity slowly tracking north/northwestward.
Showers and isolated thunderstorms are expected during the
afternoon, associated with diurnal heating and local effects
interacting with the frontal boundary remnants. The bulk of the
activity will be in interior and western Puerto Rico.

&&

.AVIATION...

Generally, VFR conditions will prevail, though periods of MVFR
conditions, due to ceilings, are possible from time to time, as well
as occasional -SHRA. This is associated with increased shower
activity from a frontal boundary progressing over the region from
the Caribbean to the Atlantic. This afternoon, SHRA/TSRA are
expected to develop over interior Puerto Rico, then shift into
northern Puerto Rico, with potential affects for TJSJ and TJBQ
through at least sunset. Brief IFR conditions are possible in and
around the thunderstorms. Winds generally out of the E to SE at 10
to 15 knots, with sea breeze variations, as well as stronger gusts,
especially in the vicinity of SHRA/TSRA. Winds diminish overnight,
becoming light.

&&

.MARINE...

Relatively tranquil seas persist, at 5 feet or less. As a northerly
swell affecting the local waters subsides, so too will the seas,
slightly; however, another swell will follow during the weekend. On
the whole, conditions will remain much as they have been for the
last couple of days. Winds are becoming more easterly/east-
southeasterly, but speeds remain around 10 to 15 knots.

There is a moderate risk of rip currents for north-facing beaches of
Puerto Rico and St. Thomas, as well as Cramer Park in St. Croix.

&&

.PREV DISCUSSION... /issued 430 AM AST Fri Apr 16 2021/

SYNOPSIS...
Moisture will increase today due to the passage of an old frontal
boundary. As a result, showers and thunderstorms are expected to
develop, with the potential for heavy rain. Drier air, along with
Saharan dust is expected for the weekend and the first part of the
next workweek.

SHORT TERM...Today through Sunday...

The remnants of an old frontal boundary, are moving across the
Caribbean waters into the Anegada Passage and across portions of the
islands. This will cause a surge in moisture and increase shower
activity in general through the evening hours. An upper level jet
will move across the Atlantic waters later today, enhancing the
potential for isolated thunderstorm development and for afternoon
heavy showers. Urban and small stream flooding is expected with the
heaviest showers. As steering winds are from the southeast today,
shower development along the Cordillera Central is expected to drift
northwards this afternoon. The remnants of the frontal boundary are
expected to slowly move into the Atlantic waters by tonight, and
moist southerly winds should continue to carry showers across the
southern and eastern sections of PR. Across the USVI, cloudy skies
and scattered shower activity are expected through much of the day.

For Saturday, the remnants of the frontal boundary are expected to
move over the offshore Atlantic waters and away of the region, while
a building ridge east of the Leeward Islands will promote drier air
intrusion and the arrival of a Saharan Air Layer (SAL) should cause
hazy skies and limit shower activity to diurnal activity over
northwestern PR. Even drier conditions are expected on Sunday, and
no significant rainfall accumulations are anticipated at this moment
across the islands. Overall, the weekend should be hazy due to the
SAL and maximum temperatures should range from the high 80s to low
90s across coastal areas.

LONG TERM...Monday through Friday...
As the workweek begins, the mid level ridge will continue to hold
over the eastern Caribbean. At the surface, high pressure extends
from the central toward the western Atlantic Ocean, generating a
southeasterly wind flow over the local islands. The latest
guidance still shows dry air at the low and mid levels. This air
mass contains Saharan dust, hence hazy skies will prevail through
at least Tuesday. By mid-week, the high pressure at the surface
will tighten the gradient along the area, resulting in an enhanced
wind flow, but so far, the models are only showing moderate winds
over the regional waters. The mid-level ridge will begin to move
into the central Atlantic by Wednesday into the latter part of the
week, while an upper level trough develops to the northeast of
the Lesser Antilles. Although the trough should continue to
deepen, the islands will remain on its subsidence side. As the
ridge begins to lose its influence, fragmented groups of clouds
embedded in the trade winds will increase in frequency. These
moisture fields will be a little deeper, reaching up to 700 mb. As
a result, the atmosphere will become more favorable for shower
development, with passing showers affecting eastern Puerto Rico
and the U.S. Virgin Islands, and convective activity developing in
the afternoon mainly over the interior and western sections of
Puerto Rico. There is still some uncertainty in the timing of
arrival of these groups of clouds, but so far, both the GFS and
ECMWF are suggesting this increase in moisture by sometime on
Thursday and Friday.

AVIATION...The remnants of an old front will move across PR and the
USVI through the day. This will cause tempo MVFR cigs across all the
local terminals, as well as intermittent periods of -SHRA. In
addition, +SHRA/TSRA is expected to develop this afternoon over
central PR, drifting to the north and impacting the northern
terminals through at least sunset with possible MVFR to brief IFR
conditions. Winds are expected from the SE at 10-15 kt, with higher
gusts at times in SHRA/TSRA.

MARINE...
Recent observations are showing a dominant period of 10-11
seconds over the northern areas of Puerto Rico, with seas 3 to 5
feet. The outer buoy, 41043, also shows 10 seconds at 6 feet. This
weak northerly swell is expected to continue today, while another
one is expected to arrive during the weekend.

For the beaches, there is a moderate rip current risk for the
northwest, northern, and northeast coast of Puerto Rico, all of
Culebra, eastern Vieques, most of St. Thomas, northwest St. John,
and the eastern tip of St. Croix.

&&

.PRELIMINARY POINT TEMPS/POPS...
SJU  87  76  89  76 /  40  40  20  20
STT  86  77  84  76 /  50  50  20  20

&&

.SJU WATCHES/WARNINGS/ADVISORIES...
PR...None.
VI...None.
AM...None.
&&

SHORT TERM...CRS
LONG TERM....LIS
PUBLIC DESK...CAM

Perspectivas sobre Condiciones Peligrosas del Tiempo
Servicio Nacional de Meteorologia en San Juan PR
507 AM AST viernes 16 de abril de 2021

AMZ710>745-PRZ001>013-170915-
San Juan y Vecindad-Noreste-Sureste-Este Interior-Norte Central-
Interior Central-Ponce y Vecindad-Noroeste-Oeste Interior-Mayaguez
y Vecindad-Suroeste-Culebra-Vieques-Las aguas costeras cercanas y
lejanas a la costa del Atlantico y Caribe-
507 AM AST viernes 16 de abril de 2021

Esta perspectiva sobre las condiciones peligrosas del tiempo es para
Puerto Rico y las aguas costeras del Atlantico.

.Dia Uno...Hoy y esta noche

.Tronadas...Existe el potencial de tronadas con lluvia fuerte y
rafagas de vientos esta tarde a traves del interior y mitad norte de
Puerto Rico.

.Inundaciones...Lluvias fuertes pudieran resultar en inundaciones
urbanas y de riachuelos.

.Corrientes Marinas...Existe un riesgo moderado de corrientes
marinas para playas desde la costa noroeste a noreste de Puerto
Rico, Culebra y playas del norte de Vieques.

.Dias dos hasta el siete...sabado a jueves

Un riesgo moderado de corrientes continuara mayormente para las
playas del norte de las islas durante la proxima semana.

.Comunicado sobre informacion reportada por observadores...

No se espera activacion amplia de observadores. Favor de reportar
cualquier informacion sobre inundaciones, vientos y corrientes
marinas al Servicio Nacional de Meteorologia en San Juan mientras
siguen las indicaciones de las autoridades locales y estatales.

AMZ715-725-VIZ001-002-170915-
San Tomas, San John e Islas Adyacentes-
Santa Cruz-Aguas cercanas del Atlantico y aguas costeras adyacentes
del Caribe-
507 AM AST viernes 16 de abril de 2021

Esta perspectiva sobre las condiciones peligrosas del tiempo es para
Islas Virgenes Estadounidenses y las aguas costeras adyacentes.

.Dia Uno...Hoy y esta noche

.Inundaciones...Lluvias moderadas a localmente fuertes pudieran
resultar en acumulacion de agua en carreteras y areas de pobre
drenaje.

.Corrientes Marinas...Existe un riesgo moderado de corrientes
marinas para las playas del norte y oeste de St. Thomas y St. John,
como para las playas del este de St. Croix.

.Dias dos hasta el siete...sabado a jueves

Se espera un riesgo moderado de corrientes para las playas del norte
de St. Thomas y a treves de St. Croix hasta temprano la proxima
semana.

.Comunicado sobre informacion reportada por observadores...

No se espera activacion amplia de observadores. Favor de reportar
cualquier informacion sobre inundaciones, vientos y corrientes
marinas al Servicio Nacional de Meteorologia en San Juan mientras
siguen las indicaciones de las autoridades locales y estatales.