[Tropical] Tropical Weather Discussion

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AXNT20 KNHC 081751
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
205 PM EDT FRI JUL 08 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 DENNIS NEAR 22.1N 80.6W AT 1800 UTC ON THE COAST OF
CUBA NEAR CIENFUEGOS MOVING NW 14 KT.  MAXIMUM SUSTAINED WINDS
ARE NOW 125 KT GUSTING TO 150 KT AND THE MINIMUM CENTRAL
PRESSURE IS 941MB.  SEE THE LATEST NHC PUBLIC ADVISORY UNDER
AWIPS/WMO HEADERS MIATCPAT4/WTNT34 KNHC AND THE
FORECAST/ADVISORY UNDER AWIPS/WMO HEADERS MIATCMAT4/WTNT24 KNHC
FOR MORE DETAILS.  THE HURRICANE HAS BEEN A RECORD-BREAKER SO
FAR... BEING THE EARLIEST CATEGORY 4 IN THE CARIBBEAN SEA AND
THE STRONGEST HURRICANE IN THE ATLC BASIN SO EARLY IN THE YEAR.
THE EYE HAS BECOME BETTER-DEFINED DURING THE DAY WITH
ANTICYCLONIC OUTFLOW CONTINUING TO BE IMPRESSIVE.  INTERACTION
WITH LAND HAS WEAKENED THE SYSTEM SOME BUT IS EXPECTED TO EMERGE
INTO THE GULF OF MEXICO OVERNIGHT WHERE UPPER LEVEL WINDS ARE
FAVORABLE FOR REINTENSIFICATION.  THERE IS A SLIGHT ASYMMETRY TO
THE CLOUD PATTERN WITH MOST OF THE SHOWERS/TSTMS ON THE SE SIDE
OF THE SYSTEM WITH A LITTLE BIT OF NW SHEAR FAVORING CONVECTIVE
DEVELOPMENT BEHIND THE HURRICANE.  A FEW RAINBANDS ARE MOVING
THRU THE FLORIDA KEYS INTO S FLORIDA... ALSO OVERSPREADING THE
CENTRAL BAHAMAS.  SCATTERED MODERATE CONVECTION IS FROM 19N-24N
BETWEEN E CUBA TO 81W.

...TROPICAL WAVES...
TROPICAL WAVE ADDED NEAR THE CAPE VERDE ISLANDS ALONG 26W S OF
18N MOVING W 10-15 KT.  THERE IS A 1013 MB LOW ALONG THE WAVE
NEAR 12N.  THE E ATLC HAS A COMPLICATED STRUCTURE RIGHT NOW WITH
TWO DISTURBANCES WITHIN ABOUT 8 DEGREES OF ONE ANOTHER... A 1014
MB LOW IS NEAR 11N34W.  THESE SYSTEMS APPEARS TO BE SLOWLY
MOVING WESTWARD AND IT IS DIFFICULT TO DETERMINE IF THEY ARE
BOTH ASSOCIATED WITH TROPICAL WAVES.  A FEW TSTMS ARE BEING
GENERATED BY THE LOWS THOUGH THE WESTERN ONE IS ABOUT TO ENTER
MUCH DRIER AIR ALOFT.

E ATLC TROPICAL WAVE IS ALONG 40W/41W MOVING W 10-15 KT.  WAVE
CAN BE SEEN IN THE STRATOCUMULUS FIELD THOUGH ITS CLOUD
SIGNATURE IS FADING.  NO SIGNIFICANT CONVECTION.

W-CENTRAL ATLANTIC TROPICAL WAVE IS ALONG 59W S OF 16N MOVING
WEST 10-15 KT.  THE 12Z SOUNDING FROM BARBADOS INDICATED THE
WAVE WAS CLOSE BY THOUGH THE MAXIMUM CURVATURE SEEN IN THE LOW
CLOUDS IS STILL A BIT FARTHER W.  IT IS POSSIBLE THAT A
MID/UPPER LOW NEAR 20N60W IS MASKING THE WAVE SIGNATURE IN THE
UPPER AIR DATA.  WIDELY SCATTERED MODERATE CONVECTION IS WITHIN
120 NM OF 12N56W WITH MORE ISOLATED ACTIVITY OVER THE WINDWARD
ISLANDS.  INCREASED LEVELS OF MOISTURE ARE LIKELY FOR TOMORROW
OVER THE WINDWARDS WITH SIGNIFICANT DRYING BY LATE SAT.

...ITCZ...

ITCZ AXIS IS ALONG 10N14W 8N30W 4N50W.  WIDELY SCATTERED
MODERATE CONVECTION IS BETWEEN 9N-11N E OF 15N.   CONVECTION IS
RATHER SUPPRESSED IN THE ITCZ TODAY COMPARED TO THE PAST FEW
WEEKS.

...DISCUSSION...

GULF OF MEXICO...
MID/UPPER RIDGING EXTENDS FROM THE NW ATLC NEAR A HIGH CENTER AT
30N79W ACROSS NE FLORIDA NEAR CEDAR KEY SW TO 26N89W IN THE
CENTRAL GULF.  THIS RIDGE IS KEEPING THE HURRICANE MOVING IN A
GENERAL NW DIRECTION AROUND THE SW SIDE OF THE HIGH.  A WEAK
MID/UPPER LOW IS NOTED OVER THE BAY OF CAMPECHE WITH A
MID-LATITUDE TROUGH AND A WEAK UPPER LOW OVER NE TEXAS ALONG THE
TROUGH FROM ARKANSAS THRU SE TEXAS.  DENNIS APPEARS LIKELY TO
MOVE IN BETWEEN THE HIGH OVER THE NW ATLC AND THE TROUGH OVER
TEXAS.  THE STRENGTH OF THESE FEATURES WILL BE CRITICAL IN
DETERMINING WHETHER DENNIS CURVES A LITTLE CLOSER TO FLORIDA...A
WEAK RIDGE SCENARIO/STRONGER TROUGH... OR TOWARD THE CENTRAL
GULF COAST... A STRONG RIDGE/WEAK TROUGH SITUATION.

OTHERWISE A WEAK COLD FRONT HAS DRIFTED IN THE FAR NW GULF WITH
A FEW SHOWERS.  OTHERWISE VERY DRY AIR IN THE MID/UPPER LEVELS
DOMINATES W OF 90W WITH LOW-LEVEL CYCLONIC FLOW FROM THE
HURRICANE S OF 26N E OF 88W.  A FEW TSTMS ARE WITHIN 75 NM OF
28N88W ALONG THE REMNANT TAIL OF CINDY.

CARIBBEAN SEA...
CATEGORY FOUR HURRICANE DENNIS IS OBVIOUSLY THE STORY WITH THE
CENTER SW OF CIENFUEGOS IN CUBA.  VERY HEAVY RAIN SHOULD
CONTINUE OVER THE ISLAND INTO TOMORROW WITH LINGERING ACTIVITY
IN W CUBA THROUGH SUN.  KINGSTON JAMAICA RECEIVED ALMOST 12
INCHES OF RAIN AS THE CYCLONE PASSED YESTERDAY.  OUTSIDE OF
DENNIS.. THE WEATHER IS RATHER QUIET WITH NE FLOW IN THE UPPER
LEVELS CONTROLLING THE REGION W OF 70W.  A MID/UPPER TROUGH
EXTENDS THRU THE LEEWARD/WINDWARD ISLANDS DOWN TO ABOUT TRINIDAD
AND IS ENHANCING A TROPICAL WAVE'S CONVECTION LOCATED NEAR
BARBADOS.  A PUSH OF DRIER AIR ALOFT IS PREVENTING MUCH SHOWER
DEVELOPMENT IN THE LEEWARD ISLANDS WITH IT PROBABLY DRYING
PUERTO RICO A BIT TODAY WITH ONLY ISOLATED SHOWERS.  MOISTURE
FROM THE TROPICAL WAVE COULD OVERSPREAD PUERTO RICO ON SUN.

ATLANTIC OCEAN...
MID/UPPER RIDGING EXTENDS FROM NE FLORIDA THROUGH BERMUDA WITH A
WEAK LOW TRAPPING BENEATH THE RIDGE NEAR 26N69W.  OUTFLOW FROM
DENNIS COVERS THE BAHAMAS AND THE REST OF THE SW ATLC S OF 26N W
OF 67W WITH VERY DRY AIR ALOFT N OF THAT REGION.  A MID/UPPER
LOW IS NEAR 21N58W EXTENDS SSW INTO THE LESSER ANTILLES.
MODERATE/STRONG SUBSIDENCE COVERS THE CENTRAL ATLC W OF 35W TO
THE TROUGH AXIS BETWEEN 10N-30N.  A BROAD TROUGH IS AT THE
NORTHERN FRINGE OF THE CENTRAL ATLC N OF 27N E OF 40W.  THE
TYPICAL AFRICAN ANTICYCLONE IS OVER WESTERN SAHARAN NEAR 22N16W
WITH RIDGE AXIS WSW TO 16N46W.  INVERTED TROUGH IS ALONG 35W S
OF 20N CREATING A SMALL BREAK IN THE RIDGE.  ELY FLOW IS A BIT
DIFFLUENT.. SUPPORTING TSTMS NEAR THE TWO UPPER LOWS.  PRESSURES
ARE HIGHER-THAN-AVERAGE IN THE DEEP TROPICS THOUGH THEY ARE NEAR
AVERAGE IN THE SUBTROPICS... SUPPORTING A PRESSURE GRADIENT
WEAKER THAN AVERAGE AND CONSEQUENTLY LIGHTER TRADES THAN
NORMAL.

$$
BLAKE

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