[Tropical] Tropical Weather Discussion

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AXNT20 KNHC 181801
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL.
205 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 1200 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH
1745 UTC.

...SPECIAL FEATURE...

HURRICANE EMILY IS CENTERED OVER THE YUCATAN PENINSULA NEAR
22.0N 90.3W AT 1800 UTC OR ABOUT 490 MILES...785
KM...EAST-SOUTHEAST OF LA PESCA MEXICO MOVING WNW AT 15 KT.
MAXIMUM SUSTAINED WIND SPEED IS 65 KT WITH GUSTS TO 80 KT AND
THE ESTIMATED MINIMUM CENTRAL PRESSURE IS 984 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.  AS WOULD BE
EXPECTED...DEEP CONVECTION NEAR THE CENTER OF EMILY WEAKENED
SIGNIFICANTLY OVERNIGHT AND THIS MORNING WHILE THE CENTER WAS
OVER LAND EVEN THOUGH THE STRUCTURE AND CLOUD PATTERN APPEARS
RELATIVELY INTACT.  SINCE EMERGING BACK OVER WATER THIS
MORNING...THE CONVECTIVE PATTERN HAS BEEN STEADY STATE.  OUTER
RAINBANDS CURRENTLY EXTEND OUTWARD UP TO 250 NM OVER THE N
SEMICIRCLE AND 200 NM OVER THE S SEMICIRCLE.  A CONVERGENCE LINE
TRAILS SEWD FROM EMILY OVER THE NE TIP OF THE YUCATAN PENINSULA
TO PANAMA WITH A NARROW BAND OF SCATTERED MODERATE CONVECTION
WITHIN 60 NM EITHER SIDE.

...TROPICAL WAVES...

TROPICAL WAVE OVER THE E ATLC 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.

TROPICAL WAVE OVER THE CENTRAL ATLC IS REPOSITIONED ALONG
51W/52W S OF 16N MOVING W NEAR 20 KT. THE WAVE CONTINUES TO
INTERACT WITH THE LEADING EDGE OF A LOW LEVEL ELY SURGE AND
AFRICAN DUST WHICH IS MASKING ITS APPEARANCE IN SATELLITE.  THE
REPOSITION IS BASED ON LONG-TERM SATELLITE IMAGERY AND UW-CIMSS
VORTICITY ANALYSIS SHOWING A LOW-AMPLITUDE PERTURBATION JUST S
OF THE ELY SURGE. SCATTERED SHOWERS AND TSTMS ACCOMPANY THE WAVE
FROM 3N-13N BETWEEN 46W-52W. THE WAVE IS FLANKED TO THE EAST BY
RELATIVELY DRIER AIR AND DUST...MAINLY N OF 14N.

TROPICAL WAVE OVER THE E CARIBBEAN IS REPOSITIONED ALONG 62W 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 SHEAR.

...ITCZ...

ITCZ AXIS IS CENTERED ALONG 15N10W 12N30W 11N50W 10N60W THEN
ACROSS N PORTIONS OF S AMERICA. SEE TROPICAL WAVE DISCUSSION.

...DISCUSSION...

GULF OF MEXICO...
HURRICANE EMILY HAS EMERGED FROM THE YUCATAN PENINSULA INTO THE
GLFMEX TODAY AND NOW DOMINATES THE ENTIRE WEATHER PATTERN.  A
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 NEAR LOUISIANA.  W OF EMILY...THE TROUGH WHICH HAS
BEEN MOVING IN TANDEM WITH THE HURRICANE OVER THE LAST FEW DAYS
CURRENTLY EXTENDING FROM SE LOUISIANA TO AN UPPER LOW OVER THE
BAY OF CAMPECHE.  THIS UPPER LEVEL SETUP APPEARS TO BE PRODUCING
SOME SLY SHEAR OVER EMILY WITH OUTFLOW AND ASSOCIATED HIGH
CIRRUS CLOUDS FANNING OUT UNRESTRICTED TO THE N AND RELATIVELY
CONFINED TO THE SOUTH.  HOWEVER...WATER VAPOR TRENDS SHOW THAT
THE UPPER TROUGH/LOW IS WEAKENING AND THE SHEAR IS FORECAST TO
RELAX A BIT PRIOR TO EMILY REACHING THE COAST OF MEXICO WITHIN
THE NEXT 36-48 HOURS.  IN THE WAKE OF EMILY...AN UPPER TROUGH IS
OBSERVED MOVING WESTWARD OVER THE W ATLC AND IS EXPECTED TO MOVE
ACROSS FLORIDA INTO THE E GLFMEX OVER THE NEXT 2 DAYS.  WATER
VAPOR IMAGERY SHOWS THE UPPER TROUGH IS ACCOMPANIED BY
SUBSIDENCE AND DRYING ALOFT.

CARIBBEAN SEA...
HURRICANE EMILY HAS NOW FULLY EXITED THE NW CARIBBEAN WITH THE
ONLY LEFTOVER EFFECT BEING A TRAILING CONVERGENCE LINE EXTENDING
OVER THE NE TIP OF THE YUCATAN PENINSULA TO PANAMA.  THIS BAND
OF CONVERGENCE IS PRODUCING A NARROW BAND OF SCATTERED
SHOWERS/TSTMS WHICH IS MOVING WEST NEAR 15 KT.  THIS BAND SHOULD
CONTINUE TO MOVE WESTWARD OVER CENTRAL AMERICA TODAY AND TONIGHT
WITH A BRIEF PERIOD OF SHOWER/TSTM ACTIVITY.  ELSEWHERE...THE
MID-OCEANIC TROUGH DOMINATES THE PICTURE WITH ASSOCIATED STRONG
SUBSIDENCE AND RELATIVELY DRY AIR ALOFT SPREADING WESTWARD OVER
MOST OF THE E AND CENTRAL CARIBBEAN BETWEEN 65W-80W. THIS
AIRMASS WILL SLOWLY 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.  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 TURKS/CAICOS.  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 20N-30N BETWEEN
55W-65W.  OVER THE CENTRAL AND E ATLC...THE PATTERN IS LARGELY
DOMINATED BY A STRONG LOW LEVEL ELY SURGE WITH LEADING EDGE
CURRENTLY NEARING 60W. VISIBLE SATELLITE IMAGERY SUGGEST THAT
AFRICAN DUST WITHIN THE SURGE IS MOST CONCENTRATED N OF THE ITCZ
BETWEEN 35W-60W. A SECOND AREA OF DUST IS OBSERVED MOVING OFF
THE COAST OF AFRICA WITH LEADING EDGE NEARING THE CAPE VERDE
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.

$$
RHOME






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