[Tropical] Tropical Weather Discussion

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AXNT20 KNHC 270605
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
205 AM EDT SAT AUG 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 0000 UTC SURFACE ANALYSIS AND
SATELLITE IMAGERY THROUGH 0345 UTC.

...SPECIAL FEATURES...
THE CENTER OF HURRICANE KATRINA WAS NEAR 24.4N 84.0W...OR ABOUT
450 MILES SOUTHEAST OF THE MOUTH OF THE MISSISSIPPI RIVER...AND
ABOUT 135 MILES WEST OF KEY WEST FLORIDA...AT 27/0300 UTC MOVING
WEST-SOUTHWEST 7 KT. THE ESTIMATED MINIMUM CENTRAL PRESSURE WAS
965 MB. THE MAXIMUM SUSTAINED WIND SPEEDS WERE 90 KT WITH GUSTS
TO 110 KT. PLEASE REFER TO THE LATEST NHC FORECAST/ADVISORY
UNDER AWIPS/WMO HEADERS MIATCMAT2/WTNT22 KNHC AND THE PUBLIC
ADVISORY UNDER HEADERS MIATCPAT1/WTNT32 KNHC FOR MORE DETAILS.
THE SATELLITE REPRESENTATION SHOWS A BEAUTIFUL COMMA-SHAPED
CLOUD PATTERN WHICH BEGINS IN THE SOUTHEASTERN GULF OF MEXICO
NEAR 25N84W AND CURVES EASTWARD TO THE FLORIDA KEYS...WITH THE
TAIL OF THE COMMA HOOKING WEST-SOUTHWESTWARD INTO WESTERN CUBA.
NUMEROUS STRONG SHOWERS AND THUNDERSTORMS ARE AROUND THE
COMMA-SHAPED PART FROM 23.5N TO 26N BETWEEN 82W AND 85W...AND IN
THE BAND WHICH IS ON TOP OF WESTERN CUBA AND A BIT INTO THE
YUCATAN CHANNEL FROM 20.5N TO 23.5N BETWEEN 81W AND 86W. UPPER
LEVEL ANTICYCLONIC OUTFLOW CURVES OVER FLORIDA AS FAR NORTH AS
29N AND THEN SOUTHEASTWARD TO AT LEAST EASTERN CUBA...AND EVEN
INTO THE NORTHWESTERN CARIBBEAN SEA AND THE GULF OF
HONDURAS/HONDURAS AND GUATEMALA. UPPER LEVEL ANTICYCLONIC FLOW
COVERS THE U.S.A. GULF COAST STATES IN THE NORTH CENTRAL GULF OF
MEXICO.

1008 MB CENTRAL ATLANTIC OCEAN LOW PRESSURE CENTER WAS NEAR
21N50W MOVING NORTHWEST 10 KT. THIS FEATURE HAS BEEN CLASSIFIED
BY THE DVORAK TECHNIQUE AS TOO WEAK TO CLASSIFY FOR THE LAST FEW
DAYS. A TROUGH WAS RUNNING THROUGH THE LOW CENTER ALONG 24N51W
21N50W 13N50W. THE SHOWER ACTIVITY ASSOCIATED WITH THIS REMAINS
POORLY ORGANIZED. UNFAVORABLE UPPER-LEVEL WINDS HAVE BECOME
ESTABLISHED OVER THE SYSTEM AND ADDITIONAL DEVELOPMENT IS LESS
LIKELY. THE NUMEROUS STRONG SHOWERS AND THUNDERSTORMS FROM 19.5N
TO 21N BETWEEN 45W AND 48W IS DETACHED FROM THE SURFACE
CIRCULATION CENTER.

...TROPICAL WAVES...
A CENTRAL ATLANTIC WAVE HAS BEEN ALONG 36W/37W FOR THE LAST FEW
MAP ANALYSES. THE 26/1815 UTC VISIBLE SATELLITE IMAGE SHOWS WHAT
APPEARS TO BE A SURFACE CYCLONIC CIRCULATION CENTER NEAR 11N38W.
WE WILL TRY TO MOVE ALONG THIS WAVE FOR THE 27/0600 UTC SURFACE
MAP ANALYSIS. THE 24 HOUR ALL-DAY VISIBLE IMAGERY DOES NOT SHOW
ANYTHING AND NOTHING JUMPS UP AT YOU IN THE INFRARED IMAGERY
EITHER. LITTLE POCKETS OF MODERATE SHOWERS AND THUNDERSTORMS
COVER THE ATLANTIC WATERS FROM 8N TO 16N BETWEEN 29W AND 43W.

WESTERN CARIBBEAN SEA TROPICAL WAVE WAS ALONG 86W/87W SOUTH OF
19N...FROM THE NORTHWESTERN CARIBBEAN SEA SOUTHWARD ACROSS
HONDURAS AND NICARAGUA...MOVING WEST 15 KT. ISOLATED MODERATE
SHOWERS TO LOCALLY STRONG THUNDERSTORMS INLAND BETWEEN 84W AND
89W ARE SEEING THE CLOUD TOPS WITH THE CONVECTIVE ACTIVITY BEING
SHEARED BY THE UPPER LEVEL EASTERLY WIND FLOW.

...THE ITCZ...
ITCZ 15N16W 15N26W 12N34W...11N40W 14N45W14N33W. SCATTERED TO
NUMEROUS STRONG THUNDERSTORMS STILL INLAND IN WEST AFRICA FROM
11N TO 15N BETWEEN 12W AND 16W. ISOLATED MODERATE SHOWERS ARE
IN THE OCEAN FROM 2N TO 10N BETWEEN 30W AND 46W...NOTHING MUCH
LOOKS TOO ORGANIZED AS FAR AS DEEP CONVECTIVE ACTIVITY WITH
THE ITCZ.

...DISCUSSION...
THE GULF OF MEXICO...
HURRICANE KATRINA IS GRABBING ALL THE HEADLINES AT THIS MOMENT.
THE CIRCULATION OF KATRINA IS BEGINNING TO DOMINATE THE ENTIRE
GULF AS NORTHEASTERLY SURFACE WINDS ARE OBSERVED PRACTICALLY
EVERYWHERE WEST OF THE LONGITUDE FOR KATRINA. NUMEROUS STRONG
CONVECTIVE ACTIVITY IS CONFINED TO THE SOUTHEASTERN CORNER OF
THE AREA SOUTH OF 26N EAST OF 86W. ISOLATED MODERATE SHOWERS
ARE OCCURRING JUST OFFSHORE THE NORTHERN YUCATAN PENINSULA COAST
AT THE TAIL END OF THE PRECIPITATION WHICH STARTS IN WESTERN
CUBA AND WHICH MAKES ITS WAY ACROSS THE YUCATAN CHANNEL. SIMILAR
PRECIPITATION IS FOUND ALSO IN THE EASTERN YUCATAN PENINSULA
FROM THE NORTHEASTERN CORNER INTO NORTHERN BELIZE AND
NORTHEASTERN GUATEMALA. UPPER LEVEL ANTICYCLONIC FLOW COVERS
THE U.S.A. GULF COAST STATES IN THE NORTH CENTRAL GULF OF MEXICO.
MOISTURE FROM KATRINA SHOULD SPREAD ACROSS THE GULF COAST ON
SATURDAY FROM EAST TO WEST...IMPACTING SOUTHEASTERN LOUISIANA
BY SUNDAY.

THE CARIBBEAN SEA...
NUMEROUS STRONG SHOWERS AND THUNDERSTORMS IN WESTERN CUBA FROM
THE RAIN BAND TO THE SOUTH OF HURRICANE KATRINA. LARGE-SCALE
UPPER HIGH PRESSURE CONTROLS THE REGION WITH GENERAL NE TO E
WINDS THROUGHOUT THE CARIBBEAN. A MIDDLE TO UPPER LEVEL TROUGH
RUNS FROM THE ATLANTIC OCEAN NEAR 31N65W...ACROSS PUERTO RICO...
INTO THE EAST CENTRAL CARIBBEAN SEA NEAR 14N66W. ISOLATED TO
WIDELY SCATTERED  MODERATE SHOWERS AND THUNDERSTORMS EXTEND FROM
THE EAST CENTRAL CARIBBEAN SEA NORTHWARD TO A FEW HUNDRED MILES
NORTH OF PUERTO RICO.

THE ATLANTIC OCEAN...
UPPER-LEVEL RIDGING EXTENDS EASTWARD INTO THE W ATLC TO ABOUT
72W WITH A WEAKENING STATIONARY FRONT ALONG 31N/32N W OF 70W.  A
FEW TSTMS ARE FORMING OFFSHORE OF GEORGIA ALONG THAT FRONT NEAR
31N80W.  A COUPLE OF LARGE-SCALE MODELS ARE SHOWING THE
POTENTIAL FOR A LOW TO GENERATE NEAR THE FRONT AND MOVE SLOWLY
EASTWARD...PERHAPS ACQUIRING SOME TROPICAL CHARACTERISTICS WITH
TIME.  THIS GENESIS SEEMS LIKE IT WOULD BE SLOW TO OCCUR WITH
STRONG SHEAR FORECAST.  FARTHER E... A DEEP TROUGH IN THE
MID/UPPER LEVELS EXTENDS SOUTHWARD FROM JUST E OF BERMUDA NEAR
32N63W TO 19N65W WITH INSTABILITY ALONG THE TROUGH AXIS
PRODUCING ISOLATED TSTMS WITHIN 60 NM OF THE AXIS.  SECOND UPPER
TROUGH IS ALONG 51W N OF 18N... RESPONSIBLE FOR SHEARING THE LOW
NEAR 20N48W.  THIS TROUGH IS FORECAST TO WEAKEN WITH TIME...
WHICH COULD LESSEN THE SHEAR AND ALLOW THE SYSTEM TO DEVELOP.
IN THE E ATLC...A SERIES OF CUTOFF UPPER LOWS HAS BEEN NEARLY A
CONSTANT FEATURE FOR THE LAST FEW WEEKS.. WITH THE LATEST LOW
NEAR 32N22W.  FARTHER S... UPPER RIDGING HAS MOVED TO 16N W OF
THE CAPE VERDE ISLANDS WITH MODEST ELY SHEAR S OF THE RIDGE
AXIS.  THE RIDGE IS COMPRISED OF TWO UPPER HIGHS... ONE NEAR
16N57W AND THE OTHER AROUND 17N38W.  THE SHEAR IS FORECAST TO
REMAIN LOW IN THE TROPICS FOR THE WEEKEND WHICH COULD ALLOW THE
SYSTEM NEAR 11N376W TO FURTHER DEVELOP.

$$
BLAKE


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