National Weather Service San Juan PR
451 AM AST Sat Feb 10 2024
.SYNOPSIS...
Generally fair weather conditions with a mixture of clouds and
sunshine with occasional rains will persist this weekend. Showery
weather is forecast for Monday and Tuesday as a modified old
frontal boundary moves across the region.
Northerly swells will maintain deteriorated marine and coastal
conditions for the Atlantic waters and local passages through
early next week. Surf Heights are rising across northern exposed
coastlines, becoming in excess of 10 feet tomorrow, which will
last through Tuesday. Exercise caution when visiting the beach
these upcoming days due to these conditions.
&&
.SHORT TERM...Today through Monday...
A subtropical surface high-pressure building across the Atlantic
Ocean to the north promotes trade winds between 10 and 15 mph
overnight. Those trade winds brought patches of stratified clouds
and showers across the northern windward sections of PR and the U.S.
Virgin Islands, while the rest of the leeward sections enjoyed
mostly clear skies with little or no rain. The tropical winter low
temperatures are finally here, and the thermometer dropped to the
low 70s along the coast and into the low 60s or upper 50s in
mountains and valleys.
A vertically stacked high-pressure system will promote an advective
pattern with stable conditions with occasional passing trade showers
this weekend and early next week. As a result, the northern and
eastern windward sections of Puerto Rico and the U.S. Virgin Islands
can expect a mixture of clouds and sunshine with stratified clouds
moving by with occasional rains, a typical winter weather pattern
for the islands. Additionally, breezy conditions and cooler-than-
normal temperatures variations are likely. We expect a similar
weather pattern on Sunday. Although a stable atmosphere with below-
normal moisture will be present, the trade wind showers will push
fragments of moisture with shallow clouds that sometimes cause rainy
conditions.
On Monday, the surface high pressure will move into the Central
Atlantic, pushing the remnants of a modified old frontal boundary
that will increase the available moisture. Thus, it may result in
showery weather from Monday afternoon to the evening hours.
&&
.LONG TERM... Tuesday through Saturday....
Mostly fair weather conditions will prevail during the long term
period as a mid to upper-level ridge holds over the eastern
Caribbean and precipitable water values remain quite low. During the
beginning of the period on Tuesday, a surface high northeast of the
region will begin to direct a southeasterly surface wind flow across
the islands, bringing in a a patch of moist air through Tuesday
afternoon. This may bring some passing showers across windward
sections and some light convection across northwestern PR. However
by Wednesday the arrival of dry air should eliminate any potential
for showers throughout the day.
Wind speed will begin to lighten on Wednesday as the surface ridge
moved further into the central Atlantic. The pattern of lighter
wind and little to no rain should last until Friday when a robust
surface ridge moving north of the region will accelerate the
trades and advect a relatively moist airmass across the islands.
This should yield a seasonal pattern of passing windward showers
with afternoon convective development, however nothing significant
is expected as pronounced ridging still remains across the mid to
upper-levels, stabilizing local conditions.
&&
.AVIATION...
(06Z TAFS)
VFR conditions will persist through the forecast periods. Clouds
will arrive from time to time across the islands and may result in
SHRA/-SHRA across JSJ/IST/ISX/JBQ at times. Winds will persist
mainly from the NE at 5-10 kt through 10/13z, increasing at around
15 kt with higher gusts up to 25 kt with sea breeze variations.
&&
.MARINE...
A broad surface high pressure is developing over the western
Atlantic as a strong low pressure moves northeast through the central
Atlantic. The low pressure system will send consistent pulses of
northerly swell into the local area, creating hazardous marine and
coastal conditions through at least Tuesday. As high pressure
stretches north of our area, northeast winds will remain moderate to
fresh through today, then turn east by Sunday into early next
week.
&&
.BEACH FORECAST...
Strong northerly swells and windy conditions will mainly effect
northern, eastern, and western beaches over the next few days.
Breaking waves in excess of 10 feet are expected across northern
exposed beaches of Puerto Rico starting tomorrow, therefore there
is a High Surf Advisory starting tomorrow lasting until Tuesday,
with a High Risk of Rip Currents remaining in place alongside
this. Beaches of southern Puerto Rico remain the calmest during
this time, however expect windy conditions, especially during the
afternoon hours.

