[Tropical] Tropical Weather Discussion

[EMWIN Server]

AXNT20 KNHC 061712
TWDAT

TROPICAL WEATHER DISCUSSION
NWS NATIONAL HURRICANE CENTER MIAMI FL
205 PM EDT TUE AUG 06 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 1200 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH
1745 UTC.

...TROPICAL WAVES...
A TROPICAL WAVE AXIS EXTENDS FROM 20N62W TO 11N63W MOVING W-NW
ABOUT 20 KT. THE NORTHERN PORTION OF THE WAVE HAS FRACTURED WITH
A SURFACE TROUGH EXTENDING FROM 28N59W TO 22N62W. METEOSAT-9 SAL
TRACKING IMAGERY INDICATED THAT THE WAVE IS EMBEDDED WITHIN A
VERY DRY STABLE ENVIRONMENT WHICH ALONG WITH STRONG
SOUTHWESTERLY WIND SHEAR IS HINDERING CONVECTION. A CLUSTER OF
MODERATE CONVECTION IS INDICATED ALONG THE TROUGH AXIS
WITHIN 60 NM OF 26.5N59W.

...THE ITCZ/THE MONSOON TROUGH...
THE MONSOON TROUGH AXIS EXTENDS FROM THE COAST OF MAURITANIA
NEAR 21N17W TO 12N25W TO 08N38W. THE INTERTROPICAL CONVERGENCE
ZONE AXIS EXTENDS FROM NEAR 08N38W AND CONTINUES INTERMITTENTLY
THROUGH 11N46W TO 12N55W TO 11N62W. A SURFACE TROUGH ASSOCIATED
WITH A 1012 MB LOW NEAR 12N49W EXTENDS FROM 09N TO 16N.
SCATTERED MODERATE/ISOLATED STRONG CONVECTION IS NOTED WITHIN
120 NM EITHER SIDE OF A LINE FROM 012N17W TO 08N28W...AND FROM
10N-12N BETWEEN 51W-54W.

...DISCUSSION...

THE GULF OF MEXICO...
AS OF 1500 UTC...ANTICYCLONIC FLOW IN THE RANGE OF 5-15 KT
SPREADS ACROSS MOST OF THE BASIN ANCHORED BY A 1018 MB HIGH NEAR
26N89W WHICH IS BEING SUPPORTED BY A BROAD MIDDLE TO UPPER LEVEL
RIDGE AND ANTICYCLONE CENTERED OVER THE NW GULF NEAR 29N95W. A
WEAK SURFACE TROUGH EXTENDS FROM A 1015 MB LOW BEAR THE BIG BEND
OF FLORIDA TO 28N86W TO 29N88W. SCATTERED TSTMS WERE ERUPTING
ALONG THE SURFACE TROUGH WITH NUMEROUS LIGHTNING STRIKES WITHIN
THE PAST HOUR. A SURFACE PREFRONTAL TROUGH EXTENDS THROUGH THE
STRAITS OF FLORIDA TO 25N84W. THIS WAS ENHANCING SCATTERED
SHOWERS AND TSTMS IN THE FLORIDA STRAITS. THE SURFACE TROUGH
OVER THE BAY OF CAMPECHE HAS DISSIPATED WITH THE ASSOCIATED
CONVECTION DISSIPATING. OTHERWISE...DRY AIR IN THE LOWER AND
MIDDLE LEVELS IS SUPPORTING FAIR WEATHER OVER THE WESTERN AND
SOUTHERN-CENTRAL GULF.

THE CENTER OF HIGH PRESSURE IS EXPECTED TO DRIFT NW AND PERSIST
OVER THE GULF UNTIL THURSDAY MORNING. THE TROUGH OVER THE
BAHAMAS IS EXPECTED TO MOVE WESTWARD AND PROVIDE TROUGHINESS TO
THE EASTERN GULF UNTIL VERY EARLY THURSDAY. SCATTERED SHOWERS
AND TSTMS ARE LIKELY TO CONTINUE OVER THE EASTERN GULF.

THE CARIBBEAN SEA...
DEEP LAYERED DRY AIR FROM A SAHARAN OUTBREAK AT THE LOW LEVELS
AND SUBSIDENCE IN THE MID TO UPPER LEVELS CONTINUES TO SPREAD
ACROSS MOST OF THE BASIN. THE DRY AIR WAS FOCUSED WITHIN 180 NM N
AND W OF AN UPPER LEVEL TROUGH WHICH EXTENDED FROM A CYCLONIC
CIRCULATION N OF HISPANIOLA THROUGH 15N73W TO THE COAST OF
NICARAGUA. A TROPICAL WAVE ALONG 62W/63W IS MOVING INTO THE FAR
E CARIBBEAN IS EMBEDDED WITHIN THIS DRY STABLE ENVIRONMENT
WITH ONLY SCATTERED LOW CLOUDS AND ISOLATED WARM TOPPED SHOWERS
NOTED ACROSS THE LEEWARD ISLANDS. TRADEWINDS RANGING FROM 20-25 KT
ARE OVER THE CENTRAL-SOUTHERN CARIBBEAN NEAR THE COAST OF COLOMBIA
WHILE WINDS OF 5-15 KT ARE ELSEWHERE IN THE BASIN. WEAKENING
ISOLATED MODERATE CONVECTION WITHIN 60 NM OFF THE COASTS OF COSTA
RICA AND PANAMA IS ASSOCIATED WITH THE MONSOON TROUGH AXIS.

WINDS OVER THE CENTRAL-SOUTHERN CARIBBEAN ARE EXPECTED TO
SUBSIDE TONIGHT. RAINSHOWERS ACTIVITY ASSOCIATED WITH THE
TROPICAL WAVE ARE EXPECTED TO DEVELOP S OF PUERTO RICO...THE
MONA PASSAGE AND DOMINICAN REPUBLIC THIS AFTERNOON BEING
ENHANCED BY AN UPPER LEVEL LOW CENTERED IN THE BASIN.

HISPANIOLA...
IN THE UPPER LEVELS...AN ELONGATED CYCLONIC CIRCULATION EXTENDS
ACROSS THE ISLAND FROM THE W ATLC TO THE SOUTHERN CARIBBEAN.
THIS IS SUPPORTING LOW VALUES OF WIND SHEAR OVER THE
ISLAND...HOWEVER DRY AIR SUBSIDENCE IS CURRENTLY ENHIBITING
CONVECTION. A FEW DIURNALLY DRIVEN SHOWERS AND TSTMS ARE
EXPECTED THIS AFTERNOON/EARLY EVENING POSSIBLY ENHANCED BY SOME
MOISTURE CARRIED TOWARDS THE ISLAND BY THE TROPICAL WAVE THAT
HAS ENTERED THE EASTERN CARIBBEAN.

THE WAVE IS EXPECTED TO START MOVING ACROSS THE ISLAND WEDNESDAY
MORNING WITH INCREASING SHOWERS AND TSTMS LIKELY TO
DEVELOP/CONTINUE THROUGH EARLY THURSDAY.

THE ATLANTIC OCEAN...
AS OF 1500 UTC...A WEAKENING STATIONARY FRONT WAS OVER THE SW N
ATLC FROM 31N70W TO 29N81W TO A 1015 MB LOW NEAR THE FLORIDA BIG
BEND. A PREFRONTAL TROUGH EXTENDS ACROSS THE NORTH CENTRAL
BAHAMAS TO THE STRAITS OF FLORIDA ALONG 28N75W TO 24N81W.
SCATTERED SHOWERS AND ISOLATED TSTMS ARE OCCURRING OVER THE
SOUTHERN AND CENTRAL BAHAMAS S OF THE SURFACE TROUGH EXTENDING
INTO THE STRAITS OF FLORIDA. A SURFACE TROUGH ASSOCIATED WITH A
1012 MB LOW IS EMBEDDED WITHIN THE ITCZ AXIS NEAR 12N48W
ASSOCIATED WITH A SURFACE TROUGH ALONG 48W WITH ONLY ISOLATED
MODERATE CONVECTION ASSOCIATED WITH IT AT THIS TIME. ELSEWHERE
SURFACE RIDGING AND FAIR WEATHER SUPPORTED BY LOWER-MIDDLE LEVEL
DRY AIR DOMINATE THE REMAINDER BASIN.

EASTERLY WAVE DIAGNOSTICS AND 12Z RAOB DATA FROM DAKAR SUGGESTS
A NEW TROPICAL WAVE IS EXPECTED TO EMERGE OFF THE WEST AFRICAN
COAST LATER TODAY. THIS FEATURE MAY BE INTRODUCED IN THE 18 UTC
ANALYSIS.

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

$$
COBB


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