[Tropical] Tropical Weather Discussion

[EMWIN Server]

AXNT20 KNHC 181751
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
205 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 1200 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH
1715 UTC.

...SPECIAL FEATURE...
EXTREMELY DANGEROUS HURRICANE DEAN THREATENS HAITI...JAMAICA AND
THE CAYMAN ISLANDS FIRST...AND AFTERWARD THE YUCATAN PENINSULA.
AT 18/1800 UTC...THE CENTER OF HURRICANE DEAN WAS LOCATED NEAR
LATITUDE 15.9 NORTH...LONGITUDE 69.4 WEST OR ABOUT 505 MILES
EAST-SOUTHEAST OF KINGSTON JAMAICA AND ABOUT 175 MILES SOUTH OF
SANTO DOMINGO IN THE DOMINICAN REPUBLIC. DEAN IS MOVING TOWARD
THE WEST-NORTHWEST NEAR 15 KT. MAXIMUM SUSTAINED WINDS REMAIN
NEAR 130 KT WITH HIGHER GUSTS. DEAN IS A MAJOR HURRICANE
CATEGORY FOUR ON THE SAFFIR-SIMPSON SCALE. THE ESTIMATED MINIMUM
CENTRAL PRESSURE REPORTED BY AN AIR FORCE HURRICANE HUNTER PLANE
IS 930 MB. 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 OR THE LATEST PUBLIC
ADVISORY UNDER MIATCPAT4/WTNT34 KNHC FOR MORE DETAILS INCLUDING
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. NUMEROUS MODERATE TO STRONG CONVECTION IS
WITHIN 180 NM OF CENTER.

...TROPICAL WAVES...
TROPICAL WAVE IS MOVING THROUGH THE E ATLC ALONG 36W SOUTH OF
20N MOVING W AT 10 TO 15 KT. THIS WAVE CONTINUES TO EXHIBIT A
BROAD ENVELOPE OF CYCLONIC TURNING WITH CLUSTERS OF MODERATE
CONVECTION ON THE SOUTHERN END OF THE WAVE AXIS FROM 5N-11N
BETWEEN 32W-40W. THE HOVMOLLER DIAGRAM CLEARLY SHOWS THE
WESTWARD PROPAGATION OF THIS CONVECTIVE ACTIVITY.

A TROPICAL WAVE IS ALONG 48W/49W SOUTH OF 20N. THIS WAVE IS
MOVING W NEAR 15 KT. THE UW-CIMSS SSMI-DERIVED TOTAL
PRECIPITABLE WATER SHOWS UP WELL A BROAD AREA OF CYCLONIC
TURNING NEAR 11N. SCATTERED MODERATE CONVECTION IS FROM 10N-12N
BETWEEN 49W-52W. THIS LARGE TROPICAL WAVE WILL ENTER THE
TROPICAL N ATLC WATERS SUN THEN MOVE INTO THE E CARIBBEAN MON.

TROPICAL WAVE IS ALONG 84W SOUTH OF 20N MOVING WEST NEAR 20 KT.
AN INVERTED V PATTERN REMAINS EVIDENT WITH THIS WAVE. THERE IS A
CLUSTER OD MODERATE CONVECTION OVER THE GULF OF HONDURAS
ASSOCIATED WITH THE WAVE. MOISTURE FROM THIS WAVE SHOULD AFFECT
BELIZE AND THE YUCATAN PENINSULA THIS AFTERNOON AND TONIGHT.

...THE ITCZ...
ITCZ AXIS IS CENTERED ALONG 13N17W 12N25W 14N35W 12N42W 8N58W.
OUTSIDE OF THE CONVECTION ALREADY DESCRIBED WITH THE TROPICAL
WAVES AND HURRICANE DEAN...DEEP CONVECTION IS MINIMAL NEAR THE
ITCZ.

DISCUSSION...

THE GULF OF MEXICO...
HIGH PRES RIDGE ALONG THE N GULF WATERS DOMINATES THE REGION
KEEPING WEATHER CONDITIONS PRETTY QUIET...BUT BIG CHANGES ARE IN
STORE FOR THE GULF NEXT WEEK AS HURRICANE DEAN MOVES IN TUE AND
WED. AN UPPER LOW OVER FLORIDA IS GENERATING SCATTERED SHOWERS
AND TSTMS OVER THE SE CORNER OF THE GULF AND THE FLORIDA KEYS.
SIMILAR ACTIVITY IS SEEN NEAR THE LOUISIANA/TEXAS BORDER AND
ADJACENT COASTAL WATERS. SURFACE WINDS OVER MOST OF THE GULF OF
MEXICO ARE FROM THE E TO SE AT 15 KT. A SFC TROUGH IS ANALYZED
OVER THE SW PORTION OF THE GULF...INCLUDING THE BAY OF CAMPECHE.
THE TROUGH RUNS FROM 22N96W TO 18N94W. SCATTERED SHOWERS ARE
RELATED TO THE TROUGH NEAR 21N96W. ALOFT...AN UPPER HIGH OVER NW
MEXICO IS PRODUCING A NELY WIND FLOW MAINLY WEST OF 86W. THESE
WINDS ARE TRANSPORTING SOME UPPER LEVEL MOISTURE ACROSS THE
AREA. CYCLONIC FLOW COVERS THE REMAINDER OF THE GULF ASSOCIATED
WITH THE AFOREMENTIONED UPPER LOW.

THE CARIBBEAN SEA...
ALL THE ATTENTION REMAINS FOCUSED ON THE FIRST MAJOR HURRICANE
OF THE SEASON NAMED DEAN. IT WILL CONTINUE TO HAVE SIGNIFICANT
IMPACTS ON THE CARIBBEAN SEA OVER THE NEXT SEVERAL DAYS.
FLUCTUATIONS IN ITS INTENSITY ARE EXPECTED REACHING THE PEAK
OVER THE NW CARIBBEAN WHERE THE OCEAN HEAT CONTENT IS VERY HIGH.
DEAN COULD BECOME A CATEGORY FIVE HURRICANE AT ANY TIME BEFORE
IT REACHES THE YUCATAN PENINSULA LATE MONDAY OR EARLY TUESDAY.
THIS TROPICAL CYCLONE IS STEERED BY A HIGH OVER THE WESTERN
ATLANTIC AND A LOW OVER FLORIDA THAT IS FORECAST TO MOVE WWD
INTO THE GULF OF MEXICO SUN. A RAIN BAND ASSOCIATED WITH DEAN IS
OVER PUERTO RICO APPROACHING DOMINICAN REPUBLIC. SAN JUAN
REPORTED HEAVY RAIN AND GUSTY WINDS OF NEAR 30 KT DURING THE
LAST FEW HOURS. DIFFLUENCE ALOFT IS ENHANCING SCATTERED SHOWERS
AND TSTMS OVER THE SW CARIBBEAN. THIS ACTIVITY IS SPREADING OVER
NICARAGUA AND COSTA RICA. IN THE UPPER LEVELS...A TROUGH EXTENDS
FROM THE ABOVE MENTIONED UPPER LOW ACROSS WESTERN CUBA AND THE
NW CARIBBEAN TO NEAR 16N83W. AN UPPER LEVEL HIGH IS OVER THE SW
CARIBBEAN. IMPRESSIVE UPPER LEVEL OUTFLOW IN ALL QUADRANTS IS
NOTED WITH HURRICANE DEAN E OF 73W.

THE ATLANTIC OCEAN...
AS IS TYPICAL FOR THIS TIME OF THE YEAR...THE AZORES-BERMUDAS
HIGH DOMINATES THE ATLANTIC OCEAN WITH A 1032 MB CENTER NEAR
39N31W. THIS FEATURE IS PRODUCING WIDESPREAD FAIR WEATHER AND
MODERATE TRADE WINDS E OF 60W. WINDS ARE A LITTLE STRONGER
BETWEEN THIS HIGH AND THE LARGE TROPICAL WAVE LOCATED ALONG
48W/49W REACHING 25 KT. IN THE UPPER LEVELS...AN UPPER LOW IS
SPINNING NEAR S FLORIDA. LIFT AHEAD OF THIS FEATURE IS
SUPPORTING SCATTERED SHOWERS AND TSTMS OVER THE BAHAMAS AND
ADJACENT WATERS S OF 28N W OF 75W. THE RISK FOR A FEW SEVERE
TSTMS REMAINS OVER SOUTH FLORIDA DUE TO THE PRESENCE OF THIS
UPPER LOW. AN UPPER RIDGING IS TO THE E OF THE UPPER LOW WHICH
IS STEERING DEAN WNW. ANOTHER UPPER LOW IS NEAR 27N52W MOVING W.
LIGHTNING DATA HAS BEEN DEPICTING A FEW ISOLATED TSTMS
ASSOCIATED WITH THIS FEATURE MAINLY ON THE WEST SIDE. UPPER
RIDGING EXTENDING W FROM AFRICA GENERALLY DOMINATES THE ERN
ATLC.

$$
GR




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