[Tropical] Tropical Weather Discussion

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AXNT20 KNHC 180004
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL.
805 PM EDT SUN JUL 17 2005

TROPICAL WEATHER DISCUSSION FOR NORTH AMERICA...CENTRAL
AMERICA...GULF OF MEXICO...CARIBBEAN SEA...NORTHEASTERN 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 1800 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH
2345 UTC.

...SPECIAL FEATURE...

HURRICANE EMILY IS CENTERED NEAR 19.6N 85.9W OR ABOUT 90
MILES...145 KM...SOUTHEAST OF COZUMEL MEXICO AND ABOUT  270
MILES...440 KM...EAST-SOUTHEAST OF PROGRESO MEXICO AT 18/0000
UTC MOVING WNW 18 KT. THE LATEST MINIMUM CENTRAL PRESSURE IS 951
MB AND THE MAXIMUM SUSTAINED WIND SPEED IS 115 KT WITH GUSTS TO
140 KT AND EMILY REMAINS A CATEGORY FOUR HURRICANE. PLEASE REFER
TO THE LATEST FORECAST/ADVISORY UNDER AWIPS/WMO HEADERS
MIATCMAT5/ WTNT25 KNHC AND THE PUBLIC ADVISORY UNDER AWIPS/WMO
HEADERS MIATCPAT5/WTNT35 KNHC FOR MORE DETAILS. EMILY CONTINUES
TO DISPLAY AN OVERALL IMPRESSIVE SATELLITE APPEARANCE WITH ALL
THE SIGNS OF A MAJOR HURRICANE...ALTHOUGH THE EYE IS SOMEWHAT
CLOUD FILLED IN VISIBLE SATELLITE IMAGERY. INFRARED IMAGERY
INDICATES THAT VERY STRONG COLD TOP CONVECTION SURROUNDS THE EYE
WITH CLOUD TOP TEMPERATURES OF -85C WITH GOOD UPPER LEVEL
OUTFLOW WITH A POLEWARD OUTFLOW CHANNEL. NUMEROUS STRONG
CONVECTION EXTENDS OUTWARD 75-125 NM FROM THE CENTER WITH
SCATTERED MODERATE/ISOLATED STRONG CONVECTION ELSEWHERE WITHIN
250 NM OF THE CENTER ESPECIALLY OVER THE N SEMICIRCLE.  THE
STRONGEST OF THIS ACTIVITY IS BRUSHING THE WESTERN TIP OF CUBA
AND PULLING AWAY FROM THE CAYMAN ISLANDS AND ISLE OF YOUTH.
OUTER RAINBANDS FROM EMILY HAVE MOVES ASHORE OVER CANCUN AND
COZUMEL. CONDITIONS WILL DETERIORATE MARKEDLY TONIGHT AS THE
CENTER MAKES LANDFALL ON THE NORTHEAST COAST OF THE YUCATAN.

...TROPICAL WAVES...

TROPICAL WAVE OVER THE E ATLC ALONG 29W S OF 18N MOVING W NEAR
20 KT. THE WELL-DEFINED MID-LEVEL CIRCULATION OBSERVED EARLIER
IN SATELLITE IMAGERY HAS BECOME LESS DISTINCT. THE WAVE REMAINS
VOID OF ANY APPRECIABLE CONVECTIVE ACTIVITY.

TROPICAL WAVE OVER THE CENTRAL ATLC ALONG 47W/48W S OF 16N
MOVING W 20 KT. THE WAVE IS EMBEDDED WITHIN A LARGE SURGE OF LOW
LEVEL EASTERLIES AND AFRICAN DUST. AS A RESULT...THE WAVE IS
MOVING FASTER THAN USUAL AND CONVECTION REMAINS SUPPRESSED BY
THE RELATIVELY DRY AIR CONTAINED WITHIN THIS SURGE. SOME
CYCLONIC ROTATION IS OBSERVED IN SATELLITE IMAGERY ALONG THE
WAVE AXIS S OF 13N.

TROPICAL WAVE PASSING THROUGH THE LEEWARD/WINDWARD ISLANDS ALONG
61W S OF 20N MOVING W 15 TO 20 KT. THE WAVE CONTINUES TO
INTERACT WITH A STRONG LOW LEVEL EASTERLY SURGE...WITH LEADING
EDGE ROUGHLY ALONG 54W...AND THE MID-OCEANIC UPPER TROUGH FROM
THE NE CARIBBEAN TO BEYOND 32N50W. THIS SETUP IS IMPARTING A
ONE-TWO PUNCH OVER THE WAVE IN TERMS OF VERTICAL SHEAR
DISPLACING MUCH OF THE ENERGY AND ASSOCIATED DEEP CONVECTION
WELL NE OF THE WAVE AXIS. IN FACT...THE WAVE HAS SPLIT WITH ONE
PIECE OF ENERGY...ALONG 21N60W TO 29N50W...LIFTING SLOWLY NW
WHILE THE S EXTENT...ALONG 61W S OF 20N..CONTINUES W AT 15-20
KT. THE INTERSECTION OF THE NORTHERN EXTENT OF THE WAVE AND THE
LOW LEVEL EASTERLY SURGE MENTIONED ABOVE CONTINUES TO PRODUCE AN
IMPRESSIVE AREA OF SCATTERED MODERATE TO STRONG CONVECTION FROM
19N-22N BETWEEN 55W-59W. WIDELY SCATTERED MODERATE ISOLATED
STRONG CONVECTION HAS DEVELOPED ALONG THE SOUTHERN EXTENT OF THE
WAVE OVER THE LESSER ANTILLES. THIS ACTIVITY IS EXPECTED TO MOVE
INTO THE E CARIBBEAN TONIGHT BRINGING INCREASING LOW LEVEL
MOISTURE AND SCATTERED SHOWERS/ISOLATED TSTMS.

...ITCZ...

ITCZ AXIS IS CENTERED ALONG 16N10W 10N35W 12N48W 8N59W THEN
ACROSS N PORTIONS OF S AMERICA.  SCATTERED MODERATE/ISOLATED
STRONG CONVECTION FROM 8N-12N BETWEEN 49W-56W.

...DISCUSSION...

GULF OF MEXICO...
MID-UPPER LEVEL TROUGH SPLITS THE GLFMEX EXTENDING FROM THE NEAR
APALACHICOLA FLORIDA SW TO AN UPPER LOW OVER THE BAY OF
CAMPECHE NEAR 20N94W. UPPER LEVEL SUBSIDENCE WITH THE TROUGH HAS
BROUGHT ABOUT SOME DRYING DURING THE LAST 24 HOURS RESULTING IN
LESS SHOWER/TSTM ACTIVITY OVER THE AREA. THE ONLY SIGNIFICANT
AREA OF ACTIVE CONVECTION LIES ALONG THE WEST COAST OF THE
YUCATAN PENINSULA...AND ACTIVITY MOVING OFF THE W COAST OF
FLORIDA. ELSEWHERE...ALL EYES ON HURRICANE EMILY OVER THE NW
CARIBBEAN WHICH IS FORECAST TO MOVE OVER THE YUCATAN PENINSULA
LATER TONIGHT AND EARLY MONDAY THEN AFFECT THE GLFMEX MON AND
TUE. OUTER RAINBANDS ARE ALREADY SWEEPING OVER THE YUCATAN
CHANNEL AND THIS ACTIVITY WILL CONTINUE TO SPREAD INTO THE GULF
WATERS OVERNIGHT AND MONDAY AS EMILY APPROACHES.

CARIBBEAN SEA...
HURRICANE EMILY CONTINUES TO DOMINATE THE WEATHER OVER THE W
CARIBBEAN SEA WITH ASSOCIATED RAINBANDS EXTENDING OUTWARD UP TO
250 NM TO THE N OF THE CENTER.  ELSEWHERE...E OF EMILY...UPPER
LEVEL SUBSIDENCE AND RELATIVELY DRIER AIR ALOFT COURTESY OF THE
MID-OCEANIC TROUGH CONTINUES TO SPREAD WESTWARD OVER THE E AND
CENTRAL CARIBBEAN. WIDELY SCATTERED SHOWERS/TSTMS ARE OVER
HISPANIOLA AND THE MONA PASSAGE. OTHERWISE...FEW ISOLATED
SHOWERS DOT THE AREA MAINLY N OF 13N.  HOWEVER...THIS DRIER
AIRMASS WILL QUICKLY GIVE WAY TO INCREASING MOISTURE BEHIND A
TROPICAL WAVE CURRENTLY MOVING OVER THE WINDWARD/ LEEWARD
ISLANDS.  EXPECT INCREASING CHANCES OF SHOWERS/TSTMS OVER THE
EXTREME SE CARIBBEAN TONIGHT THROUGH TUE AS MOISTURE
RETURNS.

ATLANTIC OCEAN...
A MIDDLE TO UPPER LEVEL RIDGE-TROUGH-RIDGE PATTERN CONTINUES
OVER THE ATLC WATERS WITH WEAK RIDGING OVER THE W ATLC...THE
MID-OCEANIC TROUGH OVER THE CENTRAL ATLC FROM 34N47W SW INTO THE
E CARIBBEAN...AND A LARGE ANTICYCLONE OVER THE E ATLC NEAR
24N41W. THE WEATHER OVER THE W ATLC REMAINS RELATIVELY TRANQUIL
ASIDE FROM SOME WIDELY SCATTERED SHOWERS/ISOLATED TSTMS WITHIN
150-200 NM OF A WEAK LOW LEVEL TROUGH FROM THE S BAHAMAS TO JUST
E OF BERMUDA NEAR 32N63W. THIS ACTIVITY IS EXPECTED TO SLOWLY
MOVE WESTWARD OVER THE NEXT FEW DAYS.  ELSEWHERE...CLOUDINESS
AND SHOWERS/THUNDERSTORMS ACCOMPANY A TROPICAL WAVE OVER THE
CENTRAL ATLC BUT HAVE WEAKENED THIS EVENING AS THE MID-OCEANIC
TROUGH IMPARTS STRONG SHEAR OVER THE WAVE. OVER THE E ATLC...A
STRONG LOW LEVEL ELY SURGE AND ASSOCIATED AFRICAN DUST IS
OBSERVED MARCHING WESTWARD ACROSS THE E AND CENTRAL ATLC WATERS
WITH LEADING EDGE CURRENTLY NEAR 55W.  THE RELATIVELY DRY/STABLE
AIR WITHIN THIS SURGE IS LIMITING DEEP CONVECTION N OF THE ITCZ
AND E OF 46W.

$$
COBB












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