[Tropical] Tropical Weather Discussion

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AXNT20 KNHC 201802
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL.
205 PM EDT WED JUL 20 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 NOW INLAND NEAR 25.0N... LONGITUDE 98.7W OR
ABOUT 105 MILES...170 KM...EAST-SOUTHEAST OF MONTERREY MEXICO
AND ABOUT 85 MILES...135 KM...SOUTH-SOUTHWEST OF MCALLEN TEXAS
AT 20/1800 UTC MOVING W 10 KT. MAXIMUM SUSTAINED WIND SPEED IS
70 KT WITH GUSTS TO 85 KT. ESTIMATED MINIMUM CENTRAL PRESSURE
REPORTED BY AIR FORCE RECONNAISSANCE IS 975 MB. 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.  THE CYCLONE MADE LANDFALL THIS MORNING
AND NOW THE MAIN THREAT IS VERY HEAVY RAINS ALONG THE
TRACK...ESPECIALLY AS IT BUMPS INTO THE HIGHER TERRAIN IN NE
MEXICO.  THE EYE HAS BECOME FILLED-IN AND LESS-DISTINCT ON RADAR
AND SATELLITE.  SCATTERED MODERATE CONVECTION WITHIN 90 NM OF
THE CENTER.

...TROPICAL WAVES...

E ATLC TROPICAL WAVE IS ADDED ALONG 21W/22W S OF 21N MOVING W
10-15 KT WITH A 1010 MB LOW ALONG THE WAVE NEAR 19N21W.  THIS IS
A VERY IMPRESSIVE WAVE WITH A LARGE WELL-DEFINED LOW-LEVEL
CIRCULATION AS SEEN BY THE LOW CLOUD FIELD AND QUIKSCAT DATA.
HUGE 24 HOUR PRESSURE FALL/RISE COUPLETS OF 8 MB WERE OBSERVED
WITH THE WAVE OVER W AFRICA WITH DEEP SLY WINDS ON THE E SIDE OF
THE WAVE TRANSPORTING MOISTURE FAR TO THE N OVER AFRICA...
ALLOWING CONVECTION TO FIRE AS FAR N AS 22N IN WESTERN SAHARA.
VISIBLE SATELLITE IMAGES ALSO REVEAL THAT THE WAVE IS SURROUNDED
BY A THICK SAHARAN DUST OUTBREAK WITH THE MILKY WHITE SIGNATURE
ON SATELLITE COVERING THE E ATLC BETWEEN 10N-25N E OF 37W.  THIS
DRY AIR SHOULD PREVENT ANY SIGNIFICANT DEVELOPMENT OF THE LOW..
AS WELL AS THE WATER TEMPERATURES BELOW 80F IN THE AREA...
THOUGH THE WAVE WILL HAVE TO BE WATCHED WHEN IT HITS WARMER
WATER W OF ABOUT 40W.

CENTRAL ATLC TROPICAL WAVE IS ALONG 41W/42W S OF 22N MOVING W 15
KT. CLEARLY DEFINED SHARP INVERTED-V SIGNATURE IN THE LOW LEVEL
CLOUDS IS OBSERVED ON VISIBLE SATELLITE IMAGERY. WAVE IS
EMBEDDED WITHIN A DRY ENVIRONMENT AS SEEN ON WATER VAPOR
PICTURES WHICH IS PREVENTING ANY CONVECTION.  A STRONG SURGE OF
DRY SAHARAN AIR AND AFRICAN DUST IS BEHIND THE WAVE.

TROPICAL WAVE E OF THE LESSER ANTILLES IS ALONG 60W S OF 15N
MOVING W 10-15 KT.  THIS IS A WEAK WAVE CONFINED TO THE ITCZ...
INCREASING SHOWERS/TSTMS IN THE WINDWARD ISLANDS TODAY.

CENTRAL CARIBBEAN TROPICAL WAVE EXTENDS FROM NE COLOMBIA THRU
CENTRAL DOMINICAN REPUBLIC TO 23N68W IS ALONG 70W/71W S OF 23N
MOVING W 10-15 KT.  THE WAVE HAS GOTTEN BETTER ORGANIZED IN THE
NORTHERN PORTION WITH DEEP CONVECTION CONSOLIDATING NEAR 21N70W
AND 1-2 MB 24 HOUR PRESSURE FALLS.  THE UPPER ENVIRONMENT LOOKS
FAVORABLE FOR SOME DEVELOPMENT AS AN UPPER ANTICYCLONE BUILDS
NEARBY.  WIDELY SCATTERED MODERATE CONVECTION FROM 21N-24N
BETWEEN 67W-72W.

...ITCZ...

ITCZ AXIS IS CENTERED ALONG 14N16W 9N23W 8N31W 12N47W 9N61W.
WIDELY SCATTERED MODERATE WITHIN 60 NM OF AXIS E OF 20W AND
BETWEEN 30W-35W.  ISOLATED MODERATE WITHIN 75 NM OF AXIS W OF
47W.

...DISCUSSION...

GULF OF MEXICO...
VERY HEAVY RAIN IS FALLING OVER NE MEXICO AND S TEXAS AS EMILY
MOVES FARTHER INLAND.  AS THE CIRCULATION OF EMILY HITS THE
HIGHER TERRAIN TORRENTIAL DOWNPOURS COULD OCCUR IN NE MEXICO
ESPECIALLY IN THE MONTERREY AREA.  THIN HIGH CLOUDINESS FROM THE
CYCLONE IS W OF 93W WITH RAINBANDS W OF 96W.  MUCH DRIER WEATHER
IS OVER THE REST OF THE GULF WITH MODERATE SUBSIDENCE
CONTROLLING THE REGION.  THIS SUBSIDENCE IS BETWEEN THE
MID/UPPER HIGH OVER NW GEORGIA AND A MID/UPPER LOW OVER THE
CAYMAN ISLANDS.  TYPICAL DIRUNAL CONVECTION SHOULD BREAK OUT
ALONG THE GULF COAST THIS AFTERNOON WITH THE NEXT SIGNIFICANT
INCREASE IN MOISTURE PROGGED FOR FLORIDA BY LATE THU WITH AN
APPROACHING TROPICAL WAVE.

CARIBBEAN...
LARGE UPPER LOW IS IN THE NW CARIBBEAN NEAR THE CAYMAN ISLANDS
WITH DIVERGENCE BETWEEN THE LOW AND RIDGING IN THE EPAC
PRODUCING A LARGE AREA OF SCATTERED TSTMS IN THE SW CARIBBEAN S
OF 15N W OF 76W.  A TROPICAL WAVE WILL BE MOVING INTO THE SW
CARIBBEAN DURING THE NEXT DAY OR TWO AND SHOULD CONTINUE TO
ENHANCE TSTMS.  OTHERWISE MID/UPPER RIDGING CONTROLS THE E
CARIBBEAN WITH ONE HIGH CENTER A COUPLE HUNDRED MILES N OF
PUERTO RICO AND ANOTHER ONE NEAR ARUBA.  VERY DRY AIR IN THE
MID/UPPER LEVELS IS BEING ADVECTED INTO THE LESSER ANTILLES
LATER TODAY AND SHOULD RESULT IN LESS SHOWERS THAN AVERAGE UNTIL
MOISTURE BEGINS TO INCREASE AHEAD OF A TROPICAL WAVE EARLY FRI.
THE AREA OF TSTMS OVER THE SW CARIBBEAN SHOULD PROGRESS SLOWLY
NORTHWESTWARD AND BRING LOCALLY HEAVY RAINS TO PORTIONS OF
CENTRAL AMERICA FROM NICARAGUA NW THRU GUATEMALA OVER THE NEXT
FEW DAYS.

ATLANTIC...
UPPER RIDGING CONTINUES TO BUILD IN THE W ATLC NEAR A HIGH
CNETER AROUND 21N66W WHICH COULD FACILITATE THE DEVELOPMENT OF
THE TROPICAL WAVE NEAR THE DOMINICAN REPUBLIC.  INCREASED
MOISTURE SHOULD RESULT IN LOCALLY HEAVY RAINS FOR THE SE BAHAMAS
LATER TODAY AS THE SYSTEM MOVES CLOSER...OVERSPREADING THE
CENTRAL BAHAMAS BY MORNING.   FARTHER E.. THE MID-OCEANIC TROUGH
IS WELL-DEFINED FROM A CLOSED LOW NEAR 32N43W SW TO 21N55W.  A
SURFACE TROUGH EXTENDS FROM 27N50W TO 31N45W AND IS HELPING TO
FIRE ISOLATED TSTMS WITHIN 60 NM OF THE AXIS IN THE COOLER AIR
ALOFT.  FARTHER E... THE TROPICAL ATLC AND NE ATLC IS COVERED BY
THE LARGE AFRICAN ANTICYCLONE WITH RIDGE AXIS FROM WESTERN
SAHARA TO 19N60W... BROKEN SLIGHTLY BY AN INVERTED TROUGH ALONG
46W S OF 18N.  VERY DRY AIR ALOFT BLANKETS THE TROPICAL ATLC
WITH ANY SIGNIFICANT CONVECTION LIMITED TO THE ITCZ.  IN
ADDITION A STRONG AFRICAN DUSK OUTBREAK IS ENTANGLED WITH THE
TROPICAL WAVE IN THE E ATLC WITH SIGNIFICANT DUST CONCENTRATIONS
E OF 38W BETWEEN 10N-25N.

$$
BLAKE


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