[Tropical] Tropical Weather Discussion

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AXNT20 KNHC 190007
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL.
805 PM EDT MON JUL 18 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 EMERGED OVER THE GULF OF MEXICO JUST AFTER 1200
UTC THIS MORNING AND IS NOW LOCATED NEAR 22.6N 91.5W OR ABOUT
410 MILES...660 KM...EAST OF LA PESCA MEXICO AND ABOUT 440
MILES...710 KM...EAST-SOUTHEAST OF BROWNSVILLE TEXAS
AT 19/0000 UTC MOVING WNW AT 14 KT. MAXIMUM SUSTAINED WIND SPEED
IS 65 KT WITH GUSTS TO 80 KT AND THE ESTIMATED MINIMUM CENTRAL
PRESSURE IS 982 MB MAKING EMILY A CATEGORY ONE HURRICANE ON THE
SAFFIR SIMPSON SCALE. SEE 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.
DEEP CONVECTION HAS DEVELOPED NEAR THE CORE OF EMILY AND THE
RATHER LARGE EYE IS SURROUNDED BY THIS CONVECTION. CLOUD TOP
TEMPERATURES HAVE COOLED OVER THE PAST SEVERAL HOURS...
ESPECIALLY IN THE SOUTHERN SEMICIRCLE. OUTER RAINBANDS CURRENTLY
EXTEND OUTWARD UP TO 240 NM OVER THE N SEMICIRCLE AND 120 NM
OVER THE S SEMICIRCLE.  A CONVERGENCE LINE TRAILS SEWD FROM
EMILY OVER THE NE TIP OF THE YUCATAN PENINSULA TO THE GULF OF
HONDURAS WITH A NARROW BAND OF SCATTERED MODERATE CONVECTION
WITHIN 60 NM EITHER SIDE.

...TROPICAL WAVES...

TROPICAL WAVE OVER THE E ATLC WAS RE-POSITIONED SLIGHTLY E TO
ALONG 33W/34W S OF 20N MOVING W 15 KT. THE WAVE REMAINS VOID OF
DEEP CONVECTION BUT IS IDENTIFIABLE BY CYCLONIC TURNING WITHIN
LOW TO MID LEVEL CLOUD FIELD ALONG 15N.

TROPICAL WAVE OVER THE CENTRAL ATLC REPOSITIONED EARLIER IS NOW
ALONG 51W/52W MOVING W NEAR 20 KT. THE WAVE CONTINUES TO
INTERACT WITH THE LEADING EDGE OF A LOW LEVEL ELY SURGE WITH
SCATTERED SHOWERS AND TSTMS ACCOMPANYING THE WAVE FROM 5N-12N
BETWEEN 45W-54W. THE WAVE IS FLANKED TO THE EAST BY RELATIVELY
DRIER AIR AND DUST...MAINLY N OF 14N.

TROPICAL WAVE OVER THE E CARIBBEAN IS ALONG 63W/64W S OF 18N
MOVING W 15 KT. THIS WAVE HAS BECOME INCREASINGLY DIFFICULT TO
LOCATE DUE TO ITS INTERACTION WITH THE MID-OCEANIC TROUGH OVER
THE E CARIBBEAN AND A STRONG LOW LEVEL ELY SURGE.  ANALYSIS OF
LONG-TERM SATELLITE IMAGERY AND UW-CIMSS VORTICITY PRODUCTS
INDICATES THAT THE WAVE BECAME TILTED FROM THE NW/SE OVER THE
LAST FEW DAYS. AS A RESULT...THE N PORTION OF THE WAVE DETACHED
AND ACCELERATED AHEAD OF THE S PORTION OF THE WAVE.  ANALYSIS OF
AREA SOUNDINGS SHOWS A WELL DEFINED LOWER TO MID-LEVEL TROUGH
PASSING THE ISLANDS YESTERDAY BUT THIS APPEARS TO BE A SURFACE
REFLECTION OF THE MID-OCEANIC TROUGH WHICH IS CURRENTLY OVER THE
AREA. REGARDLESS OF THE EXACT POSITION...AMPLE MOISTURE
ASSOCIATED WITH THE WAVE IS INTERACTING WITH THE MID-OCEANIC
TROUGH CURRENTLY OVER THE E CARIBBEAN AND PRODUCING SCATTERED TO
NUMEROUS SHOWERS/TSTMS OVER THE LEEWARD AND WINDWARD ISLANDS.
THIS ACTIVITY WILL CONTINUE TO SPREAD WESTWARD ACROSS THE E
CARIBBEAN OVER THE NEXT DAY OR TWO BUT DEVELOPMENT IS NOT
EXPECTED DUE TO STRONG SOUTHERLY SHEAR.

...ITCZ...

ITCZ AXIS IS CENTERED ALONG 12N16W 9N26W 13N33W 10N50W 9N57W
10N62W...THEN ACROSS N PORTIONS OF S AMERICA. SCATTERED MODERATE
TO STRONG CONVECTION IS WELL SOUTH OF THE ITCZ WITHIN 90 NM
EITHER SIDE OF A LINE FROM 8N13W TO 5.5N18W. OTHERWISE...REFER
TO TROPICAL WAVE DISCUSSION ABOVE.

...DISCUSSION...

GULF OF MEXICO...
HURRICANE EMILY IS NOW OVER THE SOUTHERN GULF OF MEXICO AND IS
DOMINATING VIRTUALLY THE ENTIRE WEATHER PATTERN IN THE GULF. AN
ELONGATED...BUT WELL-DEFINED UPPER LEVEL ANTICYCLONE IS SITUATED
JUST E OF EMILY OVER THE SE GLFMEX WITH ASSOCIATED RIDGE
BUILDING NW TOWARD THE N GULF COAST ALONG THE MS/ALABAMA
COAST. W OF EMILY...THE TROUGH WHICH HAS BEEN MOVING IN TANDEM
WITH THE HURRICANE OVER THE LAST FEW DAYS HAS WEAKENED AND SPLIT
WITH THE NORTHERN PORTION EXTENDING FROM SW MISSISSIPPI TO THE
UPPER TEXAS COAST WHILE THE SOUTHERN PORTION IS IN THE FORM OF A
SHEARING/WEAKENING UPPER LOW LOCATED OVER THE BAY OF CAMPECHE.
THE UPPER LEVEL RIDGE/ANTICYCLONE NOTED ABOVE IS ATTEMPTING TO
BUILD BETWEEN THE SPLIT TROUGHS AND IS ALLOWING FOR A NOTICEABLE
WESTWARD/SOUTHWARD EXPANSION OF THE UPPER LEVEL OUTFLOW
ASSOCIATED WITH EMILY TOWARD THE MEXICO/TEXAS COAST. IN ADDITION
THE SOUTHERLY SHEAR NOTED EARLIER HAS VIRTUALLY DISAPPEARED
AND THE OUTFLOW IS BECOMING MORE SYMMETRIC.  IN THE WAKE OF
EMILY...AN UPPER TROUGH IS OBSERVED MOVING WESTWARD OVER THE W
ATLC AND THE FLORIDA E COAST AND IS EXPECTED TO MOVE INTO THE E
GLFMEX OVER THE NEXT DAY OR TWO. WATER VAPOR IMAGERY SHOWS THE
UPPER TROUGH IS ACCOMPANIED BY MARKED SUBSIDENCE AND DRYING
ALOFT.

CARIBBEAN SEA...
HURRICANE EMILY'S INFLUENCE ON THE REGION IS DWINDLING WITH TIME
WITH THE ONLY LEFTOVER EFFECT BEING A TRAILING CONVERGENCE LINE
EXTENDING OVER THE NE TIP OF THE YUCATAN PENINSULA TO THE GULF
OF HONDURAS. THIS BAND OF CONVERGENCE IS PRODUCING A NARROW BAND
OF WEAKENING WIDELY SCATTERED SHOWERS/TSTMS WHICH IS MOVING WEST
NEAR 15 KT. THIS BAND SHOULD CONTINUE TO MOVE WESTWARD OVER THE
YUCATAN PENINSULA AND BELIZE TONIGHT WITH A BRIEF PERIOD OF
SHOWER/TSTM ACTIVITY. ELSEWHERE...THE MID-OCEANIC TROUGH
DOMINATES THE ERN TWO THIRDS OF THE CARIBBEAN WITH ASSOCIATED
STRONG SUBSIDENCE AND RELATIVELY DRY AIR ALOFT SPREADING
WESTWARD OVER MOST OF THE REGION. AN EMBEDDED UPPER LOW/CYCLONIC
CIRCULATION APPEARS TO BE DEVELOPING JUST S OF HISPANIOLA.
THIS DRY AIRMASS WILL SPREAD OVER THE W CARIBBEAN DURING THE
NEXT DAY OR TWO. OVER THE FAR E CARIBBEAN...STRONG UPPER LEVEL
DIVERGENCE E OF THE MID-OCEANIC TROUGH IS ASSISTING
SHOWERS/TSTMS ALONG A TROPICAL WAVE MOVING INTO THE E CARIBBEAN.
THIS ACTIVITY WILL SPREAD WESTWARD WITH THE RETROGRADING UPPER
TROUGH PRODUCING A UNSETTLED/WET PATTERN OVER THE E CARIBBEAN
DURING THE NEXT 24 HOURS.

ATLANTIC OCEAN...
MID/UPPER LEVEL TROUGH-RIDGE PATTERN PREVAILS OVER THE ATLC
WATERS WITH A BROAD TROUGH OVER THE W ATLC W OF 60W AND AN E/W
ORIENTED RIDGE OVER THE E ATLC ALONG 25N AND E OF 55W. WIDELY
SCATTERED SHOWERS AND ISOLATED TSTMS LIE WITHIN 300 NM EITHER
SIDE OF A WEAK SURFACE TROUGH OVER THE W ATLC FROM JUST W OF
BERMUDA TO THE CENTRAL BAHAMAS. A SIMILAR LOW LEVEL
TROUGH...WHICH RECENTLY DETACHED FROM A TROPICAL WAVE...LIES
OVER THE CENTRAL/WESTERN ATLC NE OF PUERTO RICO.  THIS FEATURE
IS PRODUCING WIDELY SCATTERED SHOWERS AND A FEW ISOLATED TSTMS
FROM 19N-26N BETWEEN 58W-63W. OVER THE CENTRAL AND E ATLC...THE
PATTERN IS LARGELY DOMINATED BY A STRONG LOW LEVEL ELY SURGE
WITH LEADING EDGE CURRENTLY NEARING THE NORTHEASTERN LEEWARD
ISLANDS. AT THE SURFACE...THE SUBTROPICAL RIDGE EXTENDS FROM THE
AZORES SW TO 30N50W BECOMING PARTIALLY WEAKENED OVER THE CENTRAL
TO W ATLC BY THE AFOREMENTIONED TROUGHS...THEN BECOMES RE-
ESTABLISHED FROM BERMUDA WESTWARD ACROSS N FLORIDA ALONG
30N/31N.

$$
COBB





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