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FXCA20 KWBC 161822
PMDCA
TROPICAL DISCUSSION - INTERNATIONAL DESKS
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
222 PM EDT FRI APR 16 2021
TROPICAL DISCUSSION FROM APR 16/18 UTC: WEST OVER THE DOMAIN...THE
MID/UPPER LEVEL FLOW SPLITS BETWEEN A RIDGE EXTENDING OVER THE
NORTHERN STATES OF MEXICO/SOUTHWEST USA AND A TUTT TO THE
SOUTH...WITH THE LATTER CENTERING ON A CLOSED LOW TO THE SOUTH OF
COLIMA/NAYARIT IN SOUTHWEST MEXICO. THROUGH SATURDAY THE RIDGE IS
TO COLLAPSE AS POLAR TROUGH AMPLIFIES ACROSS THE WESTERN USA TO
THE NORTHERN STATES OF MEXICO. THE TUTT TO THE SOUTH IS TO THEN
LIFT ACROSS CENTRAL/SOUTHERN MEXICO WHILE SLOWLY PHASING WITH THE
POLAR TROUGH TO THE NORTH. AT LOW LEVELS...AN ELONGATED FRONT IS
TO STRETCH ACROSS THE SOUTHERN USA EARLY IN THE CYCLE. ON SATURDAY
THIS SURGES ACROSS TEXAS/THE RIO BRAVO TO THE NORTHEAST STATES OF
MEXICO WHILE TRIGGERING A PREFRONTAL SHEAR LINE ACROSS VERACRUZ
AND INDUCING A PREFRONTAL TROUGH OVER THE YUCATAN. ON SUNDAY THE
FRONT MOVES FARTHER SOUTH ACROSS TAMAULIPAS TO VERACRUZ...WITH THE
PREFRONTAL TROUGH PERSISTING OVER GUATEMALA/THE YUCATAN WHILE THE
SHEAR LINE BECOMES ILL DEFINED. INITIALLY...LIGHT DIURNAL
CONVECTION IS TO CLUSTER ALONG THE SIERRA MADRE ORIENTAL INTO
CENTRAL MEXICO...WITH RAINFALL AMOUNTS OF 00-05MM/DAY AND MAXIMA
OF 10MM IN AFTERNOON CONVECTION. AS THE FRONT SURGES ACROSS
TAMAULIPAS-COAHUILA ON SATURDAY ACTIVITY INCREASES TO 05-10MM/DAY
AND MAXIMA OF 15-30MM...WHILE OVER VERACRUZ THE PREFRONTAL SHEAR
LINE IS TO SUSTAIN RAINFALL AMOUNTS OF 15-20MM/DAY AND MAXIMA OF
30-60MM. ON SUNDAY THIS WEAKENS TO 05-10MM/DAY AND MAXIMA OF 15MM
WHILE BUILDING SOUTH ACROSS CENTRAL MEXICO. ACTIVITY WITH THE
PREFRONTAL SHEAR LINE OVER THE YUCATAN-TABASCO IS TO LINGER
THROUGH THE WEEKEND...INCREASING FROM 00-05MM/DAY AND MAXIMA OF
10MM ON SATURDAY TO 10-15MM/DAY AND MAXIMA OF 20-30MM ON SUNDAY AS
ENHANCED BY THE REMNANTS OF THE UPPER LEVEL TUTT. THIS IS TO ALSO
FAVOR AN INCREASE ACROSS SOUTHERN GUATEMALA-SOUTHERN HONDURAS/EL
SALVADOR...WITH ACTIVITY INCREASING FROM 05-10MM/DAY AND MAXIMA OF
15MM ON SATURDAY TO 15-20MM/DAY AND MAXIMA OF 25-50MM ON SUNDAY.
DOWNSTREAM OVER THE WESTERN ATLANTIC...A BROAD/LOW AMPLITUDE
TROUGH REMAINS THE DOMINANT FEATURE NORTH OF THE ISLANDS. AT MID
LEVELS...SHORT WAVE PERTURBATIONS ROUNDING THE BASE OF THE TROUGH
ARE TO STREAM ACROSS THE BAHAMAS-NORTHERN HISPANIOLA/PUERTO RICO
DURING THROUGH THIS EVENING. AT 250 HPA A 70-90KT JET MAXIMA IS TO
ACCOMPANY THESE PERTURBATIONS AS THE STREAM TO THE
NORTH...FAVORING WEAK DIVERGENCE ALOFT AS IT SLOWLY RELOCATES
NORTH OF THE ISLANDS. AT LOW LEVELS...A SHALLOW FRONT LIFTS ACROSS
THE NORTHEAST CARIBBEAN TO PUERTO RICO-HISPANIOLA EARLY IN THE
CYCLE...WITH BOUNDARY FORECAST TO FRONTOLIZE EARLY ON SATURDAY
MORNING. AS IT LIFTS ACROSS THE NORTHEAST CARIBBEAN PWAT CONTENT
SURGES TO 35-40MM...THEN RAPIDLY PLUMMETS ON SATURDAY AS A DRYER
AIR MASS ENTRAINS FROM THE EAST. MEANWHILE...THIS WILL FEED
AFTERNOON CONVECTION ACROSS THE DOMINICAN REPUBLIC...PUERTO RICO
AND THE VIRGIN ISLANDS. OVER THE DOMINICAN REPUBLIC EXPECTING
RAINFALL AMOUNTS OF 05-10MM/DAY AND MAXIMA OF 15-30MM...WHILE OVER
PUERTO RICO EXPECTING ACCUMULATION OF 15-20MM/DAY AND MAXIMA OF
25-50MM. LESSER AMOUNTS ARE EXPECTED OVER THE NORTHERN LEEWARD AND
THE VIRGIN ISLES...WITH ACCUMULATION OF 00-05MM/DAY AND MAXIMA OF
10MM.
DURING THE WEEKEND...ENVIRONMENTAL CONDITIONS ACROSS THE NORTHERN
CARIBBEAN WILL QUICKLY GROW HOSTILE TO DEVELOPMENT AS MID/UPPER
LEVEL RIDGE ROLLS FROM THE WEST ACROSS THE BASIN. THE MID LEVEL
RIDGE SETTLES ON A CLOSED HIGH OVER PUERTO RICO/HISPANIOLA ON
SUNDAY-EARLY MONDAY MORNING...THEN RELOCATES TO THE CENTRAL
ATLANTIC. STARTING ON SATURDAY...UNDER THE INFLUENCE OF THIS
RIDGE...THE TRADE WINDS INVERSION ACROSS THE NORTHEAST CARIBBEAN
IS TO STRENGTHEN. AT LOW LEVELS THIS WILL COMBINE WITH A DRY AND
DUSTY SAHARAN AIR LAYER ADVECTING ACROSS THE ISLAND CHAIN TO
GENERALLY FAVOR FAIR WEATHER CONDITIONS. THIS WILL GRADUALLY
SPREAD INTO THE GUIANAS AND VENEZUELA DURING THE WEEKEND/EARLY
NEXT WEEK...WHERE IT IS TO ALSO DAMPEN CONVECTIVE DEVELOPMENT.
MEANWHILE...SOUTHERN CENTRAL AMERICA AND NORTHERN SOUTH AMERICA
WILL LIE UNDER THE INFLUENCE OF AN UPPER LEVEL CELL OF THE
SUBEQUATORIAL RIDGE. THIS IS TO EXTEND WEST ACROSS THE
GUIANAS-VENEZUELA TO COLOMBIA/SOUTHERN CENTRAL AMERICA. THE RIDGE
ALOFT IS TO VENT DIURNAL CONVECTION. EARLY IN THE CYCLE IT
COMBINES WITH AN ATMOSPHERIC KELVIN WAVE STREAMING ACROSS THE
CENTRAL TO THE EASTERN CARIBBEAN TO SUSTAIN THE NORTHWARD
MODULATION OF THE EASTERN PACIFIC ITCZ INTO PANAMA/COSTA
RICA-NORTHWEST COLOMBIA. OVER PANAMA-COSTA RICA THIS IS TO
INITIALLY FAVOR RAINFALL AMOUNTS OF 15-20MM/DAY AND MAXIMA OF
35-70MM. DURING THE WEEKEND...AS THE KELVIN WAVE PULLS AWAY...THIS
DECREASES TO 10-15MM/DAY AND MAXIMA OF 20-40MM. ON THE ANDEAN
REGION OF COLOMBIA INITIALLY EXPECTING RAINFALL AMOUNTS OF
20-30MM/DAY AND MAXIMA OF 40-80MM...DECREASING TO 15-20MM/DAY AND
MAXIMA OF 30-60MM ON SATURDAY. ON SUNDAY IT DROPS TO 10-15MM/DAY
AND MAXIMA OF 20-40MM. LESSER AMOUNTS ARE EXPECTED TO THE NORTH
ACROSS NORTHERN COLOMBIA TO SANTANDERES/MARACAIBO VENEZUELA...WITH
ACCUMULATION OF 05-10MM/DAY AND MAXIMA OF 15-25MM. OVER AMAZONIA
TO THE SOUTH...EXPECTING RAINFALL AMOUNTS OF 10-15MM/DAY AND
MAXIMA OF 20-45MM...WITH LOCALLY HIGHER AS ENHANCED BY IRREGULARLY
SPACED EASTERLY WAVES STREAMING ACROSS BRASIL.
TROPICAL WAVES/TUTT INDUCED PERTURBATIONS/TRADE WIND SURGES
NONE SIGNIFICANT
DAVISON...WPC (USA)
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