Tropical Weather Discussion
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000
AXNT20 KNHC 041820 AAA
TWDAT

TROPICAL WEATHER DISCUSSION...AMENDED
NWS NATIONAL HURRICANE CENTER MIAMI FL
205 PM EDT TUE AUG 04 2015

AMENDED FOR ADDITION OF SPECIAL FEATURE

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
1715 UTC.

...SPECIAL FEATURES...
A STRONG PRESSURE GRADIENT EXISTS BETWEEN SURFACE RIDGING
ANCHORED ACROSS THE SW NORTH ATLC AND LOWER PRESSURE ANALYZED
ACROSS NORTHERN COLOMBIA AND EASTERN PANAMA. NEAR GALE TO GALE
FORCE WINDS ARE FORECAST TO CONTINUE THROUGH 05/1800 UTC FROM
11N-13N BETWEEN 74W-77W. SEE LATEST NWS HIGH SEAS FORECAST UNDER
AWIPS/WMO HEADERS MIAHSFAT2/FZNT02 KNHC FOR MORE DETAILS.

A 1011 MB LOW CENTERED ALONG THE SOUTH CAROLINA COAST NEAR
33N80W CONTINUES TO GENERATING SCATTERED SHOWERS AND TSTMS
OFFSHORE OF THE SE CONUS STRETCHING FROM OFFSHORE OF
JACKSONVILLE FLORIDA NE TO OFFSHORE OF THE NORTH CAROLINA OUTER
BANKS. VISIBLE SATELLITE IMAGERY INDICATES THE LOW LEVEL
CIRCULATION CENTER IS EXPOSED AT THIS TIME WITH MOST OF THE
CONVECTION OUT ACROSS THE OPEN WATERS OF THE SW NORTH ATLC.
THERE IS A MEDIUM CHANCE FOR THIS AREA OF LOW PRESSURE TO BECOME
A TROPICAL CYCLONE DURING THE NEXT 48 HOURS BEFORE IT LIKELY
MERGES WITH A FRONTAL BOUNDARY.

...TROPICAL WAVES...
TROPICAL WAVE EXTENDS FROM 10N18W TO 18N21W MOVING W AT 15-20
KT. THE WAVE COINCIDES WITH 700 MB TROUGHING BETWEEN 13W-26W...
FOCUSED ON A MID-LEVEL MONSOONAL GYRE CENTERED ON A 1014 MB LOW
CENTERED NEAR 09N15W. THE WAVE IS EXPECTED TO CONTINUE
PROPAGATING WESTWARD AND COME INTO PHASE WITH A MID-LATITUDE 700
MB TROUGH BY WEDNESDAY IN THE VICINITY OF 28W-32W. WIDELY
SCATTERED MODERATE CONVECTION IS FROM 05N-13N BETWEEN 12W-22W.

TROPICAL WAVE EXTENDS FROM 12N38W TO 18N37W MOVING W AT 10-15
KT. THE WAVE COINCIDES WITH LOW-AMPLITUDE 700 MB TROUGHING
BETWEEN 34W-40W. GLOBAL MODEL GUIDANCE ALSO INDICATED AN AREA OF
MAXIMUM 850 MB RELATIVE VORTICITY ALONG THE WAVE AXIS NEAR 15N.
NO SIGNIFICANT CONVECTION IS OCCURRING WITH THE WAVE AT THIS
TIME.

TROPICAL WAVE EXTENDS FROM 09N52W TO 17N50W MOVING W AT 15 KT.
THE WAVE COINCIDES WITH BROAD 700 MB TROUGHING BETWEEN 48W-
55W...WITH A PORTION OF ENERGY N-NE OF THE WAVE AXIS AS A
SURFACE TROUGH FROM 18N49W TO 23N44W. THIS NORTHEASTERN AREA OF
ENERGY COINCIDE PRIMARILY WITH A MID-LATITUDE 700 MB TROUGH
NEARLY IN PHASE WITH THE TROPICAL 700 MB TROUGHING TO THE SOUTH.
NO SIGNIFICANT DEEP CONVECTION IS NOTED WITH THIS WAVE.

TROPICAL WAVE EXTENDS FROM 08N80W TO 19N80W MOVING W AT 15 KT.
THIS WAVE COINCIDES WITH WEAK AND SUBTLE 700 MB TROUGHING
BETWEEN 78W-84W. NO SIGNIFICANT CONVECTION IS OCCURRING WITH THE
WAVE AT THIS TIME.

...ITCZ/MONSOON TROUGH...

THE MONSOON TROUGH EXTENDS FROM NEAR 09N16W TO 13N28W TO 12N33W.
THE INTERTROPICAL CONVERGENCE ZONE AXIS EXTENDS FROM 12N33W TO
12N43W TO 09N51W TO 08N59W. ASIDE FROM CONVECTION OCCURRING WITH
THE TROPICAL WAVE ALONG 20W...ISOLATED MODERATE CONVECTION IS
FROM 10N-12N BETWEEN 26W-31W...AND FROM 06N-11N BETWEEN 40W-49W.

...DISCUSSION...

GULF OF MEXICO...
NORTHEASTERLY FLOW ALOFT INFLUENCES MUCH OF THE GULF THIS
AFTERNOON ON THE SOUTHEASTERN PERIPHERY OF AN UPPER LEVEL
ANTICYCLONE CENTERED OVER CENTRAL TEXAS. THE RIDGING ALOFT IS
PROVIDING SUPPORT FOR WEAK RIDGING AT THE SURFACE WITH AN AXIS
EXTENDING FROM THE SOUTHERN FLORIDA PENINSULA W-SW TO THE EAST-
CENTRAL MEXICO COAST. BETWEEN THIS RIDGE AND WEAK RIDGING ACROSS
THE SE CONUS...A SURFACE TROUGH EXTENDS FROM THE SOUTHERN
GEORGIA TO COASTAL LOUISIANA. THE WEAK BOUNDARY IS PROVIDING
FOCUS FOR LOW-LEVEL MOISTURE CONVERGENCE AND GENERATING
SCATTERED SHOWERS AND ISOLATED TSTMS N OF 26N BETWEEN 82W-93W.
OTHERWISE...THE REMAINDER OF THE GULF IS EXPERIENCING LIGHT TO
GENTLE BREEZE CONDITIONS AROUND THE RIDGE WHICH IS EXPECTED TO
STAY FAIRLY STATIONARY THROUGH THE WEEK.

CARIBBEAN SEA...
WHILE NEAR GALE TO GALE FORCE WINDS ARE OCCURRING WITHIN CLOSE
PROXIMITY TO THE COAST OF COLOMBIA...THE REMAINDER OF THE BASIN
REMAINS RELATIVELY TRANQUIL THIS AFTERNOON. AN ELONGATED UPPER
LEVEL LOW IS CENTERED OVER NORTHERN NICARAGUA NEAR 14N84W AND IS
PROVIDING INCREASED CLOUDINESS ACROSS THE NW CARIBBEAN...HOWEVER
ONLY GENERATING ISOLATED SHOWERS AND POSSIBLE ISOLATED TSTMS W
OF 80W AND IN THE ADJACENT COASTAL WATERS OF EASTERN CUBA. WHILE
PRIMARILY ASSOCIATED WITH THE UPPER LEVEL LOW...THE PRESENCE OF
A TROPICAL WAVE ALONG 80W IS ADDING ENERGY AND LOW-LEVEL
MOISTURE CONVERGENCE TO THE OCCURRING CONVECTION. FARTHER
EAST...THE WESTERN PERIPHERY OF AN UPPER LEVEL RIDGE CENTERED
NEAR 17N58W IS PROVIDING VERY DRY AND STABLE AIR ALOFT TO THE
EASTERN CARIBBEAN KEEPING SKIES MOSTLY CLEAR WITH FAIR
CONDITIONS. DURING THE NEXT COUPLE OF DAYS...THE PRIMARILY MARINE
IMPACT WILL CONTINUE TO BE AN AREA OF FRESH TO STRONG TRADES
WITH THE EMBEDDED AREA OF NEAR GALE TO GALE FORCE. THE AREA IS
FORECAST TO SHRINK LATE ON THURSDAY AS THE PRESSURE GRADIENT
RELAXES SOMEWHAT DUE TO A WEAKER RIDGE ACROSS THE SW NORTH ATLC
REGION.

...HISPANIOLA...
DRY AIR AND STABLE CONDITIONS ALOFT CONTINUE TO SPREAD OVER THE
ISLAND FROM THE EAST DUE TO AN UPPER LEVEL ANTICYCLONIC
CIRCULATION CENTERED NEAR 17N58W. WITH LITTLE MOISTURE TO WORK
WITH AND STRONG STABILITY IN THE REGION...NO SIGNIFICANT
CONVECTION IS EXPECTED ACROSS THE ISLAND DURING THE NEXT 12 TO
24 HOURS.

ATLANTIC OCEAN...
AN UPPER LEVEL LONGWAVE TROUGH IS NOTED ON WATER VAPOR IMAGERY
OVER THE NE CONUS WITH AN EMBEDDED SHORTWAVE CENTERED IN THE
VICINITY OF 36N71W. THE TROUGHING ASSOCIATED WITH THE SHORTWAVE
EXTENDS S-SW OVER THE EASTERN SEABOARD AND SUPPORTS A 1011 MB
LOW CENTERED AT THE SOUTH CAROLINA COAST NEAR 33N79W. A SURFACE
TROUGH AXIS EXTENDS FROM THE LOW ACROSS SOUTHERN GEORGIA TO
COASTAL LOUISIANA. SCATTERED SHOWERS AND TSTMS ARE OCCURRING N
OF 29N W OF A LINE FROM 29N79W TO 34N73W. THE SOUTH ACROSS THE
REMAINDER OF THE SW NORTH ATLC...A WEAK SURFACE RIDGE AXIS
EXTENDS FROM NEAR BERMUDA SW TO THE SOUTHERN FLORIDA PENINSULA.
HOWEVER...EMBEDDED WITHIN THE RIDGING IS ENERGY...LIKELY
FRACTURED AWAY FROM THE TROPICAL WAVE ALONG 80W...ANALYZED AS A
SURFACE TROUGH FROM CENTRAL CUBA NEAR 22N79W TO 27N75W. THIS
BOUNDARY IS PROVIDING FOCUS FOR SCATTERED SHOWERS AND TSTMS FROM
24N-29N BETWEEN 74W-78W. FINALLY...THE REMAINDER OF THE CENTRAL
AND EASTERN ATLC IS UNDER THE INFLUENCE OF A SURFACE RIDGE
ANCHORED BY A 1027 MB HIGH CENTERED NEAR 35N53W.

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

$$
HUFFMAN



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