Advisory NPW Special Advisory — Fri Aug 30, 2024 3:54 AM

NPWSJU) are in effect.

Winds are expected to shift from the east to southeast later in the
short-term period. However, similar weather condtions are expected
on Saturday and Sunday, as pockets of moisture will bring passing
showers across the windward areas of the islands during the night,
followed by diurnally induced afternoon showers and thunderstorms
over the interior and northwestern PR. Heat advisory conditions will
likely continue each day due to max temps in the low-to mid-90s with
dewpoints in the low 80s across most lower elevations of the
islands.

&&

.LONG TERM....Monday through Friday...

At this time, there is some discrepancy between the models, which
is normal due to how far in time the system of interest is. The
Global Forecast System (GFS model) suggests that the now tropical
wave will move south of Puerto Rico and the U.S. Virgin Islands by
late Monday into Tuesday. Based on the GFS, the passage of this
wave to the south of us will increase the precipitable water
values to 1.8 to 2.0 inches (near normal), and most of the
moisture content will stay at the low levels of the atmosphere.
However, the European Center for Medium-Range Weather Forecasts
(ECMWF model) suggests that the system will move closer to the
forecast area by mid-week but as a well-developed low-pressure
system, allowing precipitable water values to increase to 2.00 and
2.30 inches (above normal values for this time of the year).
Despite the discrepancy between the well-known models, we suggest
people stay updated with the changes that may arise as we get
closer in time. That being said, the National Hurricane Center
continues to give this tropical wave over the central Tropical
Atlantic a 50 percent chance of development in the next 7 days. In
other words, this wave has a medium percent change in
development.

The current long-term forecast leans towards what the GFS is suggesting
by having the tropical wave move to the south and increasing the
precipitable water to normal and slightly above normal. Due to the
proximity of this wave, we anticipate an increase in shower and
thunderstorm activity across the islands on both days. Some of the
potential hazards of this weather event are urban and small-
stream flooding, as well as localized flash flooding, which can be
expected too.

On Thursday, expect to see a gradual change in weather conditions
as a mass of dry air will filter across the islands from the
east, reducing the precipitable water values to the 50th (near
normal )and 25th percentile (below normal). However, diurnally
induced afternoon showers and thunderstorms are expected to
develop over the interior and western sections of PR while passing
trade wind showers with lighter rainfall amounts are expected
across the USVI.

By the end of the workweek into the weekend, the latest model guidance
suggests the passage of another tropical wave. Nonetheless, it is
too early to determine the direct impact that this could have on
Puerto Rico and the U.S. Virgin Islands.

&&

.AVIATION...
(06Z TAFS)

Mainly VFR conditions are expected to prevail across all terminals
during the next 24 hours. However, SHRA and iso TSRA en route fm the
Leeward Islands may cause tempo MVFR conds at TIST/TISX thru 30/12z.
Diurnally induced afternoon SHRA/TSRA over western PR may cause
brief MVFR cigs at TJPS/TJBQ btw 30/18z-22z. East winds expected at
12-16 kt with locally higher gusts and sea breeze variations aft
30/14z.

&&

.MARINE...

Expect lighter winds through Saturday. Moderate to locally fresh
easterly winds will dominate over the next few days. Isolated to
scattered showers are expected across the local waters, with isolated
thunderstorms affecting the coastal waters of western Puerto Rico
each afternoon. Consequently, locally choppy conditions for small
craft are likely. The passage of the next tropical wave could further
deteriorate marine conditions by next week.


&&

.BEACH FORECAST...

Moderate rip current risk should prevail across northern and
eastern Puerto Rico, Culebra, Vieques, St. Thomas, and St. John
today.

&&

.SJU WATCHES/WARNINGS/ADVISORIES...
PR...Heat Advisory from 10 AM this morning to 5 PM AST this afternoon
     for PRZ001-003-005-007-008-010-011.

VI...Heat Advisory from 10 AM this morning to 5 PM AST this afternoon
     for VIZ001.

     Excessive Heat Warning from 10 AM this morning to 5 PM AST this
     afternoon for VIZ002.

AM...None.
&&

$$