Graphical Hazardous Weather Outlook


Lightning THREAT





FXCA62 TJSJ 270821

Area Forecast Discussion
National Weather Service San Juan PR
421 AM AST Mon May 27 2024


A tropical wave located southwest of the region will promote
shower activity throughout the day. With the expected activity,
there is an enhanced risk for minor flooding, lightning, and gusty
winds. As the wave departs the local area today, a deep southeasterly
flow will continue to bring plenty of moisture into the islands
enhancing unstable conditions until at least mid-week.


.SHORT TERM...Today through Wednesday...

NHC`s TAFB analyses the axis of a tropical wave just southwest of
Puerto Rico this morning. Moisture associated with the wave is
evident in satellite imagery, with precipitable water values greater
than 2.2 inches, which is well above normal. At the mid levels, a
ridge is centered just of the east of the Leeward Islands. At the
upper levels, a trough over the western Caribbean is inducing a
southerly flow, bringing plenty of clouds to the area.

Since this morning, weak scattered showers have been streaming
across eastern Puerto Rico and over the northern Virgin Islands. The
islands will remain in a favorable spot for showers generation. The
high resolution guidance show that shower frequency will increase
this morning, mainly in the vicinity of the Virgin Islands and
eastern Puerto Rico. In the afternoon, especially if sunshine peeks
across western Puerto Rico, additional activity is anticipated for
the west. Enough water could be collected in the ground, increasing
the chances of urban and small stream flooding. There is the
potential for thunderstorms, producing occasional to frequent
lightning and gusty winds.

As the tropical wave departs today, a deep southeasterly flow will
continue to bring plenty of moisture into the islands. This will be
enough to generate strong thunderstorms in the afternoon, mainly for
the interior and western Puerto Rico.  Additional activity is also
expected elsewhere at times. The risk for flooding will stay
elevated these days.Also, breaks of sunshine will be more frequent
tomorrow and Wednesday, allowing for temperatures and heat indices
to climb up, so it will feel muggy too.

.LONG TERM...Thursday through Monday...

No significant changes have been introduced to the long term
forecast. A mid-to-upper level ridge over the eastern Caribbean is
forecast to persist for much of the period. A drier airmass is
expected to filter into the region, promoting stable weather
conditions and warm temperatures. The general wind flow will
prevail from the southeast and will shift from the south by early
Sunday in response to a building surface high pressure in the
central Atlantic. Despite of the drier air, there is sufficient
low- level moisture from the Caribbean Sea moving into the local
area. This moisture in combination with daytime heating, and
local effects will result in afternoon convective activity across
the interior, north- central and northwestern portions of Puerto
Rico every afternoon. With the expected activity, there is a
limited to elevated risk of urban and small stream flooding in
roads and poor drainage areas. Latest precipitable water model
guidance suggest values between 1.80 to 2.00 inches between Friday
and Sunday. By Friday through Monday a relatively wet pattern is
expected to prevail across Puerto Rico and the U.S. Virgin Islands
as a weak surface trough develop between the Dominican Republic
and the local region. In response, an enhancement in shower and
thunderstorm activity is anticipated as moisture increases. By
Sunday, winds are expected to shift from the south and prevailing
from this direction until at least mid- week. With this
meteorological scenario, warmer temperatures are going to be
present with values between the upper 80s to low 90s along the
coastal and urban areas of the islands. Heat indices are
anticipated to surpass the mid 100s, and could result in
excessive heat conditions for the islands.


(06z TAFs)

SHRA and isolated TSRA associated with a tropical wave will stream
across the Caribbean and Atlantic waters, reaching the USVI, TJSJ
and TJPS terminals at times. After 17Z, additional, stronger
activity is expected for NW PR, with mountain obscuration across the
Cordillera Central and TJBQ. These will result in periods of reduced
VIS and low ceilings. Winds will be from the ESE at 8-13 kts, with
stronger gusts, especially around TSRA.



A moderate east to southeast wind flow will prevail across the region
over the next few days. A tropical wave will move across the Caribbean
waters today, increasing shower and thunderstorm activity through at
least Tuesday across the local waters.



There is a low risk of rip currents today across all beaches of Puerto
Rico and the U.S. Virgin Islands. Moderate to heavy showers and isolated
thunderstorms are possible with the influence of a tropical wave
just southwest of the region.





NWS SJU Office Area Forecast Discussion



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