[Tropical] Tropical Weather Discussion

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AXNT20 KNHC 232349
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
805 PM EDT SAT JUL 23 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 FEATURES...

TROPICAL DEPRESSION SEVEN HAS FORMED NEAR 19.5N 93.8W...OR ABOUT
190 NM ESE OF TUXPAN MEXICO...AT 24/0000 UTC MOVING WNW 8 KT.
MAXIMUM SUSTAINED WIND SPEED IS 25 KT WITH GUSTS TO 35 KT.
ESTIMATED MINIMUM CENTRAL PRESSURE IS 1011 MB. SEE LATEST NHC
FORECAST/ADVISORY UNDER AWIPS/WMO HEADERS MIATCMAT2/WTNT22 KNHC
AND THE PUBLIC ADVISORY UNDER AWIPS/WMO HEADERS MIATCPAT2/WTNT32
KNHC FOR MORE DETAILS. T.D. SEVEN HAS A BROAD CIRCULATION WITH A
WELL-DEFINED SFC CENTER NOT MORE THAN 65 NM OFF THE MEXICAN
COAST...BUT THE CONVECTIVE PATTERN LEAVES MUCH TO BE DESIRED FOR
A TROPICAL CYCLONE. THERE HAVE BEEN THREE MAIN CONVECTIVE AREAS
THROUGH THE AFTERNOON...ONE HUGGING THE COAST FROM TAMPICO TO
VERACRUZ...THE SECOND NEAR BUOY 42055...AND THE THIRD MOVING OFF
THE W COAST OF THE YUCATAN PENINSULA. IT DOES APPEAR THE
CONVECTION IS FILLING IN A BIT AND ORGANIZATION WILL MOST LIKELY
CONTINUE THROUGH THE NIGHT. MEXICAN RADAR FROM ALVARADO...JUST S
OF VERACRUZ...SHOWS THE CENTER JUST N OF THE STATE OF TABASCO
WITH A HEAVY BAND OF RAIN PREPARING TO MOVE ONSHORE S OF CABO
ROJO. SCATTERED MODERATE CONVECTION IS FROM 17N-24N BETWEEN
89W-98W.

TROPICAL STORM FRANKLIN IS CENTERED NEAR 29.9N 74.3W...OR ABOUT
510 NM WSW OF BERMUDA...AT 23/2100 UTC MOVING ENE 8 KT. MAXIMUM
SUSTAINED WIND SPEED IS 60 KT WITH GUSTS TO 75 KT. ESTIMATED
MINIMUM CENTRAL PRESSURE IS 1001 MB. SEE LATEST NHC FORECAST/
ADVISORY UNDER AWIPS/WMO HEADERS MIATCMAT1/WTNT21 KNHC FOR MORE
DETAILS. THE UPPER LEVEL ANTICYCLONE ASSOCIATED WITH FRANKLIN
HAS SHIFTED OVER THE WRN PERIPHERY OF THE SYSTEM AND HAS BEGUN
TO INDUCE NLY SHEAR AS THE LOW-LEVEL CENTER MOVES TO THE E.
THERE IS EXCELLENT OUTFLOW OVER THE SRN SEMICIRCLE WHICH IS
KEEPING ALL DEEP CONVECTION NEAR AND TO THE S OF THE CENTER.
NUMEROUS MODERATE CONVECTION IS FROM 27N-30N BETWEEN 72W-78W. IF
THE CURRENT FORECAST HOLDS...FRANKLIN COULD BEGIN AFFECTING
BERMUDA BY TUE WITH HEAVY SHOWERS/TSTMS AND INCREASING
WINDS...ESPECIALLY IF THE CENTER MOVES JUST N OF THE ISLAND.

...TROPICAL WAVES...

TROPICAL WAVE INTRODUCED BETWEEN THE AFRICAN COAST AND CAPE
VERDE ISLANDS ALONG 20W S OF 16N MOVING W 10-15 KT. UPPER AIR
DATA FROM DAKAR SHOWS THE WINDS BETWEEN 800 AND 950 MB VEERING
FROM N/NE TO E/SE OVERNIGHT AND VISIBLE IMAGERY SHOWS A FAIRLY
NICE CIRCULATION IN THE CLOUD PATTERN ALONG THE ITCZ. DEEP
CONVECTION IS ALIGNED ALONG THE ITCZ.

CENTRAL ATLANTIC TROPICAL WAVE ALONG 44W/45W S OF 22N MOVING W
15-20 KT WITH A 1011 MB LOW ALONG THE AXIS NEAR 11N45W. THE LOW
IS FAINTLY VISIBLE IN SATELLITE IMAGERY AND IS EMBEDDED WITHIN A
BROAD AREA OF LOW PRES NEAR THE ITCZ. WIDESPREAD DUST/HAZE
CONTINUES TO MOVE W WITH THE WAVE AND THE DRY AIR IS LIMITING
DEEP CONVECTION NEAR AND W OF THE AXIS. LOW-LEVEL MOISTURE BEING
PULLED NWD TO THE E IS PRODUCING BROKEN STRATUS WITH POSSIBLE
SHOWERS S OF 17N BETWEEN 34W-44W.

CENTRAL CARIBBEAN TROPICAL WAVE ALONG 70W S OF 20N MOVING W 20
KT. SAN JUAN UPPER AIR DATA SHOW THE MID-LEVEL PART OF THE WAVE
PASSING BETWEEN 12Z AND 00Z YESTERDAY...AND THE LOW-LEVEL
SIGNATURE PASSED ALMOST 12 HRS LATER. SATELLITE IMAGERY SUGGESTS
THAT THE WAVE MAY BE FARTHER W NEAR 74W BASED ON SELY STREAMER
CLOUDS EXTENDING FROM THE SRN WINDWARD ISLANDS TO JAMAICA...AND
THIS MAY BE REFLECTED IN THE 00Z ANALYSIS. THE WAVE MARKS THE
LEADING EDGE OF THE AFRICAN DUST SURGE...BUT DUST CONCENTRATIONS
DO NOT APPEAR TO BE AS THICK AS THEY WERE FOR THE PAST SEVERAL
DAYS. SCATTERED MODERATE/STRONG CONVECTION OVER NW VENEZUELA AND
NRN COLOMBIA.

SW CARIBBEAN TROPICAL WAVE ALONG 79W S OF 15N MOVING W 15-20 KT.
THE WAVE HAS A POOR SIGNATURE BUT IS STILL TRIGGERING WIDELY
SCATTERED MODERATE CONVECTION S OF 12N W OF 80W INTO COSTA RICA.
THE FASTER MOVING WAVE TO THE E MAY OVERTAKE THIS WAVE OVER THE
NEXT COUPLE OF DAYS.

TROPICAL WAVE WHICH SPAWNED TROPICAL DEPRESSION SEVEN IS NOW S
OF THE AREA NEAR THE GULF OF TEHUANTEPEC.

...ITCZ...

ITCZ AXIS IS CENTERED ALONG 20N12W 7N28W 14N42W...THEN ALONG
9N47W 8N64W. SCATTERED MODERATE CONVECTION MAINLY WITHIN 250 NM
N/NW OF THE AXIS BETWEEN 18W-32W. WIDELY SCATTERED MODERATE S OF
THE AXIS FROM 1N-8N BETWEEN 37W-41W. ISOLATED SHOWERS/TSTMS
WITHIN 100 NM N OF THE AXIS BETWEEN 48W-54W.

...DISCUSSION...

GULF OF MEXICO...
HIGH PRES IS SANDWICHED OVER THE N/CNTRL GULF BETWEEN T.S.
FRANKLIN TO THE E AND T.D. SEVEN TO THE SW AND IS KEEPING THE NW
AND SE PART OF THE AREA UNDER GENERALLY FAIR WEATHER. THE SFC
HIGH IS COLLOCATED WITH A STRONG MID/UPPER LEVEL ANTICYCLONE...
WHICH INCIDENTALLY WILL STEER T.D. SEVEN WWD TOWARDS MEXICO. SEE
SPECIAL FEATURES ABOVE FOR FURTHER DISCUSSION ON T.D. SEVEN.
FARTHER E...AN UPPER LOW IS CENTERED NEAR LAKE OKEECHOBEE IN
FLORIDA AND DIFFLUENCE ALOFT TO THE N OF THIS FEATURE IS
INTERACTING WITH A SFC TROF OVER THE FL PANHANDLE TO TRIGGER
SCATTERED MODERATE CONVECTION FROM 28N-31N BETWEEN 81W-86.5W
NEAR THE FL BIG BEND. THE MOISTURE AXIS IS EXPECTED TO SHIFT S
OVER THE NEXT 24 HRS WHICH COULD PUT THE FOCUS FOR CONVECTION
OVER S/CNTRL FLORIDA TOMORROW.

CARIBBEAN...
WATER VAPOR IMAGERY SHOWS VERY LITTLE DEEP MOISTURE OVER THE
CARIBBEAN BASIN AT THE MOMENT NOW THAT THE SHOWERS/TSTMS
ASSOCIATED WITH T.D. SEVEN ARE MOVING INLAND ACROSS THE YUCATAN
PENINSULA AND CNTRL AMERICA. DRY AIR WITH SUSPENDED AFRICAN DUST
HAS PENETRATED INTO THE AREA ABOUT AS FAR W AS 74W AND IS
ESSENTIALLY PRECLUDING THE DEVELOPMENT OF DEEP CONVECTION. THE
ONLY CURRENT TSTM ACTIVITY IS OVER LAND AREAS OF E CUBA...
HISPANIOLA...VENEZUELA...AND COLOMBIA WHERE DAYTIME INSTABILITY
IS GREATEST. THE DUST HAS BEGUN TO PRODUCE HAZY SKIES OVER THE
LESSER ANTILLES BUT THE ONLY ISLANDS WHICH HAVE REPORTED HAZE
HAVE BEEN GRENADA...ANTIGUA...AND NEVIS. GRENADA REPORTED
VISIBILITY DROPPING TO NEAR 5 MILES AT 1900Z TODAY. A LITTLE BIT
OF MOISTURE MAY MOVE OVER THE WINDWARD ISLANDS ON SUN AND
PRODUCE ISOLATED SHOWERS/TSTMS...BUT OTHERWISE DRY AND HAZY
CONDITIONS WILL CONTINUE FOR MUCH OF THE COMING WEEK.

ATLANTIC...
SEE SPECIAL FEATURES ABOVE FOR DISCUSSION ON T.S. FRANKLIN AND
THE SURROUNDING ENVIRONMENT. ELSEWHERE...AN UPPER LEVEL HIGH IS
CENTERED E OF FRANKLIN NEAR 29N66W AND BUTTS UP AGAINST THE
MID-OCEANIC TROF WHICH LIES ALONG 28N50W 19N69W. AN UPPER LOW IS
EMBEDDED IN THE TROF NEAR 24N58W WITH MODERATE 30 KT NELY WINDS
ON ITS N SIDE. A SFC TROF LIES ALONG 26N63W 31N57W AND IS
PRODUCING WIDELY SCATTERED SHOWERS/TSTMS FROM 26N-31N BETWEEN
54W-62W...BUT THE NELY SHEAR IS PROHIBITING ANY ORGANIZED
ACTIVITY. A MONSTROUS UPPER LEVEL ANTICYCLONE IS CENTERED E OF
THE LESSER ANTILLES NEAR 17N50W AND IS PRODUCING STRONG
SUBSIDENCE TO ITS E AND S...ESSENTIALLY CAPPING THE ENVIRONMENT
OVER THE CNTRL CARIBBEAN AND KEEPING THE AFRICAN DUST TRAPPED
WITHIN THE TRADE WIND LAYER. THE BACK END OF THE MOST
CONCENTRATED DUST IS NEAR 38W BUT ANOTHER AREA OF DUST IS
LINGERING N OF THE CAPE VERDE ISLANDS E OF 40W. FARTHER S...DEEP
EASTERLY FLOW EXTENDS ACROSS THE E/CNTRL ATLC S OF 16N WITH JUST
ENOUGH UPPER DIFFLUENCE CENTERED OVER THE ITCZ TO SUPPORT
SCATTERED CONVECTION E OF 32W.

$$
BERG



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