[Tropical] Tropical Weather Discussion

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AXNT20 KNHC 121744
TWDAT

TROPICAL WEATHER DISCUSSION
NWS NATIONAL HURRICANE CENTER MIAMI FL
205 PM EDT MON AUG 12 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...
TROPICAL WAVE EXTENDS FROM 11N32W TO 18N31W MOVING W AT 15-20
KT. THE WAVE COINCIDES WITH A BROAD LOW-LEVEL MONSOONAL GYRE
FOCUSED IN THE VICINITY OF A 1010 MB LOW CENTERED NEAR 11N32W.
IN ADDITION...A MID-LEVEL 700 MB TROUGH AXIS ALSO EXTENDS ALONG
32W NORTHWARD TO NEAR 20N. TOTAL PRECIPITABLE WATER IMAGERY
INDICATES MAXIMUM VALUES FROM 07N-19N BETWEEN 24W-35W.
CONVECTION REMAINS LARGELY EMBEDDED WITHIN THE MONSOON TROUGH
AXIS WITH SCATTERED MODERATE FROM 08N-11N BETWEEN 28W-38W.

TROPICAL WAVE EXTENDS FROM 09N53W TO 19N56W MOVING W AT 20 KT.
THE WAVE REMAINS ON THE LEADING EDGE OF SAHARAN DUST WHICH IS
NOTED ON VISIBLE SATELLITE IMAGERY TO THE EAST OF THE WAVE AXIS.
THIS SAHARAN AIR LAYER IS INHIBITING ANY DEEP CONVECTION AND
RESULTING IN ONLY A FEW POSSIBLE SHOWERS WITHIN 180 NM EITHER
SIDE OF THE WAVE AXIS.

...ITCZ/MONSOON TROUGH...
THE MONSOON TROUGH EXTENDS FROM THE AFRICAN COAST NEAR 15N17W TO
14N27W TO 11N32W TO 07N43W. THE INTERTROPICAL CONVERGENCE ZONE
AXIS EXTENDS FROM 07N43W TO 06N57W. SCATTERED MODERATE
CONVECTION IS WITHIN 180 NM EITHER SIDE OF A LINE FROM 13N17W
TO 07N37W.

...DISCUSSION...

GULF OF MEXICO...
NORTHEASTERLY UPPER LEVEL FLOW IS NOTED ON WATER VAPOR IMAGERY
OVER THE GULF THIS AFTERNOON BETWEEN AN UPPER LEVEL ANTICYCLONIC
CIRCULATION CENTERED OVER NORTHERN MEXICO NEAR 30N106W AND AN
UPPER LEVEL LOW CENTERED OVER THE NORTHWESTERN CARIBBEAN SEA
NEAR 22N83W. OVERALL A DRIER AIRMASS IS ADVECTING WESTWARD WITH
MOST MIDDLE TO UPPER LEVEL MOISTURE REMAINING W OF 93W. AS A
RESULT...A SURFACE RIDGE ANCHORED BY A 1021 MB HIGH CENTERED
ACROSS THE FLORIDA PANHANDLE NEAR 31N86W CONTINUES TO FURTHER
SUPPORT THE STABLE CONDITIONS ALOFT WITH MOSTLY CLEAR SKIES AND
FAIR CONDITIONS. A FEW ISOLATED SHOWERS AND TSTMS ARE HOWEVER
OCCURRING ON THE NORTHERN PERIPHERY OF THE UPPER LEVEL LOW
ACROSS THE FLORIDA STRAITS AND SE GULF S OF 24N E OF 88W...
INCLUDING THE YUCATAN CHANNEL AREA. FARTHER WEST...A WEAKENING
SURFACE TROUGH ANALYZED FROM 19N96W TO 24N98W CONTINUES TO
PROVIDE FOCUS FOR WIDELY SCATTERED SHOWERS AND ISOLATED TSTMS S
OF 24N BETWEEN 91W-98W. OTHERWISE...E-SE WINDS IN THE RANGE OF
10 TO 20 KT PREVAIL AND WITH A GRADUAL SHIFT WESTWARD OF THE
SURFACE HIGH...LIGHT ANTICYCLONIC FLOW IS EXPECTED TO PERSIST
THROUGH LATE TUESDAY. THEREAFTER...A RIDGE AXIS IS FORECAST TO
ANCHOR ALONG 27N/28N UNTIL FRIDAY AS A SURFACE TROUGH PROGRESSES
W-NW OUT OF THE NW CARIBBEAN SEA INTO THE SE GULF.

CARIBBEAN SEA...
AN UPPER LEVEL LOW IS CENTERED OVER THE NW CARIBBEAN NEAR 22N83W
AND STRETCHES AN UPPER LEVEL TROUGH AXIS EASTWARD ALONG 22N TO
66W. MUCH OF THE BASIN LIES WITHIN WESTERLY UPPER LEVEL FLOW
ALOFT ON THE SOUTHERN PERIPHERY OF THIS TROUGHING WITH WATER
VAPOR IMAGERY INDICATING PLENTY OF MIDDLE TO UPPER LEVEL
MOISTURE IN WHICH TO WORK WITH FOR CONVECTIVE PROCESSES. AS FOR
THE UPPER LEVEL LOW...WIDELY SCATTERED SHOWERS AND ISOLATED
TSTMS ARE OCCURRING N OF 16N BETWEEN 76W-89W...INCLUDING THE
YUCATAN CHANNEL...CAYMAN ISLANDS...THE GULF OF HONDURAS...AND
INLAND PORTIONS OF BELIZE. FARTHER SOUTH...CONVECTION BECOMES
MORE SCATTERED IN COVERAGE WITH SHOWERS AND TSTMS OCCURRING S OF
16N BETWEEN 73W-84W. MUCH OF THIS CONVECTION IS AIDED BY LOW-
LEVEL MOISTURE CONVERGENCE AND THE PRESENCE OF THE MONSOON
TROUGH AXIS EXTENDING FROM NORTHERN COLOMBIA NEAR 12N73W TO
NORTHERN COSTA RICA NEAR 11N85W. FINALLY...THE LAST FEATURE TO
DISCUSS IS A SURFACE TROUGH ANALYZED FROM 12N71W TO EASTERN
HISPANIOLA NEAR 19N69W. THIS SURFACE FEATURE COINCIDES WITH A
BROAD 700 MB TROUGH AXIS ACROSS THE CENTRAL CARIBBEAN AND LIES
BENEATH A MAXIMUM IN UPPER LEVEL DIFFLUENCE ACROSS THE EASTERN
CARIBBEAN. SCATTERED SHOWERS AND WIDELY SCATTERED TSTMS ARE
OCCURRING PRIMARILY EAST OF THE SURFACE TROUGH AXIS FROM 11N-19N
BETWEEN 64W-72W.

HISPANIOLA...
CURRENTLY LOW-LEVEL MOISTURE AND INSTABILITY IS ON THE INCREASE
ACROSS HISPANIOLA THIS AFTERNOON AS A SURFACE TROUGH EXTENDS
FROM THE EASTERN TIP NEAR 19N69W SOUTHWARD INTO THE OPEN WATERS
OF THE CENTRAL CARIBBEAN SEA. THE SAN JUAN PUERTO RICO AND
CAYMAN ISLANDS SOUNDINGS FROM 12/1200 UTC INDICATE THIS
TROUGHING EXTENDS INTO THE VERTICAL UP TO ABOUT 500 MB AND
REMAINS RELATIVELY BROAD. MOST OF THE ONGOING CONVECTION IS
NOTED S OF 18N...HOWEVER AS THE SURFACE TROUGH MOVES WESTWARD
SCATTERED SHOWERS AND TSTMS ARE EXPECTED TO INCREASE ACROSS THE
ISLAND FOR THE REMAINDER OF THIS AFTERNOON AND INTO THE EVENING.
THE TROUGH IS FORECAST TO CLEAR WEST OF THE ISLAND BY LATE
TUESDAY WITH E-SE WINDS PREVAILING IN THE RANGE OF 10 TO 20 KT.

ATLANTIC OCEAN...
A MIDDLE TO UPPER LEVEL ANTICYCLONIC CIRCULATION IS CENTERED
NEAR 32N72W THAT INFLUENCES A LARGE PORTION OF THE SW NORTH ATLC
THIS AFTERNOON. THE RIDGING ALOFT CONTINUES TO SUPPORT A SURFACE
RIDGE OF HIGH PRESSURE ANCHORED BY A 1021 MB HIGH CENTERED NEAR
29N77W. THE SURFACE RIDGE AXIS EXTENDS WESTWARD TO THE NORTHERN
FLORIDA PENINSULA. MOSTLY FAIR SKIES AND CONDITIONS ACCOMPANY
THIS FEATURE W OF 63W...HOWEVER A FEW WIDELY SCATTERED SHOWERS
AND ISOLATED TSTMS CONTINUE TO DRIFT WESTWARD UNDER LIGHT
EASTERLY SURFACE FLOW FROM 22N-26N BETWEEN 76W-82W...AND N OF
31N BETWEEN 63W-70W. FARTHER EAST ACROSS THE CENTRAL ATLC...AN
UPPER LEVEL LOW IS CENTERED NEAR 30N57W AND SUPPORTS A SURFACE
TROUGH ANALYZED FROM 24N55W TO 30N52W. SCATTERED SHOWERS AND
ISOLATED TSTMS ARE OCCURRING FROM 23N-31N BETWEEN 50W-63W IN
ASSOCIATION WITH BOTH THE FEATURES AT THE SURFACE AND ALOFT.
OTHERWISE...FAIRLY BENIGN CONDITIONS ARE NOTED ON SATELLITE
IMAGERY E OF 50W AS A SURFACE RIDGE DOMINATES. THE RIDGING IS
ANCHORED BY A 1026 MB HIGH CENTERED SW OF THE AZORES NEAR
33N41W. ASIDE FROM THE TROPICAL WAVES DISCUSSED IN DETAIL
ABOVE...BETWEEN THE WAVES AND THE REGION TO THE NORTH OF THE
WAVES...AN AREA OF SAHARAN DUST IS LOCATED GENERALLY N OF 15N E
OF 50W.

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

$$
HUFFMAN


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