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Tropical Discussion
 
(Caution: Version displayed is not the latest version. - Issued 1104Z Aug 27, 2014)
 
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TROPICAL DISCUSSION - INTERNATIONAL DESKS
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
704 AM EDT WED AUG 27 2014

PRELIMINARY DISCUSSION FOR PUERTO RICO AND THE USVI. RETROGRESSING
TUTT LOW NOW CENTERS NEAR 20N 55W. THIS IS INTERACTING WITH THE
ATLANTIC ITCZ AND A COUPLE OF TROPICAL WAVES...WITH ONE MOVING
ACROSS THE WINDWARD ISLES EARLY THIS MORNING WHILE THE OTHER
TRAILS ALONG 50W/51W. AT LOW LEVELS...UNDER INFLUENCE OF A BROAD
RIDGE OVER THE ATLANTIC...PREVAILING EASTERLY WINDS RETURNED TO
THE EASTERN CARIBBEAN.

TUTT LOW MOVES NORTH OF THE FORECAST AREA BY MIDDAY ON
THURSDAY...AND IT IS TO SLOWLY MEANDER TO THE WEST-NORTHWEST
THROUGH SATURDAY MORNING. AS IT MEANDERS NORTH OF THE FORECAST
AREA...BASE OF THE SHORT WAVE TROUGH IS TO GRAZE THE NORTHEAST
CARIBBEAN ISLES. AT MID LEVELS THIS IS TO REFLECT AS AN INVERTED
TROUGH...WITH AXIS ACROSS THE VIRGIN ISLES LATER ON
THURSDAY...INTO PUERTO RICO EARLY ON FRIDAY MORNING. AT LOW
LEVELS...EASTERLY TRADES ARE TO PREVAIL. EMBEDDED IN THIS
FLOW...FIRST TROPICAL WAVE MOVES ACROSS THE WINDWARD ISLES TO THE
EASTERN CARIBBEAN EARLY THIS MORNING. THIS IS TO REMAIN SOUTH OF
16N AS IT PULLS ACROSS THE EASTERN CARIBBEAN...REACHING 70W AROUND
18UTC ON THURSDAY. AS A RESULT...MODEL GUIDANCE SHOWING MOST
ACTIVE CONVECTION FAR TO THE SOUTH. ASSOCIATED MOIST PLUME IT TO
COME CLOSE TO THE SOUTH COAST OF PUERTO RICO...AND THAT MIGHT BE
ENOUGH TO FEED AN INCREASE IN SEA BREEZE CONVERGENCE. INTERACTION
WITH AFOREMENTIONED MID LEVEL TROUGH IS HIGHLY LIKELY...WITH THE
UKMET AND GFS BOTH SHOWING ACTIVITY CLUSTERING ACROSS SOUTHEAST
PUERTO RICO. IN THIS AREA THEY PROJECT 24HRS RAINFALL AMOUNTS OF
15-20MM...WITH LESSER AMOUNTS ACROSS REST OF THE ISLAND.

NEXT PERTURBATION LIFTS ACROSS THE VIRGIN ISLES TO PUERTO RICO
DURING THE DAY ON SATURDAY. GLOBAL MODELS DIVERGE ON THE INTENSITY
OF THIS WAVE...WITH THE GFS FAVORING A STRONGER PERTURBATION THAN
THE UKMET. THE ECMWF APPEARS AS THE COMPROMISE SOLUTION...SHOWING
WAVE PATTERN SLIGHTLY WEAKER THAN THE GFS BUT STRONGER THAN THE
UKMET. SO UNCERTAINTY IS HIGH AND CONFIDENCE IS LOW DURING THE
MEDIUM RANGE PERIOD. ALTHOUGH POSITIVE INTERACTION BETWEEN THIS
FEATURE AND THE TUTT TO THE NORTH IS
POSSIBLE...INTENSITY/ORGANIZATION OF THE CONVECTION WILL BE HIGHLY
DEPENDENT ON AMPLITUDE OF THE LOW LEVEL TROUGH. FOR NOW GOING WITH
WORST CASE SCENARIO...PROJECTING AN INCREASE IN ACTIVITY DURING
THE WEEKEND.

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