Prognostic Meteorological Discussion
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FXCA20 KWBC 231113
PMDCA

TROPICAL DISCUSSION - INTERNATIONAL DESKS
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
712 AM EDT TUE SEP 23 2014

PRELIMINARY DISCUSSION FOR PUERTO RICO AND THE USVI. UPPER LEVEL
ANALYSIS SHOWS A RETROGRESSING TUTT LOW WITH CLOSED CIRCULATION
NEAR 24N 56W EARLY THIS MORNING. THIS LOW EXTENDS A SHORT WAVE
TROUGH TO THE SOUTHWEST TO THE NORTHEAST CARIBBEAN. AT LOW
LEVELS...TROPICAL WAVE MOVED ACROSS THE MONA PASSAGE...WITH
TRAILING MOIST PLUME ENVELOPING THE EASTERN CARIBBEAN ISLANDS.
DEEP TUTT IS DRAWING MOISTURE NORTH OF PUERTO RICO...WITH
CONVECTION CLUSTERING TO THE NORTH OF THE FORECAST AREA.

MODELS ARE HAVING A SURPRISINGLY HARD TIME DEALING WITH CURRENT
UPPER FLOW PATTERN...AND THEY MADE MAJOR PATTERN CORRECTIONS OVER
THE LAST COUPLE OF RUNS. THEY NO LONGER FORECAST THE TUTT LOW TO
RETROGRESS NORTH OF PUERTO RICO. INSTEAD...THEY ARE FORECASTING
THE LOW TO REMAIN TO THE NORTHEAST OF THE LEEWARD ISLES WHILE
EXTENDING A SHORT WAVE TROUGH ACROSS THE NORTHEAST CARIBBEAN
ISLES. AT 250 HPA...THE BEST INFLOW OF SHORT WAVE ENERGY IS
EXPECTED ON FRIDAY TO SATURDAY WHEN STRONG CYCLONIC VORTEX RAMS
PUERTO RICO AND THE USVI. THIS...HOWEVER...DOES NOT CARRY OVER TO
MID LEVELS...WHERE MODELS SHOW AN OPEN TROUGH ACROSS THE FORECAST
AREA LATER IN THE WEEK AND WEAK CYCLONIC ROTATION. AT LOW
LEVELS...PREVAILING EASTERLIES RETURN TO THE FORECAST AREA LATER
THIS EVENING. THIS IS TO HOLD THROUGH MIDMORNING ON FRIDAY...WHEN
TUTT INDUCED PERTURBATION IN THE TRADES ENTERS THE FORECAST AREA.
PWAT IS TO PEAK AT 50-60MM THROUGH WEDNESDAY AFTERNOON...AND
AROUND 40-45MM THEREAFTER. THIS SHOULD BE ENOUGH TO FEED
CONVECTIVE DEVELOPMENT ACROSS THE FORECAST AREA.

EVOLVING TUTT PATTERN ALOFT IS TO CONTINUE FAVORING DEEP LAYER
CONVECTIVE INSTABILITY ACROSS THE FORECAST AREA. IN A
SOUTHEASTERLY FLOW...CONVECTION BUILDING ACROSS SAINT CROIX IS TO
THEN STREAM ACROSS THE CARIBBEAN TO HUMACAO/PATILLAS IN SOUTHEAST
PR...TO HELP SUSTAIN MODERATE CONVECTIVE DEVELOPMENT. MOST INTENSE
IS EXPECTED ACROSS NORTHWEST PUERTO RICO DURING THE EARLY
AFTERNOON HOURS...WHERE WE EXPECT LOCALIZED MAXIMA IN EXCESS OF 3
INCHES. AS EASTERLY TRADES RETURN...FOCUS OF THE CONVECTION WILL
SHIFT TO WESTERN INTERIOR PORTIONS OF PUERTO RICO. UNLESS MODELS
MAKE ADDITIONAL CORRECTIONS...LOOKS LIKE FRIDAY AFTERNOON MIGHT BE
THE MOST ACTIVE WITH WIDESPREAD CONVECTION ENVELOPING THE FORECAST
AREA. BUT...THIS IS A BIG IF.

VALVERDE...IMN (COSTA RICA)
MEDINA...ONAMET (REPUBLICA DOMINICANA)
DAVISON...WPC (USA)
$$





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