Prognostic Meteorological Discussion
Issued by NWS
Issued by NWS
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052 FXCA20 KWBC 071826 PMDCA TROPICAL DISCUSSION - INTERNATIONAL DESKS NWS WEATHER PREDICTION CENTER COLLEGE PARK MD 225 PM EDT TUE MAY 07 2024 FORECAST BULLETIN 07 MAY 2024 AT 1900 UTC: THE PRESENCE OF A PERSISTENT ROBUST MID-LEVEL RIDGE IN SOUTHERN MEXICO WILL CONTINUE TO FAVOR DRY WEATHER CONDITIONS THROUGH THE FORECAST CYCLE. HOWEVER...THE PERSISTENT RIDGE IS FAVORING THE PERSISTENCE OF MID/UPPER TROUGH PATTERN ACROSS THE CENTRAL EASTERN CARIBBEAN. IN AREAS TO THE WEST OF HISPANIOLA...DRY AIR IN THE MID-TROPOSPHERE WILL LIKELY LIMIT ANY SIGNIFICANT PRECIPITATION AMOUNTS. HOWEVER...HISPANIOLA...PUERTO RICO AND THE LEEWARD ISLANDS ARE PRONE TO WETTER CONDITIONS AS THE UPPER DIVERGENT TIER OF THE UPPER TROUGH INTERACTS WITH A WEAK SURFACE FRONT AND A MOIST PLUME THAT IS EXCEEDING 50MM IN TERMS OF PRECIPITABLE WATER AMOUNTS. REGARDING THE POSITIONS OF THE AFOREMENTIONED FRONT...ON TUESDAY EXPECT THE BOUNDARY TO CONTINUE EXTENDING ZONALLY ALONG THE LEEWARD ISLANDS...PUERTO RICO...NORTHERN HISPANIOLA AND SOUTHEAST CUBA. BY WEDNESDAY EVENING EXPECT A WEAKENING OF THE BOUNDARY IN AREAS TO THE WEST OF HISPANIOLA WHILE THE FRONT HOLDS IN AREAS TO THE EAST. BY THURSDAY...EXPECT THE FRONT TO MEANDER NORTHWARD AWAY FROM THE LEEWARD ISLANDS AND PUERTO RICO WHILE WEAKENING. THROUGH WEDNESDAY MORNING...EXPECT 15-20MM/DAY AND MAXIMA OF 30-60MM IN HISPANIOLA...INCLUDING A MARGINAL RISK OF SEVERE CONVECTION. IN PUERTO RICO AND THE LEEWARD ISLANDS EXPECT GENERALLY MAXIMA OF 20-35MM ALSO WITH A MARGINAL RISK FOR SEVERITY. A SHEAR LINE STRUCTURE ACROSS THE SOUTHERN LEEWARD ISLANDS WILL FAVOR ISOLATED MAXIMA OF 15-20MM. ON WEDNESDAY...INTERACTIONS BETWEEN A SHORT WAVE TROUGH AND THE SURFACE FRONT WILL FAVOR MAXIMA OF 20-45MM IN THE LEEWARD ISLANDS...WHILE IN PUERTO RICO AND HISPANIOLA EXPECT MAXIMA OF 20-35MM. NOTE A CONTINUED MARGINAL RISK FOR SEVERE CONVECTION IN PUERTO RICO AND THE LEEWARD ISLANDS. EXPECT A NOTICEABLE DECREASE IN THE COVERAGE AND INTENSITY OF CONVECTION ON THURSDAY. TO THE SOUTH...THE SUBEQUATORIAL RIDGE CONTINUES TO PROVIDE VENTILATION FOR DEEP CONVECTION IN NORTHERN SOUTH AMERICA AND SOUTHERN CENTRAL AMERICA. ADDITIONAL FORCING FOR ASCENT IS OCCURRING IN THE BASE OF THE MID-LEVEL TROUGH LOCATED IN THE CENTRAL CARIBBEAN. THIS...IN COMBINATION WITH EASTERLY WAVES PROPAGATING INTO COLOMBIA WILL FAVOR A SEASONALLY ACTIVE CONVECTIVE REGIME AND MODERATE TO LOCALLY HEAVY PRECIPITATION AMOUNTS IN COLOMBIA AND SOUTHERN CENTRAL AMERICA DURING THE FORECAST CYCLE. MODELS CONTINUE RESOLVING A STREGTHENING OF THE PANAMANIAN LOW CIRCULATION. THEY DO DIFFER IN RESOLVING THE PRECISE EVOLUTION...BUT THEY ARE SUGGESTING A WEAK CENTRAL AMERICAN GYRE (CAG) - LIKE CIRCULATION DEVELOPING NEAR PANAMA WEDNESDAY...WHICH IS THEN FORECAST TO MEANDER WEST INTO THE EASTERN PACIFIC BY FRIDAY. THE PRESENCE OF THE PERSISTENT MID-LEVEL RIDGE OVER MEXICO AND WEST CENTRAL AMERICA WILL LIKELY LIMIT THE MIGRATION OF HEAVY RAIN PRODUCING CELLS INTO AREAS WEST AND NORTH OF NICARAGUA...LIMITING THE WETTER POTENTIAL TO COSTA RICA AND PANAMA. IN TERMS OF ACCUMULATION...THE HEAVIEST PERCIPITATION THROUGH WEDNESDAY MRONING IS EXPECTED IN WESTERN COLOMBIA AND THE DARIEN...WHERE EXPECT MAXIMA OF 50-100MM AND A RISK FOR MCS FORMATION. IN NORTHERN COLOMBIA...AN EASTERLY WAVE WILL TRIGGER MAXIMA OF 30-60MM. BY WEDNESDAY THROUGH EARLY THURSDAY EXPECT MAXIMA OF 50-100MM DEVELOPING IN WESTERN PANAMA...WHILE IN EASTERN PANAMA AND WESTERN COLOMBIA EXPECT MAXIMA OF 40-80MM. BY THURSDAY...AN APPROACHING EASTERLY WAVE WILL AID WITH THE ENHANCEMENT OF ONSHORE FLOW INTO THE MAGDALENA MEDIO. THIS WILL ENHANCE THE RISK FOR NOCTURNAL MCS FORMATION AND POTENTIAL MAXIMA OF 75-125MM. IN NORTHWEST COLOMBIA...CONTINUED ONSHORE FLOW WILL FAVOR MAXIMA OF 30-60MM. IN SOUTHERN COSTA RICA AND MOST OF PANAMA...INTERACTIONS WITH A DISSIPATING EASTERLY WAVE AND THE ENHANCED PANAMANIAN LOW WILL FAVOR MAXIMA GENERALLY IN THE 20-40MM/DAY RANGE. NOTE THAT THERE IS SIGNIFICANT UNCERTAINTY ON THE PRECISE EVOLUTION OF THE PANAMANIAN LOW/WEAK CAG IN SOUTHERN CENTRAL AMERICA BY THURSDAY/FRIDAY...THUS THE LATTER FORECAST IS PRONE TO ADJUSTMENTS. OTHER REGIONS WHERE MODERATE PRECIPITATION IS EXPECTED ARE ALONG THE ITCZ/NET IN NORTHERN SOUTH AMERICA...WHERE PROPAGATING EASTERLY WAVES WILL ALSO PLAY A ROLE. GIVEN ENHANCEMENT OF UPPER DIVERGENT ALONG THE SOUTHERN PERIPHERY OF A CELL OF THE SUBEQUATORIAL RIDGE...EXPECT PERIODS WITH MAXIMA EXCEEDING 2 INCHES/50MM FROM NORTHERN BRAZIL AND FRENCH GUIANA INTO SOUTHERN VENEZUELA. GALVEZ/CLARKE/LEDESMA...WPC (USA) $$