National Weather Service San Juan PR
451 AM AST Sun Nov 27 2022
.SYNOPSIS...A mid- to upper- level ridge over the area will
result in another day with a mixture of sunshine and clouds with
the exception of occasional showers across the windward sections
of the local islands. Limited showers will also affect the
interior and western half during the afternoon. The passage of a
weak tropical wave by tomorrow and patches of low- level moisture
filtering in during the next few days will also result in limited
shower activity.
From tomorrow afternoon through at least early Wednesday, a
northeasterly long- period swell will create dangerous breaking
waves resulting in life-threatening rip currents along the
Atlantic Coastline of Puerto Rico and the U.S. Virgin Islands.
&&
.SHORT TERM...Today through Tuesday...
Another day with a mixture of sunshine and clouds will prevail
today, with the arrival of occasional showers across the windward
sections in the U.S. Virgin Islands and Puerto Rico. This weather
pattern is associated with a mid to upper-level ridge over the
islands, which promotes subsidence and dry air aloft. Moisture is
trapped below 700 MB; therefore, the trade winds will advect those
patches of clouds and showers over the islands throughout each day.
A weak tropical wave will move well south across the Caribbean Sea
later today into Monday without significantly impacting the weather
conditions. The trade winds will increase somewhat moisture content
by late Monday night into Tuesday. Under this scenario, expect a
typical weather pattern with a mixture of sunshine/clear skies and
clouds with the arrival of occasional pesky showers. Then, isolated
to scattered brief showers will develop across the mountains and
western sections each afternoon.
The main threat through the period is the arrival of a northeasterly
long-period swell that will create dangerous breaking waves
resulting in life-threatening rip currents along the Atlantic
Coastline of Puerto Rico and the U.S. Virgin Islands around Monday
afternoon onward.
&&
.LONG TERM...Wednesday through Monday...
Mainly fair weather conditions, along with the seasonal weather
pattern continue to be expected for most of the long term forecast
period. Northeasterly winds will prevail for most of the period and
heat indices up to the upper 90s will be observed each afternoon,
especially across areas of northern Puerto Rico. Unfavorable
conditions will prevail for most of the period as a mid- to upper-
level ridge prevails, promoting subsidence; dry air will also
prevail in the mid- to upper- levels. Relatively dry air will
dominante over the local islands at the surface level.
Nevertheless, patches of more moist air, with slightly below
normal to normal precipitable water values, will filter into the
local areas from time to time. Ridging and dry air will limit the
development of shower activity leaving a limited variation of the
seasonal weather pattern. This pattern, under northeasterly winds,
includes showers advecting mainly into the eastern forecast area
during the morning and, during the afternoon, limited convective
development due to diurnal and local effects affecting mainly
western and southwestern Puerto Rico.
Increased rain chances will depend on the timing of patches of
moisture filtering into the area. Model guidance continues to show
areas with precipitable water values of between 1.5 to around 1.7
inches, remnants of a frontal boundary, reaching the area on Tuesday
and into Wednesday. Model guidance has continued to vary on the
timing of areas of humid air filtering into the area, but is
generally showing a dry pattern at least until Sunday. Several upper-
level low pressure systems will form in the Atlantic but will remain
far east of our region, not affecting us directly. It is only
until late Saturday and into Sunday, that model guidance shows
both moisture increasing, with precipitable water values of around
1.5 in, and an upper-level low pressure system approaching the
area, increasing instability and rain chances.
A northeasterly long-period swell will continue to affect the region
at least until Wednesday. This swell will result in dangerous
breaking waves along with life-threatening rip currents along the
Atlantic Coastline of Puerto Rico and the U.S. Virgin Islands.
Another swell is also possibly arriving next weekend, please stay
tuned to forecast updates and future products issued by your
National Weather Service WFO San Juan.
&&
.AVIATION...VFR conditions will prevail throughout the forecast
period. However, occasional passing -SHRA/SHRA will affect
TJSJ/IST/ISX. SHRA will develop over the Cordillera Central in the
afternoon, btwn 27/17- 22z. Expect calm to light/VRB winds
through 27/13z, returning from the ENE at 10-15 kt afterward with
higher gusts and sea breeze variations.
&&
.MARINE...Moderate easterly winds will promote a moderate chop
today across most of the local waters and passages. Expect seas
up to 5 feet for the local Atlantic Waters and seas of 4 feet or
less elsewhere. A weak tropical wave will move across the
northeastern Caribbean by tomorrow and a long-period northeasterly
swell will deteriorate marine and coastal conditions from early
tomorrow through at least early Wednesday.
There is a moderate risk of rip currents for the northern beaches
of Puerto Rico, the beaches of Culebra and western beaches of
Vieques and St. Croix. Tonight, the moderate risk of rip currents
will extend to the beaches of St. Thomas and St. John as well as
to the northern beaches of Vieques. Life-threatening rip currents
often occur in the vicinity of groins, jetties, reefs, and piers.
&&
.SJU WATCHES/WARNINGS/ADVISORIES...
PR...None.
VI...None.
&&
$$
SHORT TERM...CAM
LONG TERM....MRR