[Tropical] Tropical Weather Discussion

[EMWIN Server]

AXNT20 KNHC 211759
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
205 PM EDT MON AUG 21 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 1200 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH
1715 UTC.

...SPECIAL FEATURE...
A STRONG TROPICAL WAVE HAS MOVED OFF THE AFRICAN COAST...NOW
ALONG 21W WITH A WELL DEFINED LOW CENTERED NEAR 12N. AT 12Z...IT
WAS ANALYZED AT 1011 MB. THIS WAVE IS PROBABLY THE MOST
VIGOROUS IN THE E ATLC SO FAR THIS YEAR. CONVECTION HAS
DECREASED SOME FROM THIS MORNING BUT REMAINS WELL ORGANIZED WITH
NUMEROUS SHOWERS AND TSTMS IN AN BANDED FEATURE WHICH WRAPS
TWO-THIRDS AROUND THE LOW. SCATTERED MODERATE CONVECTION IS ALSO
FOUND S OF THE LOW FROM 6N-10N BETWEEN 19W-25W. THIS AREA MAY
DEVELOP INTO A TROPICAL DEPRESSION DURING THE NEXT DAY OR TWO AS
IT MOVES WNW AT 10-15 KT. ONE OF THE POSSIBLE LIMITING FACTORS
FOR FURTHER DEVELOPMENT IS THE LARGE AREA OF DUST TO THE N AND W
OF THE LOW...BUT IT IS DIFFICULT TO DETERMINE HOW MUCH OF A
FACTOR IT WILL BE.

...TROPICAL WAVES...

TROPICAL WAVE IN THE E ATLC HAS BEEN ADJUSTED AHEAD ALONG 41W S
OF 19N MOVING W NEAR 20 KT. A 1012 MB LOW IS PLACED ON THE
WAVE NEAR 10N. THIS SFC LOW IS VERY BROAD...BUT SFC OBS AND A
09Z QUIKSCAT PASS HAS HELPED LOCATE THE LOW CENTER. THE WAVE
ITSELF IS ALSO BROAD...BUT IS HIGH AMPLITUDE WITH CYCLONIC
TURNING COVERING A LARGE AREA ABOUT THE AXIS. FURTHER
DEVELOPMENT DOES NOT APPEAR LIKELY AT THIS TIME DUE TO ITS VERY
BROAD NATURE AND THE LARGE AREA OF SAHARAN DUST THAT SURROUNDS
THE NRN EXTENSION OF THE WAVE.

TROPICAL WAVE IS ABOUT 400 NM E OF THE WINDWARD ISLANDS ALONG
54W S OF 19N MOVING W 15-20 KT. WELL DEFINED WAVE STRUCTURE WITH
AN INVERTED V-SHAPE EVIDENT ON IR AND VIS IMAGES. THIS WAVE ALSO
APPEARS TO BE THE LEADING EDGE OF THE SAHARAN DUST. SCATTERED
SHOWERS AND TSTMS ARE WITHIN 300 NM EITHER SIDE OF THE AXIS
MAINLY S OF 13N. THE WRN EXTENT OF THE MOISTURE IS SPREADING
OVER THE WINDWARD ISLANDS.

TROPICAL WAVE IS IN THE E CARIBBEAN ALONG 71W S OF 18N MOVING W
NEAR 15 KT OVER THE PAST 24 HOURS. LITTLE SIGNATURE IS APPARENT
ON SATELLITE IMAGERY AND ONLY ISOLATED SHOWERS ARE NEAR THE WAVE
AXIS.

TROPICAL WAVE IS IN THE W CARIBBEAN ALONG 86W S OF 18N MOVING W
10-15 KT. THIS WAVE IS MAINLY INLAND OVER CNTRL AMERICA. NO
ORGANIZATION TO THE WAVE IS NOTED...BUT IN COMBINATION WITH
UPPER DIFFLUENCE...CLUSTERS OF SCATTERED MODERATE CONVECTION ARE
IN THE W CARIBBEAN FROM 17N-20N BETWEEN 79W-82W MOVING N. MORE
CONVECTION HAS FORMED FARTHER S FROM 11N-14N BETWEEN 81W-85W.

...THE ITCZ...
ITCZ AXIS IS CENTERED ALONG 9N22W 11N39W 9N61W ACROSS NRN S
AMERICA AND PANAMA INTO THE E PAC. BESIDES FOR THE TROPICAL
WAVES...CLUSTERS OF SCATTERED MODERATE CONVECTION IS OVER N S
AMERICA AND PANAMA MOVING INTO THE E PAC W OF 77W FROM 2N-11N.

...DISCUSSION...
GULF OF MEXICO...
AN UPPER LOW IS SPINNING IN THE SW GULF NEAR 23N94W WITH
TROUGHING EXTENDING E TO A SMALL UPPER LOW IN THE CNTRL GULF
NEAR 25N86W TO CENTRAL FLORIDA. CONSIDERABLE CLOUDINESS LIES S
OF 27N...BUT THERE ARE ONLY SOME PATCHES OF DEEP MOISTURE.
SCATTERED SHOWERS AND TSTMS ARE NEAR THE UPPER LOW IN THE SW
GULF FROM 21N-25N BETWEEN 91W-97W AND ISOLATED SHOWERS LIE E OF
85W S OF 27N. UPPER RIDGING COVERS THE N GULF...ANCHORED BY A
STRONG HIGH CENTER OVER N TEXAS. DRY STABLE AIR LIES N OF 27N.
AT THE SFC...HIGH PRES RIDGING FROM THE ATLC STRETCHES INTO THE
AREA. WINDS ARE LIGHT AND GENERALLY FROM THE SE DRAWING SOME
TROPICAL MOISTURE FROM THE CARIBBEAN INTO THE SRN GULF. LITTLE
CHANGE IN THE SFC PATTERN IS EXPECTED OVER THE NEXT COUPLE OF
DAYS.

CARIBBEAN SEA...
A BROAD UPPER RIDGE EXTENDS ACROSS THE CARIBBEAN FROM HONDURAS E
THRU MUCH OF THE CARIBBEAN ALONG 16N. UPPER DIFFLUENCE BETWEEN
THIS HIGH AND THE TROUGHING IN THE GULF...IN ADDITION TO THE
NEARBY TROPICAL WAVE IS PRODUCING NUMEROUS SHOWERS AND TSTMS IN
THE W CARIBBEAN FROM 15N-20N BETWEEN 79W-82W. THIS ACTIVITY IS
MOVING SLOWLY N. MORE PATCHES OF SIMILAR CONVECTION LIES S OF
11N BETWEEN 78W-81W...HIGHLY CONTRIBUTED TO THE ITCZ. ANOTHER
TROPICAL WAVE IS IN THE CNTRL CARIBBEAN...HOWEVER THIS ONE
REMAINS WEAK PRODUCING ONLY ISOLATED SHOWERS. SCATTERED SHOWERS
AND TSTMS ARE BEGINNING TO SPREAD ACROSS THE WINDWARD
ISLANDS...CURRENTLY E OF 66W S OF 16N. THIS ACTIVITY IS AHEAD OF
THE NEXT TROPICAL WAVE. THE COMBINATION OF THE BUILDING ATLC SFC
RIDGE N OF THE AREA AND THE TROPICAL WAVES HAVE INCREASED TRADE
WINDS TO 20-25 KT ACROSS A GOOD PORTION OF THE AREA. THESE WINDS
WILL LIKELY REMAIN THAT WAY OVER THE NEXT COUPLE OF DAYS AS THE
SFC PATTERN CHANGES LITTLE.

ATLANTIC OCEAN...
SEVERAL UPPER LEVEL LOWS ARE SEEN SPINNING IN WATER VAPOR
IMAGERY ACROSS THE WRN AND CNTRL ATLC. THE WRN-MOST IS ABOUT 60
NM E OF DAYTONA BEACH FL. UPPER DIFFLUENCE ON THE S SIDE OF THE
LOW IS PRODUCING SCATTERED SHOWERS AND TSTMS ACROSS THE BAHAMAS
AND S FLORIDA FROM 22N-27N BETWEEN 76W-81W. ANOTHER UPPER LOW IS
ABOUT 250 NM SE OF BERMUDA NEAR 30N61W. DIFFLUENT FLOW ON THE S
AND E SIDE OF THE CIRCULATION IS PRODUCING PATCHES OF SHOWERS
AND TSTMS. A SFC TROF IS EVIDENT IN QUIKSCAT DATA TO THE S OF
THE UPPER LOW ALONG 23N70W 28N65W. SCATTERED SHOWERS AND
ISOLATED TSTMS ARE WITHIN 120 NM TO THE E OF THE BOUNDARY.
SIMILAR ACTIVITY LIES WITHIN 60 NM OF A LINE ALONG 26N54W
30N59W. ANOTHER UPPER LOW IS NEAR 25N41W. THIS FEATURE IS
EMBEDDED IN DRY AIR PRODUCING LITTLE WEATHER. AN UPPER RIDGE
EXTENDS FROM THE CARIBBEAN ACROSS HISPANIOLA TO NEAR 24N66W. THE
E ATLC IS DOMINATED BY AN UPPER RIDGE WITH A HIGH CENTER NEAR
16N39W...THE RIDGE AXIS STRETCHES NE TO BEYOND 32N17W. DRY
STABLE UPPER LEVEL AIR COVERS THE AREA UNDER THIS RIDGE. IN
ADDITION TO THE DRY UPPER LEVEL AIR...WIDESPREAD SAHARAN DUST IN
THE MID-LEVELS HAS SURGED OUT TO NEAR 55W BETWEEN 11N-25N.
BESIDES FOR THE SPECIAL FEATURE...TROPICAL WAVES AND SFC TROUGH
MENTIONED...HIGH PRES RIDGING DOMINATES WITH THE SURFACE HIGHS
ANALYZED N OF THE REGION. THIS FAIRLY STRONG SFC RIDGE HAS
INCREASED TRADE WINDS IN THE TROPICS.

$$
CANGIALOSI




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