Flash Flood and Debris Flow in Puerto Rico, May 23 to 26, 2022

Area Forecast Discussion...CORRECTED
National Weather Service San Juan PR
1120 AM AST Mon May 23 2022

.UPDATE... Recently taken 23/12z TJSJ sounding is adding
confidence to the forecast of heavy shower activity this afternoon
with a CAPE of 2580, a weak capping inversion, and a Convective
Temperature of 85F. Yesterday had very similar parameters and
widespread thunderstorm development occured after 16z, lasting
late into the day. This morning, showers passed over St Thomas and
St Croix, breaking the dry spell they have had over the last few
days. Currently GOES-16 satellite imagery is already showing the
development of streamers off the islands upstream of Puerto Rico,
storm development south of the San Juan Metro area, and thick
cumulus clouds along the Cordillera Central. As widespread
downpours and thunderstorms are likely for the rest of the day,
exercise caution especially while driving. Affected areas with
poor drainage may experience some urban and small stream flooding
and the ponding of water in roadways.

&&

.AVIATION...Mainly VFR conditions are expected to prevail across
all terminals. However, SHRA/TSRA expected to develop in and
around the PR terminals from 16z-22z, which may cause tempo MVFR
conditions and mtn tops obscd. The 23/12z TJSJ sounding indicated
east winds up to 14 kt blo FL050

&&

.MARINE...Currently the Waverider buoy in Arecibo is hardly
detecting the fading northerly swell with 0.7 feet at 11 seconds
and wind waves remain weak. Expect the same conditions for the
next few days as moderate trade winds continue. This all being
said, there has been no update to the forecast and a moderate risk
of rip currents remains for most of Puerto Rico and the U.S.
Virgin Islands.

&&

.PREV DISCUSSION... /issued 500 AM AST Mon May 23 2022/

SYNOPSIS...Relatively unstable conditions are forecast over the
next few days under the influence of an upper level trough/TUTT.
Surface high over the western Atlantic is supporting moderate
trade winds across the local islands. Max temperatures for the
week will be near normal, with highs in the upper 80s.

SHORT TERM...Today through Wednesday...

Residents in Puerto Rico and the U.S. Virgin Islands can expect the
islands to move to a more unstable and wetter pattern than last
week. Expect more frequent passing showers moving across the
windward sections each day, followed by organized convection across
the interior and western areas.

&&
Afternoon showers and thunderstorms will likely be more intense and
long-lasting due to a TUTT combined with a set of short wave
troughs, which are forecast to increase atmospheric instability,
especially today and Wednesday. Some instability parameters that
indicate favorable conditions for the formation of organized
convection are near to below-normal 250MB Heights, steep lapse rate
at low and mid-levels, below-normal temperatures at 500MB, the
disappearance of the trade wind cap, and MU CAPE ranging between
1500 and 2300, especially in the afternoon. Therefore, we are
anticipating the formation of thunderstorms, especially each
afternoon across the interior and western sections of Puerto Rico.
Also, we cannot rule out thunderstorm formation across the local
waters each night. This activity will produce periods of heavy
rainfall leading to urban and small stream flooding each afternoon.

LONG TERM...Thursday through Tuesday...

An upper-level low/TUTT northeast of Puerto Rico and the U.S.
Virgin Islands will dominate the weather conditions. The proximity
of the TUTT will provide colder temperatures aloft, increasing the
instability late in the workweek. Although moisture will remain
near normal for this time of the year, high convective instability
associated with the TUTT will combine with the sea breeze convergence
to fuel afternoon showers and thunderstorms along the Cordillera
Central and western Puerto Rico. Aerosol models suggest some Saharan
Dust Thursday and Friday. This will limit the shower coverage but
the dust particles may enhance the thunderstorm activity as
concentrations are forecast to remain low. Another high pressure
builds over the western Atlantic late in the week into the
weekend, allowing the trade winds to veer from the east-southeast.
A drier and more stable pattern is possible during the weekend as
the upper-level trough moves away from the region. This will likely
result in mostly sunny conditions and warmer than normal temperatures
under a southeasterly flow from Saturday into early next week.

AVIATION...VFR conditions will prevail through much of the forecast period.
However, at times, quick passing SHRA with moderate to heavy rain
periods could lower VIS at JSJ/IST/ISX. TSRA will also form across
the mountain areas of PR and near JBQ during the afternoon, where
mountain obscurations are also expected. Expect calm to
light/variable winds overnight, returning from the E-ENE at 10-15 kt
with higher gusts and sea breeze variations after 23/13z.

MARINE...Moderate easterly winds of 10-15 kts and seas of 2-4
feet can be expected across the Atlantic and Caribbean waters most
of the week. Unstable conditions will increase the potential for
showers and thunderstorms across the regional waters. Moderate
risk of rip currents will continue for most of the beaches in
Puerto Rico and the U.S. Virgin Islands.

&&

.PRELIMINARY POINT TEMPS/POPS...
SJU  89  76  88  76 /  50  50  50  50
STT  86  76  87  76 /  30  40  40  50

&&

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

UPDATE/MARINE...RC
AVIATION...DSR

Perspectivas sobre las Condiciones Peligrosas del Tiempo Servicio
Nacional de Meteorologia en San Juan PR
504 AM AST lunes 23 de mayo de 2022

AMZ710>745-PRZ001>013-240915-
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 del
Caribe-
504 AM AST lunes 23 de mayo de 2022

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

.Dia Uno...Hoy y esta noche

.Tronadas...Existe un riesgo de tronadas aisladas con lluvia fuerte
y rafagas de viento esta tarde a traves del interior y oeste de
Puerto Rico.

.Inundaciones...Lluvia fuerte puede resultar en inundaciones urbanas
y de pequenos riachuelos.

.Corrientes Marinas...Existe un riesgo moderado de corrientes, con
excepcion de las playas del oeste desde el sur de Rincon hasta
Boqueron y cerca de Ponce donde el riesgo es bajo.

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

Una vaguada en los niveles altos se fortalecera al noreste de Puerto
Rico y Las Islas Virgenes Americanas durante gran parte de la semana
laboral. Esta vaguada en la altura aumentara los aguaceros
arrastrados por el viento en horas de la manana, asi como tambien
algunas tronadas fuertes cada tarde. El potencial de inundaciones
urbanas y de riachuelos permanecera posible todos los dias. El
viento estara aumentando a traves de las areas locales despues del
miercoles.

.Comunicado sobre informacion reportada por observadores...

No se espera activacion amplia de observadores. Sin embargo, le
agradeceriamos reportar cualquier informacion sobre inundaciones y
corrientes marinas al Servicio Nacional de Meteorologia en San Juan.

AMZ715-725-VIZ001-002-240915-
San Tomas, San John e Islas Adyacentes-
Santa Cruz-Aguas cercanas del Atlantico y aguas costeras adyacentes
del Caribe-
504 AM AST lunes 23 de mayo de 2022

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

.Dia Uno...Hoy y esta noche

.Corrientes Marinas...Existe un riesgo moderado de corrientes
marinas para todas las playas de las Islas Virgenes Estadounidenses,
excepto para el oeste de Santa Cruz.

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

Una vaguada en los niveles altos se fortalecera al noreste de Puerto
Rico y Las Islas Virgenes Americanas durante gran parte de la semana
laboral. Esta vaguada en la altura aumentara los aguaceros
arrastrados por el viento en horas de la manana, asi como tambien
algunas tronadas fuertes cada tarde. El potencial de inundaciones
urbanas y de riachuelos permanecera posible todos los dias. El
viento estara aumentando a traves de las areas locales despues del
miercoles.

.Comunicado sobre informacion reportada por observadores...

No se espera activacion amplia de observadores. Sin embargo, le
agradeceriamos reportar cualquier informacion sobre vientos y
corrientes marinas al Servicio Nacional de Meteorologia en San Juan.