[Tropical] Tropical Weather Discussion

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AXNT20 KNHC 210556
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
205 AM EDT FRI APR 21 2006

TROPICAL WEATHER DISCUSSION FOR NORTH AMERICA...CENTRAL
AMERICA...THE GULF OF MEXICO...THE CARIBBEAN SEA...NORTHEASTERN
SECTIONS OF SOUTH AMERICA...AND THE 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 0000 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH
0345 UTC.

...ITCZ...
ITCZ AXIS IS CENTERED ALONG 8N13W 1N30W 1N48W. SCATTERED SHOWERS
AND ISOLATED TSTMS ARE NOTED WITHIN 240 NM EITHER SIDE OF AXIS
BETWEEN 10W AND 26W AND BETWEEN 35W AND 47W. ISOLATED SHOWERS
AND TSTMS WERE ALSO NOTED WITHIN 15 NM OF LINE 6N27W 4N34W.

...DISCUSSION...
GULF OF MEXICO...
ALOFT...A BROAD SHORTWAVE RIDGE DOMINATES THE GULF OF MEXICO
ORIGINATING FROM A TROPICAL ANTICYCLONE CENTERED OVER THE E PAC
NEAR 8N98W. THUS THE UPPER AIR IS DRY AND THE FLOW NEARLY ZONAL
OVER MOST OF THE GULF. THE EXCEPTION IS THAT UPPER DIFFLUENCE IS
ENHANCING CONVECTION ALONG A SURFACE FRONT OVER THE EXTREME NE
TEXAS COASTAL PLAINS...WITH THE DEBRIS MOISTURE ADVECTED ENE AND
JUST BARELY ENTERING THE EXTREME NW GULF OF MEXICO COASTAL
WATERS. DEBRIS MOISTURE ORIGINATING FROM AFTERNOON SEABREEZE
CONVECTION OVER OLD MEXICO...BETWEEN 17N TO 25N...IS NOW
SPREADING ENE ACROSS THE SW WATERS...ROUGHLY S OF 25N W OF 90W.
A 1016 MB HIGH IS CENTERED OVER THE FLORIDA BIG BEND WITH A
RIDGE EXTENDING W ALONG 29N. THIS HIGH IS EXPECTED TO SHIFT E OF
THE GULF TODAY WITH ITS ASSOCIATED RIDGE SHIFTING SLIGHTLY S TO
ALONG 28N AS THE WEAK SURFACE FRONT MOVES INTO THE NW WATERS AND
DISSIPATES.

CARIBBEAN SEA...
ALOFT...A BROAD SHORTWAVE RIDGE DOMINATES THE CARIBBEAN W OF 77W
ORIGINATING FROM A TROPICAL ANTICYCLONE CENTERED OVER THE E PAC
NEAR 8N98W. THE UPPER WLY FLOW TURNS CYCLONIC TO THE E OF 77W
AND INTO AN UPPER TROUGH EXTENDING S INTO THE CARIBBEAN WITH ITS
MEAN AXIS N OF 14N ALONG 72W. UPPER DEBRIS MOISTURE FROM
AFTERNOON CONVECTION OVER GUATEMALA...BELIZE...AND HONDURAS IS
NOW SPREADING E OVER THE GULF OF HONDURAS.  AT THE LOW LEVELS
ELY TRADES DOMINATE THE CARIBBEAN WITH THE GRADIENT STRONGEST S
OF 13N AND OVER THE GULF OF HONDURAS. LATEST IMAGERY SUGGESTS A
TROUGH IS DEVELOPING JUST NE OF THE GULF OF HONDURAS WITH
CYCLONIC TURNING CENTERED ON 18N83W. AN AREA OF OVERCAST LOW
CLOUDS AND SCATTERED SHOWERS IS NOTED WITHIN 90 NM OF 16N80W.
THE CONVECTION IN THIS AREA MAY BE ENHANCED LATER TODAY IF THE
LOW LEVEL TROUGH CONTINUES TO DEVELOP. OTHERWISE...LITTLE CHANGE
EXPECTED NEXT FEW DAYS.

ATLANTIC OCEAN...
A LONG WAVE TROUGH DOMINATES THE UPPER LEVELS OF THE NW ATLC. AN
EMBEDDED DEEP-LAYERED CYCLONE IS CENTERED NEAR 40N60W WITH A
TROUGH EXTENDING S INTO THE DISCUSSION AREA ALONG 32N63W TO
BEYOND 20N68W INTO THE CARIBBEAN. AN EMBEDDED CYCLONE WAS NOTED
EARLIER NEAR 28N74W BUT HAS WEAKENED WITH ONLY WEAK TROUGHINESS
SUGGESTED AT THE LOW LEVELS JUST N OF THE BAHAMAS...ROUGHLY FROM
27N79W TO 30N76W. BROKEN LOW AND MID LAYERED CLOUDS...AND WEAK
SHOWERS...ARE NOTED WITHIN 90 NM OF 28N76W. A FRONTAL TROUGH
CONTINUES TO WEAKEN ALONG 32N50W 23N65W. BROKEN TO LOCALLY
OVERCAST LOW AND MID LAYERED CLOUDS ARE OBSERVED WITHIN 360 NM
EITHER SIDE OF THIS DECAYING FRONT. UPPER DIFFLUENCE E OF THE
UPPER TROUGH IS ENHANCING CONVECTION WITHIN 30 NM EITHER SIDE OF
LINE 32N45W 19N57W...LIKELY ALONG A WEAKENED PRE-FRONTAL TROUGH.
DEBRIS MOISTURE FROM THIS CONVECTION IS ADVECTED NE AND E IN
ASSOCIATION WITH AN UPPER RIDGE THAT ORIGINATES NEAR 6N60W...AND
EXTENDS NE TO WELL BEYOND 32N43W AND CRESTING NEAR 50N33W ATTM.
CONVECTIVE DEBRIS MOISTURE SPILLS E ACROSS THE RIDGE COVERING
THE DISCUSSION AREA N OF 23N BETWEEN 49W AND 35W.

AN UPPER TROUGH ORIGINATES FROM A CYCLONE JUST OFF THE NW COAST
OF SPAIN AND EXTENDS SW INTO THE DISCUSSION AREA ALONG 32N19W
23N27W TO A BASE NEAR 12N47W. A BAND OF DRY UPPER AIR IS NOTED
WITHIN 240 NM EITHER SIDE OF LINE 30N1W 22N17W 13N48W. UPPER
MOISTURE IS INDICATED NW OF THE UPPER TROUGH E OF 35W. A BROAD
UPPER ANTICYCLONE IS NOTED OVER AFRICA NEAR 15N5E WITH A RIDGE
EXTENDING W OFF THE AFRICAN COAST AT 10N16W TO S AMERICA NEAR
2N46W. UPPER DIFFLUENCE IS ENHANCING ITCZ CONVECTION DESCRIBED
ABOVE. AT THE LOW LEVELS HIGH PRES IS CENTERED NEAR 33N33W WITH
A RIDGE SW TO NEAR 18N60W. LOCALLY BROKEN STRATOCUMULUS IS NOTED
SE OF THE RIDGE AXIS. SAHARAN DUST WAS OBSERVED ON YESTERDAYS
VISIBLE IMAGERY E OF 25W FROM 10N-20N.

$$
NELSON



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