[Tropical] Tropical Weather Discussion

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AXNT20 KNHC 131158
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
805 AM EDT THU SEP 13 2007

TROPICAL WEATHER DISCUSSION FOR NORTH AMERICA...CENTRAL
AMERICA...THE GULF OF MEXICO...THE CARIBBEAN SEA...NORTHERN
SECTIONS OF SOUTH AMERICA...AND THE ATLANTIC OCEAN TO THE
AFRICAN COAST FROM THE EQUATOR TO 32N. THE FOLLOWING INFORMATION
IS BASED ON SATELLITE IMAGERY...METEOROLOGICAL ANALYSIS...
WEATHER OBSERVATIONS...AND RADAR.

BASED ON 0600 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH
1115 UTC.

...SPECIAL FEATURES...

HUMBERTO MADE LANDFALL AS A CATEGORY ONE HURRICANE CROSSING THE
TEXAS COAST JUST EAST OF HIGHLAND AROUND 07 UTC. AT 13/1200
UTC...THE CENTER OF HURRICANE HUMBERTO WAS LOCATED INLAND NEAR
30.3N 93.6W OR ALONG THE TEXAS/LOUISIANA BORDER MOVING TOWARD
THE NE AT 10 KT. ESTIMATED MINIMUM CENTRAL PRESSURE IS 987 MB.
MAXIMUM SUSTAINED WIND SPEED IS 70 KT WITH HIGHER GUSTS. SEE
LATEST NHC FORECAST/ADVISORY UNDER AWIPS/WMO HEADERS
MIATCMAT4/WTNT24 KNHC FOR MORE DETAILS. HUMBERTO HAS BEEN A VERY
IMPRESSIVE SYSTEM STRENGTHENING FROM A TROPICAL DEPRESSION TO A
HURRICANE IN LESS THAN 24 HOURS. DOPPLER RADAR DATA DISPLAYED AN
IMPROVED STRUCTURE UP UNTIL LANDFALL WITH AN EYE-LIKE FEATURE
AND WELL DEFINED BANDING N OF THE CENTER. SINCE MOVING
INLAND...THE RADAR PRESENTATION HAS DETERIORATED SOME...BUT THE
NRN EYEWALL AND RAINBANDS REMAIN WELL DEFINED. THE STORM CROSSED
VERY NEAR BEAUMONT TEXAS WHICH REPORTED A GUST TO 73 KT WHEN IN
THE NRN EYEWALL. RAINFALL IS ALSO A CONCERN WITH TOTAL
ACCUMULATIONS OF 5 TO 10 INCHES EXPECTED FROM SOUTHWESTERN TO
NORTHEASTERN LOUISIANA...ACROSS FAR SOUTHEASTERN ARKANSAS AND
INTO CENTRAL AND NORTHERN MISSISSIPPI...WITH ISOLATED MAXIMUM
ACCUMULATIONS OF 15 INCHES POSSIBLE. CURRENTLY NUMEROUS
MODERATE/SCATTERED STRONG CONVECTION IS WITHIN 150 NM NE AND 60
NM SW SEMICIRCLES.

TROPICAL DEPRESSION EIGHT IS CENTERED NEAR 13.9N 47.5W AT
13/0900 UTC OR ABOUT 800 NM EAST OF THE LESSER ANTILLES MOVING
WEST-NORTHWEST AT 9 KT. ESTIMATED MINIMUM CENTRAL PRESSURE IS
1006 MB. MAXIMUM SUSTAINED WIND SPEED REMAINS 30 KT WITH GUSTS
TO 40 KT. SEE LATEST NHC FORECAST/ADVISORY UNDER AWIPS/WMO
HEADERS MIATCMAT3/WTNT23 KNHC FOR MORE DETAILS. THIS DEPRESSION
HAS GENERALLY CHANGED LITTLE THROUGHOUT THE OVERNIGHT HOURS WITH
THE LOW-LEVEL CENTER LOCATED TO THE N OF A PERSISTENT AREA OF
MODERATE CONVECTION WHICH EXTENDS OUT ROUGHLY 120-150 NM. A
BROAD BAND HAS BECOME A LITTLE BETTER ORGANIZED TO THE N AND NE
OF THE SYSTEM BUT STILL REMAINS SEPARATED FROM THE CONVECTIVE
MASS. SOME STRENGTHENING IS EXPECTED IN THE SHORT TERM AS THE
SHEAR  RELAXES SOME. HOWEVER...WEAKENING IS FORECAST TOWARD THE
END OF THE PERIOD AS THE TROPICAL CYCLONE MOVES INTO A HIGHER
SHEAR ENVIRONMENT.

...TROPICAL WAVES...

TROPICAL WAVE HAS BEEN INTRODUCED ON THE 06Z ANALYSIS ALONG
19W/20W S OF 18N ESTIMATED TO BE MOVING W 10-15 KT. BASED ON
SOUNDING DATA...THIS WAVE PASSED DAKAR SOMETIME BETWEEN 12Z AND
23Z YESTERDAY. SYNOPTIC 24-HOUR PRES TRENDS CLEARLY
SHOW THE PRESCIENCE OF THIS WAVE WITH 1-3 MB PRES RISES E OF THE
WAVE OVER W AFRICA AND 1 MB FALLS W OVER THE CAPE VERDE ISLANDS
SINCE 06Z YESTERDAY. VISIBLE IMAGERY...LOW-LEVEL SATELLITE DRIFT
WINDS AND A 07Z QSCAT PASS SHOW A FAIR AMOUNT OF CYCLONIC
TURNING WITH A WEAK AREA OF LOW PRESSURE ALONG THE WAVE AXIS
NEAR 10N...ANALYZED 1010 MB. SHOWERS AND TSTMS ARE WIDELY
SCATTERED WITHIN 240 NM OF THE WAVE AXIS.

HIGH AMPLITUDE TROPICAL WAVE IS IN THE E ATLC ALONG 38W S OF 21N
MOVING W 10-15 KT. THE NRN PART OF THE WAVE IS BEGINNING TO
FRACTURE BASED ON THE POLEWARD MOVEMENT OF MOISTURE SEEN ON
SATELLITE AND THE UW CIMSS TPW ANIMATION. A TROUGH WAS ANALYZED
TO REFLECT THIS ALONG 37W/38W FROM 22N-26N. OTHERWISE...THE
OVERALL STRUCTURE HAS CHANGED LITTLE OVER THE PAST COUPLE OF
DAYS WITH A LARGE SHIELD OF CYCLONIC TURNING NOTED IN THE LOW TO
MID LEVEL CLOUD FIELD.  DESPITE THE CONTINUED FAIR
STRUCTURE...DEEP MOISTURE IS SPARSE WITH WIDELY SCATTERED
MODERATE CONVECTION WITHIN 180 NM OF THE AXIS. SLIGHTLY MORE
ORGANIZED ACTIVITY IS SITUATED AT THE BASE OF THE WAVE WITHIN
THE ITCZ.

TROPICAL WAVE IS IN THE CENTRAL CARIBBEAN ALONG 78W S OF 23N
MOVING W 15 KT.  A SURGE OF MOISTURE ASSOCIATED WITH THIS
FEATURE IS STILL EVIDENT ON THE TPW ANIMATION FROM CIMSS...WHICH
WAS THE PRIMARY TOOL USED TO TRACK THIS WAVE AS LITTLE SIGNATURE
IS APPARENT IN CONVENTIONAL SATELLITE IMAGERY. THE INTERACTION
WITH AN UPPER LOW CENTERED JUST S OF CENTRAL CUBA IS SUPPORTING
ISOLATED SHOWERS AND TSTMS OVER CUBA AND A PORTION OF THE NW
CARIB N OF 18N BETWEEN 79W-83W.

...THE ITCZ...
ITCZ AXIS IS CENTERED ALONG 8N21W 11N33W 13N39W 15N45W 10N52W
9N62W. SCATTERED MODERATE CONVECTION IS NEAR THE BASE OF AN E
ATLC WAVE FROM 6N-10N BETWEEN 35W-38W AND SE OF THE DEPRESSION
FROM 10N-13N BETWEEN 40W-45W. SIMILAR ACTIVITY IS WITHIN 120 NM
N OF THE AXIS W OF 56W.

DISCUSSION...

THE GULF OF MEXICO...
THE HIGHLIGHT TODAY IS HURRICANE HUMBERTO WHICH HAS NOW MOVED
INLAND ACROSS SE TEXAS AND SW LOUISIANA. REFER TO THE SPECIAL
FEATURE SECTION FOR DETAILS. THE REMAINDER OF THE REGION REMAINS
EMBEDDED IN A MOIST ENVIRONMENT AS INDICATED BY WATER VAPOR
IMAGERY AND THE CIMSS TPW ANIMATION. THE UPPER FEATURES
MAINTAINING THIS WIDESPREAD HIGH LEVEL MOISTURE PLUME CONSIST OF
AN ELONGATED UPPER HIGH STRETCHED ACROSS THE N GULF AND AN UPPER
LOW JUST S OF CUBA. IR IMAGERY SHOWS ONLY ISOLATED SPOTS OF
PRECIP. ONE SOMEWHAT PERSISTENT AREA...ALSO EVIDENT ON MOSAIC
RADAR IMAGERY...IS A STREAM OF SHOWERS AND TSTMS ADVECTED FROM
THE ATLC INTO THE SE GULF ROUGHLY S OF 26N E OF 85W. WEAKENING
POCKETS OF SCATTERED MODERATE CONVECTION ARE OVER THE S BAY OF
CAMPECHE AND OVER SRN MEXICO WHERE DIFFLUENCE ALOFT IS MORE
PRONOUNCED. ISOLATED SHOWERS AND TSTMS ARE POSSIBLE JUST ABOUT
ANYWHERE ELSE IN THE REGION GIVEN THE MOIST ENVIRONMENT.

THE CARIBBEAN SEA...
A BROAD UPPER LOW HAS BEEN DRIFTING WWD CENTERED S OF CENTRAL
CUBA NEAR 21N80W. DIFFLUENCE ALOFT TO THE S OF THE UPPER LOW
COUPLED WITH THE LOW-LEVEL CONVERGENCE ALONG THE ITCZ IS
ENHANCING CLUSTERS OF SCATTERED MODERATE CONVECTION OVER THE W
CARIBBEAN AND PORTIONS OF CENTRAL AMERICA ROUGHLY S OF 17N W OF
78W. THE INTERACTION BETWEEN A WEAK TROPICAL WAVE AND THE UPPER
LOW IS PRODUCING SOME ISOLATED SHOWER ACTIVITY ACROSS THE NW
CARIB AND OVER CUBA...FOR DETAILS SEE ABOVE. THE ERN CARIB IS
EXPERIENCING MOSTLY FAIR WEATHER AS DRIER AIR FROM THE TROPICAL
ATLC HAS BEEN ADVECTED INTO THE AREA AROUND AN UPPER HIGH.
HOWEVER...THERE ARE WWD MOVING SCATTERED SHOWERS AND TSTMS
WITHIN THE ITCZ THAT MAY MOVE ACROSS THE EXTREME SRN WINDWARD
ISLANDS LATER TODAY. MODERATE TO STRONG TRADE WINDS ARE BLOWING
ACROSS THE REGION...STRONGEST BETWEEN COLOMBIA AND HISPANIOLA
WHERE QSCAT DEPICTED A SOLID AREA OF 20-25 KT WINDS.

THE ATLANTIC OCEAN...
TROPICAL DEPRESSION EIGHT IS THE MAIN FEATURE OF INTEREST ACROSS
THE TROPICAL AND SUBTROPICAL ATLC DISCUSSION ZONE. FOR DETAILS
AND REFERENCES REFER TO THE SPECIAL FEATURE SECTION ABOVE.
OTHERWISE...THE ATLC BASIN IS FAIRLY QUIET THIS MORNING. THE SFC
PATTERN HAS GENERALLY CHANGED LITTLE OVER THE PAST COUPLE OF
DAYS. A PAIR OF 1022 MB HIGHS ARE ANALYZED ALONG AND JUST N OF
OUR BORDER IN THE CENTRAL AND W ATLC NEAR 32N60W AND 36N49W. A
1028 MB HIGH IS CENTERED IN THE E ATLC NEAR 44N23W WITH RIDGING
EXTENDS SW TO 28N35W. A SLIGHT WEAKNESS IN THE SUBTROPICAL
RIDGING LIES BETWEEN 35W-45W ASSOCIATED WITH A TROUGH OF LOW
PRES IN THE N CENTRAL ATLC. THIS WEAKNESS HAS ALLOWED WINDS TO
BE FAIRLY LIGHTER IN THAT VICINITY...WITH MODERATE TRADES
OBSERVED ELSEWHERE.

ALOFT...A COMPLEX PATTERN IS IN PLACE ACROSS THE SW ATLC. THE
CONTRIBUTING LARGE SCALE FEATURES CONSIST OF A WESTWARD MOVING
UPPER LOW CENTERED JUST S OF CENTRAL CUBA...THE ERN PERIPHERY OF
THE GULF RIDGE AND ANOTHER UPPER LOW CENTERED NEAR 28N64W. THE
LATTER UPPER LOW ACTUALLY BECAME CUT OFF FROM THE TAIL END OF
THE EXTENSIVE TROUGHING COVERING THE CENTRAL ATLC N OF OF 20N
BETWEEN 32W-53W...ASSOCIATED WITH AFOREMENTIONED TROUGH OF LOW
PRES IN THE N CENTRAL ATLC. THIS PATTERN IS ONLY GENERATING A
SHIELD OF MID TO HIGH LEVEL CLOUDINESS AND ISOLATED SHOWERS AND
TSTMS W OF 70W AND N OF 29N BETWEEN 35W-42W. MUCH OF THE
REMAINDER OF THE AREA IS DOMINATED BY AN E-W RIDGE COVERING THE
AREA FROM THE LESSER ANTILLES EWD WITH A MEAN AXIS ALONG 17N
WITH SEVERAL EMBEDDED ANTICYCLONES. THIS RIDGE AND A CONFLUENT
PATTERN...TO THE S OF A LARGE UPPER LOW NEAR SRN PORTUGAL...IS
KEEPING WEATHER CONDITIONS FAIRLY TRANQUIL.

$$
CANGIALOSI




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