Info HWO Hazardous Weather Outlook — Wed Aug 25, 2021 11:57 AM

HWOSJU) issued by the National
Weather Service San Juan forecast office for details.

SHORT TERM...Today through Friday...

At the mid levels, a drier airmass embedded in a ridge will result
in relatively fair weather conditions for the first part of the
short term cycle. Satellite derived products indicate below normal
PWAT values for today and tomorrow. However, satellite imagery from
GOES-16 shows fragments of moisture that will result in a few
isolated showers during the morning hours. Afternoon convection will
be limited, however, local effects and diurnal heating could spawn
showers for parts of interior and northwestern sections of Puerto
Rico. Showers that do develop will be short-lived and produce light
rainfall amounts.

Current model guidance suggest an increase in moisture content by
Friday due to the passage of a weak tropical wave. PWAT values are
expected to briefly reach above-normal values around 1.70 inches in
the afternoon. At the upper levels, a westward-moving Upper Level
Tropospheric Trough (TUTT) will generate favorable conditions to
support deep convection across the forecast area. Hence, expect a
more seasonal weather pattern, with diurnal shower activity and
isolated thunderstorms over parts of northwestern Puerto Rico in the
afternoon hours.

Satellite imagery together with aerosol transport models suggest
another Saharan dust cloud filter in the local islands. Thus, hazy
skies will return once again under a warm easterly wind flow for the
latter part of the short term period.

LONG TERM...Saturday through Wednesday...

No significant changes were introduced to the long-term forecast
period, with the most recent model guidance supporting a
generally stable and dry weather pattern with mid to upper level
ridging as the dominant feature. Model-estimated precipitable
water (PWAT) suggests below normal values of 1.60 inches or
lower, with driest conditions expected by Monday, when PWAT are
forecast to fall around 1.00 inches. Despite the expected
conditions, localized convective development is still possible,
favoring the northwestern quadrant of Puerto Rico and downwind
from the local islands and El Yunque each afternoon. A high
concentration Saharan dust event is anticipated for Saturday and
Sunday, though lower concentrations are anticipated thereafter.
Daytime highs are forecast to peak into the lower 90s across lower
elevations and urban areas, with heat index that could reach the
lower to mid 100s each day. Thus, expect hot and hazy conditions
with reduced visibilities throught most of the period.

AVIATION...VFR conditions are expected across all terminals through
the 24 hour forecast period. No significant impacts to operations is
anticipated. Winds will be up to 10KT gusting to 15-20KT from the E
with sea breeze variations. Winds will decrease after 25/23Z.

MARINE...Small craft operators should continue to exercise
caution due to choppy seas up to 6 feet and/or winds up to 20
feet expected across the Caribbean waters and Mona Passages.
Elsewhere, tranquil marine conditions with seas up to 5 feet and
winds up to 15 mph will continue.

A moderate risk of rip currents continues for all north-facing
beaches of Puerto Rico, as well as some beaches along the south
and east coast of Puerto Rico, Vieques, Culebra, and Saint Croix.

&&

.PRELIMINARY POINT TEMPS/POPS...
SJU  90  79  89  79 /  10  20  20  20
STT  90  81  90  81 /  10  10  10  30

&&

.SJU WATCHES/WARNINGS/ADVISORIES...
PR...None.
VI...None.
AM...None.
&&

$$