977
FXCA20 KWBC 301215
PMDCA
TROPICAL DISCUSSION - INTERNATIONAL DESKS
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
715 AM EST FRI DEC 30 2022
..NEXT ON TUESDAY 3 JANUARY 2023
PRELIMINARY DISCUSSION FOR PUERTO RICO AND THE USVI FROM DEC
30/12UTC: IN THE UPPER LEVELS...A TROUGH EXTENDS ACROSS THE
LEEWARD ISLANDS INTO THE ABC ISLANDS. THIS IS DESTABILIZING THE
MARINE LAYER...WHICH IS RESULTING IN SOME VERTICAL DEVELOPMENT IN
TRADE WIND CONVECTION PROPAGATING FROM THE EAST. SATELLITE IMAGERY
SHOWS CLUSTERS OF TRADE WIND CONVECTION PROPAGATING WESTWARD
ACROSS THE VI...AND RADAR CONFIRMS MODERATE PRECIPITATION IN THE
NORTHERN VI AND CULEBRA. SATELLITE DATA INDICATE THAT THESE CELLS
HAVE CLOUD TOP TEMPERATURES NEAR FREEZING AND LOCALLY COOLER.
CONSIDERING OBSERVED AND GFS MODEL SOUNDINGS...IT APPEARS THAT THE
STRONGEST CELLS ARE ABLE TO GROW TO NEAR 500 HPA. YET...DRY AIR
ENTRAINMENT BECOMING IMPORTANT ONCE CELLS GROW OVER THE 700 HPA
LEVEL ARE LIMITING THE COVERAGE OF PRECIPITATING CLOUD CLUSTERS.
MODELS SHOW THE CURRENT UPPER TROUGH MEANDERING WESTWARD WHILE
WEAKENING ON FRIDAY. YET...AS A MID-UPPER RIDGE BUILDS OVER THE
NORTHWEST CARIBBEAN...NORTHERLY FLOW ALONG ITS EASTERN PERIPHERY
WILL ADVECT COOL AIR AND ENHANCE THE AMPLIFICATION OF THE TROUGH
OVER THE EASTERN CARIBBEAN. THIS WILL CONTINUE TO DESTABILIZE THE
MARINE LAYER...PRIMARILY EAST OF THE LEEWARD ISLANDS...ALLOWING
FOR DEEPER TRADE WIND CONVECTION AND HIGHER RAINFALL RATES THAN
NORMALLY EXPECTED FOR THIS TIME OF THE YEAR. THIS IS TRUE
PRIMARILY FOR FRIDAY AND SATURDAY...AND SUNDAY TO A LESSER EXTENT.
THE TROUGH LIFTS ON MONDAY WHICH LEADS TO SOME STABILIZATION AND
DRYING. YET...ANOTHER TROUGH MOVES IN RAPIDLY FROM THE NORTH ON
TUESDAY TO FAVOR UPPER DIVERGENCE ON TUESDAY AND WEDNESDAY.IN THE
LOW-LEVELS...EASTERLY TRADES DURING THE WEEKEND ARE FORECAST TO
SHIFT TO NORTHEASTERLIES ON MONDAY...AS A LOW-LEVEL RIDGE
STRENGTHENS TO THE NORTHWEST. THE NORTHEASTERLY TRADES WILL SHIFT
THE LOCATION OF AFTERNOON CONVECTION TO SOUTHWEST PUERTO
RICO...WHILE MORNING CONVECTION FOCUSES ON NORTHEAST PUERTO RICO.
AS THE UPPER TROUGH ENHANCES UPPER DIVERGENT AND ASCENT ON
TUESDAY/WEDNESDAY...IT WILL POTENTIALLY COINCIDE WITH THE ARRIVAL
OF A SHEAR-LINE STRUCTURE. MODELS ARE STILL STRUGGLING ON THIS
EVOLUTION...BUT THE POTENTIAL FOR MODERATE PRECIPITATION IN
NORTHEAST PUERTO RICO IN TUESDAY/WEDNESDAY SHOULD BE MONITORED.
IN THE MEANTIME...EASTERN AND NORTHEASTERN PUERTO RICO SHOULD
REMAIN UNSEASONABLY WET ON A DAILY BASIS STARTING TODAY...WHEN
EXPECT MAXIMA OF 0.4-0.7 INCHES AND ISOLATED HIGHER AMOUNTS IN EL
YUNQUE. EXPECT ACTIVITY TO EXPAND INTO NORTH-CENTRAL PUERTO RICO
AND SOME AFTERNOON DEVELOPMENT IN THE SOUTHWEST CORDILLERA WHERE
EXPECT MAXIMA OF 0.5-0.75 INCHES. ON SATURDAY AND SUNDAY...THE
LARGEST AMOUNTS ARE EXPECTED TO CLUSTER IN NORTHEAST PUERTO RICO
AND VIEQUES WHERE EXPECT MAXIMA OF 0.3-0.5 INCHES. AFTERNOON
CONVECTION IN THE WESTERN CORDILLERA WILL FAVOR ISOLATED MAXIMA OF
0.2-0.4 INCHES. A GENERAL DECREASE IN AMOUNTS IS EXPECTED ON
MONDAY. ON TUESDAY...A NOTICEABLE INCREASE IN ACCUMULATIONS IS
EXPECTED. YET...THERE IS UNCERTAINTY ON THE RAINFALL TOTALS. AT
THE MOMENT THE FORECAST INDICATES MAXIMA OF 0.3-0.4 INCHES IN MOST
OF NORTHERN AND EASTERN PUERTO RICO...AND MAXIMA OF 0.5-0.75
INCHES IN NORTHEAST PUERTO RICO.
GALVEZ...WPC (USA)
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