[Tropical] Tropical Weather Discussion

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AXNT20 KNHC 271153
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
805 AM EDT WED JUL 27 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 0600 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH
1115 UTC.

...SPECIAL FEATURE...

TROPICAL STORM FRANKLIN CENTER NEAR 33.1N 68.8W...OR ABOUT 210
NM WNW OF BERMUDA...AT 27/0900 UTC MOVING NORTH 6 KT. ESTIMATED
MINIMUM CENTRAL PRESSURE IS 1005 MB. MAXIMUM SUSTAINED WIND
SPEED IS 35 KT GUSTS TO 45 KT. SEE THE LATEST NHC FORECAST/
ADVISORY UNDER AWIPS/WMO HEADERS MIATCMAT1/WTNT21 KNHC FOR MORE
DETAILS. T.S. FRANKLIN IS SHEARED...THE LOW LEVEL CENTER HAS
BECOME EXPOSED. SCATTERED STRONG SHOWERS AND THUNDERSTORMS
REMAIN FROM 30N TO 32N BETWEEN 68W AND 70W. THE CLOUD TOP
TEMPERATURES IN THIS AREA ARE NEAR -67C. FRANKLIN IS FORECAST TO
MOVE NORTHWARD AND THEN NORTHEASTWARD DURING THE NEXT FEW DAYS.

...TROPICAL WAVES...

EASTERN ATLANTIC OCEAN TROPICAL WAVE ALONG 29W/30W SOUTH OF 17N
MOVING WEST 15 TO 20 KT. ISOLATED MODERATE TO LOCALLY STRONG
SHOWERS AND THUNDERSTORMS FROM 8N TO 15N BETWEEN 30W AND 36W.

CENTRAL ATLANTIC OCEAN TROPICAL WAVE IS ALONG 45W/46W SOUTH
OF 20N MOVING WEST 20 KT. A SURFACE 1013 MB LOW PRESSURE CENTER
IS ALONG THE WAVE NEAR 11.5N. ISOLATED MODERATE TO LOCALLY STRONG
SHOWERS AND THUNDERSTORMS ARE IN A CURVED LINE...30 TO 60 NM
WIDE...CENTERED ALONG 10N55W 8N50W 10N45W 14N43W...AND FROM 16N
TO 19N BETWEEN 40W AND 50W. 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 SEA TROPICAL WAVE ALONG 78W/79W SOUTH OF 18N
...FROM JAMAICA...SOUTHWARD. IT IS MOVING WEST 20 KT. NUMEROUS
STRONG SHOWERS IN THE SOUTHWESTERN CORNER OF THE AREA AGAINST
THE PANAMA COAST JUST EAST OF COSTA RICA. IT IS MORE LIKELY
THAT THIS ACTIVITY IS RELATED TO THE ITCZ.

TROPICAL WAVE MOVING THROUGH THE ISTHMUS OF TEHUANTEPEC OF
MEXICO ALONG 94W/95W SOUTH OF 19N MOVING WEST 10 TO 15 KT.
BARELY EVEN ISOLATED MODERATE SHOWERS ARE BEING SEEN IN THE
CURRENT SATELLITE IMAGERY...AT THE EDGE OF LAND AND THE
MEXICO GULF COAST IN THE SOUTHWESTERN CORNER OF THE AREA.

...ITCZ...

ITCZ AXIS IS CENTERED ALONG 12N14W 11N20W 12N28W...12N32W
14N43W...10N47W 10N54W 9N61W. WIDELY SCATTERED MODERATE TO
ISOLATED STRONG SHOWERS AND THUNDERSTORMS FROM 7N TO 10N BETWEEN
20W AND 26W.

...DISCUSSION...

THE GULF OF MEXICO...
A WEAK SURFACE PRESSURE GRADIENT EXISTS IN THE GULF OF MEXICO. A
SURFACE TROUGH RUNS FROM 29N69W IN THE ATLANTIC OCEAN TO AN EAST
OF THE BAHAMAS 1014 MB LOW PRESSURE CENTER NEAR 26N76W...THROUGH
THE NORTHERN BAHAMAS AND ACROSS SOUTH FLORIDA...TO AN EASTERN
GULF OF MEXICO 1013 MB LOW PRESSURE CENTER ALONG THE FLORIDA
WEST COAST NEAR 27N83W...TO 26N85W TO 27N88W. THE NORTH CENTRAL
GULF OF MEXICO SURFACE LOW PRESSURE CENTER IS NOT APPARENT ANY
MORE. ISOLATED MODERATE SHOWERS APPEAR FROM 25N TO 30N BETWEEN
84W AND 94W. ONE UPPER LEVEL ANTICYCLONIC CIRCULATION CENTER
IS IN THE NORTHWESTERN GULF...AND ANOTHER ONE IS OVER THE
SOUTHEASTERN UNITED STATES. A NARROW SHEAR AXIS IS BETWEEN THESE
FEATURES FROM NORTHWESTERN CUBA TO SOUTHEASTERN LOUISIANA. THE
UPPER LEVELS ARE DOMINATED BY RELATIVELY DRY AIR OVER THE AREA.
MOISTURE WILL BEGIN TO INCREASE NEAR THE NORTHERN GULF COAST ON
THURSDAY WITH THE APPROACH OF A RARE SUMMERTIME COLD FRONT...AND
MAY TRIGGER SCATTERED THUNDERSTORMS INTO THE WEEKEND...THOUGH IT
IS LIKELY THAT THE FRONT WILL BECOME QUITE WEAK IF IT EVER
ENTERS THE GULF WATERS.

THE CARIBBEAN SEA...
BROAD SURFACE LOW PRESSURE COVERS THE SOUTHWESTERN CORNER OF THE
AREA...FOLLOWING THE SURFACE ISOBARIC PATTERN. ITCZ SHOWERS AND
THUNDERSTORMS ALONG PANAMA COAST...AND WEAKENING BUT REMNANT
ISOLATED MODERATE TO LOCALLY STRONG SHOWERS AND THUNDERSTORMS
STRETCH FROM NORTHEASTERN NICARAGUA TO BELIZE. THE 78W/79W
TROPICAL WAVE IS APPROACHING THIS AREA. AFRICAN DUST AND DRY
CONDITIONS ALOFT COMBINE TO KEEP ALMOST ALL THE THUNDERSTORMS
OVER LAND. THE MID-OCEANIC TROUGH SITS FROM THE SOUTHEASTERN
BAHAMAS THROUGH HAITI TO NORTHEASTERN HONDURAS...TRIGGERING THE
SHOWERS IN CENTRAL AMERICA.

THE WEST AND CENTRAL ATLANTIC OCEAN...
TROPICAL STORM FRANKLIN STILL IS IN THE AREA.
ISOLATED SHOWERS ARE SEEN FROM 27N TO 32N BETWEEN 60W AND 66W
SOUTHEAST OF FRANKLIN...AND FROM 24N TO 27N BETWEEN 73W AND 77W
WITH THE 1014 MB ATLANTIC LOW. ISOLATED MODERATE TO LOCALLY
STRONG SHOWERS AND THUNDERSTORMS FROM 18N TO 25N BETWEEN 54W AND
65W WITH THE 25N53W 17N64W SURFACE TROUGH...AND FROM 29N TO 32N
BETWEEN 48W AND 54W. 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 NORTHERLY 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. MORE
TO THE EAST A SHARP UPPER LEVEL TROUGH CONTINUES ALONG 30N51W
18N55W AND IS INTERACTING WITH THE SURFACE TROUGH NORTHEAST OF
THE LESSER ANTILLES TO PRODUCE THE CONVECTIVE ACTIVITY IN THAT
AREA.

THE EASTERN ATLANTIC OCEAN...
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.

$$
MT


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