NWS San Juan, PR wrote its last area forecast discussion before the first event at Aug 31, 9:19 PM AST, 2 hours 41 minutes earlier.
Area forecast discussion, Aug 31, 9:19 PM AST, 2 hours 41 minutes before
Area Forecast Discussion
National Weather Service San Juan PR
919 PM AST Thu Aug 31 2023
.UPDATE...Cloudiness and afternoon convection continued to diminish
and dissipated over land areas while a few showers lingered across
the local waters. Recent TJSJ 01/00Z upper air sounding showed a
relatively dry shallow layer at low levels with relative humidities
dropping below 30% at 900 mb. This has caused a gradual clearing of
skies across the region. Expect mostly clear skies to partly cloudy
skies throughout the night with limited or no shower activity over
land areas, particularly for the western half of Puerto Rico. A few
passing showers over the local waters may reach windward coastal
areas at times. Sounding suggests a precipitable water value of
around 1.72 inches, and is expected to fluctuate within 1.5 and 1.8
inches through tomorrow as drier air filters in. However, enough low-
level moisture along with diurnal heating and local effects will
still promote afternoon shower and thunderstorm activity once again,
particularly across western portions of Puerto Rico. Otherwise, no
major changes made to the inherited short-term grids and forecast
reasoning at this time.
&&
.AVIATION...Mainly VFR conditions are expected to prevail across
all terminals during the next 24 hours. The 01/00z TJSJ sounding
indicated up to 17 kt ESE winds blo 5000 ft.
&&
.FROM PREV DISC.../418 PM AST Thu Aug 31 2023/
.SYNOPSIS...
Showers over the western and central interior sections of Puerto
Rico should continue to dissipate. Saharan dust particles will
begin reach the islands latter in the workweek, therefore skies
will become hazy. A northerly swell is forecast to reach the
islands by Saturday, although seas are expected to remain at 5
feet or less.
&&
.SHORT TERM...Tonight through Saturday...
Today, mostly warm and variable weather conditions prevail across
the islands. In the morning, some light trade wind showers did
develop across the eastern half of Puerto Rico, leaving less than
0.25 inches. However, the El Yunque streamer developed by late
morning and extended into the afternoon, leaving up/around 3
inches across the northeastern municipalities. Throughout the day,
the wind flow remains from the east with a slight southerly
component. Therefore, most of the afternoon convection took place
over the interior and western quadrants of the island, where
Special Weather Statements and Flood Advisories were issued. The
daily maximum temperatures along the coastal areas fluctuated in
the upper 80s to low 90s. While in the mountains, they remain in
the 80s. As far as heat indices, they ranged around 105 and 112
degrees Fahrenheit across the islands, with the highest heat index
observed across north- central Puerto Rico. No official weather
stations reported heat indices slightly higher than 112 degrees
Fahrenheit in some areas of north-central Puerto Rico. The highest
heat index reported at the Luis Munoz Marin International Airport
was 108 degrees Fahrenheit.
Overnight, expect mainly calm weather with occasional trade wind
showers. At this time, model guidance suggests near-normal
precipitable water content for the rest of today into Friday and
decrease to below-normal by the beginning of the weekend. On
Friday, expect seasonal weather conditions to prevail, with
typical periods of sunshine, mostly clear skies, and a few passing
showers across the windward sections each night and morning. The
usual convection will occur across western/northwestern Puerto
Rico every afternoon, driven by sea breeze fluctuations, local
effects, and diurnal heating. However, some afternoon rainfall is
possible over the eastern and northeastern sections of PR if the
streamers do develop. From Friday into the weekend, expect a
gradual increase in Saharan Dust particles across the area,
leading to hot days across Puerto Rico and the U.S. Virgin
Islands.
&&
.LONG TERM...Sunday through Friday...
Low to mid level ridge will drive the steering wind from the
southeast on Sunday through Tuesday. Then, as the high moves just
north of the local islands, the trade winds will shift from the
east. On these days, moisture appear limited, and confined to the
lower levels of the atmosphere, as the mid level ridge maintains a
dry air mass at those levels. This air mass will contain some
Saharan dust too, so skies will be hazy. Even with the lack of
dynamics, strong heating should be enough to fire up a few showers
each afternoon, but mainly for western areas in Puerto Rico. Other
areas may receive a shower or two, dragged by the trade winds, but
with no significant rainfall accumulation. By the end of the
workweek, some moisture may reach the islands, increasing the
potential for showers. In general, a seasonal pattern, with
summer-hot temperatures should prevail for at least the first
couple of days of September.
&&
.AVIATION...Mainly VFR conds will prevail at all TAF sites during the
prd. However, afternoon convection across the NW PR will result in
VCTS/VCSH across TJBQ til 31/22Z. E-ESE winds at 10-15 knots,
becoming calm to LGT/VRB aft 31/22Z. Higher gusts near the
TSRA/SHRA.
&&
.MARINE...Small pulses of northerly swells will continue through
the end of the week, promoting a moderate risk of rip currents
along the northern beaches of Puerto Rico, and St. Thomas. Seas
will range between 2 and 5 feet, with the highest seas across the
offshore waters. East to southeast winds will prevail in general
between 10 and 15 knots, and occasionally higher.
&&
.SJU WATCHES/WARNINGS/ADVISORIES...
PR...None.
VI...None.
AM...None.
&&
SHORT TERM/AVIATION...CVB
LONG TERM....MMC
PUBLIC...MRR
Hazardous weather outlook, Aug 31, 4:48 AM AST, 19 hours 12 minutes before
Perspectiva sobre las Condiciones Peligrosas del Tiempo
Servicio Nacional de Meteorología San Juan PR
431 AM AST jueves 31 de agosto de 2023
AMZ711>745-PRZ001>013-010845-
San Juan y Vecindad-Noreste-Sureste-Este Interior- Norte Central-
Central Interior-Ponce y Vecindad-Noroeste- Oeste Interior-Mayagüez
y Vecindad-Suroeste-Culebra-Vieques- La costa cerca y fuera de la
costa del Atlántico y las Aguas Costeras del Caribe-
431 AM AST jueves 31 de agosto de 2023
Esta perspectiva sobre las condiciones peligrosas del tiempo es para
Puerto Rico.
.DÍA UNO...Hoy y esta noche
.Rayos...Tormentas eléctricas aisladas posibles a través del
cuadrante noroeste. Esté atento de las tormentas eléctricas en su
área y esté preparado para refugiarse.
.Lluvia Excesiva...Inundaciones de áreas urbanas, carreteras y
arroyos pequeños. Inundaciones repentinas aisladas posibles.
.Calor Excesivo...Índice de Calor 112-114 grados a través de áreas
bajas y urbana desde San German (a lo largo de la costa norte) hasta
Carolina. Agotamiento por calor o golpe de calor probable con
exposición prolongada. Índice de calor 108-111 grados para las áreas
urbanas y costeras de Puerto Rico. Agotamiento por calor probable
con exposición prolongada.
.Corrientes Marejadas...Las corrientes marinas que amenazan la vida
son posibles en la zona de oleaje particularmente la costa norte de
Puerto Rico.
.DÍAS DOS A SIETE...Viernes hasta el miércoles
Las inundaciones menores y urbanas son posibles cada tarde,
principalmente sobre el oeste de Puerto Rico debido a las tormentas
eléctricas. La amenaza de calor excesivo es posible para las
elevaciones más bajas y las áreas urbanas de Puerto Rico, Culebra y
Vieques. Un riesgo moderado de corrientes marinas posible para
algunas de las playas orientadas al norte y al este.
.DECLARACIÓN DE INFORMACIÓN DEL OBSERVADOR...
Se alienta la activación de los Observadores. Favor de transmitir
cualquier información sobre inundaciones, vientos, olas y corrientes
marinas hasta el Servicio Nacional de Meteorología en San Juan.
AMZ716-726-VIZ001-002-010845-
St. Thomas St. John Islas adyacentes-Santa Cruz-
Cerca de la costa del Atlántico y Aguas costeras del Caribe
adyacentes-
431 AM AST jueves 31 de agosto de 2023
Esta Perspectiva de Tiempo Peligro es para sectores de las USVI.
.DÍA UNO...Hoy y esta noche
.Calor Excesivo...Índice de Calor 112-114 grados a través de las
áreas urbanas y bajas. Agotamiento por calor o golpe de calor
probable con exposición prolongada.
.DÍAS DOS A SIETE...Viernes hasta el miércoles
Una amenaza de calor excesivo es posible para las elevaciones más
bajas y las áreas urbanas. Un riesgo moderado de corrientes marinas
posible para algunas de las playas orientadas al norte y al este.
. DECLARACIÓN DE INFORMACIÓN DEL OBSERVADOR...
Se alienta la activación de los Observadores. Favor de transmitir
cualquier información sobre inundaciones, vientos, olas y corrientes
marinas hasta el Servicio Nacional de Meteorología en San Juan.