Scientific Forecaster Discussion
Area forecast discussion
National Weather Service San Juan PR
543 am AST Monday Jul 28 2014
Synopsis...surface high pressure across the central Atlantic will
remain dominating the general weather pattern for the next few
days with easterly winds and lower than normal precipitable water
values as it slowly moves north. TUTT to the north of the local
islands will remain in place to the north of the islands for the
next few days. Showers and thunderstorms are expected each
afternoon across portions of western PR for the next several days.
Saharan dust will be present today...improving on Tuesday.
Discussion...very little shower activity was observed overnight
across the local area. The combination of the limited available
moisture with the local effects and the TUTT...may cause shower
and thunderstorm development today across western and southwestern
PR in the afternoon. The rest of Puerto Rico and the USVI should
remain with fair weather and warm with hazy skies due to the
Saharan dust that is present. According to the naaps aerosol
model...the Saharan dust will exit our area this evening...giving
US a break from the dust tomorrow Tuesday.
For the next few days...showers and thunderstorm development is
expected across portions of western PR in the afternoon hours.
For Tuesday through Thursday...the development of the showers and
thunderstorms is expected to be across the northwestern quadrant
of PR...while only isolated showers are expected across the rest
of the local area...including the USVI.
According to the National Hurricane Center...a tropical wave roughly
around 10 north and 31 west...or around 550 miles to the southwest
of the Cape Verde Islands...has a 30 percent of developing in to a
tropical cyclone in the next 48 hours and a 70 percent within the
next 5 days. It is too early to precise just how much or even if
this wave will affect the local area as a wave or tropical
cyclone...if at all. There is just too much uncertainty at the
time and there is great differences between global models. GFS
model develops it into a tropical cyclone and tracks it to the
north of the local islands while the European model (ecmwf) model does not do
anything with it. We are observing the tropical wave closely and
its evolution...but it is just too early yet to precise how or
even if this will affect the local area.
Aviation...VFR conditions will prevail across all taf sites through
the forecast period. However after 28/18z...obscured mountain and brief MVFR
ceilings are expected due rain showers/thunderstorms and rain developing across the western
interior and SW-PR affecting mainly tjmz. Easterly winds 5 to 15
Marine...surface pressure gradient across the northeast Caribbean
will continue to relax as the surface high pressure
ridge...centered over the north-central Atlantic...continues to
slowly retreat north. As a result surface winds will slacken with
seas subsiding to well below 6 feet through the week.
Preliminary point temps/pops...
sju 89 76 88 77 / 20 20 30 20
stt 89 78 89 78 / 20 20 20 20