Scientific Forecaster Discussion
fxca62 tjsj 242008
Area forecast discussion
National Weather Service San Juan PR
408 PM AST Sat Jun 24 2017
diurnally induced shower activity will diminish by sunset, leaving
partly cloudy to mostly clear skies. Few passing showers will
continueto move across the coastal waters and may reach the
windward side of some islands during the over night hours. The
chance for showers and thunderstorms will increase across the
region late Sunday through Monday , as a tropical wave will move
across the eastern Caribbean, and a TUTT low develops northeast of
the region. Lesser activity is expected on Tuesday and Wednesday
except for locally induced afternoon showers and isolated
thunderstorms mainly over the west sections of Puerto Rico. Hazy
conditions will also be likely as an extensive Saharan air layer
will trail the tropical wave.
Short term...today through Monday...
A surface high pressure will continue to dominate the region during
the rest of the weekend. Under this pattern...trade wind showers and
shallow low level clouds will reach the local islands and coastal waters
at times. A tropical wave is forecast to affect the local region Sunday
night through Monday. A TUTT low is also forecast to develop and relocate
just northeast of the region while higher pressure ridge gradually
erodes aloft. As a result, an increase in cloudiness with showers and
thunderstorms is expected across coastal waters, Puerto Rico and the
U.S. Virgin Islands. Drier air is expected to filter in as Saharan
dust trailing the tropical wave will quickly spread across the region
by Monday evening. This should then limit the shower activity across
the islands and coastal waters.
Long term...Tuesday through Sunday...
As the tropical wave moves away from the local isles late Monday and
into Tuesday, low level moisture is expected to decrease across the
forecast area. However, afternoon showers with a few thunderstorms
are still expected mainly across west Puerto Rico Tuesday and Wednesday
due to local effects and diurnal heating. Hazy skies are also possible
during those days as an extensive Saharan air layer will spread across
the region trailing the tropical wave. Good pooling of tropical moisture
is so far expected across the region by Thursday and through the early
part of the upcoming weekend, as another tropical wave is forecast to
enter and moves across the eastern Caribbean. This should again bring
a moist and unstable weather pattern to the forecast area.
Aviation...VFR conds expected at all taf sites except tjbq and vcty
tjmz where brief MVFR conds are possible thru 22z due to diurnally induced
rain showers/isold thunderstorms and rain. Elsewhere...vcsh possible at times. East-southeast sfc wnds of
15-20 kts will prevail bcmg 5-10 kts aft 23z. Passing rain showers en Route
btw islands and over coastal waters durg prd...few tops btw fl080-fl100.
Marine...mariners can expect seas of 3-5 ft and winds of 10-20 kts
across the regional waters. Moderate risk of rip current will continue
across parts of the north and southeast coast beaches of Puerto Rico,Culebra
and Vieques as well as in St. Croix.
Preliminary point temps/pops...
sju 77 89 78 87 / 40 20 40 50
stt 79 90 79 87 / 20 20 50 50