Scientific Forecaster Discussion
Area forecast discussion
National Weather Service San Juan PR
1035 am AST sun Feb 7 2016
Update...it was mostly sunny over the USVI and western PR this
morning. However...variably cloudy skies prevailed over the
eastern half of PR as a band of showers streamed from the
southeastern coastal sections of PR northward across San Juan and
vicinity. Between 1 to near 2 inches of rain were reported by
rain gages at Aguas Buenas...Caguas...Juncos and Las Piedras.
Between half to three quarters of an inch was reported across
other areas of the eastern interior and northeast coastal areas.
By middle morning a few showers developed over Ponce and
vicinity...with rainfall generally around a tenth of an inch or
less. For this afternoon...skies should be sunny to partly cloudy
over the islands...with showers forming mainly over the northwest
quadrant of PR and streamers off the USVI. No changes so far made
to short term grids.
Aviation update...latest 07/12z tjsj upper air sounding indicated
S to east-southeast winds below fl150 at 10-20 kts...becoming north-northwest above at 25-39
kts by the way fl250-400. -Shra/rain showers will continue to develop over
Mainland PR through at least 22z...creating periods of mountain top obscured
over El Yunque and over the interior. But overall mainly vcsh
over northwest terminals and jsj are expected through the afternoon hours.
Marine update...near shore buoys across PR and the USVI are
indicating wave heights between 3-5 feet and east-southeast winds around 15
knots with gusts in the low 20s. Small craft should continue to
exercise caution across much of the local waters. Moderate risk of
rip currents continue for most of the beaches of St.
Croix...Puerto Rico...Culebra and the southern beaches of
Vieques...St. Thomas and St. John.
Previous discussion... /issued /
Synopsis...a middle to upper level ridge will continue to build
across the area from the west...as TUTT across the tropical
Atlantic moves further east while weakening. Continue to expect
southeast winds across the local islands the next few days.
Discussion...as weak surface perturbation and associated
moisture moves away from the area early this morning...passing
showers will remain possible across the USVI...east PR and Atlantic
waters. Lingering moisture will then combine with local effects
to produce showers across northwest PR in the afternoon.
As the ridge pattern aloft continues to build from the west...low
level moisture will then erode late tonight with precipitable
water near normal values much of the work week. Therefore Monday
through at least Friday...under ridge pattern...enough moisture
and east southeast winds...expect passing showers across the USVI
and southeast Puerto Rico in the morning...followed by isolated to
locally scattered afternoon showers over northwest Puerto Rico
with the driest day being Friday. Warm temperatures are also
expected along the north coast of Puerto Rico those days under the
southeast wind flow. Moisture is expected to pool across the local
islands next weekend as a frontal boundary approaches from the
Aviation...isolated to scattered showers will continue to move
across part of the local flying area through the morning hours
affecting mainly tncm...tkpk...tist...tisx and tjsj. However
mostly vicinity showers are expected. Latest tjsj sounding
indicated a southerly wind flow up to 20 knots all the way from
the surface to around 10k feet becoming north northwesterly and
stronger above 10k feet.
Marine...seas up to 6 feet and winds around 18 knots across the
Atlantic... Caribbean offshore waters and local passages.
Therefore...small craft should exercise caution. Long period
northwest swell... associated with a developing area of low
pressure across the western Atlantic...will reach the Atlantic
waters on Tuesday.
Preliminary point temps/pops...
sju 88 74 88 74 / 30 10 20 20
stt 85 75 85 75 / 40 20 20 30