National Weather Service San Juan PR
518 AM AST Wed Aug 22 2018
.SYNOPSIS...Weak tropical wave now located over the east Caribbean
basin will continue to move west and across the local forecast
area later today through Thursday morning. This will increase the
cloud, shower and thunderstorms coverage. Another tropical wave
is forecast to enter the eastern Caribbean by next Wednesday.
&&
.SHORT TERM...Today through Thursday...
Surface high pressure will remain anchored across the north central
Atlantic to maintain a moderate east to southeast wind flow.
Gradually eroding mid to upper high pressure ridge extending across
the northeastern Caribbean will shift westward while a Tutt slowly
retrogrades over the region during the next few days. This feature
will therefore continue to enhance tradewind showers as they make
their way across the coastal waters and reach parts of the islands
mainly during the late evenings an the earl morning hours. Local and
diurnal effects along with this weakening upper level ridge, will
give way to locally enhanced showers and thunderstorms mainly across
portions of the interior and northwestern PR this afternoon.
Some of the afternoon convection will cause urban and small stream
flooding particularly over parts of western PR as well as ponding of
water on roadways and in poor drainage areas around the San Juan
metro area. Several areas across Puerto Rico remain fairly saturated
and as a result river and small streams will quickly react and may
lead to rapid rises in water levels. Mudslides will remain possible
in areas of steep terrain across the interior and west section of
Puerto Rico. Lesser showers activity is expected around Culebra,
Vieques and the U.S. Virgin Islands today as a dry slot will move
across the area.
A weak tropical wave is forecast to move across the region on
Wednesday, therefore expected another round of early morning g and
afternoon convection with areas of enhanced showers and thunderstorms
possible particularly over the interior, north and west sections of
Puerto Rico. There is still good potential for river and urban and
small stream flooding with the development of strong thunderstorms
in isolated areas, as well as mudslides in areas of steep terrain.
A gradual improvement in the weather conditions is expected by
Thursday afternoon as the upper trough fills and moisture transport
decrease across the region. Locally induced afternoon showers and
isolated thunderstorms cannot be ruled out but the activity should be
of short duration and less intense.
.LONG TERM...Saturday through Tuesday...
During this period we should continue to receive the moisture
influx mainly through the incoming weekend. Therefore expect
showers and thunderstorms to develop each afternoon, mainly over
the interior and western portions of Puerto Rico. Model guidance
have push back the arrival of a better organized tropical wave,
now expected for Wednesday with the bulk of moisture moving across
the local forecast area between Wednesday night and Thursday
morning.
&&
.AVIATION...VFR. Mostly SCT cld lyrs nr FL025...FL050...FL080 with
passing SHRA ovr regional waters and between PR and the Northern
Leeward Islands. Fm 21/17z-21/22z...SHRA/Isold TSRA ovr W-NW PR and
vcty TJMZ/TJBQ and WNW of El Yunque vcty TJSJ. Brief Mtn Tops obsc
psbl ovr E PR til 21/12z...and ovr W interior PR durg aftn due to
SHRA/TSRA. Wnds E-ESE 5-10kts bcmg 15-20 kt aft 21/14z.
&&
.MARINE...Mariners should exercise cautions as winds will between
15 to 20 knots across the local waters generating waves between 3
to to 5 feet in choppy seas. A weak tropical wave will move
across the regional waters today through Thursday morning.
Mariners should expect and increase on showers and thunderstorms.
&&
.PRELIMINARY POINT TEMPS/POPS...
SJU 87 78 88 78 / 40 40 30 30
STT 90 80 89 78 / 50 20 20 20