[Tropical] Tropical Weather Discussion

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AXNT20 KNHC 211109
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
805 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 0600 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH
1045 UTC.

...ITCZ...
ITCZ AXIS IS CENTERED ALONG 5N7W 4N17W THE EQ30W 2S44W.
SCATTERED SHOWERS AND ISOLATED TSTMS ARE NOTED WITHIN 300 NM N
OF THE AXIS BETWEEN 14W AND 34W AND WITHIN 210 NM N OF THE AXIS
BETWEEN 33W AND 49W. THE HEAVIEST CONVECTION WAS NOTED WITHIN 15
NM OF LINE 4.2N33.9W 1.6N38.6W WITH CONVECTIVE TOPS TO -76C AND
ACTIVITY GENERALLY INCREASING.

...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 9N95W. 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 S CENTRAL TEXAS.
THE RESULTANT DEBRIS MOISTURE IS ADVECTED E ACROSS THE NW
GULF OF MEXICO...NW OF LINE 27N97W 30N91W. ADDITIONALLY...
DEBRIS MOISTURE ORIGINATING FROM YESTERDAY AFTERNOON SEABREEZE
CONVECTION OVER OLD MEXICO...FROM 17N TO 23N...IS NOW SPREADING
ENE ACROSS THE SW GULF WATERS...ROUGHLY S OF 25N W OF 90W. A
1017 MB HIGH IS CENTERED OVER N FLORIDA NEAR 30N83W WITH A RIDGE
EXTENDING W ALONG 29N. THIS HIGH IS EXPECTED TO SHIFT E OF THE
GULF LATER TODAY MERGING WITH HIGH PRES NEAR 33N 72W. ITS
ASSOCIATED RIDGE WILL SHIFT SLIGHTLY S TO ALONG 28N OVER THE
GULF ALLOWING A WEAK SURFACE FRONT OVER TEXAS TO SLIP SE INTO
THE NW COASTAL PLAINS...STALL AND QUICKLY LOSE IDENTITY.

CARIBBEAN SEA...
ALOFT...A BROAD SHORTWAVE RIDGE DOMINATES THE CARIBBEAN W OF 77W
ORIGINATING FROM A TROPICAL ANTICYCLONE CENTERED OVER THE E PAC
NEAR 9N95W. THE UPPER LEVEL WLY FLOW TURNS CYCLONIC JUST TO THE
E OF 77W AND INTO AN UPPER TROUGH EXTENDING S INTO THE CARIBBEAN
WITH ITS MEAN AXIS N OF 14N ALONG 68W. UPPER DEBRIS MOISTURE
FROM AFTERNOON CONVECTION OVER GUATEMALA...BELIZE...AND HONDURAS
IS NOW SPREADING E OVER THE WESTERN GULF OF HONDURAS...BUT SEEMS
TO EVAPORATE ALONG 83W. 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
BETWEEN THE GULF OF HONDURAS AND GRAND CAYMAN WITH SLIGHT
CYCLONIC TURNING CENTERED ON 19N83W. AN AREA OF OVERCAST LOW
CLOUDS AND SCATTERED SHOWERS IS NOTED WITHIN 90 NM OF 17N81W.
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 40N58W WITH A
TROUGH EXTENDING S INTO THE DISCUSSION AREA ALONG 32N61W TO
20N67W AND CONTINUING SW INTO THE CARIBBEAN. WEAK LOW LEVEL;
TROUGHINESS IS SUGGESTED IN LOW LEVEL PRESSURE FIELD JUST N OF
THE BAHAMAS...ROUGHLY FROM 27N80W TO 30N77W. BROKEN LOW AND MID
LAYERED CLOUDS...AND WEAK SHOWERS...ARE NOTED WITHIN 90 NM OF
28N76W. A FRONTAL TROUGH CONTINUES TO WEAKEN ALONG 32N50W
23N70W. 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 21N53W 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 7N61W...AND EXTENDS NE TO WELL BEYOND 32N45W...
CRESTING NEAR 50N35W ATTM. CONVECTIVE DEBRIS MOISTURE SPILLS E
ACROSS THE RIDGE COVERING THE DISCUSSION AREA N OF 23N BETWEEN
53W AND 33W.

AN UPPER TROUGH ORIGINATES FROM A CYCLONE JUST OFF THE NW COAST
OF SPAIN AND EXTENDS SW INTO THE DISCUSSION AREA ALONG 32N16W
26N19W TO A BASE NEAR 14N42W. A BAND OF DRY UPPER AIR IS NOTED
WITHIN 240 NM EITHER SIDE OF LINE 27N4W 21N21W 14N47W. UPPER
MOISTURE IS INDICATED NW OF THE UPPER TROUGH E OF 32W. A BROAD
UPPER ANTICYCLONE IS NOTED OVER AFRICA ESTIMATED NEAR 15N5E WITH
A RIDGE EXTENDING W OFF THE AFRICAN COAST AT 11N15W TO S AMERICA
NEAR 4N51W. UPPER DIFFLUENCE IS ENHANCING ITCZ CONVECTION
DESCRIBED ABOVE. AT THE LOW LEVELS HIGH PRES IS CENTERED NEAR
43N27W 1030 MB WITH A RIDGE SW ALONG 32N34W TO NEAR 22N53W.
LOCALLY BROKEN STRATOCUMULUS IS NOTED SE OF THE RIDGE AXIS.
SAHARAN DUST WAS OBSERVED ON THIS MORNINGS VISIBLE IMAGERY FROM
9N TO 20N E OF 26W.

$$
NELSON




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