Rip Current in Puerto Rico, March 31, 2021

Area Forecast Discussion
National Weather Service San Juan PR
1202 PM AST Wed Mar 31 2021

.UPDATE...
Not changes were made on the inherited forecast. Brisk easterly
winds will continue through at least tomorrow dominated by the
strong high pressure ridge north of the region. At this moment,
passing showers are moving over the Atlantic nearshore waters and
are affecting eastern and northern coastal sections of Puerto
Rico. However, not significant rainfall acumulacion were reported.
In the afternoon hours, shower activity would affect interior and
western sections of Puerto Rico with a few isolated thunderstorms
possibles.

&&

.AVIATION...VRF conditions will prevail for most of the TAF sites.
VCSH is possible over TJSJ between 31/17Z to 31/19Z. Winds will
remain from E-NE at 15- 20 mph with occasionally higher winds
gust.

&&

.MARINE...
Hazardous marine conditions will prevail for today as moderate to
fresh easterly wind flow persist over the CWA. At this moment,
San Juan bouy report 5 feet with winds up to 16 knots. The marine
conditions will improve by late Thursday into Friday with seas
between 4-6 feet and winds up to 15 knots.

&&

.PREV DISCUSSION... /issued 450 AM AST Wed Mar 31 2021/

SYNOPSIS...

A typical weather pattern will continue across the local islands.
Instability aloft, however, brings the potential for some
afternoon thunderstorms today, mostly in western Puerto Rico.
There is the potential for urban and small stream flooding. Winds
will gradually subside for the second half of this week, and
rainfall activity will also decrease. Increasing shower activity
is expected for this weekend.

SHORT TERM...Wednesday through Friday...

Isolated to scattered showers will continue moving across the
surrounding waters of St Croix, the Atlantic and Caribbean Waters,
and the northern and eastern portions of Puerto Rico. Moisture will
erode later this morning, leaving a mixture of sunshine and clouds
across most of the islands of Puerto Rico and the U.S. Virgin
Islands. However, local effects will trigger afternoon convection
across the interior and west PR, where isolated thunderstorms may
form, especially near Mayaguez and Cabo Rojo. This activity will
likely move over the shoreline, creating hazardous marine
conditions. Furthermore, some areas with persistent rainfall
activity may observe urban and small-stream flooding.

Windy conditions will persist due to a surface high pressure
across the Atlantic Ocean. An upper-level short wave will linger
aloft, with a jet stream, leading to an increase in instability.
This jet will exit the islands by Thursday afternoon as a mid to
upper-level ridge build-in. A somewhat drier air mass is possible
on Thursday.

Patches of moisture will continue to move in embedded in the trades
on Friday, which interacting with diurnal heating and sea breeze
variations will result in afternoon convection across the western
portions, the San Juan Metro area, and downwind from the U.S. Virgin
Islands.

LONG TERM...Saturday through Wednesday...

On Saturday morning, the remnants of an old frontal boundary will be
affecting the region, lingering and then drifting northward. With
the slow movement of the front, moisture convergence is likely. The
front is forecast to stall out near the northern extent of the CWA
during the weekend. This is due to the approach from the
west/northwest of a front moving off the east coast of the US. This
newer front will make its way towards the region, bringing
additional moisture. Aloft, a mid- to upper-level ridge will be
gradually eroded, from the top and bottom. The surface trough with
which the newer frontal boundary is associated is expected to be
reflected aloft, as well. This will lead to decreasing stability
across the region, which will also support increasing shower
activity during the weekend, in a typical pattern.

A small dry slot is forecast to be south of this frontal boundary,
and is likely to affect the region on Monday. Aloft, a weak mid- to
upper-level trough is forecast to move to just east of the region
before diminishing; this would then cause an increase in stability
for the region. As such, a (temporary) decrease in shower activity
is expected.

On Tuesday, a disturbance is forecast to approach the region from
the southeast, bringing significant moisture with it. The
aforementioned dry slot is expected to diminish and nearly
disappear, with the frontal boundary stalled out in the north, as
the surface low with which it is associated is forecast to have its
progression eastward halted by a blocking high in the north central
Atlantic, leaving it to churn off the coast of Atlantic Canada.
Model guidance continues to suggest that this increase will push
precipitable water values to significantly above normal levels,
possibly as high as around 2.0 inches. Aloft, a deep-layer trough
approaching from the west will help return instability to the
region, allowing for moisture to extend through the mid-levels by
Tuesday into Wednesday. There has been generally good consistency
between model runs of the GFS for this scenario, and both the Euro
and the CMC suggest similar solutions. This does increase confidence
somewhat, though the timing is relatively uncertain still, and has
changed a little between model runs, and it is still several days
out. And with this increased confidence, the potential that midweek
next week will bring significant, and possibly hazardous levels of,
rainfall to the region also increases. Future forecasts should be
monitored for updates.

AVIATION...

Expect winds between 10 and 15 knots, increasing between 15 and 20
knots with higher gusts, even around the mid-30s after 31/13z. Also,
sea breeze variations may form after 31/13z. These breeze conditions
will push showers and clouds across the terminals at times. SHRA
will develop across the interior/SW-PR and in the VCTY of JSJ/JPS
between 31/16z-31/02z.

MARINE...

Breezy conditions continue across the region, under the persisting
influence of a surface ridge to the north of the islands. These
winds are still causing choppy to hazardous conditions for most of
the local waters, and will continue to do so for a couple days yet,
still. Hazardous conditions are expected to persist for the offshore
Atlantic waters and Anegada Passage into tomorrow night. Diminishing
winds are forecast for the second half of the week, which will cause
gradual subsiding of the seas.

For the beachgoers, there is a high risk of rip currents for beaches
of northern Puerto Rico, northern and eastern St. Croix, as well as
Culebra. Most other local beaches have a moderate risk of rip
currents.

&&

.PRELIMINARY POINT TEMPS/POPS...
SJU  83  72  85  73 /  30  40  30  50
STT  84  72  83  73 /  20  20  30  50

&&

.SJU WATCHES/WARNINGS/ADVISORIES...
PR...High Rip Current Risk through late Thursday night for Culebra-
     North Central-Northeast-Northwest-San Juan and Vicinity-
     Southeast.

VI...High Rip Current Risk through late Thursday night for St Croix.

AM...Small Craft Advisory until 2 PM AST Thursday for Caribbean
     Waters of Puerto Rico from 10 NM to 17N-Coastal Waters of
     Northern Puerto Rico out 10 NM-Coastal Waters of Northern
     USVI and Culebra out 10 NM-Coastal Waters of Southern USVI
     Vieques and Eastern Puerto Rico out 10 NM-Mona Passage
     Southward to 17N.

     Small Craft Advisory until 2 AM AST Friday for Anegada Passage
     Southward to 17N-Atlantic Waters of Puerto Rico and USVI
     from 10 NM to 19.5N.

&&

SHORT TERM...RAM
LONG TERM....ERG
PUBLIC DESK...LIS

Perspectivas sobre Condiciones Peligrosas del Tiempo
Servicio Nacional de Meteorologia en San Juan PR
445 AM AST miercoles 31 de marzo de 2021

AMZ710>745-PRZ001>013-010845-
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-
445 AM AST miercoles 31 de marzo 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 la posibilidad de tronadas con lluvia fuerte y
vientos en rafaga breves esta tarde sobre sectores del interior y
oeste de Puerto Rico.

.Inundaciones...Lluvias fuertes pueden causar inundaciones urbanas y
de riachuelos.

.Viento...Se esperan vientos en exceso de 20 mph (17 nudos) a traves
de las aguas locales y sectores costeros.

.Oleaje...Se espera oleaje fuerte de hasta 10 pies a traves de
las aguas locales.

.Corrientes Marinas...Existe un riesgo alto de corrientes marinas
para las playas del norte y este de Puerto Rico y Culebra.

.Fuego...Riesgo alto de Incendios Forestales para la costa sur de
Puerto Rico.

.Dias dos hasta el siete...de jueves a martes

Actividad de aguaceros, especialmente en las tardes, pudiera
producir acumulacion de agua en carreteras y sectores de pobre
drenaje, particularmente en el interior y oeste de Puerto Rico.
Riesgo alto de corrientes marinas prevalecera a traves de la mayoria
de las playas. Se pronostica que el viento continue peligroso hasta
al menos tarde el jueves en la noche. Advertencias para operadores
de embarcaciones pequenas estan en efecto para la mayoria de las
aguas regionales. La humedad pudiera aumentar un poco para el fin de
semana.

.Comunicado sobre informacion reportada por observadores...

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

AMZ715-725-VIZ001-002-010845-
San Tomas, San John e Islas Adyacentes-
Santa Cruz-Aguas cercanas del Atlantico y aguas
costeras adyacentes del Caribe-
445 AM AST miercoles 31 de marzo 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

.Viento...Se esperan vientos en exceso de 20 mph (17 nudos) a traves
de las aguas locales y sectores costeros.

.Oleaje...Se espera oleaje picado de hasta 10 pies a traves de las
aguas locales.

.Corrientes Marinas...Existe un riesgo alto de corrientes marinas
para las playas de la esquina este de St Cruz.

.Dias dos hasta el siete...de jueves a martes

Riesgo de alto a moderado de corrientes marinas prevalecera a traves
de la mayoria de las playas. Se pronostica que el viento y el oleaje
continue peligroso hasta tarde el jueves en la noche. Advertencias
para los operadores de embarcaciones pequenas estan en efecto para
las aguas regionales. La humedad pudiera aumentar algo durante el
fin de semana.

.Comunicado sobre informacion reportada por observadores...

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