[Tropical] Tropical Weather Discussion

[EMWIN Server]

AXNT20 KNHC 290006
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
805 PM EDT SUN AUG 28 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...

THE CENTER OF POTENTIALLY CATASTROPHIC CATEGORY FIVE HURRICANE
KATRINA IS NEAR LATITUDE 26.9 NORTH... LONGITUDE 89.0 WEST OR
ABOUT 150 MILES SOUTH OF THE MOUTH OF THE MISSISSIPPI RIVER.  IT
IS MOVING NW 11 KT. THE ESTIMATED MINIMUM CENTRAL PRESSURE IS
902 MB. THE MAXIMUM SUSTAINED WINDS ARE NEAR 145 KT WITH GUSTS
TO 175 KT. LANDFALL IS EXPECTED IN LESS THAN 24 HOURS ALONG THE
N GULF COAST.  PLEASE READ THE 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.  KATRINA HAS STRENGTHENED RAPIDLY TODAY INTO A CATEGORY
FIVE HURRICANE OVER THE VERY WARM AND DEEP LOOP CURRENT OF THE
GULF OF MEXICO.  THE HURRICANE HAS AN ANNULAR APPEARANCE ON
SATELLITE WITH A WELL-DEFINED EYE AND SYMMETRIC OUTFLOW
PATTERN... REFLECTIVE OF NEAR ZERO SHEAR.  THIS IS THE MOST
SIGNIFICANT THREAT TO THE GULF COAST SINCE HURRICANE CAMILLE OF
1969.  NUMEROUS STRONG CONVECTION IS FROM 24N-29N BETWEEN
87W-92W.  IN ADDITION SCATTERED MODERATE CONVECTION EXTENDS FROM
22N-32N BETWEEN 84W-93W.

TROPICAL DEPRESSION THIRTEEN IS OVER THE CENTRAL ATLANTIC NEAR
15.4N 46.8W MOVING WEST-NORTHWEST 11 KT.  THE ESTIMATED MINIMUM
CENTRAL PRESSURE IS 1007 MB. THE MAXIMUM SUSTAINED WINDS ARE
NEAR 25 KT WITH GUSTS TO 35 KT. PLEASE READ THE LATEST NHC
FORECAST/ADVISORY UNDER AWIPS/WMO HEADERS MIATCMAT3/WTNT23 KNHC
AND THE PUBLIC ADVISORY UNDER AWIPS/WMO HEADERS MIATCPAT3/WTNT33
KNHC FOR MORE DETAILS.  SCATTERED MODERATE TO STRONG CONVECTION
IS MOSTLY W OF THE CENTER FROM 14N-19N BETWEEN 46W-49W.

E ATLC WAVE IS ALONG 20W S OF 19N WITH A 1008 MB LOW ALONG THE
WAVE NEAR 11N.  SATELLITE IMAGERY SHOWS THAT THIS SYSTEM HAS
WELL-DEFINED CURVED BAND SIGNATURE WITH LITTLE VERTICAL WIND
SHEAR APPARENT FROM CIRRUS CLOUDS.  THIS SYSTEM HAS THE
POTENTIAL TO BE A TROPICAL CYCLONE IN THE NEXT DAY OR TWO.
PRESENTLY SCATTERED MODERATE CONVECTION IS FROM 11N-13N BETWEEN
20W-22W.

...TROPICAL WAVES...

W ATLC WAVE IS ALONG 59W SOUTH OF 17N MOVING W 10 KT.  STRONG
SHEAR IS OVER THE WAVE.  IT HAS A WEAK SIGNATURE ON SATELLITE
IMAGERY WITH NO CONVECTION.

...ITCZ...

ITCZ AXIS IS ALONG 13N16W 7N28W 15N46W 12N60W.  IN ADDITION TO
CONVECTION DUE TO TROPICAL SYSTEMS MENTIONED ABOVE...WIDELY
SCATTERED MODERATE CONVECTION IS ALONG THE COAST OF W AFRICA
FROM 7N-14N BETWEEN 12W-18W.  SIMILAR CONVECTION IS FROM 5N-10N
BETWEEN 22W-31W.  SCATTERED MODERATE TO ISOLATED STRONG
CONVECTION IS FROM 11N-16N BETWEEN 50W-53W.

...DISCUSSION...

GULF OF MEXICO...
KATRINA DOMINATES THE CENTRAL GULF OF MEXICO WITH A VERY
DANGEROUS CIRCULATION.  EYE DIAMETER IS 25 NM.  HURRICANE FORCE
WINDS EXTEND 90 NM FROM THE CENTER.  SEE SPECIAL FEATURES FOR
MORE DETAILS.  THE RAINBANDS ARE NOW INLAND TO 32N COVERING
SOUTHERN ALABAMA...MISSISSIPPI...AND LOUISIANA...AND SHOULD
SLOWLY OVERSPREAD POINTS NORTH.  IN THE UPPER LEVELS... A LARGE
ANTICYCLONIC CIRCULATION IS OVER KATRINA ENHANCING UPPER LEVEL
OUTFLOW.  EXPECT RELATIVELY MOIST CONDITIONS TO PRODUCE
AFTERNOON AND EVENING THUNDERSTORMS OVER THE FLORIDA PENINSULA.
ALSO EXPECT FAIR WEATHER OVER TEXAS DUE TO DRY MID/UPPER
FLOW.

CARIBBEAN SEA...
DEEP LAYERED ELYS ARE OVER THE CENTRAL AND EASTERN CARIBBEAN
SEA.  SOUTHERLY INFLOW SURFACE WINDS COVERS THE WESTERN
CARIBBEAN W OF 90W DUE TO KATRINA.  NORTHERLY OUTFLOW UPPER
LEVEL WINDS COVERS THE SAME AREA.  SCATTERED MODERATE CONVECTION
IS OVER THE YUCATAN PENINSULA FROM 19N-22N BETWEEN 87W-89W.
PATCHES OF SCATTERED MODERATE CONVECTION ARE INLAND OVER CENTRAL
AMERICA BETWEEN PANAMA AND GUATEMALA.  WIDELY SCATTERED MODERATE
CONVECTION IS OVER THE N CENTRAL CARIBBEAN SEA FROM 15N-21N
BETWEEN 72W-78W...AND FROM 20N-23N BETWEEN 78W-83W.  EXPECT
CONTINUED CONVECTION OVER CENTRAL AMERICA AND CUBA IN THE NEXT
24 HOURS.

ATLANTIC OCEAN...
UPPER TROUGH EXTENDS FROM 32N57W TO 23N60W THEN SW TO
HISPANIOLA.  NLY SHEAR IS PREVENTING THE DEVELOPMENT OF A SMALL
LOW JUST OFFSHORE OF CAPE FEAR N CAROLINA AS WELL AS A WEAK
TROUGH N OF THE BAHAMAS ALONG 26N BETWEEN 72W-77W.  HOWEVER THIS
IS A FAVORABLE PATTERN FOR TSTM DEVELOPMENT WITH ISOLATED TO
WIDELY SCATTERED TSTMS N OF 25N BETWEEN BERMUDA AND 76W.  NARROW
UPPER RIDGE LIES ALONG 48W N OF 20N WITH A PERSISTENT UPPER
TROUGH CONTROLLING THE AREA N OF 27N E OF 40W.  IN THE DEEP
TROPICS... UPPER HIGH IS NEAR 15N47W... PROVIDING ELY SHEAR OVER
T.D. THIRTEEN NEAR 46W.  MODERATE/STRONG SUBSIDENCE IS S OF 20N
E OF THE T.D. TO 30W WITH A SAHARAN DUST OUTBREAK NOTED.  SE OF
THE CAPE VERDES... MOISTURE INCREASES WITH UPPER RIDGING
SUPPRESSED FROM GAMBIA TO 11N30W.  ITCZ CONVECTION IS MINIMAL
WITH NO LOW-LEVEL CONVERGENCE AS ALL THE TROPICAL WAVES/SYSTEMS
ARE DOMINATING THE CIRCULATION.

$$
FORMOSA


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