TROPICAL DISCUSSION - INTERNATIONAL DESKS
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
715 AM EDT TUE JUN 18 2013

PRELIMINARY DISCUSSION FOR PUERTO RICO AND THE USVI. FORECAST AREA
REMAINS UNDER INFLUENCE OF A TUTT THAT EXTENDS SOUTH FROM A CLOSED
LOW NORTH OF THE ISLANDS...ACROSS PUERTO RICO TO THE EASTERN
CARIBBEAN. THE TROUGH IS ENHANCING ITCZ RELATED CONVECTION ACROSS
THE WINDWARD ISLANDS WHILE ALSO INTERACTING WITH A TROPICAL WAVE
PROPAGATING ALONG THE CONVERGENCE ZONE/THE GUIANAS. PUERTO RICO
AND THE USVI...MEANWHILE...LIE ON THE CONVERGENT/SUBSIDENT SIDE OF
THIS FEATURE.

BUILDING CELL OF THE SUBEQUATORIAL RIDGE IS TO DISPLACE TUTT TO
THE WEST...WITH AXIS TO RELOCATE TO HISPANIOLA LATER ON WEDNESDAY
EVENING. AS THE TROUGH PULLS AWAY...ENVIRONMENTAL CONDITIONS ARE
TO BECOME MORE CONDUCIVE TO DEEP CONVECTION...WITH MODEL GUIDANCE
SHOWING AN UPPER DIVERGENT PATTERN ESTABLISHING ACROSS THE
NORTHEAST CARIBBEAN ISLANDS. THIS IS TO COINCIDE WITH ARRIVAL OF
TROPICAL WAVE...EXPECTED TO ENTER THE VIRGIN ISLES AROUND 00UTC ON
THURSDAY...CROSSING THE MONA PASSAGE TO EASTERN HISPANIOLA THROUGH
12UTC. AS THEY INTERACT...PWAT IS TO INCREASE TO 40-50MM DURING
THE DAY ON WEDNESDAY. BUT FOLLOWING WAVE PASSAGE THIS IS TO
QUICKLY ERODE AS A LOW LEVEL CAP INVERSION DEVELOPS THROUGH THE
DAY ON THURSDAY.

GLOBAL GUIDANCE DIVERGE ON IMPACT THIS IS GOING TO HAVE ACROSS
FORECAST AREA. THE GFS APPEARS AS THE MOST ACTIVE...WHILE THE
UKMET AND ECMWF APPEAR SOMEWHAT MORE CONSERVATIVE ON THEIR
RAINFALL AMOUNTS. CONSIDERING THE POSITIVE INTERACTION WITH UPPER
TUTT AND EFFECTS OF DAYTIME HEATING...WE ARE LEANING TOWARDS THE
WETTER GFS SOLUTION. AS A RESULT...EXPECTING RAINFALL AMOUNTS OF
10-15MM AND MAXIMA OF 20-45MM...WITH MOST INTENSE TO CLUSTER
ACROSS THE VIRGIN ISLES-EASTERN PUERTO RICO (LUQUILLO TO HUMACAO).
NIGHTTIME CONVECTION IS LIKELY TO THEN AFFECT SOUTH COAST OF
PUERTO RICO AS THE WAVE PULLS ACROSS THE BASIN. IF THE WAVE HAS AS
MUCH VORTICITIY AS THE GFS IS SUGGESTING...CONSIDER POTENTIAL FOR
MCS FORMATION OVER THE MONA PASSAGE DURING EARLY MORNING HOURS ON
THURSDAY.

MCKENZIE...BDM (BAHAMAS)
ROBINSON...MSJ (JAMAICA)
DAVISON...WPC (USA)