117
FXCA20 KWBC 091421
PMDCA
TROPICAL DISCUSSION - INTERNATIONAL DESKS
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
921 AM EST THU JAN 09 2025
WEEKLY DISCUSSION FOR PUERTO RICO AND THE USVI JAN 09 14 UTC:
THE ANALYSIS OF EQUATORIAL WAVES SHOWS A VERY DISORGANIZED MJO
SIGNAL ACROSS THE GLOBE. NEVERTHELESS... A KELVIN WAVE IS EXPECTED
TO ENTER THE CARIBBEAN EARLY NEXT WEEK. CONSIDERING THE PRESENCE
OF A ROBUST AND EXTENSIVE MID-LEVEL RIDGE AND ASSOCIATED TRADE
WIND CAP EXTENDING ACROSS THE ENTIRE CARIBBEAN...EXPECT LIMITED
EFFECTS FROM THIS KELVIN WAVE IN THE ENHANCEMENT OF CONVECTION AND
PRECIPITATION.
A POTENT UPPER TROUGH IS CURRENTLY LOCATED IN THE NORTH ATLANTIC
BETWEEN NEW FOUNDLAND AND ICELAND. THIS TROUGH IS RESPONSIBLE FOR
THE ARCTIC OUTBREAK IN THE UNITED STATES AND IS CURRENTLY
SUSTAINING AN ELONGATED FRONT THAT EXTENDS INTO NORTHERN
HISPANIOLA AND AS FAR SOUTH AS NICARAGUA/COSTA RICA. THE CURRENT
PATTERN OF STRONG POLAR MID-UPPER TROUGHS AND EXTENSIVE FRONTS IN
THE NORTH ATLANTIC AND CARIBBEAN IS CONSISTENT WITH A PERSISTENTLY
NEGATIVE NORTH ATLANTIC OSCILLATION (NAO). THE NAO IS EXPECTED TO
REMAIN NEGATIVE THROUGH EARLY NEXT WEEK...FAVORING A PERSISTENCE
OF THE PATTERN AND RECURRENCE OF EXTENSIVE COLD FRONTS IN THE
NORTHWEST ATLANTIC AND NORTHERN CARIBBEAN THROUGH MID-LATE NEXT
WEEK. MODELS SUGGEST THE NAO BECOMING POSITIVE AFTER JANUARY 17TH
OR LATE NEXT WEEK...WHICH COULD YIELD TO A CHANGE IN PATTERN INTO
A WARMER ONE FOR THE NORTHEAST CARIBBEAN.
THE ANALYSIS OF SATELLITE DATA SHOWS THAT THE FRONT CURRENTLY
PROPAGATING ACROSS HISPANIOLA HAS LIMITED CLOUDINESS ASSOCIATED
WITH IT. THIS IS PARTLY IN RESPONSE TO LIMITED AMOUNTS OF
AVAILABLE MOISTURE IN THE TROPOSPHERE...AND TO THE PRESENCE OF A
MID-LEVEL RIDGE AND ASSOCIATED STABLE LAYER. THE ANALYSIS OF THE
MID-LEVELS SHOWS A RIDGE AXIS EXTENDING ZONALLY FROM AN
AITICYCLONE IN BELIZE INTO THE LEEWARD ISLANDS. THE INTERNATIONAL
DESKS' TWIN ALGORITHM SHOWS A STABHLE LAYER LOCATED NEAR 700-750
HPA OVER PUERTO RICO...AND NEAR 800-850 HPA OVER THE VI. THIS IS
CONFIRMED BY THE SAN JUAN SOUNDING...WHICH SUGGESTS THE PRESENCE
OF SUBSIDENCE IN THE MID TROPOSPHERE...AND IS ALSO CONSISTENT WITH
STRATIFORM SIGNATURES IN SATELLITE DATA.
REGARDING THE FORECAST...EXPECT VERY LIMITED PRECIPITATION AMOUNTS
THROUGH MID/LATE NEXT WEEK GIVEN ENHANCED STABILITY IN THE MID-LOW
TROPOSPHERE AND LIMITED AMOUNTS OF AVAILABLE MOISTURE. MOST
PRECIPITATION WILL ORGANIZE WITH THE PASSAGE OF THE SURFACE FRONTS
AND WILL PERSIST FOR SEVERAL HOURS MAINLY IN NORTHERN PUERTO
RICO...DUE TO THE INFLUENCE OF NORTHEASTERLY LOW-LEVEL WINDS. THE
EXPECTED STRENGTHENING OF THE MID-LEVEL RIDGE AND DECREASE OF
AVAILABLE MOISTURE THROUGH NEXT WEEK WILL FAVOR VERY CONSERVATIVE
RAINFALL AMOUNTS. GFS/RAOB INTERCOMPARISON DATA SHOWS PRECIPITABLE
WATER VALUES PLUMMETING TO AMOUNTS WELL BELOW THE NORMAL STARTING
ON FRIDAY...REACHING A MINIMA FROM SATURDAY THROUGH SUNDAY. THE
CURRENT FRONT IS EXPECTED TO ARRIVE IN PUERTO RICO ON THURSDAY
AFTERNOON...YIELDING TO AN INCREASE IN THE COVERAGE OF SHOWERS
THIS AFTERNOON...LASTING THROUGH FRIDAY MORNING ALONG THE NORTH
COAST OF PUERTO RICO...AND EXTENDING INTO INTERIOR PORTIONS OF
NORTHERN PUERTO RICO THROUGH FRIDAY AFTERNOON. EXPECT MAXIMA OF
0.5-0.75 INCHES IN THE CORDILLERA AND MAXIMA OF 0.2-0.4 INCHES
ALONG THE NORTH COAST OF PUERTO RICO. SHOWER ACTIVITY WILL
GRADUALLY WANE LEADING TO VERY LITTLE OR NO PRECIPITATION ON
SUNDAY.
THE NEXT FRONTAL PASSAGE IS POSSIBLE LATE SUNDAY INTO MONDAY.
EXPECT LITTLE PRECIPITATION WITH THE FRONT ITSELF...BUT ENHANCED
TRADE WIND SHOWERS IN VERY SHALLOW CONVECTION IN THE POST FRONTAL
AIR MASS ON MONDAY. THIS WILL LIKELY FAVOR MAXIMA GENERALLY UNDER
0.25 INCHES ALONG THE NORTH COAST OF PUERTO RICO MOSTLY ON MONDAY
MORNING...EXTENDING INTO TUESDAY MORNING. A THIRD FRONT IS
EXPECTED TO ARRIVE SOMETIME BETWEEN WEDNESDAY AND THURSDAY NEXT
WEEK BUT THE PRECISE TIMING IS NOT CERTAIN AT THIS POINT. THIS
SYSTEM WILL LIKELY PRODUCE HIGHER AMOUNTS THAN THE MONDAY MORNING
SYSTEM. HOWEVER...LIMITED AVAILABLE MOISTURE WILL STILL FAVOR
CONSERVATIVE MAXIMA...EXPECTED GENERALLY UNDER 0.4 INCHES ALONG
NORTHERN PUERTO RICO.
GALVEZ...WPC(USA)
CLICK HERE TO GO TO PREVIOUS BULLETINS.
Main Text Page