Rip Current in Puerto Rico, June 19, 2021

Area Forecast Discussion
National Weather Service San Juan PR
1132 AM AST Sat Jun 19 2021

.UPDATE...Mostly sunny to partly cloudy skies prevailed across the
islands during the morning hours, as well as hazy skies. The 12z
SJU upper air sounding indicated just under 1.50 inches of
precipitable water and drier air between 850-500 MB. Having said
that, moisture advection from the leading edge of a disorganized
and weak tropical wave will aid in the development of afternoon
showers across the islands this afternoon. Therefore, diurnally
induced afternoon showers are expected to develop mainly over the
interior and western sections of PR, and from streamers downwind
of the USVI and eastern sections of PR. Isolated thunderstorms can
not be ruled out due to the proximity of an upper level trough and
a 500 mb temp of -7.4C, mainly over west PR.

&&

.AVIATION...Mainly VFR early in the fcst cycle. However, diurnally
induced afternoon showers with possible iso thunderstorms over
west PR may cause areas of MVFR in and around TJPS/TJBQ. The
19/12z TJSJ sounding indicated E-ESE winds at 17-26 kt blo FL090.

&&

.MARINE...Choppy seas up to 6 feet expected across most of the
local waters due to 15-20 kt trades and approaching tropical wave
from the east. There is a moderate risk of rip currents across all
the islands.

&&

.PREV DISCUSSION... /issued 458 AM AST Sat Jun 19 2021/

SYNOPSIS...
Moisture will increase later in the weekend as a tropical wave
approaches the local area. Then, another wave will move by the end
of the week. Choppy marine conditions will continue throughout the
weekend, with seas up to 6 feet.

SHORT TERM...Today through Monday...

Moisture behind a weak tropical wave will increase later this
morning, but the best moisture will not arrive until late Sunday
night according to the latest GFS model run. Total precipitable
water imagery shows the best precipitable water with a more
pronounced wave that is still over the Windward Islands and the
western tropical Atlantic. High pressure will continue across the
central Atlantic at lower levels with a nearly east-west ridge
across the western Atlantic at around 25 degrees north Latitude.
High pressure at mid latitudes extends from the central Atlantic
across or just north of the local area through the period. At upper
levels a trough will dig southwest toward the windward passage and
cut off such that by Monday evening the low will be between Jamaica
and Cuba. This will leave relatively weak and variable upper level
flow through the period. Areas of dust will continue through Monday,
but showers and isolated thunderstorms should be able to overcome
the relatively dry conditions usually associated with the Saharan
air on Sunday and Sunday night.

The increase in moisture on Sunday will enhance the risk of urban
and small stream flooding across Puerto Rico. The U.S. Virgin
Islands should also see an increase in shower activity of lesser
amounts. Drying at 700 mb is expected Monday morning.

LONG TERM...Tuesday through Sunday...
A surface to mid-level ridge over the western Atlantic will hold
north of the region at the beginning of the long-term forecast
period. At the upper levels, a low pressure develops over
Hispaniola, which could act to increase divergence aloft somewhat.
However, the mid-level ridge should result in dry air, and moisture
being confined to the lowest 850 mb of the atmosphere. Some patches
of low level clouds are expected to be dragged by the trade winds
over the islands, which should result in a typical pattern of
advective morning showers over eastern Puerto Rico and the U.S.
Virgin Islands, followed by afternoon convection over western Puerto
Rico. By the middle of the week, the mid level ridge weakens as a
trough begins to develop north of the region and then lingers for
the rest of the workweek. A similar weather pattern should be
expected for Wednesday and Thursday.

For Friday, some uncertainty is added to the forecast, as a tropical
wave approaches from the east. The 19/00Z GFS had most of the wave
over the Caribbean waters, but the ECMWF run had the moisture field
crossing the islands. For now, the forecast showed increased shower
and thunderstorm activity on this day across the area. Moving into
the weekend, the weather pattern seems to be dependent on how
quickly the wave clears the area. For now, the GFS forecast
soundings shows precipitable water values climbing to around 1.75 to
Saturday, and near 2.0 inches on Sunday. These values are above the
climatological value for this time of year, meaning that a period of
enhanced shower activity can be expected. The ECMWF also shows
lingering moisture on Saturday, but with drier air moving on Sunday.
Confidence is low on the forecast for now, and adjustment will be
made as the models reach a better agreement.

AVIATION...

VFR conditions are expected thru the period, except briefly MVFR
under widely sct SHRA ovr ern PR and aft 19/16Z ovr wrn and interior
PR and down stream from El Yunque. Mtn obscurations. Isold TSRA psbl
btwn 19/17-21Z. Easterly flow will influence sfc winds less than 10
kt in land breezes. Then, aft 19/14Z, sea breezes of 10-20kt with
gusts to 26kt psbl. Max winds E 20-25 kt btwn FL015-055 and also NNE
20-25 kt btwn FL320-430, but becoming lighter at these levels later
in the day.

MARINE...
Choppy seas up to 6 feet and winds up to 20 knots will continue
across the area, and small craft operators should exercise
caution. These conditions should continue through the weekend. A
tropical wave should move across the area later tonight into
tomorrow, increasing showers and thunderstorms. For the beaches, a
moderate rip current risk is expected to continue across all
islands.

&&

.PRELIMINARY POINT TEMPS/POPS...
SJU  89  77  89  78 /  20  70  70  60
STT  88  78  88  78 /  40  70  60  60

&&

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

DSR/LIS/ICP

Perspectivas sobre Condiciones Peligrosas del Tiempo
Servicio Nacional de Meteorologia en San Juan PR
420 AM AST sabado 19 de junio de 2021

AMZ710>745-PRZ001>013-200830-
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-
420 AM AST sabado 19 de junio 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 aisladas con lluvias
fuertes y vientos en rafaga breves esta tarde a traves del oeste e
interior de Puerto Rico.

.Inundaciones...Lluvias fuertes pudieran resultar en acumulacion de
agua en carreteras e inundaciones urbanas y de riachuelos
localizadas.

.Viento...Se esperan vientos sostenido en exceso de 20 mph (17
nudos) a traves de las costas norte y sur de Puerto Rico y aguas
locales.

.Oleaje...Se espera oleaje picado por debajo de 7 pies a traves de
las aguas expuestas y locales.

.Corrientes Marinas...Existe un riesgo moderado de corrientes
marinas para casi todas las playas, menos las del oeste al sur de
Rincon y cerca de Ponce.

.Calor...Vientos del sureste y humedad alta resultaran en indices de
calor entre 102 a 107 grados en sectores del norte central y
planicies adyacentes y otros lugares de poca elevacion.

.Dias dos hasta el siete...domingo a viernes

El riesgo moderado de corrientes marinas continuara para la mayoria
de las costas de Puerto Rico incluyendo a Culebra y Vieques para
cada dia. El indice de calor superara los 102 grados en algunos
lugares del norte de Puerto Rico durante las horas del mediodia del
domingo al martes. Existe riesgo de inundaciones urbanas y de
riachuelos en el oeste e interior de Puerto Rico de domingo a martes.

.Comunicado sobre informacion reportada por observadores...

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

AMZ715-725-VIZ001-002-200830-
San Tomas, San John e Islas Adyacentes-Santa Cruz-
Aguas cercanas del Atlantico y aguas costeras adyacentes del Caribe-
420 AM AST sabado 19 de junio 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

.Oleaje...Se espera oleaje picado por debajo de 7 pies a traves de
las aguas expuestas.

.Corrientes Marinas...Existe un riesgo moderado de corrientes
marinas para casi todas las playas.

.Dias dos hasta el siete...domingo a viernes

Un riesgo moderado de corrientes marinas continuara de domingo a
viernes.

.Comunicado sobre informacion reportada por observadores...

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