National Weather Service San Juan PR
507 AM AST Mon Dec 19 2022
.SYNOPSIS...
Hazardous marine and coastal conditions will continue today. A
surface high pressure across the Central Atlantic Ocean will bring
the moisture of the remnants of a modified old frontal boundary
(as a backdoor front), increasing the chance of rain across the
Caribbean Sea. The moisture will slowly drift northward
approaching the islands from the southeast and increasing the
chance for showery weather on Tuesday.
&&
.SHORT TERM...Today through Wednesday...
Although an upper-level short-wave trough with axis just east of the
local islands is present, the mid-level ridge continues to dominate
the weather pattern aloft. This has caused a trade wind cap at 700
mb to persist with mostly dry and stable weather conditions above
this layer. At low-levels, GOES-16 Precipitable Water imagery shows
values between 0.8 to 1.15 inches across the CWA, which is well
below normal to near normal levels for this time of year. This
weather pattern has promoted mostly fair weather conditions across
the islands with very few passing showers over the local waters
moving inland across coastal areas at times. Expect similar weather
conditions to continue today with a slight increase in showers over
eastern coastal areas of the islands during morning hours as the
area with highest moisture content moves in. Diurnally induced
isolated to scattered showers are forecast to develop over interior
and western portions of Puerto RIco during the afternoon.
For the rest of the short-term period, ridging aloft will persist
inhibiting any potential for deep convective development in the next
few days. However, low- to mid-level moisture content will gradually
increase starting tonight, eroding somewhat the trade wind cap
currently present. This will promote mostly shallow convective
activity for the latter part of the forecast period. Satellite
imagery and Doppler radar show a southwest-to-northeast oriented
band of clouds and showers associated with the remnants of an old
frontal boundary over the Caribbean waters and east of the local
islands. A surface high pressure over the central Atlantic is
forecast to slowly steer the remnants of the frontal boundary
towards the CWA. As steering winds prevail out of the northeast, a
cool advective pattern will promote showery weather by late tonight
into early Tuesday morning. Scattered to numerous showers will
affect the eastern and northern sections of Puerto Rico and U.S.
Virgin Islands during these hours. Later in the afternoon, surface
heating and local effects along with sea breeze convergence will
enhance shower development across western/southwestern Puerto Rico.
Ponding of water in roads and poorly drained areas are anticipated
with this activity. Urban and small stream flooding could be
possible in a few locations.
On Wednesday, winds will shift more out of the east/southeast. Model
guidance suggests a similar weather pattern as the remnants of the
frontal boundary linger. Therefore, expect cloudy skies and shower
development to persist across the islands, with eastern and southern
Puerto Rico to be affected this time during the morning hours and
later developing across interior and western/northwestern Puerto
Rico.
&&
.LONG TERM...Thursday through Monday...
The advective pattern will extend into the second part of this
week as the easterlies push patches of moisture with clouds and
showers across the Northeast Caribbean. A short wave trough (at
upper levels) east of the Lesser Antilles will induce trade wind
perturbations, enhancing the showers' frequency across the U.S.
Virgin Islands and Puerto Rico by Friday through the weekend.
However, model guidance shows dry air at mid and upper levels over
the local islands, so organized convection is not anticipated,
just shallow convection. That said, cold air advection across
warmer waters will promote the typical passing showers overnight
and early in the morning across E-PR/USVI, followed by limited
afternoon convection across PR's interior and western sections.
The remnants of a cold front approaching the northeast Caribbean
(remaining off to the north over the Atlantic Ocean) will induce
pre-frontal troughs near PR/USVI promoting showery weather.
Although pesky rains will affect the region, none of the guidance
indicates significant rainfall amounts through the long-term
forecast. However, ponding of water in roadways and poorly
drained areas may be possible.
&&
.AVIATION...
(06Z TAFS)
Issued at 455 AM AST Mon Dec 19 2022
VFR conditions across the local terminals, with VCSH at times for
JSJ/IST/ISX through 19/14z. SHRA is expected across the Caribbean
and near ISX during the afternoon, and later affecting JSJ/IST after
19/23z. The land breeze will prevail through 19/13z. Then, expect
E/NE winds at 10-15 kt with higher gusts and sea breeze
variations.
&&
.MARINE...
Hazardous marine and coastal conditions will continue through
this week as pulses of northerly swells move across the local
Atlantic waters and passages. The wind will be moderate to locally
fresh from the east through much of the week, increasing during
the weekend.
Small Craft Advisories, as well as High Surf Advisories and High
Rip Current Risk Statements remain in effect. Refer to the latest
Marine Weather message (MWWSJU), Coastal waters Forecast (CWFSJU)
and Coastal Hazard Message (CFWSJU) issued by WFO san Juan PR for
the latest updates and info.
Last night the ASCAT showed a broad area of Gale force winds
across the West European Basin of the Northern Atlantic,
foreshadowing a long period swell that will arrive next weekend.
This will further continue the trend of high seas and surf across
the local waters and coastlines. Stay tuned for further updates.
&&
.SJU WATCHES/WARNINGS/ADVISORIES...
PR...High Rip Current Risk through Tuesday afternoon for PRZ001-002-
005-008-010-012-013.
High Surf Advisory until 6 PM AST Tuesday for PRZ001-002-005-008-
012.
High Surf Advisory until 6 PM AST this evening for PRZ010.
VI...High Rip Current Risk through Tuesday afternoon for VIZ001-002.
High Surf Advisory until 6 PM AST this evening for VIZ001-002.
AM...Small Craft Advisory until 2 PM AST Tuesday for AMZ710-741.
Small Craft Advisory until 2 PM AST this afternoon for AMZ712-
715-722-732-742.
&&
$$
CAM, CVB