[Tropical] Tropical Weather Discussion

[EMWIN Server]

AXNT20 KNHC 221754
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
205 PM EDT FRI JUL 22 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 FEATURES...

TROPICAL STORM FRANKLIN IS CENTERED NEAR 27.4N 76.7W OR ABOUT 70
MILES... 110 KM... NORTHEAST OF MARSH HARBOR ON GREAT ABACO
ISLAND AT 22/1800 UTC MOVING N 7 KT. MAXIMUM SUSTAINED WIND
SPEED IS 45 KT WITH GUSTS TO 55 KT. ESTIMATED MINIMUM CENTRAL
PRESSURE IS 1007 MB. SEE LATEST NHC FORECAST/ ADVISORY UNDER
AWIPS/WMO HEADERS MIATCMAT1/WTNT21 KNHC AND THE PUBLIC ADVISORY
UNDER AWIPS/WMO HEADERS MIATCPAT1/WTNT31 KNHC FOR MORE DETAILS.
FRANKLIN IS A RELATIVELY SMALL SYSTEM WITH TIGHT BANDING
FEATURES AND AN ANTICYCLONE POSITIONED ALMOST OVERHEAD..
PROVIDING LIGHT SHEAR.  THE CYCLONE HAS A GOOD CHANCE OF
STRENGTHENING OVER THE NEXT COUPLE OF DAYS BEFORE INTERACTING
WITH A MID-LATITUDE TROUGH.  IT WILL BE INTERESTING TO SEE HOW
MUCH LATITUDE THE SYSTEM GAINS BECAUSE IT WILL BE CRUCIAL IN
DETERMINING HOW QUICKLY THE SYSTEM CAN RECURVE IF IT CATCHES THE
TROUGH.  SCATTERED MODERATE CONVECTION FROM 25N-29N BETWEEN
74W-78W.

A STRONG TROPICAL WAVE IS IN THE NW CARIBBEAN SEA FROM THE
YUCATAN CHANNEL INTO THE GULF OF HONDURAS MOVING W 10-15 KT.
SATELLITE IMAGES SHOW A WEAK 1011 MB LOW FORMING ALONG THE WAVE
AXIS NEAR 18N 88W.  THE LOW CLOUDS OVER THE YUCATAN ARE
MOVING FROM N TO S... SUGGESTING THE SYSTEM HAS GOTTEN BETTER
ORGANIZED OVERNIGHT WITH A BALL OF CONVECTION NEAR THE
DISORGANIZED CIRCULATION CENTER.  PROXIMITY TO LAND MAY INHIBIT
FURTHER DEVELOPMENT TODAY BUT A BUILDING UPPER RIDGE OVER THE SW
GULF OF MEXICO COULD ALLOW FORMATION OVER THE BAY OF CAMPECHE
TOMORROW AS THE SYSTEM MOVES INTO THAT AREA.  WIDELY SCATTERED
MODERATE CONVECTION IS WITHIN 60 NM OF THE E COAST OF BELIZE AND
YUCATAN AND ALSO FROM 18N-21N BETWEEN THE CAYMAN ISLANDS AND
YUCATAN.

...TROPICAL WAVES...

HIGH-AMPLITUDE E-CENTRAL ATLC TROPICAL WAVE IS ALONG ABOUT 37W S
OF 23N MOVING W 15-20 KT.  DUST CONCENTRATIONS ARE QUITE THICK
WITHIN THE BROAD CIRCULATION OF THE WAVE THOUGH THE
STRATOCUMULUS CLOUDS ARE BREAKING UP A BIT AS THE WAVE ENTERS A
MORE UNSTABLE LOW-LEVEL ATMOSPHERE.  STRONG SW WINDS ON THE S
SIDE OF THE WAVE ARE ENHANCING ITCZ CONVECTION WITH SCATTERED
MODERATE CONVECTION WITHIN 60 NM OF LINE 9N37W 11N28W.

TROPICAL WAVE IS IN THE LESSER ANTILLES ALONG ABOUT 61W S OF 18N
MOVING W 20-25 KT.  THIS WAVE HAS ACCELERATED OVER THE PAST 24
HOURS AND ITS V-SHAPE IS DEGRADING A BIT ON SATELLITE PICTURES.
WIDELY SCATTERED TSTMS ARE FROM 12N-17.5N BETWEEN 58W-63W...
ENHANCED BY THE MID-OCEANIC TROUGH TO THE NW.

WEAK TROPICAL WAVE OVER THE S CARIBBEAN ALONG 72W S OF 14N
MOVING W 10 KT.  THE BEST EVIDENCE OF THE WAVE COMES FROM TSTMS
OVER S AMERICA... OTHERWISE NO EFFECTS OVER THE AREA SAVE
PERHAPS AN INCREASE IN TRADES OVER THE CENTRAL CARIBBEAN.

NW CARIBBEAN TROPICAL WAVE IS NOW A SPECIAL FEATURE.

...ITCZ...

ITCZ AXIS IS CENTERED ALONG 12N16W 11N29W 9N36W 11N56W.
SCATTERED MODERATE FROM 8.5N-11N BETWEEN 52W-55W.  SIMILAR
CONVECTION WITHIN 75 NM OF LINE 9N37W 11N28W.

...DISCUSSION...

GULF OF MEXICO...
UPPER RIDGING CONTROLS THE SE GULF OF MEXICO WHILE A MID/UPPER
LOW IS MOVING WESTWARD OVER THE BAY OF CAMPECHE NEAR 20N95W.
WHILE WEAK UPPER RIDGING IS OVER THE NORTHERN GULF COAST
STATES...DEEP-LAYERED MOISTURE FROM LOUISIANA EASTWARD THRU SW
GEORGIA COMBINED WITH DIURNAL HEATING SHOULD PRODUCE AN
ABOVE-AVERAGE COVERAGE OF TSTMS LATER TODAY WITH MORE TYPICAL
TSTMS OVER TEXAS.  HIGH CLOUDS OVER THE SOUTHERN GULF ARE A SIGN
THAT THINGS ARE CHANGING WITH A TROPICAL WAVE FORECAST TO MOVE
INTO THE SRN GULF BY TOMORROW.  COMPUTER MODELS ARE SUGGESTIVE
THAT THE WAVE WILL ENCOUNTER A FAVORABLE ENVIRONMENT ALOFT FOR
FURTHER DEVELOPMENT.  MOISTURE FROM THE WAVE COULD REACH PARCHED
AREAS OF S TEXAS ON SUN.

CARIBBEAN...
MID/UPPER HIGH LIES OVER NW CUBA WITH ANTICYCLONIC FLOW ALOFT
COVERING THE W CARIBBEAN W OF 76W.  UPPER DIVERGENCE NEAR THE
YUCATAN PENINSULA IS CAUSING PLENTY OF TSTMS NEAR A TROPICAL
WAVE AND SHOULD PRODUCE A RATHER WET DAY FOR BELIZE NORTHWARD
THRU YUCATAN INTO SAT.  THINGS DRY OUT CONSIDERABLY IN THE
EASTERN CARIBBEAN WITH MODERATE SUBSIDENCE ALOFT LIMITING TSTM
DEVELOPMENT.  THE ONLY AREA ABLE TO BREAK THE TROPICAL INVERSION
IS IN THE SE CARIBBEAN NEAR A TROPICAL WAVE.  MOISTURE FROM THE
LARGE TROPICAL WAVE IN THE E-CENTRAL ATLC COULD REACH THE LESSER
ANTILLES ON SUN.  AN INCREASE IN AFRICAN DUST IS E OF 58W AND
SHOULD OVERSPREAD THE AREA LATER TODAY.

ATLANTIC...
AN UPPER HIGH IS FORMING NEAR 28N76W... JUST NE OF FRANKLIN...
WITH LITTLE SHEAR OVER THE SYSTEM.  A MID-LATITUDE TROUGH IS
SWINGING THRU THE GREAT LAKES INTO THE OHIO VALLEY AND COULD
TURN THE STORM MORE TO THE NE AS IT GRADUALLY BREAKS DOWN
MIDDLE-LEVEL RIDGING OVER THE CAROLINAS.  THE MID-OCEANIC TROUGH
IS ESTABLISHED FROM 25N55W TO PUERTO RICO WITH SW SHEAR
ENHANCING A BIT OF CONVECTION OVER THE LESSER ANTILLES.
MODERATE/STRONG SUBSIDENCE COVERS THE ATLC FROM 30W-60W WITH ANY
TSTMS LIMITED TO THE ITCZ.  SHEAR IS AS HIGH AS IT HAS BEEN FOR
QUITE A WHILE N OF 15N W OF 40W WITH THE AFRICAN ANTICYCLONE A
BIT WEAKER THAN RECENTLY.  E OF 40W... UPPER RIDGING EXTENDS
FROM WESTERN SAHARA TO 20N40W WITH MID/UPPER ELYS S OF THE RIDGE
AXIS.  STRONG DIFFLUENCE NEAR THE ITCZ ALONG WITH A TROPICAL
WAVE IS ENHANCING TSTMS NEAR 10N35W.  A NEW TROPICAL WAVE OVER W
AFRICA IS CAUSING WIDELY SCATTERED TSTMS FROM 6.5N-11N E OF
17W.  IMPRESSIVE DUST OUTBREAK ASSOCIATED WITH A TROPICAL WAVE
IS FROM 40W-55W S OF 25N WITH GENERALLY LIGHT SURFACE WINDS S OF
15N E OF 40W IN THE BASIN.  THE NEXT TROPICAL WAVE LOOKS TO BE
EMERGING MUCH FARTHER S WITH LESS OF A DRY AIR INTRUSION.
SURFACE RIDGE AXIS EXTENDS FROM A 1029 MB HIGH NEAR THE AZORES
TO 31N37W TO 26N55W THEN 29N71W.

$$
BLAKE



This weather bulletin was brought to you by:
www.nashvilleweather.net