[Tropical] Tropical Weather Discussion

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AXNT20 KNHC 171801
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL.
205 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 1200 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH
1715 UTC.

...SPECIAL FEATURE...

HURRICANE EMILY IS CENTERED NEAR 19.0N 84.4W OR ABOUT 195 MILES
MILES...315 KM...EAST SOUTHEAST OF COZUMEL MEXICO AT 17/1800 UTC
MOVING WNW 18 KT. THE LATEST MINIMUM CENTRAL PRESSURE IS 948 MB
AND THE MAXIMUM SUSTAINED WIND SPEED IS 125 KT WITH GUSTS TO 155
KT MAKING EMILY A STRONG 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 IMPRESSIVE SATELLITE APPEARANCE WITH ALL THE SIGNS
OF A MATURE HURRICANE INCLUDING A WELL-DEFINED EYE...VERY STRONG
SURROUNDING CONVECTION...AND GOOD UPPER LEVEL OUTFLOW WITH A
POLEWARD OUTFLOW CHANNEL. ASSOCIATED 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 PULLING AWAY FROM THE CAYMAN ISLANDS BUT
SCATTERED RAINBANDS CONTAINING BRIEF PERIODS OF VERY HEAVY
RAINFALL AND GUSTY WINDS REMAIN POSSIBLE THROUGH THE REST OF
TODAY.  OUTER RAINBANDS WILL ALSO BEGIN AFFECTING THE YUCATAN
PENINSULA THIS AFTERNOON/EVENING WITH NUMEROUS TSTMS AND VERY
HEAVY RAIN SPREADING ACROSS THE YUCATAN PENINSULA TONIGHT AND
MONDAY.

...TROPICAL WAVES...

TROPICAL WAVE OVER THE E ATLC ALONG 28W S OF 18N MOVING W NEAR
20 KT.  THIS POSITION IS SEVERAL DEGREES AHEAD OF THE EXPECTED
EXTRAPOLATED POSITION BASED UPON A WELL-DEFINED MID-LEVEL
CIRCULATION OBSERVED IN LATEST SATELLITE IMAGERY.  EARLIER
CONVECTION WHICH ACCOMPANIED THE WAVE AS IT MOVE OFF THE COAST
OF AFRICA YESTERDAY HAS SINCE DISSIPATED AND THE WAVE IS NOW
VOID OF ANY APPRECIABLE CONVECTIVE ACTIVITY.

TROPICAL WAVE OVER THE CENTRAL ATLC ALONG 46W S OF 19N MOVING W
20 TO 25 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 AHEAD OF THE
WAVE BUT THIS APPEARS TO BE THE LEADING EDGE OF THE SURGE AS
OPPOSED TO THE WAVE ITSELF.

TROPICAL WAVE NEARING THE LEEWARD/WINDWARD ISLANDS ALONG 59W/60W
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 INCREASINGLY NE OF
THE WAVE AXIS. IN FACT...THE WAVE APPEARS TO BE SPLITTING WITH
ONE PIECE OF ENERGY...ALONG 20N59W TO 29N50W...LIFTING SLOWLY NW
WHILE THE S EXTENT...ALONG 59W S OF 20N..CONTINUES W AT 15-20
KT.  THE N EXTENT OF THE WAVE CONTINUES TO PRODUCE AN IMPRESSIVE
AREA OF SCATTERED TO NUMEROUS MODERATE CONVECTION FROM 20N-28N
BETWEEN 50W-56W.  THE S EXTENT IS CURRENTLY VOID OF SIGNIFICANT
CONVECTION BUT IS EXPECTED TO TO MOVE OVER THE LESSER ANTILLES
AND ENTER THE E CARIBBEAN THIS AFTERNOON AND TONIGHT BRINGING
INCREASING LOW LEVEL MOISTURE AND SCATTERED SHOWERS/ISOLATED
TSTMS.

...ITCZ...

ITCZ AXIS IS CENTERED ALONG 15N10W 17N25W 13N40W 9N50W 9N60W
THEN ACROSS N PORTIONS OF S AMERICA.  SCATTERED MODERATE/
ISOLATED STRONG CONVECTION FROM 4N-10N BETWEEN 48W-60W.

...DISCUSSION...

GULF OF MEXICO...
MID-UPPER LEVEL TROUGH SPLITS THE GLFMEX EXTENDING FROM THE
FLORIDA PANHANDLE SW TO AN UPPER LOW OVER THE BAY OF CAMPECHE.
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 OVER THE SW GLFMEX AND COAST OF MEXICO WHERE
WIDELY SCATTERED SHOWERS/TSTMS ARE NOTED S OF 25N W OF 95W INTO
THE LOW COUNTRY OF E MEXICO. ELSEWHERE...ALL EYES POISED ON
HURRICANE EMILY OVER THE NW CARIBBEAN WHICH IS FORECAST TO MOVE
OVER THE YUCATAN PENINSULA TONIGHT AND EARLY MONDAY THEN AFFECT
THE GLFMEX MON AND TUE.  OUTER RAINBANDS ARE ALREADY OBSERVED
NEARING THE AREA OVER THE YUCATAN CHANNEL AND THIS ACTIVITY WILL
CONTINUE TO SPREAD INTO THE GULF WATERS TONIGHT 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.  ONLY WIDELY SCATTERED SHOWERS AND A 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 CHANGES OF SHOWERS/TSTMS
OVER THE E 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 34N50W SW INTO THE
NE CARIBBEAN...AND A LARGE ANTICYCLONE OVER THE E ATLC NEAR
25N40W. 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 HAS BEEN WEAKENING TODAY AS THE MID-OCEANIC
TROUGH IMPARTS STRONG SHEAR OVER THE SYSTEM.  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 54W.  THE RELATIVELY
DRY/STABLE AIR WITHIN THIS SURGE IS LIMITING DEEP CONVECTION N
OF THE ITCZ.

$$
RHOME









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