High Surf Advisory 15, NWS JSJ

Area Forecast Discussion
National Weather Service San Juan PR
1132 AM AST Thu Dec 8 2022

...New UPDATE, AVIATION, MARINE...

.UPDATE...
Issued at 1131 AM AST Thu Dec 8 2022

Coastal conditions will deteriorate even more tonight into
tomorrow as a long-period northeasterly swell spreads across the
local Atlantic Waters and Caribbean Passages. Coastal flooding and
erosion will aggravate along the Atlantic Coastline of Puerto
Rico and the U.S. Virgin Islands tonight through tomorrow. A
Coastal Flood Advisory and High Surf Warning may be required
later this afternoon.

A northerly wind flow will continue to bring showers across the
local islands, causing brief periods of moderate to locally heavy
rains. Near-to below-normal temperatures will continue across the
islands for the rest of today and tonight.

&&

.AVIATION...
(12Z TAFS) Issued at 1131 AM AST Thu Dec 8 2022

VFR conditions will prevail throughout the forecast period.
However, occasional SHRA/+SHRA will affect TJSJ/IST/ISX/JBQ. SHRA
will continue to move across the Cordillera Central thru this
evening, btwn 27/23z. Winds will continue from the N-NNE at around
10 knots with higher gusts and sea breeze variations.

&&

.MARINE...
Issued at 1131 AM AST Thu Dec 8 2022

41053 (San Juan) buoy is reporting a northeasterly swell at 7 to
8 feet with a period of around 12 seconds. This swell will
maintain hazardous marine conditions across the Atlantic Waters
and Coastal waters. Another northeasterly swell with a period
between 12 and 14 seconds and heights between 8 and 12 feet will
aggravate even more marine and coastal conditions late tonight
through early next week.

Beachgoers, expect breaking waves between 10 and 15 feet through
this evening, increasing between 15 and 20 feet tonight into
tomorrow across the Atlantic Coastline of Puerto Rico and the U.S.
Virgin Islands.

&&

.SYNOPSIS...
A seasonal pattern prevails with frequent passing showers carried by
northerly winds. Expect similar conditions during the next
several days. Hazardous marine and coastal conditions will prevail
all week into the upcoming weekend.

&&

.SHORT TERM...Today through Saturday...

Our focus continues to be on the marine situation as the most
critical part of the weather story. Northeasterly swells with
11-12 second periods will spread across the Atlantic waters today
and the Caribbean passages tonight. Please refer to the Marine
Discussion below for details, including current statements and
advisories.

Northerly flow of 10 to 20 mph will continue to be generated by the
gradient at low and mid levels between high pressure over the
northern Gulf of Mexico and a very strong low pressure almost 1300
miles northeast with a trough that extends across the southeast
quadrant of our forecast area. This low will move another 1300
miles northeast during the next 3 days. A second low may also
develop along a cold front in the western Atlantic and move toward
the area with the combined northerly flow driving a cold front
toward the area. By late Saturday night that cold front will
likely have entered our northern waters. Showers are expected to
continue in the northerly flow during the night and morning hours
along the northern coast of Puerto Rico and the northern U.S.
Virgin Islands with light amounts each day. Very dry air will
remain in place over the area above 8-10 kft and this will cap the
showers and suppress rain amounts. Thus, although showers will be
frequent and mainly during the overnight and morning hours along
the coastal regions, amounts should remain less than one tenth to
one half inch in isolated spots each day. Because of the northerly
flow, cool air advection will prevail and help to keep
temperatures a degree or two below normal for this time of year
except along the south coastal plains.

An upper level trough will also move through today, but the ridge to
our west will flatten out and a second trough will take its place
and cross through the area on Saturday. This will leave us in a
quiet area of the upper atmosphere between a 100-plus knot
subtropical jet to our north and a much weaker jet over the
Windward Islands.

&&

.LONG TERM...Sunday through Friday...

A surface high pressure will remain over the Gulf of Mexico
through Tuesday, allowing northerly wind flow over the Caribbean.
This wind flow will keep overall drier conditions across the
forecast areas. However, on Sunday, cold advection from a frontal
boundary reaching the islands could increase the potential for
more frequent showers and even scattered to numerous showers
across the northern coastal areas. As this band of moisture moves
past us, a drier airmass will filter into the region Tuesday
through Thursday, resulting in mostly clear skies punctuated by
mainly isolated showers.

On Tuesday, as the ridge moves more to the northeast into the
east coast of the United States, a relaxation in the pressure
gradient will permit lighter winds across the islands and a
slight veering to the east- northeast. This change will allow
some bands of moisture to reach the Caribbean waters, St. Croix,
and the southern sections of Puerto Rico. Therefore, expect an
increase in the frequency of the showers from late Wednesday into
late Thursday there. Regardless of the expected conditions, the
rest of the islands, including St. Thomas, should expect mainly
fair weather conditions. Surface winds will come back from the
north late Thursday into Friday as the surface high pressure moves
into the central Atlantic.

Below normal temperatures will prevail for the first part of the
period, with even lower temperatures on Monday into Tuesday.

&&

.AVIATION...Mainly VFR conditions will prevail across most local
terminals during the next 24 hours. Passing SHRA could result in
brief mtn obscurations and MVFR conditions thru 08/16Z. N-NE winds
at 5-10 knots will increase to 10-15 knots after 08/14Z with
higher gusts, mainly across northern terminals. Locally higher
winds will be found near the shower activity. Maximum winds WSW-
WNW 55-65 knots btwn FL435-510.

.MARINE...

Hazardous marine conditions will prevail for the rest of the
period due to a northeasterly swell. For today expect seas around
8-9 feet in the morning, then building seas between 9 to 12 feet
are expected for most of the Atlantic waters and the local
passages starting tonight. Advisories are in effect for those
waters for conditions dangerous to the navigation of small craft.
Breaking waves up to 15 feet will cause dangerous rip currents,
beach erosion and local coastal flooding conditions across the
islands' northern and eastern sections. High Surf Advisories are
in effect as well as statements for a high rip current risk.

Breaking waves will are expected to increase to 16-17 feet;
please stay tuned for further updates and a possible coastal
flood Advisory for the overnight hours.

&&

.MARINE...

Hazardous marine conditions will prevail for the rest of the
period due to a northeasterly swell. For today expect seas around
8-9 feet in the morning, then building seas between 9 to 12 feet
are expected for most of the Atlantic waters and the local
passages starting tonight. Advisories are in effect for those
waters for conditions dangerous to the navigation of small craft.
Breaking waves up to 15 feet will cause dangerous rip currents,
beach erosion and local coastal flooding conditions across the
islands' northern and eastern sections. High Surf Advisories are
in effect as well as statements for a high rip current risk.

Breaking waves will are expected to increase to 16-17 feet;
please stay tuned for further updates and a possible coastal
flood Advisory for the overnight hours.

&&

.SJU WATCHES/WARNINGS/ADVISORIES...
PR...High Rip Current Risk through Sunday afternoon for PRZ001-002-
     005-008-010-012-013.

     High Surf Advisory until 6 PM AST Sunday for PRZ001-002-005-008-
     010-012.

VI...High Rip Current Risk through Sunday afternoon for VIZ001-002.

     High Surf Advisory until 6 PM AST Sunday for VIZ001-002.

&&

CAM, MRR

Perspectivas sobre las Condiciones Peligrosas del Tiempo
Servicio Nacional de Meteorologia en San Juan PR
405 AM AST jueves 8 de diciembre de 2022

AMZ710>745-PRZ001>013-090815-
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-
405 AM AST jueves 8 de diciembre de 2022

Esta perspectiva sobre las condiciones peligrosas del tiempo es para
Puerto Rico.

.DIA UNO...Hoy y esta noche

.Condiciones Marinas...Se espera oleaje igual o mayor de 10 pies
desplazandose a traves de las aguas locales del Atlantico y el
pasaje de Anegada. Se esperan condiciones maritimas peligrosas.

.Corrientes Marinas...Corrientes marinas amenazantes a la vida en la
zona de olas rompientes, particularmente en las playas orientadas
hacia el norte y este. Se espera un riesgo moderado de corrientes
marinas a lo largo del resto de las costas.

.DIAS DOS A SIETE...viernes a miercoles

Corrientes marinas peligrosas continuaran durante el periodo a lo
largo de toda la costa norte y este. Se espera que permanezca oleaje
alto durante el periodo en las aguas del Atlantico y pasajes del
Caribe.

.Comunicado sobre informacion reportada por observadores...

No se requiere activacion de observadores.

AMZ715-725-VIZ001-002-090815-
San Tomas, San John e Islas Adyacentes-Santa Cruz-
Aguas cercanas del Atlantico y aguas costeras adyacentes
del Caribe-
405 AM AST jueves 8 de diciembre de 2022

Esta perspectiva sobre las condiciones peligrosas del tiempo es para
Islas Virgenes Estadounidenses.

.DIA UNO...Hoy y esta noche

.Condiciones Marinas...Se espera oleaje igual o mayor de 10 pies
desplazandose a traves de las aguas locales del Atlantico y el
pasaje de Anegada. Se esperan condiciones maritimas peligrosas.

.Corrientes Marinas...Corrientes marinas amenazantes a la vida en la
zona de olas rompientes, particularmente en las playas orientadas
hacia el norte y este. Se espera un riesgo moderado de corrientes
marinas a lo largo del resto de las costas.

.DIAS DOS A SIETE...viernes a miercoles

Corrientes marinas peligrosas continuaran durante el periodo a lo
largo de toda la costa norte y este. Se espera que permanezca oleaje
alto durante el periodo en las aguas del Atlantico y pasajes del
Caribe.

.Comunicado sobre informacion reportada por observadores...

No se requiere activacion de observadores.