[Tropical] Tropical Weather Discussion

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AXNT20 KNHC 121250 CCA
TWDAT

TROPICAL WEATHER DISCUSSION...COR
NWS NATIONAL HURRICANE CENTER MIAMI FL
805 AM EDT FRI JUL 12 2013

...CORRECTION IN ORDER TO ELIMINATE THE SPECIAL FEATURES
SECTION AND TO CORRECT THE REFERENCE MEDIUM CHANCE TO
LOW CHANCE OF DEVELOPMENT INTO A TROPICAL CYCLONE...NOW
IN THE ATLANTIC OCEAN SECTION

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 0600 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH
1015 UTC.

...TROPICAL WAVES...
TROPICAL WAVE EXTENDS FROM 10N33W TO 19N31W MOVING W AT 5-10 KT.
THE WAVE REMAINS EMBEDDED WITHIN THE ITCZ AXIS AND COINCIDES
WITH A GLOBAL MODEL INDICATED 700 MB TROUGH AND ASSOCIATED
VORTICITY MAXIMUM IN THE VICINITY OF 15N32W. TOTAL PRECIPITABLE
WATER IMAGERY SHOWS A RELATIVE MOISTURE MAXIMUM FROM 09N-20N
BETWEEN 27W-37W. SIGNIFICANT DEEP CONVECTION LACKS...HOWEVER
ISOLATED SHOWERS ARE OCCURRING FROM 08N-20N BETWEEN 26W-37W.

TROPICAL WAVE EXTENDS FROM 14N81W TO 21N81W MOVING W AT 10-15
KT. THE WAVE...THE SOUTHERN EXTENT OF ENERGY ASSOCIATED WITH THE
REMNANTS OF CHANTAL...CONTINUES WESTWARD WHILE PARTIAL ENERGY
HAS FRACTURED TO THE NORTH AS A SURFACE TROUGH AND NO DEFINED
LOW-LEVEL CIRCULATION CENTER. PLENTY OF LOW-LEVEL MOISTURE
CONVERGENCE AND MID-LEVEL VORTICITY ARE AIDING IN GENERATING
ISOLATED MODERATE CONVECTION FROM 15N-21N BETWEEN 76W-81W...
INCLUDING CUBA...JAMAICA...AND THE CAYMAN ISLANDS. THE WAVE IS
EXPECTED TO TRACK ACROSS THE NW CARIBBEAN SEA AND PORTIONS OF
CENTRAL AMERICA OVER THE WEEKEND.

...ITCZ/MONSOON TROUGH...
THE MONSOON TROUGH EXTENDS FROM THE AFRICAN COAST NEAR 09N13W TO
08N24W. THE INTERTROPICAL CONVERGENCE ZONE AXIS EXTENDS FROM
08N24W TO 12N32W TO 06N54W. SCATTERED MODERATE CONVECTION IS
FROM 07N-11N BETWEEN 13W-22W. ISOLATED MODERATE CONVECTION IS
WITHIN 120 NM EITHER SIDE OF THE ITCZ AXIS BETWEEN 38W-56W.

...DISCUSSION...

GULF OF MEXICO...
WATER VAPOR IMAGERY INDICATES EAST-NORTHEASTERLY UPPER LEVEL
FLOW NORTH OF A BROAD TROUGH AXIS EXTENDING FROM AN UPPER LEVEL
LOW CENTERED OVER THE FLORIDA STRAITS NEAR 23N80W TO OVER EAST-
CENTRAL MEXICO NEAR 22N100W. MOSTLY DRY AND STABLE AIR ALOFT IS
NOTED OVER A NARROW EAST-WEST SECTION OF THE CENTRAL GULF THIS
MORNING FROM 23N-27N AS A SURFACE RIDGE ANCHORED BY A 1016 MB
HIGH CENTERED NEAR 26N92W LIES BENEATH PROVIDING FOR OVERALL
TRANQUIL CONDITIONS. THE SURFACE RIDGING HAS WEAKENED ITS
INFLUENCE OVER THE NORTHERN GULF COAST WITH ISOLATED SHOWERS AND
TSTMS OCCURRING N OF 27N THIS MORNING DUE TO A MID-LEVEL
SHORTWAVE TROUGH MOVING OVER PORTIONS OF THE SE CONUS AND NE
GULF. ANOTHER WEAKNESS IN THE SURFACE RIDGE IS NOTED ACROSS THE
FLORIDA STRAITS AS THE SPECIAL FEATURE...REMNANTS OF CHANTAL...
BEGIN TO IMPACT THE SOUTHERN FLORIDA PENINSULA AND ADJACENT
COASTAL WATERS SURROUNDING THE FLORIDA KEYS. ACROSS PORTIONS OF
THE SW GULF...WITHIN MOSTLY WESTERLY FLOW ALOFT ON THE SOUTHERN
PERIPHERY OF THE UPPER LEVEL TROUGH AXIS...MIDDLE TO UPPER LEVEL
MOISTURE INCREASES WITH ISOLATED SHOWERS OCCURRING S OF 23N.
LOOKING AHEAD...SURFACE RIDGING IS EXPECTED TO REMAIN IN PLACE
ACROSS THE BASIN THROUGH EARLY NEXT WEEK WITH GENERALLY E-SE
WINDS PERSISTING.

CARIBBEAN SEA...
THE PRIMARY FOCUS FOR THE CARIBBEAN REMAINS ON THE SOUTHERN
EXTENT OF ENERGY...REMNANT ENERGY OF CHANTAL...MOVING WESTWARD
AS A TROPICAL WAVE ALONG 81W IN THE WESTERN CARIBBEAN. THE
TROPICAL WAVE CONTINUES GENERATING WIDELY SCATTERED SHOWERS AND
ISOLATED TSTMS FROM 16N-22N BETWEEN 76W-81W...INCLUDING PORTIONS
OF CUBA...JAMAICA...AND THE CAYMAN ISLANDS THIS MORNING. THE
WAVE IS EXPECTED TO DRIFT WESTWARD OVER THE WEEKEND BRINGING
INCREASED CHANCES OF PRECIPITATION TO THE NW CARIBBEAN AND
PORTIONS OF CENTRAL AMERICA. OTHERWISE...THE MONSOON TROUGH AXIS
EXTENDS ALONG 10N IN THE SW CARIBBEAN AND IS GENERATING A FEW
ISOLATED SHOWERS AND TSTMS S OF 14N BETWEEN 80W-85W. THE
REMAINDER OF THE CENTRAL AND EASTERN CARIBBEAN HAS RESUMED AN
OVERALL QUIET PATTERN WITH WATER VAPOR IMAGERY INDICATING DRY
AIR AND SUBSIDENCE ALOFT...ALONG WITH LIGHT NORTHEAST TO EAST
TRADES. THE TRADES ARE FORECAST TO INCREASE GRADUALLY BETWEEN
65W-80W BY EARLY TUESDAY DUE TO AN INCREASE PRESSURE GRADIENT
BETWEEN A CENTRAL ATLC RIDGE AND LOWER PRESSURE ACROSS THE SW
CARIBBEAN AND NORTHERN SOUTH AMERICA.

HISPANIOLA...
CURRENTLY...MOST OF THE REMNANTS OF CHANTAL HAVE SHIFTED NW OF
THE ISLAND WITH ONLY A FEW ISOLATED SHOWERS OCCURRING OVER FAR
NW PORTIONS OF THE ISLAND THIS MORNING. SURFACE RIDGING TO THE
NORTH AND EAST WILL CONTINUE TO BUILD WESTWARD OVER THE NEXT 24
TO 36 HOURS AS CONDITIONS ACROSS HISPANIOLA ARE EXPECTED TO
IMPROVE LATE FRIDAY INTO EARLY SATURDAY. THEREAFTER...TRADES
WILL RESUME ACROSS THE REGION WITH THE MORE TYPICAL AFTERNOON
SCATTERED SHOWERS AND TSTMS OCCURRING ACROSS THE ISLAND DURING
THE WEEKEND INTO EARLY NEXT WEEK.

ATLANTIC OCEAN...
A SURFACE TROUGH...THE REMNANTS OF CHANTAL...IS ANALYZED FROM
THE FLORIDA STRAITS NEAR 23N80W TO 27N78W. SUPPORTED ALOFT BY AN
UPPER LEVEL LOW CENTERED OVER THE FLORIDA STRAITS NEAR 23N80W...
THE ENTIRE SYNOPTIC SYSTEM IS GENERATING SCATTERED MODERATE
CONVECTION ACROSS THE SW NORTH ATLC S OF 27N W OF 72W. WHILE THE
AREAL COVERAGE OF CONVECTION REMAINS RELATIVELY LARGE DUE TO
MAXIMUM UPPER LEVEL DIFFLUENCE COVERING THE REGION...
ORGANIZATION LACKS DUE TO AN INCREASED AMOUNT OF UPPER LEVEL
WIND SHEAR. THE SURFACE TROUGH IS FORECAST TO DRIFT NORTHWARD
OVER THE NEXT 36 TO 48 HOURS WITH A LOW CHANCE OF BECOMING A
TROPICAL CYCLONE. AN UPPER LEVEL LOW IS CENTERED OVER THE
FLORIDA STRAITS NEAR 24N80W THAT IS PROVIDING SUPPORT FOR THE
CONVECTION ASSOCIATED WITH THE SPECIAL FEATURES SURFACE
TROUGH...THE REMNANTS OF CHANTAL...THIS MORNING ACROSS THE
EASTERN FLORIDA STRAITS... BAHAMAS...AND ADJACENT COASTAL WATERS
EAST OF THE BAHAMAS. SCATTERED SHOWERS AND TSTMS ARE OCCURRING S
OF 28N W OF 71W. THIS FEATURE IS EXPECTED TO SLIP NORTHWARD OVER
THE NEXT 24 TO 36 HOURS AROUND THE WESTERN PERIPHERY OF SURFACE
RIDGING ACROSS THE REMAINDER OF THE SW NORTH ATLC. THE RIDGE IS
ANCHORED BY A 1022 MB HIGH CENTERED NE OF BERMUDA NEAR 34N63W.
FARTHER EAST...AN UPPER LEVEL LOW IS CENTERED NEAR 30N60W THAT
REMAINS AT THE SOUTHWESTERN EXTENT OF A STATIONARY FRONT
ANALYZED FROM 32N43W TO 31N50W TO 28N55W. MOISTURE ASSOCIATED
WITH THE UPPER LEVEL LOW AND A WEAK SURFACE TROUGH ANALYZED FROM
20N54W TO 30N56W ARE GENERATING ISOLATED SHOWERS AND TSTMS FROM
27N-33N BETWEEN 53W-62W. GLOBAL MODELS INDICATE THIS UPPER LEVEL
FEATURE AND ASSOCIATED SURFACE TROUGHING WILL DRIFT WESTWARD
ACROSS THE SW NORTH ATLC OVER THE COMING DAYS. FINALLY...THE
EASTERN ATLC IS UNDER THE INFLUENCE OF A SURFACE RIDGE ANCHORED
BY A 1020 MB HIGH CENTERED NEAR 31N35W. A SAHARAN AIR LAYERS
CONTINUES TO BE THE OVERALL DOMINATE FEATURE PROVIDING FAIRLY
STABLE CONDITIONS N OF 18N E OF 50W.

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

$$
HUFFMAN

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