National Weather Service San Juan PR
500 AM AST Fri Feb 25 2022
.SYNOPSIS...Easterly winds are forecast today continuing for the
next several days. This is due to a surface high pressure over
the east central Atlantic, which will dominate the local wind
flow. Even though we still expect below normal moisture today, the
available moisture is expected to increase slightly, bringing
isolated to scattered showers. The slightly below normal moisture
is expected through the weekend, but near normal to above normal
moisture is expected for the upcoming workweek. Marine conditions
will be choppy to hazardous into this afternoon for the offshore
Atlantic waters, but will remain choppy elsewhere today and
through the rest of the weekend. The high risk of rip currents
will continue for the next several days.
&&
.SHORT TERM...Today through Sunday...
A mid to upper level low is currently located to the northeast of
the Leeward Islands. This feature, along with a mid level ridge
centered over Florida is generating a wind flow coming out of the
north, and carrying dry air at these levels. An induced surface
trough associated with this low is moving westward, and as a result,
the low level winds are expected to shift from the east today.
Recent satellite imagery shows an area of slight enhanced moisture
moving across the area. This should promote an advective pattern
along the U.S. Virgin Islands and eastern Puerto Rico throughout the
day. In the afternoon, local effects will trigger additional
activity over southwestern Puerto Rico, with moderate rainfall
amounts expected.
On Saturday, a similar pattern is expected to prevail across the
region. The upper level low will open into a trough, but remaining
to the northeast of the islands. By Sunday, the mid-level ridge
weakens, allowing for moisture to reach 500 mb. The moisture will be
provided by another induced surface trough that should cross the
islands during the day. Conditions appear favorable for an increase
in the frequency of showers, but basically following the same
pattern as before: advective showers moving over the eastern
sections of the forecast area during the day, followed by convection
developing over western Puerto Rico in the afternoon.
.LONG TERM...Monday through Saturday...
A surface high pressure across the east central Atlantic is still
forecast to promote easterly winds through the log term period.
The available moisture will be near to slightly above normal from
Monday onward, with Monday having the highest amount of
precipitable water according to the global models. The weather
pattern will be typical for easterly winds with near normal
moisture. Isolated to scattered showers in the morning across the
USVI, eastern PR and the local waters, followed by afternoon
convection across the central to western sections of PR. However,
with the additional moisture expected on Monday, the latest
guidance suggests a wider coverage of shower activity over the
islands compared to the rest of the week. In previous model runs,
the GFS model suggested a mid to upper level trough approaching
the local area late in the workweek. However, this is not the case
with the latest model run, keeping the local islands under a mid
and upper level ridge, while a trough develops well to the east of
the local islands, not for this weekend, but for next weekend.
Given the changes in model guidance from one day to another, the
long term forecast confidence is low.
&&
.AVIATION...SHRA will affect TJSJ/TIST through the morning hours, but conditions
should mainly remain MVFR. In the afternoon, additional SHRA
activity is expected for TJPS, which could result in brief
reductions in VIS and low ceilings. Winds will shift from the east
after 12Z, at 10 to 12 knots with stronger gusts and sea breeze
variations.
&&
.MARINE...The local nearshore buoys are reporting seas of under 6
feet, and the outer buoys are hovering just over 6 feet. The
latest guidance is not suggesting seas reaching 7 feet, but
showing that it will be just over 6 feet across the offshore
Atlantic waters. Model guidance and observation comparison, has
suggested that the models are under-estimating wave heights
slightly. Because of that, it was decided to keep the Small Craft
Advisory for the offshore Atlantic waters through early this
afternoon. If by chance the models are under-estimating more than
it si currently, the advisory may be extended until early
Saturday. As it is currently in the forecast, seas up to 6 feet
but occasionally to 8 feet are expected across the offshore
Atlantic waters for later this afternoon and tonight. Elsewhere,
seas up to 5 or 6 feet are expected with easterly winds up to 15
knots.
There is still a high risk of rip currents for many of the local
beaches, such as those from the northwest to northeast Puerto
Rico, Culebra, northwest St Thomas and most beaches of St Croix.
&&
.PRELIMINARY POINT TEMPS/POPS...
SJU 83 72 84 73 / 50 40 30 30
STT 83 72 84 74 / 40 40 20 50