[Tropical] Tropical Weather Discussion

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AXNT20 KNHC 041758
TWDAT

TROPICAL WEATHER DISCUSSION
NWS NATIONAL HURRICANE CENTER MIAMI FL
205 PM EDT SUN AUG 04 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
1715 UTC.

...TROPICAL WAVES...
A BROAD TROPICAL WAVE EXTENDS FROM 10N38W TO 21N40W MOVING W AT
ABOUT 20 KT. THE WAVE IS PART OF A LARGER AREA OF OVERALL BROAD
TROUGHING IN THE CENTRAL ATLANTIC AND IS COUPLED WITH MID-
LATITUDE MID-LEVEL TROUGHING NOTED TO THE NW OF THE WAVE IN THE
VICINITY OF 21N47W. WHILE NEITHER FEATURE EXHIBITS A STRONG
SIGNAL ON SATELLITE IMAGERY AND IN GLOBAL MODEL DATA...ENERGY
ASSOCIATED WITH EACH ARE FORECAST TO MERGE WITHIN THE NEXT 12 TO
24 HOURS ACROSS THE CENTRAL ATLC AND CONTINUE A FAIRLY RAPID
WESTWARD MOVEMENT TOWARD THE LESSER ANTILLES REACHING 60W BY
TUE. THE WAVE IS SURROUNDED BY A MASSIVE AREA OF SUSPENDED
SAHARAN DUST AT THIS TIME WITH NO DEEP CONVECTION OCCURRING IN
THE VICINITY OF THE WAVE. GOES-R PROVING GROUND SAL AND AIRMASS
IMAGERY SUGGESTED THIS DUST OUTBREAK WAS FAIRLY SIGNIFICANT.

...ITCZ/MONSOON TROUGH...
THE MONSOON TROUGH AXIS EXTENDS FROM THE COAST OF MAURITANIA
NEAR 16N17W TO 14N25W TO 10N33W. THE INTERTROPICAL CONVERGENCE
ZONE AXIS EXTENDS FROM 10N33W TO 10N45W TO 06N55W. WIDELY
SCATTERED MODERATE CONVECTION IS WITHIN 120 NM EITHER SIDE OF A
LINE FROM 11N16W TO 10N25W. SCATTERED MODERATE CONVECTION WAS
NOTED WITHIN 180 NM S OF THE ITCZ BETWEEN 33W AND 46W.

...DISCUSSION...

GULF OF MEXICO...
A MIDDLE TO UPPER LEVEL ANTICYCLONIC CIRCULATION IS CENTERED
OVER NORTH-CENTRAL TEXAS NEAR 33N99W AND IS PROVIDING THE GULF
WITH NORTHEAST TO EASTERLY FLOW ALOFT. WATER VAPOR IMAGERY
INDICATES IT REMAINS MODERATELY DRY AND STABLE WITH UPPER LEVEL
CONVECTIVE DEBRIS CLOUDINESS COVERING THE EAST-CENTRAL GULF FROM
22N-28N E OF 90W. OTHERWISE...THE GULF IS UNDER THE INFLUENCE OF
A SURFACE RIDGE ANCHORED BY A 1021 MB HIGH CENTERED OVER THE
CENTRAL GULF NEAR 25N88W. VISIBLE SATELLITE IMAGERY AND COASTAL
WSR-88D IMAGERY ARE INDICATING WIDELY SCATTERED POPCORN SHOWERS
AND TSTMS ARE OCCURRING WITHIN 120 NM OF THE COAST FROM
GALVESTON TEXAS AROUND THE GULF TO THE SW COAST OF FLORIDA NEAR
FORT MYERS. THE ACTIVITY APPEARED TO BE MORE CONCENTRATED OVER
NORTH-CENTRAL FLORIDA. LOOKING AHEAD...RIDGING WILL DOMINATE
OVER THE BASIN THROUGH WEDNESDAY WITH SOUTHERLY WINDS PREVAILING
W OF 90W IN THE RANGE OF 10-20 KT.

CARIBBEAN SEA...
A MID TO UPPER LEVEL ANTICYCLONIC CIRCULATION IS CENTERED OVER
THE WESTERN CARIBBEAN NEAR 13N82W. EASTERLY FLOW ON THE SOUTH
SIDE OF THE FEATURE WAS ADVECTING MOISTURE WESTWARD OVER CENTRAL
AMERICA. LOW LEVEL CONVERGENT FLOW ALONG THE COAST FROM
NICARAGUA TO PANAMA IN COMBINATION WITH UPPER LEVEL DIFFLUENCE
AND THE PRESENCE OF THE MONSOON TROUGH AXIS WAS RESULTING IN
SCATTERED SHOWERS AND TSTMS IN THE AREA. ON THE EASTERN
PERIPHERY OF THE UPPER LEVEL ANTICYCLONE...A DRIER NORTHWESTERLY
FLOW PREVAILS BETWEEN 70W-80W WITH MOSTLY CLEAR SKIES AND FAIR
CONDITIONS. FINALLY...OVER THE EASTERN CARIBBEAN AN UPPER LEVEL
LOW IS CENTERED NORTH OF PUERTO RICO NEAR 23N66W WAS RESULTING
IN BROAD TROUGHING E OF 70W. WATER VAPOR IMAGERY INDICATES THE
TROUGHING EXHIBITS RELATIVELY DRY AIR ALOFT AND THIS IS
RESULTING IN ONLY A FEW ISOLATED LOW-TOPPED SHOWERS OCCURRING
FROM 16N-18N BETWEEN 69W-73W...AND E OF 66W...INCLUDING THE
LESSER ANTILLES. OTHERWISE...THE EXTENSIVE SAHARAN AIR
LAYER/DUST IS CONTRIBUTING TO THE OVERALL STABILITY OF THE BASIN
E OF 80W.

HISPANIOLA...
VISIBLE SATELLITE IMAGERY INDICATED ONLY A FEW STREETS OF LOW
CLOUDS IN AND AROUND HISPANIOLA WITH SIGNIFICANT SAHARAN DUST
NOTED AS WELL. SURFACE OBSERVATIONS SO FAR DO NOT INDICATE ANY
RESTRICTIONS TO VISIBILITIES AS A RESULT OF THE SAHARAN DUST.
NONETHELESS THE SAHARAN AIR LAYER WILL PROVIDE AN OVERALL STABLE
ATMOSPHERE OVER THE NEXT FEW DAYS WITH VERY LITTLE IN THE WAY
OF CONVECTIVE ACTIVITY EXPECTED.

ATLANTIC OCEAN...
NORTHEASTERLY UPPER LEVEL FLOW IS NOTED ON WATER VAPOR IMAGERY
BETWEEN 70W AND THE SE CONUS. A NARROW SHEARED MID-LEVEL TROUGH
IS IN THE VICINITY OF 28N77W WAS WEAKENING AS IT APPROACHED A
COL IN THE SW NORTH ATLC. THIS TROUGH SUPPORTS A 1010 MB LOW
CENTERED NEAR 34N73W AND A SURFACE TROUGH EXTENDING FROM THE LOW
TO 29N77W. GENERALLY AN OVERALL WEAKNESS IN THE SURFACE RIDGING
EXTENDING FROM THE CENTRAL ATLC TO THE GULF OF MEXICO... MAXIMUM
MIDDLE TO UPPER LEVEL DIFFLUENCE IN THE REGION IS GENERATING
OVERCAST CLOUDINESS WITH ISOLATED SHOWERS AND TSTMS WITHIN 150
NM EITHER SIDE OF A LINE FROM 32N71W TO 25N79W. THIS AREA OF
TROUGHING...ALONG WITH THE LOW PRESSURE CENTER IS EXPECTED TO
MOVE NORTHEAST WELL NORTH OF THE DISCUSSION AREA OVER THE NEXT
12 HOURS. OTHERWISE THE REMAINDER OF THE SW NORTH ATLC...CENTRAL
ATLC...AND EASTERN ATLC ARE UNDER THE INFLUENCE OF A SURFACE
RIDGE ANCHORED BY A 1022 MB HIGH CENTERED NEAR 29N58W AND A 1030
MB HIGH CENTERED S OF THE AZORES NEAR 34N30W. EMBEDDED WITHIN
THE SOUTHERN PERIPHERY OF THE RIDGE... MID-LATITUDE MID-LEVEL
ENERGY IS LOCATED IN THE VICINITY OF 21N47W. WHILE NO
SIGNIFICANT CONVECTION IS OCCURRING WITH THIS FEATURE...IT IS
FORECAST TO MERGE WITH ENERGY ASSOCIATED WITH THE TROPICAL WAVE
ALONG 38W/40W OVER THE NEXT 24 HOURS. FINALLY...ONE OF THE MORE
EXTENSIVE AREAS OF SAHARAN DUST THUS FAR THIS SEASON COVERS MUCH
OF THE TROPICAL ATLC AND IS PROVIDING OVERALL STABLE CONDITIONS
THIS MORNING. AS NOTED ABOVE...GOES R PROVING GROUND PRODUCTS
HAVE BEEN INSTRUMENTAL IN IDENTIFYING THE EXTENT OF THIS LATEST
DUST OUTBREAK.

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

$$
COBB


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