Scientific Forecaster Discussion
Area forecast discussion
National Weather Service San Juan PR
550 am AST sun Aug 28 2016
the influence of Hurricane Gaston, well northeast of the region
across the central Atlantic, and a broad area of low pressure
near the Florida Straits, will continue to induce a moist
southeast wind flow across the region through at least Monday. A
TUTT low to the northeast of the area will retrogress westward to
meander across the region at least until Tuesday as an upper level
ridge builds over the region by midweek.
the proximity of a TUTT low produced showers across the local
waters overnight, some of these showers, though they were brief,
moved inland across the windward sections of PR and the U.S.
Virgin Islands. In addition, the diffluence aloft induced the
formation of thunderstorms in the far southwest corner, between
the Mona Passage and the local Caribbean offshore waters.
The combination of the TUTT low, an induce surface trough and the
available low level moisture will continue to enhance shower
activity across the surrounding waters and some of these showers
are going to reach the windward sections of PR and the U.S. Virgin
Islands from time to time during the morning hours. Then, another
round of afternoon convection is expected along the Cordillera
Central and the western sections of Puerto Rico, but also, some
of these showers could affect the metropolitan area of San Juan.
As the TUTT low moves away from the region on Tuesday, a ridge
pattern aloft will build from the east northeast, over the
northeast Caribbean. In addition, the surface winds are expected
to become from the east and precipitable water will drop near or
below normal by midweek. This pattern will result in limited
shower and thunderstorm activity across the local islands.
mostly VFR conditions expected over most of the local flying
area. However vicinity showers are possible until 28/14z across
the leeward and USVI taf sites. Isolated tstms will affect the
vicinity of tjsj/tjbq and tjmz after 28/17 and through 28/23z with
mountain top obscuration across the Cordillera Central of PR. Low
level winds will be mainly east at 10 knots overnight increasing
to 10 to 15 knots after 28/13z.
Marine...a small, but long east-northeast swell, generated by tropical
cyclone Gaston will continue to affect the local Atlantic waters
and Anegada through at least late tonight, followed by arrival of
another small but long NE swell by late Tuesday. Although this
swells, seas are expected below 6 feet and winds around 15 knots.
At this moment, marine weather conditions are expected below small
craft criteria. However, isolated thunderstorms with areas of
locally heavy rainfall and dangerous lightning will remain
possible across the regional waters as the TUTT low moves across
Preliminary point temps/pops...
sju 90 78 91 80 / 30 20 30 10
stt 86 80 87 81 / 30 30 30 10