Scientific Forecaster Discussion

Return to Local Conditions & Forecast

Without Abbreviations
With Abbreviations

fxca62 tjsj 211748 

Area forecast discussion
National Weather Service San Juan PR
148 PM AST Sat Jan 21 2017

Synopsis...weak boundary just north of the islands will continue
to move over the islands today. Surface high over the Bahamas
will continue to move north of the islands during the next few
days. As it enters the central Atlantic, winds will shift from the
south as front moves from the west and another surface high builds
across the western Atlantic by midweek next week. Short wave trof
will exit the local area as mid to upper ridge holds thru Tuesday,
when another trof swings aloft from the west.


Discussion...sunny to partly cloudy skies were observed today
across the islands. A weak boundary over the Atlantic waters
increased cloudiness and showers...but mainly over the Atlantic
coastal waters with some showers under a northerly steering wind
flow moved over sections of northwest PR. Sea breeze convergence led to
light showers and partly cloudy skies across the Cordillera
Central and southern slopes of PR. For tonight, showers should
remain mainly across the coastal Atlantic waters of the islands but
with the northerly component of the wind some could reach portions
of the islands at times.

Remnants of the old frontal boundary could linger through Monday,
but overall dry and fair weather conditions are expected to
prevail. Winds are expected to shift from the southeast to south
through Tuesday as the surface high moves into the central
Atlantic and a front and associated surface low moves across the
western Atlantic approaching the forecast area. Some cloudiness
and the chances for showers should increase briefly by Tue-Wed.
However, a strong surface high and ridge aloft are expected to
build and spread across the western Atlantic into the local area
by midweek next week. Returning a cool northerly wind flow and
drier conditions through the end of next week.


Aviation...VFR is expected to continue over all taf sites. Vcsh may
occur at tjsj after 21/22z from rain showers offshore north of PR and tncm,
but conditions should remain VFR. A few mountain obscurations may
occur in the central interior of Puerto Rico til aft 22/02z. Sfc
winds less than 10 kt with land/sea breeze variations. Winds aft
22/15z becoming more easterly 6-12 kt. Maximum winds fl410-460 northwest 50-
70 kt.


Marine...small pulses of northerly swell are expected to
continue across the Atlantic waters and passages for the next few
days. At the moment, northwest swell should peak by Wednesday around 6
feet. Increasing rip currents and surf height along the northern
beaches of the islands. Across the southern waters of the islands,
seas should continue at 4 feet or less through the forecast


Preliminary point temps/pops...
sju 72 82 72 86 / 20 20 20 20
stt 71 83 72 83 / 20 20 20 20


Sju watches/warnings/advisories...

National Weather Service Glossary of Abbreviations