[Tropical] Tropical Weather Discussion

[EMWIN Server]

AXNT20 KNHC 290556
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
205 AM EDT MON AUG 29 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 POTENTIALLY CATASTROPHIC CATEGORY FIVE HURRICANE
KATRINA IS NEAR 28.1N 89.6W OR ABOUT 65 NM SSW OF THE MOUTH OF
THE MISSISSIPPI RIVER MOVING NNW AT 9 KT AT 29/0600 UTC.
ESTIMATED MINIMUM CENTRAL PRESSURE IS 904 MB. MAXIMUM SUSTAINED
WIND SPEED IS 140 KT WITH GUSTS TO 170 KT. HURRICANE FORCE WINDS
WILL BE ONSHORE ALONG THE MISSISSIPPI DELTA WITH THE NEXT FEW
HOURS. SEE 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 MAY EXPERIENCE FLUCTUATIONS IN STRENGTH BEFORE LANDFALL
AND MAY ACTUALLY DROP TO A CATEGORY FOUR...BUT WILL STILL BE A
DEVASTATING HURRICANE. A WELL-DEFINED EYE AND SYMMETRIC OUTFLOW
PATTERN IS OBSERVED ON SATELLITE IMAGERY WITH NEAR ZERO SHEAR.
THIS IS THE MOST SIGNIFICANT THREAT TO THIS PORTION OF THE NORTH
GULF COAST SINCE HURRICANE CAMILLE OF 1969. CONVECTION IS FAIRLY
SYMMETRICAL WITH SCATTERED MODERATE TO STRONG CONVECTION N OF
25N BETWEEN 85W-92W WHICH COVERS PORTIONS THE COAST FROM THE W
FLORIDA  PANHANDLE TO CENTRAL LOUISIANA. OUTER RAINBANDS EXTEND
FROM THE YUCATAN PENINSULA BETWEEN THE FLORIDA PENINSULA TO
HOUSTON TEXAS.

TROPICAL DEPRESSION THIRTEEN IS OVER THE CENTRAL ATLC NEAR 15.9N
47.4W MOVING NW AT 10 KT AT 29/0300 UTC. ESTIMATED MINIMUM
CENTRAL PRESSURE IS 1007 MB. MAXIMUM SUSTAINED WIND SPEED IS 25
KT WITH GUSTS TO 35 KT. SEE 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. T.D. THIRTEEN IS IN A MODERATE SHEAR ENVIRONMENT THUS
HAS NOT BECOME ANY BETTER ORGANIZED OVER THE PAST 6 HOURS.
SCATTERED MODERATE/STRONG CONVECTION IS TO THE W OF THE LOW
LEVEL CENTER WITHIN 90/120 NM OF LINE 16N49W-21N48W. SCATTERED
MODERATE/ ISOLATED STRONG CONVECTION IS SW OF THE LOW WITHIN 75
NM OF 53W FROM 13N-17N.

E ATLC TROPICAL WAVE IS ALONG 21W S OF 20N WITH A 1008 MB LOW
ALONG THE WAVE NEAR 12N. 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.
SCATTERED MODERATE/ISOLATED STRONG CONVECTION IS NW OF THE LOW
FROM 12N-14N BETWEEN 21W-23W.

...TROPICAL WAVES...
W CARIBBEAN TROPICAL WAVE IS ALONG 62W S OF 17N MOVING W 10-15
KT. WEAK WAVE SIGNATURE CURVATURE IS OBSERVED IN THE LOW CLOUDS.
WAVE IS EMBEDDED WITH VERY DRY AIR...THUS NO ASSOCIATED
SHOWERS/CONVECTION.

...ITCZ...

ITCZ AXIS IS CENTERED ALONG 16N17W 7N28W 14N44W THEN ALONG
14N50W 12N61W. SCATTERED MODERATE/STRONG CONVECTION IS WITHIN
150 NM OF THE AXIS FROM 25W-35W. SCATTERED MODERATE/ISOLATED
STRONG CONVECTION IS MOVING OFF AFRICA WITHIN 60/75 NM OF LINE
7N12W-9N16W.

...DISCUSSION...

GULF OF MEXICO...
KATRINA DOMINATES THE GULF OF MEXICO WITH A VERY DANGEROUS
CIRCULATION. EYE DIAMETER IS NEAR 30 NM. TROPICAL STROM FORCE
WINDS ARE ALREADY BEING REPORTED AT NEW ORLEANS WITH HURRICANE
FORCE WINDS EXPECTED WITHIN THE NEXT COUPLE OF HOURS. IN THE
UPPER LEVELS...A LARGE HIGH IS OVER KATRINA ENHANCING UPPER
LEVEL OUTFLOW IN ALL QUADRANTS. ALL OF BUT THE FAR W GULF W OF
96W IS MOISTURE LADEN AND EXPECT SHOWERS/ISOLATED THUNDERSTORMS.

CARIBBEAN SEA...
DEEP LAYERED EASTERLY FLOW DOMINATES THE CARIBBEAN. THE BROAD
UPPER LEVEL HIGH CENTERED NEAR KATRINA EXTENDS OVER THE W
CARIBBEAN N OF 13N W OF 70W. OUTFLOW FROM KATRINA IS AIDING THE
CLUSTERS OF SCATTERED MODERATE/ISOLATED STRONG CONVECTION OVER
THE YUCATAN PENINSULA...CENTRAL AMERICA...GULF OF HONDURAS...AND
W CUBA. THE E CARIBBEAN IS UNDER STRONG SUBSIDENCE AND VERY DRY
AIR FROM A BROAD UPPER HIGH OVER THE CENTRAL ATLC.

ATLANTIC OCEAN...
BROAD UPPER HIGH OVER KATRINA COVERS THE W ATLC W OF 70W.
EMBEDDED WITHIN THIS FLOW...IS A SMALL WEAK 1012 MB LOW THAT IS
RAPIDLY DISSIPATING. NARROWING UPPER TROUGH EXTENDS FROM THE
CENTRAL/W ATLC THROUGH 32N62W TO 20N65W. BROAD MID/UPPER LEVEL
HIGH IS IN THE CENTRAL ATLC NEAR 17N49W...NEAR T.D. THIRTEEN AND
COVERS THE AREA BETWEEN THE UPPER TROUGH TO THE W AND 35W. THIS
IS LIMITING CONVECTION WITHIN THE ITCZ W OF 40W. LARGE UPPER LOW
IS OVER THE NE ATLC N OF THE REGION AND EXTENDS INTO THE AREA N
OF 25N FROM THE CANARY ISLANDS TO NEAR 35W. SE OF THE CAPE VERDE
ISLANDS MOISTURE INCREASES WITH UPPER RIDGING SUPPRESSING THE
ITCZ AND CONVECTION TO THE S.

$$
WALLACE


This weather bulletin was brought to you by:
www.nashvilleweather.net