[Tropical] Tropical Weather Discussion

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AXNT20 KNHC 262358
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
805 PM EDT TUE JUL 26 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...

TROPICAL STORM FRANKLIN IS CENTERED NEAR 32.3N 68.4W...OR ABOUT
180 NM W OF BERMUDA...AT 27/0000 UTC NEARLY STATIONARY. MAXIMUM
SUSTAINED WIND SPEED IS 35 KT WITH GUSTS TO 45 KT. THE ESTIMATED
MINIMUM CENTRAL PRESSURE IS 1002 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. CONVECTION IS COMING AND GOING NEAR FRANKLIN
WITH THE CENTER MOSTLY EXPOSED DURING THE DAYS WITH ANOTHER
BURST GOING UP JUST S OF THE CENTER CURRENTLY.  NLY SHEAR
CONTINUES OVER THE STORM THOUGH COMPUTER MODELS SUGGEST THE
SHEAR WILL LESSEN TOMORROW... ALLOWING A SMALL POTENTIAL FOR
SOME INTENSIFICATION.  WIDELY SCATTERED MODERATE CONVECTION IS
FROM 30.5N-32N BETWEEN 67W-69.5W.

...TROPICAL WAVES...

E ATLC TROPICAL WAVE ADDED ALONG 28W S OF 17N MOVING W 15-20
KT.  LONG-TERM SATELLITE LOOPS... UPPER-AIR TIMESECTIONS FROM
DAKAR AND SAL... PLUS COMPUTER MODEL DATA SUGGEST THAT A
PERSISTENT AREA OF TSTMS SW OF THE CAPE VERDES IS A REFLECTION
OF A TROPICAL WAVE.  THIS WAVE IS SMALLER IN AMPLITUDE THAN THE
ONE IN THE CENTRAL ATLC AND THE ONE SOON TO EMERGE OFF W
AFRICA.  MOST OF THE WAVE'S SIGNAL IS IN THE MID-LEVELS WITH
ONLY A SMALL SURFACE REFLECTION NOTED... THOUGH THE GFS SUGGESTS
SOME DEVELOPMENT IS POSSIBLE AS THE SYSTEM MOVES A LITTLE S OF
DUE W.  IT SEEMS LIKE EVERY WAVE RECENTLY HAS BEEN A CANDIDATE
FOR FURTHER DEVELOPMENT WITH THE VERY WARM WATER AND LIGHT
VERTICAL SHEAR MORE REMINISCENT OF MID AUG THAN LATE JUL.
SCATTERED MODERATE CONVECTION FROM 10N-14N BETWEEN 28W-32W.

CENTRAL ATLANTIC TROPICAL WAVE IS TILTED NE TO SW ALONG 20N40W
TO 7N43W WITH A 1013 MB LOW ALONG THE WAVE NEAR 10N42W MOVING W
20 KT.  THE WAVE HAS A LITTLE MORE CONVECTION THAN YESTERDAY AS
IT MOVES INTO THE PROGRESSIVELY MORE UNSTABLE ATMOSPHERE IN THE
WESTERN TROPICAL ATLC.  ISOLATED TSTMS ARE WITHIN 60 NM OF A
LINE FROM 7N43W TO 15N39W.  THERE IS STILL PLENTY OF DRY AIR IN
THE LARGER WAVE CIRCULATION BUT THIS SHOULD SLOWLY MIX OUT AS
TSTM ACTIVITY INCREASES.  MOISTURE FROM THE WAVE SHOULD ENTER
THE LESSER ANTILLES ON FRIDAY WITH A PRECEDING "TAIL" OF
MOISTURE ENTERING TOMORROW.

CENTRAL CARIBBEAN TROPICAL WAVE ALONG 74W S OF 16N MOVING W 120
KT.  ANY SIGN OF THE WAVE HAS DISAPPEARED IN THE VERY FAST
LOW/MID-LEVEL FLOW OF THE CENTRAL CARIBBEAN.  LONG-TERM
SATELLITE LOOPS SUGGEST THE WAVE IS RATHER LOW-LATITUDE AND
COULD BE A COUPLE OF DEGREES FARTHER WEST BUT THE DATA ARE
INCONCLUSIVE.  NO SIGNIFICANT CONVECTION.

TROPICAL WAVE OVER SRN MEXICO AND GUATEMALA ALONG 92W/93W S OF
19N MOVING W 10-15 KT. TSTMS HAVE FORMED WITHIN 60 NM OF A LINE
FROM 14N92W IN SW GUATEMALA TO 19N92W OVER SE MEXICO THOUGH
THERE ARE NO MAJOR EFFECTS OVER THE BAY OF CAMPECHE.

...ITCZ...

ITCZ AXIS IS CENTERED ALONG 9N13W 16N38W...THEN ALONG 9N41W
12N52W AND IS ILL-DEFINED W OF 52W.  ISOLATED MODERATE
CONVECTION FROM 3N-10N BETWEEN 40W-52W.  WIDELY SCATTERED
MODERATE WITHIN 45 NM OF LINE 6N16W 7N20W 10N21W.

...DISCUSSION...

GULF OF MEXICO...
IT'S HARD TO DRAW AN ISOBAR OVER THE GULF TODAY WITH WEAK
PRESSURE GRADIENT RESULTING IN LIGHT AND VARIABLE WINDS OVER THE
GULF.  A PAIR OF WEAK LOWS ARE ALONG A SURFACE TROUGH FROM THE
FIRST LOW NEAR 27N83.5W W OF TAMPA TO 28N90W ABOUT 100 MILES S
OF GRAND ISLE LOUISIANA.  THE LOWS ARE LOCALLY ENHANCING NEARBY
CONVECTION OTHERWISE PARTLY CLOUDY SKIES ARE OVER THE GULF.  IN
THE MID/UPPER LEVELS... A HIGH IS NEAR 28N94W OVER THE NW GULF
WITH A SECOND HIGH OVER THE SE UNITED STATES.  BETWEEN THESE
FEATURES IS A NARROW SHEAR AXIS FROM NW CUBA TO SE LOUISIANA...
WITH A LITTLE BIT OF INSTABILITY NEAR THE AXIS CAUSING ISOLATED
TSTMS OVER THE GULF AND MORE WIDELY SCATTERED ACTIVITY OVER SE
LOUISIANA EASTWARD THRU S ALABAMA.   OTHERWISE THE UPPER LEVELS
ARE DOMINATED BY RELATIVELY DRY AIR OVER THE AREA.  MOISTURE
WILL BEGIN TO INCREASE NEAR THE N GULF COAST ON THU WITH THE
APPROACH OF A RARE SUMMERTIME COLD FRONT...AND COULD TRIGGER
SCATTERED TSTMS INTO THE WEEKEND...THOUGH THE FRONT WILL LIKELY
BECOME QUITE WEAK IF IT EVER ENTERS GULF WATERS.

CARIBBEAN...
THE ABSENCE OF DEEP CONVECTION IS QUITE AMAZING OVER THE AREA
WITH AFRICAN DUST AND DRY CONDITIONS ALOFT COMBINING TO KEEP
ALMOST ALL THE TSTMS OVER LAND.  BASICALLY HAZY SKIES AND
ISOLATED SHOWERS ARE THE MAIN WEATHER CONDITIONS OVER WATER.
THE MID-OCEANIC TROUGH SITS FROM THE SE BAHAMAS NEAR 22N71W THRU
HAITI TO NE HONDURAS... TRIGGERING WIDELY SCATTERED MODERATE
CONVECTION OVER CENTRAL NICARAGUA AND E HONDURAS.  A FEW TSTMS
ARE ALSO OVER TRINIDAD WITH PERHAPS A FEW MORE SHOWERS OVER THE
LEEWARD ISLANDS TOMORROW AS A TROUGH THAT BROKE OFF FROM A
TROPICAL WAVE GRAZES THE AREA.

WEST/CENTRAL ATLANTIC...
T.S. FRANKLIN CONTINUES TO MEANDER W OF BERMUDA BUT HAS NUDGED
N OF 32N. A TRAILING SFC TROF EXTENDS FROM NEAR BERMUDA SW TO
28N66W TO NEAR NASSAU BAHAMAS AND HAS TRIGGERED ISOLATED
MODERATE CONVECTION FROM 26N-30N BETWEEN 60W-70W...SOME OF WHICH
WILL OCCASIONALLY SPREAD OVER BERMUDA. A SMALL UPPER LOW IS
LOCATED JUST SW OF FRANKLIN NEAR 29N69W AND THE DIFFLUENCE IS
HELPING TO OCCASIONALLY BURST CONVECTION NEAR THE CENTER... WITH
PERHAPS A LITTLE LESS NLY SHEAR THAN YESTERDAY. A SECOND BUT
DRIER UPPER LOW IS LOCATED NEAR THE TURKS AND CAICOS ISLANDS AND
IS ENHANCING THE NEARLY CLOUD-FREE SKIES OVER THE SRN BAHAMAS.
FARTHER E...A SHARP UPPER TROF CONTINUES ALONG 30N51W 18N55W AND
IS INTERACTING WITH A SFC TROF NE OF THE LESSER ANTILLES TO
PRODUCE ISOLATED MODERATE CONVECTION FROM 16N-21N BETWEEN
52W-61W.

EAST ATLANTIC...
STRONG UPPER LEVEL RIDGING IS ESTABLISHED ALONG 19N AND HAS
INCREASED THE DEEP EASTERLY FLOW OUT OF AFRICA AND ACROSS THE
ATLC WATERS.  DRY AIR WITH A BIT OF DUST CONTINUES TO SPREAD
OVER THIS AREA AS WELL AND HAS STABILIZED THE ENVIRONMENT SO
THAT DEEP CONVECTION IS MOSTLY S OF 15N.  FARTHER N...A DEEP
UPPER TROF LOCATED W OF PORTUGAL ALONG 16W IS DRIVING A
DISSIPATING COLD FRONT FROM MADEIRA ISLAND TO 28N25W THEN 31N28W
WITH ONLY SCATTERED CLOUDS AND ISOLATED SHOWERS LOCATED ALONG
THIS FRONT.  SURFACE RIDGING EXTENDS FROM A 1024 MB HIGH NEAR
30N44W ESE TO 26N16W AND WSW TO 24N65W WITH ANOTHER DAY OF LIGHT
TRADES IN THE DEEP TROPICAL ATLC DUE TO PRESSURES IN THE DEEP
TROPICS BEING HIGHER THAN AVERAGE AND SLIGHTLY BELOW AVERAGE
PRESSURES IN THE CENTRAL ATLC.  VERTICAL WIND SHEAR IS MUCH LESS
THAN AVERAGE S OF 17N E OF THE LESSER ANTILLES.

$$
BLAKE

WWWW
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