Atlantic Tropical Weather Discussion

000
AXNT20 KNHC 202339
TWDAT 

TROPICAL WEATHER DISCUSSION
NWS NATIONAL HURRICANE CENTER MIAMI FL
805 PM EDT MON MAY 20 2013

TROPICAL WEATHER DISCUSSION FOR NORTH AMERICA...CENTRAL 
AMERICA...GULF OF MEXICO...CARIBBEAN SEA...NORTHERN SECTIONS OF 
SOUTH AMERICA...AND ATLANTIC OCEAN TO THE AFRICAN COAST FROM THE 
EQUATOR TO 32N. THE FOLLOWING INFORMATION IS BASED ON SATELLITE 
IMAGERY...WEATHER OBSERVATIONS...RADAR...AND METEOROLOGICAL 
ANALYSIS.

BASED ON 1800 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 
2245 UTC.

...TROPICAL WAVES...                                     
TROPICAL WAVE EXTENDS FROM 7N34W TO EQ36W MOVING WEST AT 10-15 
KT. THE WAVE SHOWS A GOOD SIGNAL IN 700 MB STREAMLINES AND 
SATELLITE DERIVED WINDS. IT ALSO COINCIDES WITH A MAXIMUM IN 
DEEP LAYER MOISTURE EVIDENT IN TOTAL PRECIPITABLE WATER IMAGERY. 
ISOLATED MODERATE CONVECTION IS WITHIN 100 NM OF THE AXIS. 

TROPICAL WAVE EXTENDS FROM 14N62W TO 9N63W MOVING W AT 5-10 KT. 
THE WAVE IS PARTIALLY OVER SOUTH AMERICA...BUT THE MOISTURE 
SIGNAL IN TOTAL PRECIPITABLE WATER IMAGERY EXTENDS UP TO 15N. 
SCATTERED MODERATE CONVECTION IS WITHIN 200 NM TO EITHER SIDE 
SOUTH OF 12N. THE DEEPEST MOISTURE ASSOCIATED WITH THE WAVE IS 
STILL MOVING OVER THE WINDWARD ISLANDS...SO A RISK OF HEAVY 
RAINFALL IS STILL PRESENT OVER THIS AREA.  

...ITCZ/MONSOON TROUGH...                                     
THE MONSOON TROUGH EXTENDS FROM THE COAST OF GUINEA-BISSAU NEAR 
11N15W TO ALONG 5N20W 4N30W. THE ITCZ BEGINS NEAR 4N30W AND 
CONTINUES ALONG EQ38W 3S49W. SCATTERED MODERATE/ISOLATED STRONG 
CONVECTION IS FROM 4N-8N BETWEEN 17W-20W. ISOLATED MODERATE 
CONVECTION IS FROM 1N-7N BETWEEN 22W-32W.

...DISCUSSION...

GULF OF MEXICO...                                            
MOSTLY FAIR WEATHER SPREADS ACROSS THE GULF OF MEXICO...WITH THE 
EXCEPTION OF FLORIDA...ALONG WITH BROAD SURFACE RIDGING 
EXTENDING FROM THE W ATLC. DRY AIR ALOFT COVERS THE MAJORITY OF 
THE BASIN AROUND BROAD UPPER LEVEL RIDGING EXTENDING FROM THE 
EAST PACIFIC JUST SOUTH OF GUATEMALA. HOWEVER...A SHORTWAVE 
UPPER TROUGH EXTENDS DOWN THE WEST COAST OF FLORIDA PROVIDING 
DIFFLUENCE ALOFT ACROSS THE PENINSULA. THIS COMBINED WITH 
DAYTIME HEATING AND INSTABILITY HAS LED TO HEAVY SHOWERS AND 
THUNDERSTORMS ACROSS FLORIDA WITH SOME BEING SEVERE. THE 
ACTIVITY OVER SOUTH FLORIDA HAS DIED DOWN SOME...BUT HEAVY 
ACTIVITY STILL SPREADS OVER MUCH OF THE WEST CENTRAL AND 
NORTHERN PORTIONS. PRIMARILY SOUTHEAST WINDS SPREAD THROUGHOUT 
THE BASIN RANGING FROM 10-15 KT WITH A FEW AREAS OF 20 KT WINDS 
OVER THE WESTERN GULF ESPECIALLY ALONG THE TEXAS COAST. LITTLE 
CHANGE IS EXPECTED OVER THE NEXT 24 HOURS. MODEL GUIDANCE 
CONTINUES TO SHOW HIGH MOISTURE AND PRECIPITATION POTENTIAL 
THROUGHOUT THE FLORIDA PENINSULA. 

CARIBBEAN SEA...                                              
NORTHWEST TO WEST FLOW ALOFT COVERS THE CARIBBEAN ALONG WITH 
MOSTLY DRY AIR. THE DRY AIR IS PROVIDING FAIR CONDITIONS ACROSS 
MUCH OF THE BASIN. HOWEVER...DAYTIME HEATING AND INSTABILITY 
HAVE LED TO WIDESPREAD SHOWERS AND THUNDERSTORMS OVER THE 
NORTHERN CARIBBEAN ISLANDS INCLUDING 
CUBA...HISPANIOLA...JAMAICA...AND PUERTO RICO. HEAVY SHOWERS AND 
THUNDERSTORMS ARE ALSO IN THE FAR SW CARIBBEAN SOUTH OF 11N FROM 
COSTA RICA TO COLOMBIA INCLUDING PANAMA. THIS ACTIVITY IS 
CONNECTED TO THE MONSOON TROUGH EXTENDING THROUGH BOTH COSTA 
RICA AND PANAMA. THE ACTIVITY IS ENHANCED BY DIFFLUENT FLOW 
ALOFT ACROSS THAT AREA. A TROPICAL WAVE HAS MOVING INTO THE SE 
CARIBBEAN JUST WEST OF THE WINDWARD ISLANDS. SCATTERED SHOWERS 
ARE EAST OF 63W SOUTH OF 16N. THERE IS STILL SOME MOISTURE WITH 
THE WAVE EAST OF THE WINDWARD ISLANDS...AND AS THE WAVE MOVES 
WEST MORE SHOWERS AND POSSIBLE THUNDERSTORMS COULD OCCUR OVER 
THE ISLANDS. ELSEWHERE...TRADEWIND FLOW OF 15-20 KT DOMINATES 
WITH A FEW 25 KT WINDS OFF THE COAST OF COLOMBIA. MOIST 
CONDITIONS AND LIKELY PRECIPITATION WILL REMAIN OVER THE SW 
CARIBBEAN AS WELL AS THE NORTHERN CARIBBEAN ISLANDS ESPECIALLY 
IN THE AFTERNOON HOURS. AS THE TROPICAL WAVE IN THE SE CORNER 
MOVES WEST...MOISTURE WILL INCREASE AND WILL SUPPORT HEAVIER 
THAN NORMAL AFTERNOON CONVECTION. THIS WILL LIKELY BE THE CASE 
TOMORROW OVER PUERTO RICO AND SPREAD WESTWARD ON WEDNESDAY.

HISPANIOLA...                                           
CURRENTLY AFTERNOON SHOWERS AND THUNDERSTORMS CONTINUE TO IMPACT 
THE ISLAND OF HISPANIOLA MAINLY CONCENTRATED BETWEEN 70W-73W. AS 
THE SUN GOES DOWN THIS ACTIVITY SHOULD DIE DOWN. MODEL GUIDANCE 
INDICATES A SIMILAR PATTERN WILL PERSIST TOMORROW WITH THE MOST 
LIKELY PRECIPITATION TO BE DURING THE AFTERNOON AND EARLY 
EVENING HOURS ACROSS THE ISLAND WHEN PEAK DAYTIME HEATING AND 
INSTABILITY OCCUR. ANY AREAS THAT RECEIVE MEASURABLE AMOUNTS OF 
RAINFALL WILL LIKELY BE PRONE TO LOCALIZED FLOODING. MOISTURE 
FROM A TROPICAL WAVE MAY INCREASE ACTIVITY OVER THE ISLAND ON 
WEDNESDAY.

ATLANTIC OCEAN...                                               
A SHORTWAVE UPPER TROUGH ALONG THE WEST COAST OF FLORIDA IS 
SUPPORTING HEAVY SHOWERS AND THUNDERSTORMS ACROSS THE FLORIDA 
PENINSULA...WHICH CONTINUE INTO THE ATLC TO NEAR 78W. AN UPPER 
LEVEL RIDGE IS ALONG 76W SUPPORTING A SURFACE RIDGE ACROSS THE 
WEST ATLC AROUND A 1026 MB HIGH NEAR 35N62W. FARTHER EAST...AN 
UPPER LEVEL TROUGH ALONG 49W SUPPORTS A COLD FRONT THAT ENTERS 
THE DISCUSSION AREA NEAR 32N49W AND CONTINUES ALONG 29N55W 
27N59W. ISOLATED SHOWERS ARE WITHIN 30 NM OF THE AXIS. A WEAK 
1019 MB SURFACE LOW IS TO THE EAST NEAR 27N48W. A SURFACE TROUGH 
EXTENDS THROUGH THE LOW CENTER FROM 30N49W 24N44W. NO SHOWERS 
ARE ASSOCIATED WITH THE SYSTEM. THE REMAINDER OF THE EASTERN 
ATLC IS DOMINATED BY BROAD SURFACE RIDGING ANCHORED BY A 1034 MB 
HIGH NEAR 44N29W. THE RIDGE IS SUPPORTED BY AN UPPER LEVEL RIDGE 
CENTERED NEAR 43N26W. BROAD UPPER RIDGING ALSO COVERS THE 
TROPICAL ATLC. 

FOR ADDITIONAL INFORMATION PLEASE VISIT 
WWW.HURRICANES.GOV/MARINE

$$
WALTON