TROPICAL DISCUSSION - INTERNATIONAL DESKS
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
249 PM EDT THU APR 25 2024

FORECAST BULLETIN 25 APR 2024 AT 1900 UTC: A MID/UPPER TROUGH IS
PROPAGATING EASTWARD ACROSS THE WESTERN USA. AS THIS TROUGH
PRESSES AGAINST AN UPPER RIDGE CENTERING SOUTH OF MEXICO...A
BRANCH OF THE SUBTROPICAL UPPER JET IS BECOMING ENHANCED ACROSS
CENTRAL MEXICO. AS THE TROUGH MOVES EASTWARD...EXPECT FAVORABLE
DYNAMICS FOR PERIODS OF SEVERE CONVECTION IN NORTHEAST MEXICO.
ALTHOUGH THE CORE OF THE EVENT IS EXPECTED TO STAY IN US
TERRITORY...THERE IS A SLIGHT RISK FOR ISOLATED SEVERE
THUNDERSTORMS IN NORTHERN COAHUILA ON THURSDAY...AND ON FRIDAY TO
A LESSER EXTENT.

A STATIONARY FRONT EXTENDS FROM THE NORTH ATLANTIC TO THE
SOUTHEAST BAHAMAS/EASTERN CUBA ON THURSDAY. ASSOCIATED WITH THIS
SYSTEM...A PREFRONTAL TROUGH STRUCTURE EXISTS AHEAD OF THE FRONT
EXTENDING TO HISPANIOLA. BY FRIDAY MORNING...THE FRONT IS EXPECTED
TO START ADVANCING AS A COLD FRONT AGAIN AS A STRONG UPPER LEVEL
TROUGH DRIFTS ACROSS THE EAST COAST OF THE US INTO THE NORTH
ATLANTIC. THUS BY FRIDAY EVENING...EXPECT THE FRONT TO EXTEND
ACROSS THE SOUTHEAST BAHAMAS WHILE STARTING TO ACCELERATE
SOUTHEASTWARD. BY SATURDAY EVENING...EXPECT THE FRONT EXTENDING
SOUTH OF THE TURKS AND CAICOS/INAGUA AND INTO SOUTHEAST CUBA. BY
SATURDAY...EXPECT A SHEAR LINE TRYING TO ORGANIZE ACROSS THE
LEEWARD ISLANDS...ST. CROIX INTO THE CENTRAL CARIBBEAN. BOTH FRONT
AND SHEAR LINE ARE FORECAST TO CONTINUE MEANDERING TO THE
SOUTHEAST ON SUNDAY.

IN TERMS OF RAINFALL ACCUMULATIONS...THE HEAVIEST PRECIPITATION IS
EXPECTED ALONG THE PREFRONTAL TROUGH ON THURSDAY. AS THE TROUGH
INTERACTS WITH TERRAIN IN HISPANIOLA IN A PRECIPITABLE WATER POOL
OF 50-60MM...EXPECT THE POTENTIAL FOR HEAVY RAIN PRODUCING
THUNDERSTORMS. THIS INCLUDES A SLIGHT RISK FOR
SEVERITY...ESPECIALLY IN ELEVATED TERRAIN AND WESTERN PORTIONS OF
THE ISLAND. THROUGH EARLY FRIDAY...EXPECT AMOUNTS OF 25-50MM/DAY
AND MAXIMA OF 75-125MM. THE RISK FOR LOCALLY HEAVY PRECIPITATION
CONTINUES ON FRIDAY GIVEN THE ARRIVAL OF A MOIST PLUME FROM THE
EAST. THIS WILL LIKELY FAVOR 15-20MM/DAY AND MAXIMA OF 40-80MM. ON
SATURDAY...EXPECT A CHANGE IN THE LOW-LEVEL WINDS TO
NORTHEASTERLIES IN RESPONSE TO THE BUILDING OF A POLAR HIGH OFF
THE EAST COAST OF THE USA. AS THE LOW-LEVEL FLOW CHANGES...EXPECT
THE MOIST PLUME TO DRIFT SOUTHWARD ACROSS PUERTO RICO INTO THE
SOUTHEAST CARIBBEAN. THUS...EXPECT A DECREASE IN AMOUNTS IN
HISPANIOLA TO 10-15MM/DAY AND MAXIMA OF 20-35MM. ALSO ON
SATURDAY...THE MOIST PLUME WILL FAVOR AN INCREASE IN AMOUNTS IN
PUERTO RICO TO SUSTAIN 10-15MM/DAY AND MAXIMA OF 20-35MM. SIMILAR
AMOUNTS ARE EXPECTED IN SOUTHEAST CUBA WITH THE FRONT...AS IT
INTERACTS WITH NORTHEASTERN SLOPES OF THE SIERRA MAESTRA.

REGARDING THE WET SPELL IN SOUTHERN CENTRAL AMERICA...MODELS
CONTINUE SHOWING MODERATE RAINFALL AMOUNTS IN COSTA RICA AND
PANAMA AS A TROUGH MEANDERS WESTWARD SLOWLY THROUGH THE
CYCLE...WHILE INTERACTING WITH THE PANAMANIAN LOW. ON
THURSDAY...EXPECT MAXIMA OF 30-60MM IN CENTRAL AND WEST PANAMA.
THIS WILL ALSO FAVOR MAXIMA OF 35-70MM IN WESTERN COLOMBIA. ON
FRIDAY...EXPECT THE HIGHER ACCUMULATIONS IN WEST PANAMA AND IN
EASTERN COSTA RICA...WHERE EXPECT MAXIMA OF 20-45MM. IN EASTERN
PANAMA EXPECT MAXIMA OF 20-35MM. ON SATURDAY...EXPECT MAXIMA OF
35-70MM IN THE PACIFIC BASIN OF SOUTHWEST PANAMA...WHILE IN
CENTRAL PANAMA EXPECT MAXIMA OF 20-35MM. ALSO OF RELEVANCE...AN
EASTERLY WAVE IS PROPAGATING WESTWARD FROM WESTERN VENEZUELA ON
THURSDAY TO TO EASTERN PANAMA BY SATURDAY. THIS WILL FAVOR
MODERATE TO LOCALLY HEAVY AMOUNTS AS IT MOVES ACROSS THE REGION.

GALVEZ/CLARKE/LEDESMA...WPC (USA)