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346
AXNT20 KNHC 241107
TWDAT

TROPICAL WEATHER DISCUSSION
NWS NATIONAL HURRICANE CENTER MIAMI FL
805 AM EDT THU APR 24 2014

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
1045 UTC.

...THE ITCZ/THE MONSOON TROUGH...
THE MONSOON TROUGH EXITS W AFRICA AND PASSES THROUGH COASTAL
SECTIONS OF SENEGAL NEAR 14N16.5W AND ON TO NEAR 02N21W...WHERE
IT TRANSITIONS TO ITCZ. THE ITCZ THEN EXTENDS WESTWARD THROUGH
01N23.5W TO 00N38W TO COASTAL BRAZIL NEAR 01.5S46W. ISOLATED
MODERATE CONVECTION WAS NOTED FROM 03S TO 07N BETWEEN 13W AND
23W...WHILE SCATTERED STRONG CONVECTION WAS NOTED N OF 04N TO
WELL INLAND BETWEEN 10W AND 23W. SCATTERED MODERATE TO STRONG
CONVECTION WAS NOTED FROM 03S TO COASTAL AFRICA BETWEEN 03E AND
08W. ISOLATED MODERATE CELLS WERE OCCURRING IN A NARROW LINE
FROM 60 TO 150 NM N OF THE ITCZ BETWEEN 34W AND 45W.

...DISCUSSION...

...THE GULF OF MEXICO...
MILDLY DIFFLUENT UPPER LEVEL FLOW PREVAILS ACROSS THE W GULF
THIS MORNING AS UPPER RIDGING IS SHIFTING SLOWLY E ACROSS THE E
CENTRAL U.S. AND BROAD TROFFING EXTENDS FROM THE N CENTRAL GULF
S-SW THROUGH THE YUCATAN PENINSULA AND INTO THE TROPICAL EPAC
ALONG 93W. A WEAK MIDDLE LEVEL CYCLONIC VORTEX CAN BE SEEN IN
WATER VAPOR IMAGERY ACROSS THE N CENTRAL GULF NEAR 28N87W AND
SHIFTING EASTWARD...AND IS BECOMING SEPARATED FROM MIDDLE TO
UPPER LEVEL TROFFING ACROSS THE NW ATLC. THIS IS YIELDING DRY
AND GENERALLY STABLE CONDITIONS ALOFT N OF 25N. THE UPPER RIDGE
WILL SHIFT E TO ALONG 80W BY 00Z THIS EVENING...FOLLOWED BY A
DEEP LAYERED TROUGH CURRENTLY SHIFTING E ACROSS THE GREAT PLAINS
AND WILL SHIFT E INTO THE MS VALLEY TODAY. THIS DEEP LAYERED
TROUGH WILL SUPPORT A FRONTAL SYSTEM MOVING SE THROUGH TEXAS
TODAY...THEN SLOW TONIGHT ACROSS SE TEXAS AND NW LOUISIANA.
CURRENTLY...A 1015 MB HIGH IS CENTERED ACROSS THE NE GULF NEAR
27N83.5W...WITH MODERATE SE TO S RETURN FLOW PREVAILING ACROSS W
AND NW PORTIONS. THE HIGH WILL SHIFT E TO THE FLORIDA PENINSULA
TODAY AHEAD OF THE APPROACHING FRONT...AND COLLAPSE. RETURN FLOW
ACROSS ALL BUT SE PORTIONS WILL PROVIDE SUFFICIENT MOISTURE FOR
LATE AFTERNOON AND EVENING CONVECTION ACROSS N AND NW COASTAL
PORTIONS AS UPPER CONDITIONS DESTABILIZE IN ADVANCE OF THE
APPROACHING UPPER TROUGH. THE FRONT IS FORECAST TO STALL LATE
TONIGHT-EARLY FRI MORNING ACROSS THE NORTHERN COASTS AND COASTAL
WATERS ALONG ABOUT 30N...AND WEAKEN.

...THE CARIBBEAN SEA...
A BROAD UPPER RIDGE DOMINATES ALL BUT FAR NW PORTIONS OF THE
CARIBBEAN THIS MORNING...YIELDING MODEST UPPER CONFLUENCE AND
MOSTLY STABLE CONDITIONS ALOFT. THE ATLANTIC RIDGE IS PRESENTLY
CENTERED ACROSS THE NE ATLC AND EXTENDS SW AND WEAKLY TO PUERTO
RICO AND THE NE CARIBBEAN...MAINTAINING GENERALLY LIGHT TO
MODERATE TRADE WINDS ACROSS THE CARIBBEAN BASIN THIS MORNING.
THE EXCEPTION IS ALONG THE COAST OF VENEZUELA...THE ABC ISLANDS
AND NE COLOMBIA...WHERE WINDS TO 20 KT WERE NOTED. ACTIVE DEEP
CONVECTION IS OCCURRING ACROSS MUCH OF N COLOMBIA ATTM AND
SPREADS N INTO THE IMMEDIATE WATERS WITHIN 45 NM OF THE COAST.
AN OLD FRONTAL ZONE PERSISTS FROM THE ATLANTIC W-SW ACROSS THE
NW COAST OF HAITI AND THROUGH THE WINDWARD PASSAGE TO JUST W OF
THE CAYMAN ISLANDS NEAR 19N83W. ISOLATED TO WIDELY SCATTERED
SHOWERS ARE SEEN NEAR THE BOUNDARY...MOSTLY W OF THE CAYMANS.
HIGH PRES WILL BUILD N OF THE AREA THIS WEEKEND...ALLOWING TRADE
WINDS TO INCREASE OVER THE SOUTH CENTRAL CARIBBEAN AND GULF OF
HONDURAS. ADDITIONALLY...A BROAD ZONE OF LOW LEVEL MOISTURE
ACROSS THE TROPICAL N ATLC S OF 15N WILL MOVE W-NW ACROSS THE
LESSER ANTILLES TODAY AND ACROSS THE E CARIBBEAN THROUGH TONIGHT
TO YIELD WIDELY SCATTERED TO SCATTERED BRIEF PASSING SHOWERS.

...HISPANIOLA...
AN OLD FRONTAL ZONE MENTIONED ABOVE...IN THE FORM OF A
TROUGH...EXTENDS W-SW ACROSS THE NW COAST OF HAITI. TPW
ANIMATIONS SUGGEST THE BEST MOISTURE IS CONVERGING N OF THIS
TROUGH AND ACROSS N COASTAL SECTIONS AND INTO THE TURKS AND
CAICOS ISLANDS. THIS BOUNDARY WILL CONTINUE TO WEAKEN
TODAY...BUT SUFFICIENT LLVL MOISTURE WILL COMBINE WITH
PREVAILING LIGHT TO MODERATE E-SE LLVL FLOW TO FOCUS AFTERNOON
AND EVENING CONVECTION ACROSS N CENTRAL AND NW PORTIONS OF THE
ISLAND. DUE TO A NARROW MID LEVEL RIDGE ACROSS THE AREA...
CONDITIONS ARE NOT EXPECTED TO BE VERY UNSTABLE...AND ONLY
ISOLATED MODERATE TSTMS ARE EXPECTED.

...THE ATLANTIC OCEAN...
A BROAD MID TO UPPER LEVEL TROUGH CONTINUES TO MOVE EASTWARD
OVER THE NW ATLANTIC...REACHING FROM OFFSHORE OF NEW ENGLAND SE
TO A BASE NEAR 28N59W. MIDDLE TO UPPER LEVEL DYNAMICS AHEAD OF
THIS TROUGH ARE INTERACTING WITH A STALLED AND WEAKENING FRONTAL
ZONE...EXTENDING FROM 31N54W TO NW HAITI...TO PRODUCE AN AREA OF
SCATTERED MODERATE CONVECTION WITHIN 180 NM SE OF THE FRONTAL
TROUGH N OF 26N. THE BROAD DEEP LAYERED TROUGH ALSO SUPPORTS A
FRONTAL BOUNDARY THAT HAS SWEPT THROUGH BERMUDA IN THE PAST
COUPLE OF HOURS AND ACROSS N CENTRAL PORTIONS OF THE AREA. A
WEAK 1015 MB HIGH WAS NOTED BETWEEN THESE TWO BOUNDARIES...
CENTERED OVER THE SE BAHAMAS. THE NEW FRONT WILL SHIFT SE
THROUGH FRIDAY AND THEN DRIFT S TO ALONG 24N EARLY SAT AND
STALL...FOLLOWED BY MODERATE RIDGING. THIS WILL INCREASE TRADE
WIND FLOW S OF 22N W OF 60W THIS WEEKEND.

FARTHER EAST...THE ATLC RIDGE EXTENDS FROM 1028 MB HIGH NEAR
34N28W TO PUERTO RICO AND THE WATERS JUST N OF THE MONA PASSAGE.
RECENT ASCAT DATA INDICATED MODERATE TRADEWINDS 15-20 KT
OCCURRING S OF THE RIDGE W OF 30W...AND GENERALLY S OF 18-20N...
WITH SEAS 8 TO 9 FT AS NOTED BY ALTIMETER SATELLITE PASSES
BETWEEN 40W AND 45W. MODERATE TO FRESH N TO NE FLOW IS NOTED
OVER THE FAR EASTERN TROPICAL ATLC WATERS EAST OF 35W TO THE
COAST OF AFRICA. LIMITED TRADE WIND CONVERGENCE IS INHIBITING
SIGNIFICANT CONVECTION ALONG THE ITCZ...ALTHOUGH UPPER RIDGING
ACROSS EQUATORIAL E ATLC AND CENTRAL AFRICA ARE ENHANCING
SHOWERS AND THUNDERSTORMS IN THE DEEP TROPICS SOUTH OF 10N
AND EAST OF 10W.

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

$$
STRIPLING




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