Atlantic Hurricane Season 2024 Storm Names

175
FXCA62 TJSJ 131407
AFDSJU

Area Forecast Discussion
National Weather Service San Juan PR
1007 AM AST Sun Oct 13 2024

.UPDATE...
Minor changes were introduced to the forecast. The Heat Advisory
was cancelled for St. Croix as clouds and showers maintained the
temperatures around 80 degrees. Warming is still expected, with
hot conditions at times. The Heat Advisory was also stretched into
southwestern Puerto Rico, from Cabo Rojo to Guanica, since this
part of the island heat up pretty quickly. Based on the latest
observations, the risk of rip currents was extended into St.
Thomas.

For today, a trough will increase the potential for showers and
thunderstorms, with passing showers over eastern Puerto Rico, and
heavy rain for the interior and northwestern Puerto Rico.

The National Hurricane Center is monitoring a tropical wave,
Invest 94L, which is located west of the Cabo Verde Islands. The
potential for development is low at this time, but the system
could encounter conditions more favorable for development for the
middle or latter part of the week. Since the system is still 5 to
7 days away from the local islands, uncertainty is high, but users
should stay tuned for further updates.


&&

.PREV DISCUSSION... /issued 537 AM AST Sun Oct 13 2024/

SYNOPSIS...
Hazardous marine and coastal conditions will persist the rest today
as long-period northerly swells arrive into our local waters. Hot and
humid conditions will continue for the next several days across the
region. An increase in tropical moisture is expected today into the
early part of the upcoming week due to the approach of an upper- level
trough and an induce surface trough crossing the region. This pattern
will increase the chance for showers and isolated thunderstorm development
across the coastal waters and U.S. Virgin Islands the rest of the morning
hours, then spreading over the interior and northwestern to northern
sections of Puerto Rico during the afternoon hours.

SHORT TERM...Today through Tuesday...

Satellite and radar imagery indicated partly cloudy conditions overnight,
with isolated to scattered showers moving across the Caribbean local
waters, the U.S. Virgin Islands, and the eastern sectors of Puerto
Rico. Surface observations showed overnight temperatures ranging
from the upper 70s to low 80s along the coasts and valleys, including
the U.S. Virgin Islands, while higher elevations experienced slightly
cooler temperatures in the upper 60s to mid-70s.

During the short-term forecast period, we will have a more conducive
atmosphere for the development of showers and thunderstorms. At the
surface, a weak high-pressure pattern will maintain predominantly
southeast winds, with variations of sea breezes developing each day.
Aloft, the upper ridge is expected to erode as a Tropical Upper
Tropospheric Trough (TUTT) low moves into the local area from the
east. According to the latest precipitable water (PWAT) models,
values are projected to gradually rise today to around 2.0 to 2.1
inches, which is at the high end of the normal range. Therefore,
expect the development of scattered to numerous showers and isolated
thunderstorms today, particularly over the southern slopes and
interior between late morning and late afternoon, gradually
spreading north to northwest as the day progresses, heightening the
risks of flooding, lightning, and gusty winds. Across the U.S.
Virgin Islands, expect the showery weather to continue throughout
the morning hours.

On Monday, patches of drier air are expected to move into the area,
and PWAT values are projected to decrease slightly, ranging from 1.7
to 1.9 inches. Overall, this may somewhat limit the development of
showers; however, daytime heat, local effects, and existing humidity
could still lead to some trade wind showers, with additional
afternoon rain focused on the northwest quadrant of Puerto Rico. On
Tuesday, moisture content is anticipated to increase again to around
2 inches, which should enhance shower and thunderstorm development
early morning hours over the waters and in the afternoon across the
islands. This could lead to flooding in urban areas and small
streams. The potential for thunderstorm development with the
afternoon showers and over the waters will persist throughout this
period, as 500 mb temperatures decrease to around -6 to -7 degrees
Celsius today and remain at that temperature over the next several
days. According to the Galvez-Davidson Index (GDI), we have a
higher chance of observing thunderstorm development today and
Tuesday.

Despite any rain, warm to hot conditions are likely to persist over
the next several days. The 925 mb temperatures are expected to
remain two standard deviations above the normal range today. Highs
are projected to reach the low to mid-90s in coastal, lower-
elevation, and urban areas of the islands, with heat indices
exceeding 100F.

LONG TERM...Wednesday through Sunday...

Based on recent model guidance and the overall weather pattern,
the easterly winds will increase while low level moisture will
continue to erode Wednesday through Thursday. By Friday and
through at least late Saturday or early Sunday, moisture pooling
and low level convergence and instability will increase due to
the approach of a vigorous tropical wave and broad low level
moisture field so far forecast to spread across the region. The
latest layered precipitable water (PWAT) products suggest overall
values to diminish and range between 1.65 to 1.80 inches Wednesday
through Thursday but significantly increasing to between 2.0 to
2.5 inches Friday through Saturday. This along with good ventilation
aloft, will aid in enhancing overnight and afternoon shower development
across the islands and coastal waters during the latter portion of
the period and at least until early Sunday. Overall weather
conditions are expected to improve thereafter with a return of
light to moderate east to southeast winds. The increasing chance
for overnight and afternoon convection Friday through Saturday
will also increase the potential for localized flooding impacts in
urban areas, on roads, and along some rivers and small streams
across Puerto Rico and the U.S. Virgin Islands Friday through
Saturday.

Mostly sunny to partly cloudy skies area expected through Thursday
becoming variably cloudy with a mix of sunshine and clouds by Friday
into the weekend, due to increasing moisture and the approach of the
aforementioned tropical wave. Passing overnight and early morning
showers will remain possible along parts of the east coastal sections
of the islands with afternoon convection expected but mainly focused
across the central interior and west sections of Puerto Rico each
afternoon through Thursday. There is however increasing chance
for more widespread showers across the coastal waters and portions
of the islands Friday through Saturday when the overall weather
conditions are expected to be the most active part of the period.
Meanwhile the driest and hottest period will be Wednesday through
Thursday when a more typical weather pattern is expected with limited
showers and isolated thunderstorms focused mainly over the east coastal
sections, and across the interior and western Puerto Rico during
the afternoon.

AVIATION...
Mainly VFR conditions expected to prevail through the morning
period. SHRA will increase in frequency across the Anegada Passage,
reaching the USVI terminals at times. Periods of reduced VIS and low
ceilings are possible. Around 13/17Z onwards, SHRA and TSRA are
expected over the western Cordillera Central, with some impacts to
operations across TJBQ. General wind flow will remain from the SE at
10 knots or less, stronger gusts may occur near rain and t-storm
activity.

MARINE...
Gentle to moderate east southeast winds will prevail through the
holiday weekend as a weak surface high pressure pattern continues
northeast of the region. Slowly decaying long-period northerly
swells generated from distant storms and areas of low pressure
will continue to affect the local Atlantic waters and passages
over the next few days, promoting hazardous seas.

BEACH FORECAST...
Slowly decaying long-period north northeasterly swells will
continue to reach the local waters from distant storms over the
Atlantic. A High Rip Current Risk remains in effect for the
northwestern, northern, and eastern beaches of Puerto Rico and
Culebra. There is a moderate risk of rip currents for the north
facing beaches of St Thomas and St John and Vieques. For more
details, please refer to the latest Surf Zone Forecast (SRFSJU)
and Coastal Hazard Message (CFWSJU).

&&

.SJU WATCHES/WARNINGS/ADVISORIES...
PR...High Rip Current Risk through late tonight for PRZ001-002-005-
     008-010-012.

     Heat Advisory until 4 PM AST this afternoon for PRZ001-005-008-
     010-011.

VI...High Rip Current Risk until 6 PM AST this evening for VIZ001-002.

AM...Small Craft Advisory until 6 AM AST Monday for AMZ711.

     Small Craft Advisory until noon AST today for AMZ712-741-742.

&&

$$

SHORT TERM...ERG
PUBLIC DESK....MNG

NWS SJU Office Area Forecast Discussion