[Tropical] Tropical Weather Discussion

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AXNT20 KNHC 170005
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL.
805 PM EDT SAT JUL 16 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
2315 UTC.

...SPECIAL FEATURE...

HURRICANE EMILY IS CENTERED NEAR 17.1N 79.5W OR ABOUT 140 MILES
MILES...230 KM...SOUTHWEST OF MONTEGO BAY JAMAICA AND ABOUT 195
MILES...315 KM...SOUTHEAST OF GRAND CAYMAN AT 17/0000 UTC MOVING
WNW 16 KT. THE LATEST MINIMUM CENTRAL PRESSURE IS DOWN TO 929 MB
AND THE MAXIMUM SUSTAINED WIND SPEED IS AT THE THRESHOLD OF A
CATEGORY 4/5 HURRICANE...135 KT WITH GUSTS TO 165 KT. 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 DANGEROUSLY STRONG HURRICANE INCLUDING A WELL-DEFINED AND
CLEAR EYE...STRONG SURROUNDING CONVECTION WITH VERY COLD CLOUD
TOPS...AND GOOD UPPER LEVEL OUTFLOW WITH A POLEWARD OUTFLOW JET.
LATEST SATELLITE IMAGERY SHOWS NUMEROUS CONVECTION WITH EMILY IS
WITHIN 90 NM OVER THE SW SEMICIRCLE AND WITHIN 150-175 NM OVER
THE NE SEMICIRCLE INCLUDING JAMAICA.  THIS ACTIVITY WILL
CONTINUE TO PRODUCE VERY HEAVY RAINFALL...STRONG WINDS...AND
POSSIBLE LIFE THREATENING FLOODING OVER JAMAICA AND THE CAYMAN
ISLANDS THIS EVENING AND TONIGHT EVEN THOUGH EMILY IS FORECAST
TO BYPASS THESE LOCATIONS TO THE SOUTH.

...TROPICAL WAVES...

TROPICAL WAVE INTRODUCED ALONG 20N FROM 9N TO 20N IS MOVING W AT
15 KT. THE WAVE WAS CHARACTERIZED BY A WELL DEFINED SWIRL OF
LOW AND MID LEVEL CLOUDS OVER THE CAPE VERDE ISLANDS. 1700 UTC
RAOB FROM SAL INDICATED LIGHT NE TO NW WINDS IN THE 1000-925 MB
LAYER SUGGESTING THE WAVE IS TO THE E OF THAT LOCATION. THIS
WAVE AS WAS THE CASE FOR SEVERAL PREVIOUS WAVES IS WELL
ORGANIZED FOR MID JULY. ONLY POCKETS OF ISOLATED MODERATE
CONVECTION ARE OCCURRING ALONG THE PERIPHERY OF THIS WAVE AND
THE INTERSECTION OF THE ITCZ.

TROPICAL WAVE OVER THE E ATLC ALONG 39W/40W S OF 17N MOVING W
20 KT. THE WAVE IS EMBEDDED WITHIN A LARGE SURGE OF LOW LEVEL
EASTERLIES AND AFRICAN DUST/DRY AIR.  AS A RESULT...THE WAVE IS
MOVING FASTER THAN USUAL AND CONVECTION IS SUPPRESSED N OF THE
ITCZ.  THE SATELLITE SIGNATURE HAS ALSO BECOME A BIT LESS
DEFINED AND THE AREA OF SCATTERED MODERATE/ISOLATED STRONG
CONVECTION HAS BECOME ISOLATED WITHIN THE ITCZ AND MOVING W WITH
THE WAVE.

HIGH-AMPLITUDE TROPICAL WAVE OVER THE CENTRAL ATLC ALONG 54W/55W
S OF 19N IS MOVING W 15 TO 20 KT. THE WAVE APPEARS TO HAVE
FRACTURED WITH A SURFACE TROUGH NOW EXTENDING FROM 20N55W TO
28N50W. THE WAVE IS INTERACTING WITH THE LEADING EDGE OF A
STRONG LOW LEVEL EASTERLY SURGE AND ASSOCIATED AFRICAN DUST/DRY
AIR. FURTHER NORTH...THE SURFACE TROUGH IS INTERACTING WITH AN
AN UPPER LEVEL TROUGH TO THE WEST. DIFFLUENT FLOW EAST OF THE
TROUGH HAS RESULTED IN SCATTERED MODERATE AND ISOLATED STRONG
CONVECTION WITHIN 240 NM E OF THE TROUGH AXIS FROM 20N TO 25N.
STRONG SW SHEAR IS EXPECTED TO CONTINUE OVER THIS SYSTEM DURING
THE NEXT FEW DAYS PULLING MUCH OF ENERGY AND ASSOCIATED DEEP
CONVECTION POLEWARD OF 20N. HOWEVER...LOW LEVEL MOISTURE FROM
THIS WAVE IS EXPECTED TO ENTER THE WINDWARD ISLANDS SUN POSSIBLY
PRODUCING INCREASING SHOWERS/TSTMS.

...ITCZ...

ITCZ AXIS IS CENTERED ALONG 15N17W 11N30W 10N40W 11N52W 9N60W
THEN ACROSS N PORTIONS OF S AMERICA. SCATTERED MODERATE TO
STRONG CONVECTION IS WITHIN 120-150 NM S OF THE AXIS BETWEEN
50W-55W. WIDELY SCATTERED MODERATE CONVECTION IS WITHIN 60-90
NM EITHER SIDE OF AXIS BETWEEN 41W-50W.

...DISCUSSION...

GULF OF MEXICO...
THE PATTERN ALOFT OVER THE GLFMEX IS FAIRLY COMPLEX AND CONSISTS
OF A STRONG MID-UPPER LEVEL RIDGE EXTENDING EXTENDING FROM THE
SE UNITED STATES SW THROUGH 27N92W TO CENTRAL MEXICO...A MIDDLE
TO UPPER LEVEL TROUGH EXTENDING SWD FROM THE CENTRAL UNITED
STATES OVER TEXAS INTO N CENTRAL MEXICO WITH A WELL DEFINED
CIRCULATION NEAR THE RIO GRANDE RIVER/29N102W...AND LASTLY A
RETROGRADING UPPER LOW OVER THE EXTREME SE BAY OF CAMPECHE.
TWO AREAS OF ACTIVE CONVECTION ARE NOTED THIS EVENING...ONE
ALONG AND WITHIN 90 NM OF THE SE COAST OF TEXAS/NE MEXICO...AND
THE SECOND OVER THE E BAY OF CAMPECHE AND COAST OF YUCATAN S OF
PROGRESO TO CUIDAD DE CARMEN. BOTH AREAS ARE EXPECTED TO SLOWLY
SHIFT WESTWARD OVER THE NEXT DAY OR SO AS THE CENTRAL U.S.
TROUGH FRACTURES AND BEGINS TO RETROGRADE.  ELSEWHERE...AREA
SOUNDINGS SHOW THAT DEEP-LAYERED MOISTURE REMAINS HIGH
SUPPORTING ISOLATED TO WIDELY SCATTERED SHOWERS AND TSTMS OVER
THE OPEN WATERS OF THE GLFMEX WITH TYPICAL AFTERNOON
SHOWERS/TSTMS EXPECTED OVER FLORIDA.  HURRICANE EMILY IS
FORECAST TO MOVE ACROSS THE YUCATAN PENINSULA SUN AND ENTER THE
GULF OF MEXICO ON MON. SOME OF THE UPPER LEVEL OUTFLOW FROM
EMILY IS ALREADY SPREADING OVER PORTIONS OF THE EXTREME SE GULF
AND FLORIDA STRAITS.

CARIBBEAN SEA...
HURRICANE EMILY DOMINATES THE WEATHER OVER THE CENTRAL AND W
CARIBBEAN SEA WITH ASSOCIATED RAINBANDS EXTENDING OUTWARD UP TO
225 NM TO THE N OF THE CENTER.  AN AREA OF SCATTERED
SHOWERS/TSTMS IS ALSO NOTED FURTHER W ALONG THE COAST OF YUCATAN
AND ALONG THE IMMEDIATE COAST OF HONDURAS AS WELL PORTIONS OF
EASTERN NICARAGUA...HONDURAS AND GUATEMALA. THIS ACTIVITY IS IN
ASSOCIATION WITH AN UPPER LOW OVER THE YUCATAN PENINSULA.  THE
UPPER LOW CONTINUES TO MOVE AWAY FROM EMILY THUS RELAXING THE
SHEAR AND ALLOWING IMPROVED POLEWARD OUTFLOW AND FAVORABLE
CONDITIONS FOR THE STRENGTHENING OBSERVED TODAY. THE UPPER LOW
IS FORECAST TO CONTINUE MOVING WESTWARD AND WEAKEN. E OF
EMILY...UPPER LEVEL CONFLUENCE/SUBSIDENCE AND RELATIVELY DRIER
AIR ALOFT IS BEGINNING TO MOVE INTO THE E CARIBBEAN COURTESY OF
A RETROGRADING UPPER LOW OVER THE CENTRAL ATLC. THIS AIRMASS IS
EXPECTED TO CONTINUE SPREADING WESTWARD OVER THE E CARIBBEAN
PRODUCING MORE STABLE CONDITIONS.

ATLANTIC OCEAN...
THE UPPER LEVEL PATTERN OVER THE ATLC FEATURES A FAIRLY HIGH
AMPLITUDE MIDDLE TO UPPER LEVEL RIDGE OVER THE W ATLC WITH AXIS
ALONG 74W/75W...THE MID-OCEANIC TROUGH FROM 34N48W TO AN UPPER
LOW NEAR 22N58W TO THE E CARIBBEAN NEAR 15N64W...AND E/W
ORIENTED RIDGING OVER THE ATLC ALONG 23N/24N E OF 45W. THE
WEATHER OVER THE W ATLC REMAINS RELATIVELY TRANQUIL WITH THE
EXCEPTION OF WIDELY SCATTERED SHOWERS/TSTMS FROM 20N TO 25N
BETWEEN 48W AND 51W IN ASSOCIATION WITH A SURFACE TROUGH AND
HIGH AMPLITUDE TROPICAL WAVE ALONG 54W/55W. THE WAVE/SURFACE
TROUGH ARE CURRENTLY EXPERIENCING STRONG SHEAR WHICH IS LIMITING
DEVELOPMENT AND FOCUSING THE STRONGEST SHOWERS/TSTMS N OF 20N. E
OF THE WAVE...A STRONG LOW LEVEL ELY SURGE AND ASSOCIATED
AFRICAN DUST IS OBSERVED MARCHING WESTWARD ACROSS THE E AND
CENTRAL ATLC WITH LEADING EDGE CURRENTLY NEAR 50W.  THE
RELATIVELY DRY/STABLE AIR WITHIN THIS SURGE IS LIMITING DEEP
CONVECTION TO THE ITCZ.

$$
COBB












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