TROPICAL DISCUSSION - INTERNATIONAL DESKS
NWS HYDROMETEOROLOGICAL PREDICTION CENTER CAMP SPRINGS MD
732 AM EST MON FEB 13 2012
 
PRELIMINARY DISCUSSION FOR PUERTO RICO AND THE USVI. UPPER LEVEL
ANALYSIS SHOWS BUILDING RIDGE ACROSS THE CENTRAL/EASTERN
USA...WHILE A DEEP TROUGH EXTENDS ACROSS THE WESTERN ATLANTIC TO
ABOUT 23N. THIS IS PRESSING AGAINST A WEAK CELL OF THE
SUBEQUATORIAL RIDGE OVER THE CARIBBEAN BASIN/NORTHERN SOUTH
AMERICA. AT LOW LEVELS...POLAR FRONT EXTENDS ALONG 24N
60W...NORTHERN HISPANIOLA-JAMAICA TO NORTHERN HONDURAS. A
PREFRONTAL SHEAR LINE PRECEDES THIS BOUNDARY AS IT EXTENDS ACROSS
THE MONA PASSAGE/EASTERN HISPANIOLA TO SOUTHERN NICARAGUA/COSTA
RICA. PWAT ANALYSIS SHOWS MOISTURE CONVERGING ALONG THIS BOUNDARY
AS IT MOVES ACROSS HISPANIOLA TO THE NORTHEAST CARIBBEAN.

AT UPPER LEVELS...MODELS SHOWING RIDGE PATTERN STRENGTHENING
ACROSS CENTRAL AMERICA/WESTERN CARIBBEAN TO GULF OF MEXICO DURING
THE NEXT THREE DAYS. THIS...IN-TURN...IS INDUCING SOUTHWARD
AMPLIFICATION OF A TROUGH OVER AND EAST OF THE LESSER
ANTILLES...WITH AXIS TO GRADUALLY STRETCH TO THE WEST/SOUTHWEST
ALONG NORTHERN VENEZUELA. AS THE TROUGH AMPLIFIES...BEST INFLOW OF
SHORT WAVE ENERGY IS GOING TO BE ACROSS THE ISLAND CHAIN/NORTHEAST
VENEZUELA...WITH MODELS THEN SHOWING UPPER PERTURBATION ENTERING
NORTHEAST CARIBBEAN ISLES LATER ON FRIDAY. ALSO AT UPPER
LEVELS...THE BUILDING RIDGE WILL REPOSITION SUBTROPICAL JET
MAXIMA...WITH ITS RIGHT (CONVERGENT) EXIT REGION TO MOVE JUST
NORTH OF PUERTO RICO LATER TODAY/EARLY TOMORROW MORNING. THE
UNFAVORABLE UPPER ENVIRONMENT WILL THEN PERSIST DURING THE NEXT
FEW DAYS.

AT MID LEVELS... RIDGE PATTERN EXTENDS ACROSS THE BASIN AS IT
ORIGINATES ON A CLOSED HIGH OVER CENTRAL AMERICA/WESTERN
CARIBBEAN. MODELS SHOW GRADUAL INTENSIFICATION OF THIS RIDGE
THROUGH WEDNESDAY AFTERNOON...WHEN RIDGE PATTERN REACHES MAXIMUM
AMPLITUDE. AS IT STRENGTHENS...A STRONG SUBSIDENCE CAP IS TO
QUICKLY ESTABLISH ACROSS THE NORTHEAST CARIBBEAN ISLANDS. AT LOW
LEVELS...SURFACE FRONT WILL STALL TO THE NORTH OF 21N/22N LATER
THIS EVENING...WHILE FRONTAL SHEAR LINE MOVES ACROSS PUERTO RICO
TO THE VIRGIN ISLES DURING THE DAY. IT IS TO THEN MEANDER BETWEEN
PUERTO RICO/VIRGIN ISLES THROUGH WEDNESDAY AFTERNOON...WHEN IT
WILL BECOME ILL DEFINED.

BEST MOISTURE CONVERGENCE IS EXPECTED THROUGH TODAY/EARLY ON
TUESDAY...AS MOISTURE POOLS BETWEEN THE MEANDERING SHEAR LINE AND
WANING POLAR FRONT TO THE NORTH. RAPID EROSION OF MOISTURE IS THEN
EXPECTED LATER ON TUESDAY-THURSDAY MORNING. THE GLOBAL MODELS AND
REGIONAL NAM SHOW MOST ACTIVE CONVECTION ALONG THE SURFACE FRONT
TO THE NORTH...AND THEY SEEM TO BE DOWNPLAYING THE INFLUENCE OF
SHEAR LINE AS IT MOVES ACROSS THE FORECAST AREA. THE HIGH
RESOLUTION WRF...NMM VERSION OF THE MODEL...SHOWS A MORE VIABLE
ALTERNATIVE... WITH SHEAR LINE PASSAGE BRINGING A SURGE IN
ACTIVITY ACROSS THE CORDILLERA/SOUTHWEST PORTIONS OF PUERTO RICO
DURING THE DAY. AS WE EXPECT DEEP LAYER CONVECTIVE
INSTABILITY...RISK OF MODERATE TO HEAVY RAINFALL AMOUNTS IS HIGHER
THAN WHAT WE HAVE SEEN OVER THE LAST 07-10 DAYS. SO EXPECTING
HIGHER AMOUNTS THAN WHAT THE GUIDANCE SUGGEST...WITH MAXIMA TO
PEAK AT 35-50MM. ON TUESDAY...ADDITIONAL SHOWERS ARE
EXPECTED...BUT AS THE TRADE WIND CAP INTENSIFIES...WILL ONLY SEE
SHALLOW CONVECTIVE CELLS WITH LIGHT TO MODERATE AMOUNTS...WITH
MAXIMA TO THEN PEAK AT 10-15MM.

DISCUSSION FROM FEB 13/00 UTC. 

SANCHEZ...FAC (COLOMBIA)
DAVISON...NCEP (USA)