NOTE: Some of the data on this page has not been verified and should be used with that in mind. It may and occasionally will, be wrong. The tide reports are by xtide and are NOT FOR NAVIGATION. Privacy and Cookie policy

FXCA62 TJSJ 302031 AFDSJU

Area Forecast Discussion National Weather Service San Juan PR 431 PM AST Thu Nov 30 2023


SYNOPSIS

A broad surface high pressure building behind a frontal boundary to the north of the local islands will promote moderate to fresh trade winds across the regional waters through at least Saturday.
Increasing winds and northerly swells will promote choppy to hazardous seas for small craft, mainly across the local offshore waters and passages through the weekend. Increasing passing shower activity is likely by Friday into the weekend. A weak trough should increase shower activity by Monday.

SHORT TERM
Tonight through Saturday...

During the day, mostly calm weather conditions prevailed across Puerto Rico and the U.S. Virgin Islands. However, trade wind showers did developed across the islands from time to time particularly along the eastern half of PR. Temperature wise, along the coastal areas they stayed in the 80s, while in the upper 70s to low 80s in the mountainous areas.

Tonight, expect conditions to remain calm. Nonetheless as winds become easterly expect showers to filter along the eastern sections of PR and the USVI. The minimum temperatures in the mountains are forecast to reach the upper 50s.

The forecast continues on track. A mid-level ridge will hold over the islands, promoting dry air and subsidence aloft and a trade wind inversion between the 800-750 mb layer. Also, at low-levels, precipitable water will remain within the 25th to 75th percentile of the climatological normal, ranging between 1.2 to 1.75 inches through the short-term period. Winds will also remain east to east- northeast over the northeastern Caribbean through the weekend.
However, wind speeds are expected to increase as the pressure gradient tightens over the northeastern Caribbean in the next few days. Therefore, a similar pattern with mostly stable weather and pleasant temperatures will persist over the islands for the rest of today with a few passing showers over windward coastal areas tonight.

The mid-level ridge will erode tomorrow into Saturday as a polar trough deepens east of the Caribbean basin and pushes the mid-level ridge west of the area. This will weaken the trade wind inversion and allow better mixing. Instability should not increase substantially as most of the activity is expected east of the area.
However, surface-induced perturbations may be dragged by the east northeasterly trades into our local area. Therefore, an advective weather pattern and showery weather may increase for eastern and northeastern Puerto Rico and smaller islands, mostly by late Friday and Saturday night and Saturday morning hours. Isolated to scattered showers are expected each afternoon over western portions of Puerto Rico. Although showery weather will increase, no significant rainfall event is anticipated.

LONG TERM
Sunday through Thursday...

A TUTT-low is expected to develop over the eastern Caribbean early in the workweek and the local area should remain on the subsidence side of the low during the first part of the week. However, as the upper level trough deepens over and to the east of the area, a jet maxima of around 70 kt rounding the base of the trough will move over the local area on Sunday. In response the 500 mb temperature is expected to drop near minus 7.5 degrees Celsius, providing some instability aloft. In addition, at lower levels, the remnants of the frontal boundary will be pushed over the local area by the broad surface high over the central Atlantic between Sunday and Monday. Global models suggest that a weak surface trough will move over the area during this period. Therefore, shower activity should increase in coverage over the islands, but flooding rains are not expected. Otherwise, fair weather conditions should prevail from Tuesday onwards.

AVIATION
VFR conds expected through the forecast period for all TAF sites. However, VCSH/SHRA are expected after 30/23z, TJSJ/TJBQ/TIST/TISX. Winds will remain from the ENE at around 10- 15KT and occasional gusts are expected for the rest of today, weakening slightly after 30/23Z to around 10KT or less. Winds are expected to increase tomorrow, possibly 15-20 kt and higher gusts after 01/14z.

MARINE
A cold front will continue north of the region during the next few days. A broad surface high pressure building behind the front will promote moderate to locally fresh trades across the regional waters through at least Saturday. Wind-driven seas and a northerly swell will promote hazardous seas around 7 feet across portions of the Atlantic waters and passages during the weekend.

There is a moderate risk of rip currents for the northern coastline of Puerto Rico, from Aguadilla to Fajardo, and Culebra, as well as for eastern St. Croix. Elsewhere, there is a low risk today. By late Friday night into the weekend, expect the rip current risk along the northern and eastern coast to become high as conditions turn unfavorable.

SJU WATCHES/WARNINGS/ADVISORIES
PR...High Rip Current Risk from Friday evening through late Saturday night for PRZ001-002-005.

High Rip Current Risk from Saturday morning through late Saturday night for PRZ008-012.

VI...None.
AM...None.

toggle option: (graph/table)

Full Color Weather Map

Link to Loop


Other links: GEOS-West     Contential US     Full GOES-East

Virgin,Islands/San,Juan/Cayey,PR