645
FXCA20 KWBC 041824
PMDCA
TROPICAL DISCUSSION - INTERNATIONAL DESKS
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
223 PM EDT THU MAY 04 2023
FORECAST BULLETIN FROM 04 MAY 2023 AT 1500 UTC: UPPER
SOUTHWESTERLY FLOW CONTINUES OVER MEXICO. EMBEDDED IN THIS
FLOW...DISORGANIZED SHORT WAVE PERTURBATIONS ARE PROPAGATING
EASTWARD. DEEP-LAYER MOISTURE CONTINUES CLUSTERED ALONG THE SIERRA
MADRE ORIENTAL AIDED BY TRANSPORT FROM THE GULF OF MEXICO. THIS
WILL FAVOR ISOLATED THUNDERSTORM DEVELOPMENT ON A DAILY BASIS AND
PERIODS OF ISOLATED SEVERE CONVECTION IN NORTHEAST MEXICO. IN
NORTHEAST MEXICO...EXPECT A GRADUAL DECREASE FROM 05-10MM/DAY AND
MAXIMA OF 15-25MM ON THURSDAY...TO 00-05MM/DAY AND MAXIMA OF 10MM
BY FRIDAY. MORE ISOLATED ACTIVITY IS EXPECTED AFTER. YET...IN
CENTRAL AND SOUTHERN PORTIONS OF THE SIERRA MADRE/EASTERN MEXICAN
PLATEAU...EXPECT AN INCREASING TREND AIDED BY A SHORT WAVE TROUGH
ARRIVING FROM THE WEST ON SATURDAY. THIS WILL FAVOR 05-10MM/DAY
AND MAXIMA OF 15-25MM INITIALLY...INCREASING TO MAXIMA OF 20-35MM
BY SATURDAY.
TO THE EAST...A BROAD UPPER TROUGH EXTENDS ALONG THE EAST COAST OF
THE USA INTO CUBA AND THE CAYMAN ISLANDS. THIS TROUGH IS FORECAST
TO MEANDER EASTWARD THROUGH SATURDAY...WHEN ITS AXIS IS FORECAST
ALONG 65-75W INTO PUERTO RICO...LAKE MARACAIBO REGION.
PRECIPITABLE WATER REMAINS BELOW AVERAGE ACROSS MOST OF THE
CARIBBEAN...WHICH IS CONSISTENT WITH THE UPPER CONVERGENT PHASE OF
THE MJO AND ASSOCIATED ACCELERATED EASTERLY TRADES.
HOWEVER...ABOVE AVERAGE MOISTURE IS OCCURRING JUST TO THE NORTH OF
HISPANIOLA INTO THE SOUTHEAST BAHAMAS AND EASTERN CUBA. A SURFACE
FRONT IS PRESENT...AND BY THURSDAY EVENING IT IS EXPECTED ACROSS
THE CENTRAL BAHAMAS...ANDROS ISLAND...SOUTH FLORIDA. THE FRONT IS
FORECAST TO REMAIN CLOSE TO THIS POSITION THROUGH SATURDAY...WHILE
MEANDERING SOUTHWARD VERY SLOWLY. A SHEAR LINE IS FORECAST TO FORM
ON FRIDAY...AND BY FRIDAY EVENING IT IS EXPECTED INTO NORTHEAST
HISPANIOLA...HAITIAN PENINSULA...JAMAICA...WHERE IT IS FORECAST TO
PERSIST INTO SUNDAY MORNING. LIMITED AMOUNTS OF AVAILABLE MOISTURE
WILL LIMIT ACCUMULATIONS WITH THE FRONT. HOWEVER...A PREFRONTAL
TROUGH STRUCTURE WILL FAVOR 05-10MM/DAY AND MAXIMA OF 15-25MM IN
HISPANIOLA ON THURSDAY. SIMILAR AMOUNTS ARE EXPECTED ON FRIDAY IN
ASSOCIATION WITH THE SHEAR LINE. ON SATURDAY
HOWEVER...DESTABILIZATION OF SHEAR LINE CONVECTION BY THE UPPER
TROUGH WILL FAVOR AN INCREASE TO 10-15MM/DAY AND MAXIMA OF 20-45MM
IN NORTHERN AND CENTRAL HISPANIOLA. NOTE POTENTIALLY HIGHER
AMOUNTS ON SUNDAY.
QUIET CONDITIONS ARE ALSO EXPECTED IN MOST OF CENTRAL
AMERICA...WHERE AVAILABLE MOISTURE IS LIMITED. PRECIPITABLE WATER
ANALYSIS SHOWS VALUES BELOW 30MM ACROSS MOST OF THE REGION. MOST
ACTIVITY WILL CLUSTER IN REGIONS OF ENHANCED TRADE WIND
CONVERGENCE...PRIMARILY IN EASTERN COSTA RICA/WESTERN PANAMA AND
SOUTHERN BELIZE/CENTRAL GUATEMALA.
A GRADUAL DRY-TO-WET TRANSITION IS STARTING TO UNRAVEL IN NORTHERN
SOUTH AMERICA. SEVERAL FACTORS ARE IN PLACE. A KELVIN WAVE IS
FORECAST TO ENTER THE REGION ON SATURDAY/SUNDAY...TO PROVIDE
ENHANCED VENTILATION OVER NORTHWESTERN PORTIONS. FURTHERMORE...THE
UPPER TROUGH DEEPENING ACROSS THE CENTRAL CARIBBEAN WILL ALSO
FAVOR A GRADUAL DECREASE IN THE SURFACE PRESSURES IN CENTRAL AND
NORTHERN COLOMBIA...TO FAVOR AN INCREASE IN MOISTURE CONVERGENCE
AS THE CYCLE PROGRESSES. LASTLY...A WEAK TROPICAL WAVE IS
PROPAGATING ACROSS THE ATLANTIC...AND ITS STRUCTURE IS ONLY
CLEARLY VISIBLE AT 700 HPA. THE WAVE IS PROPAGATING OVER A VERY
DRY AIR MASS OVER THE TROPICAL ATLANTIC...BUT IS FORECAST TO FAVOR
AN INCREASE IN MOISTURE CONVERGENCE ONCE IT ENTERS THE GUIANAS.
THIS WILL LEAD TO A GRADUAL INCREASE IN DIURNAL AMOUNTS FROM TRACE
ACCUMULATIONS ON THURSDAY TO 05-10MM/DAY AND ISOLATED MAXIMA OF
15-25MM IN THE GUIANAS BY SATURDAY. MUCH LARGER AMOUNTS ARE
EXPECTED ALONG THE NET IN NORTHERN BRASIL. TO THE WEST...EXPECT A
MORE SIGNIFICANT INCREASE AS THE CYCLE PROGRESSES. IN WESTERN
COLOMBIA...EXPECT ISOLATED CONVECTION ON THURSDAY TO FAVOR MAXIMA
OF 15-25MM...EVOLVING TO SCATTERED CONVECTION BY SATURDAY WHEN
AMOUNTS OF 15-20MM/DAY AND MAXIMA OF 30-60MM ARE FORECAST. IN
ECUADOR...EXPECT AN INCREASE FROM 10-15MM/DAY AND MAXIMA OF
20-45MM TO 15-20MM/DAY AND MAXIMA OF 40-80MM BY SATURDAY.
GALVEZ/ACOSTA/ALAMO...WPC (USA)
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