[Tropical] Tropical Weather Discussion

[EMWIN Server]

AXNT20 KNHC 122331
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
805 PM EDT SAT AUG 12 2006

TROPICAL WEATHER DISCUSSION FOR NORTH AMERICA...CENTRAL
AMERICA...THE GULF OF MEXICO...THE CARIBBEAN SEA...NORTHEASTERN
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...WEATHER OBSERVATIONS...RADAR...
AND METEOROLOGICAL ANALYSIS.

BASED ON 1800 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH
2315 UTC.

...TROPICAL WAVES...
TROPICAL WAVE HAS PULLED OFF THE W COAST OF AFRICA ALONG 18W S
OF 19N MOVING W 5-10 KT OVER THE PAST 24 HOURS. DAKAR SOUNDINGS
SUGGESTS THAT THE WAVE HAS MOVED THRU THE STATION NEAR 06Z. GFS
HAS THIS WAVE INITIALIZED FAIRLY WELL AND INDICATES THAT IT WILL
PICK UP SPEED AS IT TRACKS UNDER A LOW-MID LEVEL RIDGE. THE
OVERALL STRUCTURE OF THE WAVE IS FAIR AT BEST AT THE MOMENT...AS
IT IS EMBEDDED IN A QUASI-STATIONARY MONSOON TROUGH. PATCHES OF
MODERATE CONVECTION LIES FROM 14N-17N BETWEEN 15W-19W.

TROPICAL WAVE IS ALONG 53W S OF 19N...ABOUT 450 NM E OF THE
LESSER ANTILLES...MOVING W 10-15 KT. THIS WAVE CONTINUES TO BE
WELL-DEFINED WITH A CLASSIC INVERTED V-SHAPE EVIDENT ON
SATELLITE IMAGERY. A 1011 MB LOW IS LOCATED ON THE WAVE NEAR
13N...MARKED ONLY BY A LOW CLOUD SWIRL. DESPITE THE VERY NICE
SIGNATURE OF THE WAVE...IT CONTINUES TO BE EMBEDDED IN A DRY
ENVIRONMENT LIMITING ANY ORGANIZED CONVECTION. THERE IS A PATCH
OF MODERATE CONVECTION AHEAD OF THE WAVE AXIS FROM 11N-13N
BETWEEN 56W-60W...LIKELY AIDED BY THE FLOW AROUND THE MID TO
UPPER HIGH JUST TO THE NW OF THE WAVE.  FURTHER DEVELOPMENT IS
NOT EXPECTED.

TROPICAL WAVE IN THE WRN CARIBBEAN IS ALONG 78W/79W S OF 21N
MOVING W NEAR 15 KT. THIS WAVE REMAINS RATHER DISORGANIZED AND
IS SHOWING NO SIGNS OF ORGANIZING. SATELLITE IMAGERY AND SURFACE
WINDS IN THE VICINITY DO SHOW SOME CYCLONIC TURNING ABOUT THE
AXIS...BUT DEEP CONVECTION NEAR THE WAVE N OF 12N REMAINS AT A
MINIMUM. THIS PORTION OF THE WAVE LIES UNDERNEATH A FAIRLY DRY
UPPER LEVEL LOW WHICH IS LIKELY HELPING TO SUPPRESS/DECOUPLE ANY
LOW LEVEL INSTABILITY.

...THE ITCZ...
ITCZ AXIS IS CENTERED ALONG 14N16W 9N31W 12N50W TO INLAND OVER
SOUTH AMERICA NEAR 10N62W. BESIDES FOR THE TROPICAL
WAVES...SCATTERED SHOWERS AND TSTMS ARE WITHIN 120 NM EITHER
SIDE OF THE AXIS BETWEEN 30W-36W. ELSEWHERE...ONLY ISOLATED
SHOWERS DOT THE AXIS.

...DISCUSSION...
GULF OF MEXICO...
QUIET WEATHER CONTINUES ACROSS THE GULF OF MEXICO THIS EVENING
WITH A SFC RIDGE STRETCHING FROM THE ATLC OCEAN ACROSS SOUTH
FLORIDA TO A 1016 MB HIGH IN THE CENTRAL GULF NEAR 26N89W. THIS
PATTERN IS KEEPING WINDS LIGHT AND ANTICYCLONIC AROUND THE SFC
HIGH. THE BREEZIEST CONDITIONS ARE IN THE THE WRN GULF WHERE
WINDS ARE FROM THE S-SE NEAR 15-20 KT. IN THE UPPER LEVELS...AN
UPPER HIGH IS CENTERED ABOUT 150 NM E OF DAYTONA BEACH NEAR
29N78W. THE UPPER LEVEL LOW THAT HAS TRACKED ACROSS THE ENTIRE
GULF OVER THE PAST FEW DAYS HAS SLOWED AND BECOME LESS ACTIVE
JUST INLAND OVER NRN MEXICO/SRN TEXAS NEAR 26N98W. THIS UPPER
LEVEL PATTERN IS PRODUCING PLENTY OF DRY STABLE AIR ACROSS THE E
AND CNTRL GULF. HIGH CLOUDINESS AND POSSIBLY SOME ISOLATED
SHOWERS ARE IN THE WRN GULF...BUT OVERALL A WARM DRY DAY IS THE
THEME ACROSS THE ENTIRE AREA. RAIN CHANCES ARE LIKELY TO
INCREASE IN THE NE GULF AND FLORIDA LATE TOMORROW AND EARLY NEXT
WEEK ASSOCIATED WITH THE TAIL END OF A BACK-DOOR COLD FRONT.
SOME INCREASE IN MOISTURE IS ALSO LIKELY LATE SUN/MON IN THE BAY
OF CAMPECHE ASSOCIATED WITH AN APPROACHING TROPICAL WAVE.

CARIBBEAN SEA...
AN UPPER TROUGH DOMINATES MUCH OF THE CENTRAL AND WRN CARIBBEAN
WITH TWO UPPER LOWS EMBEDDED IN THE TROUGH. THE AXIS EXTENDS
FROM ONE UPPER LOW LOCATED NEAR THE SE BAHAMAS TO THE OTHER LOW
ABOUT 100 NM S OF JAMAICA WITH THE BASE OF THE TROUGH DIGGING TO
NEAR 13N82W. A NARROW UPPER HIGH IS CENTERED OVER GUATEMALA.
UPPER DIFFLUENCE BETWEEN THESE FEATURES...AFTERNOON
HEATING...LOCAL SEA-BREEZES AND UPSLOPE FLOW IS SPARKING
SCATTERED SHOWERS/TSTMS OVER PORTIONS OF CENTRAL AMERICA AND
DOTTED ACROSS THE NW CARIBBEAN SEA. SIMILAR ACTIVITY IS
OCCURRING OVER CUBA. THE ERN CARIBBEAN IS DOMINATED BY MID-UPPER
RIDGING AND DRY AIR...THOUGH A FEW SHOWERS AND TSTMS ARE MOVING
E TO W ALONG THE SRN PERIPHERY OF THE UPPER HIGH ACROSS THE
WINDWARD ISLANDS. AT THE SFC...RIDGING ON THE SW SIDE OF THE
ATLC HIGH CONTINUES TO EXTEND INTO THE CARIBBEAN PRODUCING 15 TO
25 KT TRADE WINDS. AN INCREASE IN MOISTURE IS LIKELY ACROSS THE
LESSER ANTILLES LATE SUN AS THE CENTRAL ATLC TROPICAL WAVE
APPROACHES. ELSEWHERE...SIMILAR CONDITIONS ARE EXPECTED OVER
THE NEXT COUPLE OF DAYS.

ATLANTIC OCEAN...
A SPRAWLING UPPER HIGH IS CENTERED ABOUT 150 NM E OF DAYTONA
BEACH FLORIDA NEAR 29N78W WITH THE RIDGE AXIS ALONG 29N
STRETCHING OUT TO 55W. A LARGE UPPER TROUGH IS LOCATED TO THE N
OF THIS RIDGE. AN ASSOCIATED SFC COLD FRONT CONTINUES TO PRESS
SWD AND HAS ENTERED THE NRN PORTION OF THE DISCUSSION AREA...AND
AS OF 18Z EXTENDS FROM A 1005 MB LOW NEAR 35N62W TO 31N72W TO
THE GEORGIA COAST. THIS IS THE FRONT THAT HAS BROUGHT VERY
PLEASANT...EVEN CHILLY WEATHER FOR THIS TIME OF YEAR TO THE NE
AND MID-ATLC STATES. BROKEN TO OVERCAST SKIES AND SCATTERED
SHOWERS/TSTMS ARE N OF 28N W OF 51W. DOPPLER RADAR INDICATES
LINES OF STRONG STORMS MOVING OFF THE SE U.S. NEAR THE BOUNDARY.
ELSEWHERE...BESIDES FOR THE TROPICAL WAVES AND ITCZ RELATED
CONVECTION VERY LITTLE UNSETTLED WEATHER IS OCCURRING IN THE
ATLC BASIN. THERE ARE SEVERAL UPPER LEVEL FEATURES NONE OF WHICH
ARE CAUSING MUCH INSTABILITY. AN UPPER LEVEL LOW CONTINUES TO
TRACK WWD IN TANDEM WITH THE W CARIBBEAN TROPICAL WAVE NOW
LOCATED IN THE SE BAHAMAS NEAR 22N72W. AN UPPER HIGH IS LOCATED
ENE OF THE LEEWARD ISLANDS NEAR 17N56W AND ANOTHER UPPER LOW IS
NEAR 27N37W. THE ERN ATLC CONTINUES TO BE DOMINATED BY AN UPPER
RIDGE EXTENDING W FROM AFRICA. DRY/STABLE AIR LIES ABOVE THE
MAJORITY OF THE AREA. AT THE SURFACE...HIGH PRES RIDGING
CONTINUES TO BE THE THEME WITH THREE HIGH PRES CENTERS ANALYZED.
THE SFC RIDGE RUNS FROM A 1020 MB HIGH IN THE ERN ATLC NEAR
28N28W TO A 1020 MB HIGH NEAR 26N44W TO A 1018 MB IN THE CNTRL
ATLC NEAR 23N60W ACROSS SOUTH FLORIDA.

$$
CANGIALOSI


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