Area Forecast Discussion
Issued by NWS San Juan, PR
FXCA62 TJSJ 240116
Area Forecast Discussion
National Weather Service San Juan PR
916 PM AST MON MAY 23 2016
.UPDATE...A mid to upper level ridge of high pressure continues to
dominate the eastern Caribbean region. As a result moderate to
strong subsidence continues to inhibit precipitation across Puerto
Rico and the U.S. virgin islands this evening. Will expect these
conditions to persist overnight and so will only indicate
isolated showers over eastern areas of PR and over the U.S. Virgin
Islands. Southeast flow across the region combined with local
effect and topography may result in afternoon showers and
thunderstorms developing over northwestern portions of Puerto Rico
Tuesday afternoon, but only isolated to scattered showers will be
expected over the rest of the area.
.aviation...Mostly VFR cond expected during the rest of the forecast
period. VCSH pos across TJSJ/TIST/TISX. Isolated SHRA can be
expected over NW PR...pos affecting TJMZ and TJBQ after 25/17z. Sfc
winds overnight will be mainly southeast at 5 to 10 kts.
.PREV DISCUSSION... /issued 208 PM AST MON MAY 23 2016/
SYNOPSIS...Subequatorial ridge will dominate the local weather
conditions through most of the week as high amplified trough
remains over the Western Caribbean. Then...a polar low will induce
a mid to upper level trough over cuba and bahamas...favoring the
moisture transport across the central and east caribbean later in
the week. As a result...weather pattern may become more unstable
across the local area by the end of the week.
DISCUSSION...Hazy skies and southerly winds have resulted in
above normal temperatures across the islands today. Max temps
were in the lower 90s so far this afternoon. A few showers are
still possible across portions of Northwest Puerto Rico later
this afternoon. Any shower that develops later this afternoon
will shower activity will be short- lived.
Ridge aloft combined with drier air at mid level will likely
result in a generally fair weather pattern across the islands
most of the work week. Some Saharan Dust particles will continue
to affect the local islands through at at least Tuesday...diminishing
the concentrations Wednesday and Thursday. Typical showers over
northwest PR can not ruled out each afternoon...but the coverage
will be isolated to scattered through midweek. Mid to upper clouds
will stream across the islands starting on Tuesday.
GFS suggests a wetter pattern by the end of next week as a mid-
upper level trough develops over Cuba/Bahamas. However...the rest
of the operational models disagree with the GFS solution. At this
time...the location of the aforementioned of the upper trough is
still unknown at this time. Considering the persistence of the
mid-upper ridge pattern over the Eastern Caribbean...we are
leaning towards the dryer solution for the weekend and probably
AVIATION...Mostly VFR cond expected today. Brief -RA are possible
across TJPS/TIST/TISX/TJSJ this morning. Although...VFR conditions
are expected...we cannot ruled out afternoon convection and mount
obsc across the Interior/Western sections of PR this afternoon. In
addition...showers may developed downwind from El Yunque to affect
the vicinity of TJSJ late in the morning into early this afternoon.
Sfc winds will be from the east to southeast at 5 to 15 kts
increasing at 10 to 20 kt with higher gusts after 23/13z.
MARINE...Fresh winds of 15-20 kt will keep the seas around 4-6
feet through Tuesday. Winds and seas will subside sightly by
midweek as surface high pressure over the Central Atlantic
weakens. Therefore...expect moderate winds and seas of 3-5 ft
from mid to the end of the week.
.PRELIMINARY POINT TEMPS/POPS...
SJU 78 90 78 87 / 10 20 30 10
STT 78 89 80 88 / 20 30 20 10