761
FXCA20 KWBC 211931
PMDCA
TROPICAL DISCUSSION - INTERNATIONAL DESKS
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
231 PM EST THU DEC 21 2023
FORECAST BULLETIN 21 DEC 2023 AT 1930 UTC: A POTENT UPPER TROUGH
IS ROTATING OFF THE COAST OF SOUTHERN CALIFORNIA AND IS FORECAST
TO MOVE EAST TO EXTEND ALONG THE EASTERN ROCKY MOUNTAINS BY
SATURDAY. THIS POTENT TROUGH IS ACCOMPANIED BY A SURFACE FRONT
THAT IS FORECAST TO ENTER FAR NORTHWEST MEXICO LATE ON THURSDAY
EVENING. BY FRIDAY EVENING THE FRONT IS FORECAST ALONG SOUTHWEST
NEW MEXICO...CENTRAL SONORA...SOUTH-CENTRAL BAJA CALIFORNIA. BY
SATURDAY EVENING EXPECT IT ALONG WEST TEXAS...SOUTHERN
CHIHUAHUA...JUST SOUTH OF CABO SAN LUCAS. NOTE THAT THIS WILL
FAVOR 15-30KT DOWNSLOPING WINDS IN THE LEE OF THE SIERRA
TARAHUMARA PARTICULARLY ON SATURDAY AFTERNOON/EVENING. IN TERMS OF
PRECIPITATION...ON THUSDAY EXECT 10-15MM/DAY AND MAXIMA OF 20-40MM
DEVELOPING ALONG WESTERN SLOPES OF THE SIERRA SAN PEDRO MARTIR AND
ISOLATED MAXIMA OF 15-25MM TO THE EAST. ON FRIDAY...EXPECT
10-15MM/DAY AND MAXIMA OF 20-40MM IN NORTHERN SONORA...INCLUDING A
MARGINAL RISK FOR SEVERE CONVECTION. REMAINING ONSHORE FLOW WILL
FAVOR 05-10MM/DAY AND MAXIMA OF 15-30MM ALONG THE WESTERN SLOPWS
OF THE SIERRA SAN PEDRO MARTIR. ON SATURDAY EXPECT MAXIMA OF 15MM
DEVELOPING IN NORTHERN COAHUILA AND ALONG WESTERN SLOPES OF THE
SIERRA MADRE OCCIDENTAL FROM NORTHERN CHIHUAHUA INTO NORTHERN
SINALOA.
ANOTHER FRONT AND A SHEAR LINE CONTINUE EXTENDING ACROSS THE
LESSER ANTILLES INTO THE CARIBBEAN BASIN OF CENTRAL AMERICA. ON
THURSDAY EXPECT A STATIONARY FRONT ACROSS SOUTHERN
HISPANIOLA...JAMAICA...NORTHEAST HONDURAS WHILE THE SHEAR LINE
EXTENDS ALONG PUERTO RICO...PROVIDENCIA...NORTHEAST COSTA RICA. ON
FRIDAY...EXPECT THE FRONT TO REMAIN STATIONARY WHILE THE SHEAR
LINE EXTENDS JUST SOUTH OF JAMAICA INTO SOUTHEAST NICARAGUA...TO
THEN DISSIPATE. BY SATURDAY...EXPECT A DISSIPATING FRONT JUST
SOUTH OF HISPANIOLA...JUST SOUTH OF JAMAICA...INTO NORTHEAST
HONDURAS. INITIALLY...ENHANCED MOISTURE CONVERGENCE WILL DAVOR
MAXIMA OF 25-50MM IN NORTHERN HISPANIOLA. SIMILAR AMOUNTS ARE
EXPECTED IN NORTHEAST COSTA RICA/SOUTHEAST NICARAGUA WITH THE
SHEAR LINE. IN THE CARIBBEAN ISLANDS OF SAN ANDRES PROVIDENCIA
INTO EAST HONDURAS EXPECT MAXIMA OF 15-30MM. ON FRIDAY...EXPECT
MAXIMA OF 20-45MM IN NORTH COSTA RICA AND SOUTHEAST NICARAGUA WITH
THE SHEAR LINE. IN NORTHEAST NICARAGUA AND EAST HONDURAS EXPECT
MAXIMA OF 15-30MM WITH THE FRONT AND SHEAR LINE...WHILE IN JAMAICA
AND PUERTO RICO EXPECT MAXIMA OF 15MM. CONTINUED ONSHORE FLOW IN
NORTHERN HISPANIOLA WILL FAVOR 05-10MM/DAY AND MAXIMA OF
15-25MM...WHILE IN THE ATLANTIC SIDE OF EASTERN CUBA EXPECT MAXIMA
OF 15MM. ON SATURDAY...EXPECT MAXIMA OF 15-30MM IN NORTHEAST
HONDURAS/NICARAGYA...WHILE ACCUMULATIONS DECREASE ELSEWHERE.
A FRONTAL SHEAR LINE IS DISSIPATING ACROSS THE WINDWARD AND ABC
ISLANDS ON THURSDAY. STILL...THIS WILL FAVOR SCATTERED AMOUNTS OF
05-10MM/DAY AND MAXIMA OF 15MM IN THE ABC ISLANDS THROUGH EARLY
FRIDAY. NEVERTHELESS...AVAILABLE MOISTURE IS EXPECTED TO REMAIN
CLOSE TO 500MM OF PRECIPITABLE WATER THROUGH EARLY SUNDAY. THIS
WILL FAVOR SCATTERED SHOWERS ON FRIDAY AND SATURDAY IN MOST OF THE
LESSER ANTILLES TO FAVOR MAXIMA OF 15MM.
IN NORTHERN SOUTH AMERICA...THE NORTHERN DIVERGENT QUADRANT OF THE
BOLIVIAN HIGH CONTINUES WELL ESTABLISHED OVER THE WESTERN
AMAZON/PERU/ECUADOR. THIS WILL PROVIDE VENTILATION ON A DAILY
BASIS. ITCZ CONVERGENCE IS EXPECTED TO FAVOR MODERATE TO HEAVY
PRECIPITATION IN SOUTHWEST COLOMBIA AND NORTHWEST ECUADOR ON A
DAILY BASIS. INITIALLY EXPECT MAXIMA OF 20-40MM. YET...ON
FRIDAY...AN INCREASE IN THE WESTERLY COMPONENT OF LOW-LEVEL WINDS
WILL LIKELY INCREASE MOISTURE CONVERGENCE AND FAVOR AN INCREASE TO
AMOUNTS OF 15-30MM/DAY AND MAXIMA OF 40-80MM WITH A RISK OF MCS
FORMATION. ON SATURDAY EXPECT MAXIMA OF 35-70MM. IN THE WESTERN
AMAZON FROM 65W INTO THE ANDES...EXPECT MAXIMA OF 30-60MM ON BOTH
THURSDAY AND FRIDAY. THIS DECREASES TO MAXIMA OF 20-45MM ON
SATURDAY. NOTE THAT ISOLATED HIGHER AMOUNTS ARE ALWAYS POSSIBLE.
COLOMBIA WILL CONTINUE TO EXPERIENCE ABOVE AVERAGE CONVECTION AND
PRECIPITATION PRIMARILY ALONG THE ANDEAN REGION AND VELLES...GIVEN
UNUSUALLY LARGE AMOUNTS OF AVAILABLE MOISTURE AND FAVORABLE
VENTILATIONO IN THE UPPER TROPOSPHERE. THIS WILL FAVOR MAXIMA IN
THE 15-30MM/DAY RANGE ON A DAILY BASIS...ALHTOUGH THE LARGER
AMOUNTS ARE LIKELY TO CLUSTER IN THE EJE CAFETERO REGION.
POSITIONS OF TROPICAL/EASTERLY WAVES INITIALIZED AT 12 UTC
NONE
GALVEZ...WPC (USA)
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