[Tropical] Tropical Weather Discussion

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AXNT20 KNHC 190002
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
805 PM EDT SAT AUG 18 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 1800 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH
2315 UTC.

...SPECIAL FEATURE...
AS OF 19/0000 UTC THE EYE OF EXTREMELY DANGEROUS HURRICANE DEAN
WAS LOCATED NEAR 16.0 NORTH...LONGITUDE 71.0 WEST OR ABOUT 405
MILES EAST-SOUTHEAST OF KINGSTON JAMAICA AND ABOUT 165 MILES
SOUTH OF SANTO DOMINGO IN THE DOMINICAN REPUBLIC. DEAN IS MOVING
TOWARD THE WEST NEAR 15 KT. ON THIS TRACK...THE CORE OF THE
HURRICANE WILL PASS JUST SOUTH OF THE SOUTHERN COAST OF HAITI
TONIGHT AND WILL BE NEAR JAMAICA ON SUNDAY. MAXIMUM SUSTAINED
WINDS REMAIN NEAR 130 KT WITH GUSTS TO 160 KT...THIS MAKES DEAN
A STRONG CATEGORY FOUR HURRICANE. THE MINIMUM CENTRAL PRESSURE
JUST REPORTED BY AN AIR FORCE RESERVE RECONNAISSANCE AIRCRAFT
WAS 920 MB. SOME FLUCTUATIONS IN INTENSITY ARE LIKELY DURING THE
NEXT 24 HOURS. ALL INTERESTS IN THE CARIBBEAN SEA AND THE GULF
OF MEXICO SHOULD CLOSELY MONITOR THE PROGRESS OF THIS POWERFUL
HURRICANE. PLEASE SEE THE LATEST NHC FORECAST/ADVISORY UNDER
AWIPS/WMO HEADERS MIATCMAT4/WTNT24 KNHC AND THE LATEST PUBLIC
ADVISORY UNDER MIATCPAT4/WTNT34 KNHC FOR THE MOST RECENT WATCH
AND WARNING INFORMATION. FOR STORM INFORMATION SPECIFIC TO YOUR
AREA...INCLUDING POSSIBLE INLAND WATCHES AND WARNINGS ...PLEASE
MONITOR PRODUCTS ISSUED BY YOUR LOCAL WEATHER OFFICE. DEAN
REMAINS VERY IMPRESSIVE ON SATELLITE IMAGERY WITH A WELL-DEFINED
EYE AND SYMMETRIC SIGNATURE TO IT'S EYEWALL ...RAINBANDS AND
OUTFLOW. NUMEROUS MODERATE TO STRONG IS WITHIN 90 NM OF THE
CENTER. SCATTERED MODERATE TO STRONG...IN SPIRAL BANDS...IS
ELSEWHERE WITHIN 14N-20N BETWEEN 68W-73W.

...TROPICAL WAVES...
A LARGE TROPICAL WAVE IS ALONG 37W/38W S OF 19N MOVING W 20
KT. MET-9 SATELLITE HOVMOLLER DIAGRAMS CLEARLY SHOW A RATHER
QUICK WWD MOVING AREA OF CLOUDINESS ASSOCIATED WITH THIS
FEATURE. CURRENTLY...THE WAVE APPEARS EMBEDDED WITHIN A VERY
BROAD ELONGATED AREA OF LOW TO MID LEVEL CYCLONIC TURNING
ASSOCIATED WITH THIS WAVE AND THE ONE TO IT'S W. SCATTERED
SHOWERS AND ISOLATED TSTMS ARE WITHIN 180 NM EITHER SIDE OF THE
WAVE AXIS.

TROPICAL WAVE IS ALONG 50W/51W S OF 20N MOVING W 15-20 KT.
SIMILARLY TO THE WAVE TO IT'S E...SATELLITE HOVMOLLER DIAGRAMS
INDICATE A CONTINUOUS HISTORY OF THIS WAVE SINCE MOVING OFF THE
AFRICAN COAST. SHIP/BUOY OBS IN THE REGION SHOW A FAIR BIT OF
TURNING AT THE SFC...WHICH HELPED IN LOCATING THE AXIS.
SCATTERED SHOWERS AND TSTMS ARE CONFINED TO THE INTERSECTION OF
THE ITCZ FROM 9-12N WITHIN 180 NM OF THE AXIS. ON A SIDE
NOTE...LATEST SATELLITE IMAGERY SHOWS A BROAD CYCLONIC GYRE
COVERING A REGION OF ABOUT 30 DEG LONGITUDE ASSOCIATED WITH THIS
WAVE AND THE ONE ALONG 37W/38W. IT'S DIFFICULT TO PIN POINT AN
AXIS IN THIS BROAD GYRE.

TROPICAL WAVE IS OVER CENTRAL AMERICA AND THE W CARIB ALONG 87W
S OF 21N MOVING W 15-20 KT. THE WAVE WAS ADJUSTED ON THE
PREVIOUS MAP TO MATCH UP WITH A WEAK INVERTED V-SHAPE SEEN ON
VIS IMAGES. SINCE THEN...THE SATELLITE SIGNATURE HAS BECOME
QUITE BLURRY BUT THE WAVE APPEARS TO BE IN THE CORRECT PSN BASED
ON AN ANIMATION OF THE UW-CIMSS TPW LOOP WHICH SHOWS A WEAK
NARROW N-S MOISTURE SURGE APPROACHING THE YUCATAN. SCATTERED
SHOWERS AND TSTMS ARE SCATTERED NEAR THE INTERSECTION OF THE
ITCZ OVER COSTA RICA AND NICARAGUA FROM 10N-13N W OF 82W AND
ISOLATED WITHIN 120 NM OF THE AXIS N OF 18N DUE TO THE
INTERACTION WITH AN UPPER LOW.

...THE ITCZ...
ITCZ AXIS IS CENTERED ALONG 14N17W 12N31W 11N48W 7N56W 10N63W.
BESIDES FOR THE ACTIVITY MENTIONED ABOVE...NO SIGNIFICANT
CONVECTION.

DISCUSSION...

THE GULF OF MEXICO...
THE MAIN FEATURE TONIGHT IS A WWD MOVING UPPER LOW CENTERED
ABOVE THE SE GULF NEAR 25N84W. LIGHTNING DATA SHOWS SOME
SCATTERED TSTM ACTIVITY IN THE VICINITY OF THE UPPER CIRCULATION
AND WSW OF IT S OF 24N BETWEEN 86W-91W IN AN DIFFLUENT ZONE
ALOFT AND NEAR THE NRN EXTENSION OF A TROPICAL WAVE. THE
REMAINDER OF THE GULF IS FAIRLY QUIET WITH ONLY PATCHY HIGH
LEVEL CLOUDS DRIVEN QUICKLY SWWD ON THE PERIPHERY OF A LARGE
UPPER HIGH CENTERED ABOVE THE S CENTRAL U.S. AT THE SFC...THE
WRN EXTENT OF THE SUBTROPICAL ATLC RIDGE STRETCHES ACROSS THE
REGION. THIS IS KEEPING WINDS FAIRLY LIGHT ACROSS THE AREA
EXCEPT THE SW PART WHERE SE WINDS ARE NEAR 15 KT BASED ON AN
EARLIER QSCAT PASS. ALL EYES ARE ON HURRICANE DEAN WHICH IS
EXPECTED TO MOVE INTO THE W/SW PORTION OF THE AREA IN A FEW
DAYS.

THE CARIBBEAN SEA...
ALL THE ATTENTION REMAINS FOCUSED ON POWERFUL CATEGORY FOUR
HURRICANE DEAN. DEAN WILL CONTINUE TO HAVE SIGNIFICANT IMPACTS
ON THE CARIBBEAN OVER THE NEXT FEW DAYS. FOR DETAILS REFER TO
THE SPECIAL FEATURE SECTION ABOVE. ELSEWHERE...SCATTERED SHOWERS
AND TSTMS ARE OVER COSTA RICA AND NICARAGUA ASSOCIATED WITH THE
ITCZ AND A TROPICAL WAVE. FOR MORE DETAILS ON THIS REFER TO THE
TROPICAL WAVES SECTION ABOVE.

THE ATLANTIC OCEAN...
WELL WITH ALL THE ABOVE SAID...MOST OF THE ATLC DISCUSSION AREA
IS QUIET THIS EVENING. NONE OF THE TROPICAL WAVES ARE SHOWING
IMPRESSIVE ORGANIZATION AND THERE ARE NOT ANY LARGE AREAS OF
CONVECTIVE ACTIVITY. THE SFC PATTERN REMAINS DOMINATED BY A
STRONG BERMUDA-AZORES RIDGE WHICH IS PRODUCING LIGHT TO MODERATE
TRADES ACROSS THE BULK OF THE AREA...EXCEPT STRONG WINDS NEAR
THE CARIB ISLANDS WHERE THERE ARE EFFECTS FROM DEAN AND NEAR THE
COAST OF AFRICA WHERE THE GRADIENT IS TYPICALLY TIGHTER DUE TO
LOWER PRES OVER THE CONTINENT. A COLD FRONT REMAINS N OF THE
AREA ALONG 33N/34N W OF 70W...THIS LIKELY WILL PRESS TO OUR NRN
BORDER LATER TONIGHT/TOMORROW. IN THE MID AND UPPER LEVELS...A
LARGE RIDGE...WHICH HAS BEEN STEERING DEAN...IS CENTERED IN THE
SW ATLC. AN UPPER LOW IS LOCATED IN THE CENTRAL ATLC NEAR 29N54W
PRODUCING AN AREA OF STRONG WINDS ALOFT AND CIRRUS. ANOTHER
ELONGATED UPPER LOW IS LOCATED ABOVE THE E ATLC NEAR 31N28W.
STRONG RIDGING LIES FURTHER S ALONG 23N E OF 45W COVERING MUCH
OF THE TROPICAL ATLC.

$$
CANGIALOSI


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