[Tropical] Tropical Weather Discussion

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AXNT20 KNHC 212313 CCA
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
805 PM EDT FRI JUL 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 1800 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH
2300 UTC.

...TROPICAL WAVES...

AN EASTERN ATLANTIC TROPICAL WAVE IS RELOCATED APPROXIMATELY 120
NM TO THE EAST OF THE PREVIOUS POSITION BASED UPON LOW LEVEL
TURNING ON SHORTWAVE IR IMAGES. THE WAVE IS CURRENTLY ALONG
29W/30W SOUTH OF 19N. A LOW LEVEL SWIRL IS LOCATED ALONG THE
WAVE NEAR 15N. THIS POSITION IS ALSO IN A REASONABLE LOCATION
BASED UPON A FORWARD MOTION OF 15 KT OVER THE PAST 24 HOURS. THE
TROPICAL WAVE HAS FAIR STRUCTURE WITH MUCH OF THE SCATTERED
SHOWERS AND TSTMS EMBEDDED WITHIN THE ITCZ...THEREFORE IT WILL
BE DISCUSSED IN THAT SECTION.

A TROPICAL WAVE IS ALONG 48W S OF 18N MOVING WEST NEAR 15 KT.
LOW LEVEL CURVATURE IS RATHER WEAK YET DEFINED ON VIS SATELLITE
PICTURES. THIS WAVE CONTINUES TO LACK ANY DEEP CONVECTION OR
ORGANIZED SHOWERS AND APPEARS TO BE THE LEADING EDGE OF A LARGE
DENSE AREA OF SAHARAN DUST BASED UPON UW-CIMMS SAHARAN AIR LAYER
ANALYSIS AND THE HAZY LOOK ON THE LAST FEW VIS IMAGES THIS
EVENING.

A TROPICAL WAVE IS ALONG 62W S OF 20N MOVING WEST NEAR 15 KT. A
VERY FAINT INVERTED V-PATTERN IS EVIDENT ON SATELLITE IMAGERY
CONSISTING OF MAINLY LOW-MID LEVEL CLOUDS WITH ISOLATED
SHOWERS. NO DEEP CONVECTION IS ASSOCIATED WITH THIS WAVE.

A TROPICAL WAVE IS ALONG 90W S OF 21N MOVING WEST NEAR 15 KT.
THIS WAVE IS TRIGGERING SCATTERED MODERATE CONVECTION ACROSS S
MEXICO AND MANY COUNTRIES IN CENTRAL AMERICA. THE WAVE IS RATHER
EASY TO LOCATE WITH THE AXIS ALONG THE LEADING EDGE OF MODERATE
CONVECTION ACROSS THE YUCATAN PENINSULA.

...ITCZ...
ITCZ AXIS IS CENTERED ALONG 15N17W 9N28W 4N40W 3N50W. THE ITCZ
IS A LITTLE MORE ACTIVE TODAY THAN THE PAST FEW DAYS WITH
SCATTERED MODERATE CONVECTION LOCATED WITHIN 180 NM EITHER SIDE
OF THE AXIS BETWEEN 20W-26W. SCATTERED SHOWERS AND TSTMS ARE
WITHIN 180 NM TO THE NORTH OF THE AXIS BETWEEN 29W-42W.

...DISCUSSION...
GULF OF MEXICO...
A BROAD UPPER RIDGE REMAINS IN PLACE ACROSS THE SOUTH CENTRAL
U.S. COVERING THE NW GULF. AN UPPER TROUGH EXTENDS FROM THE
EXTRA-TROPICAL CYCLONE BERYL IN THE NW ATLANTIC SOUTHWARD OFF
THE EAST COAST OF THE U.S. ACROSS CENTRAL FLORIDA TO THE EASTERN
GULF. AN UPPER LEVEL LOW HAS BECOME BETTER DEFINED TODAY AT THE
BASE OF THE NARROW TROUGH CENTERED NEAR 26N86W. BUOYS/QUIKSCAT
INDICATES SOME SURFACE REFLECTION WITH CYCLONIC TURNING OF WINDS
EVIDENT. AS OF 2100 UTC...THE SURFACE TROUGH WAS ANALYZED FROM
LAKE OCKEECHOBEE FLORIDA TO 25N86W. THIS UPPER LEVEL PATTERN IS
PRODUCING NUMEROUS SHOWERS AND TSTMS E OF 86W ACROSS FLORIDA
AND THE BAHAMAS BETWEEN 22N-26N. IN THE CENTRAL/WEST
GULF...ISOLATED MODERATE CONVECTION HAS DEVELOPED ON THE WEST
SIDE OF THE TROUGH AXIS SOUTH OF THE LOUISIANA COAST THROUGH
25N. SCATTERED MODERATE/ISOLATED STRONG CONVECTION PERSISTS IN
THE BAY OF CAMPECHE TRIGGERED BY THE TROPICAL WAVE ACROSS THE
YUCATAN AND DUE TO AN UPPER RIDGE EXTENDING WEST THROUGH S
MEXICO. WEAK SFC PRES GRADIENT IS PRODUCING LIGHT WINDS ACROSS
THE AREA. MODELS KEEP A FAIR AMOUNT OF MOISTURE IN THE GULF THIS
WEEKEND...ALTHOUGH IT DOES NOT APPEAR TO BE AS UNSETTLED AS
TODAY IN THE E GULF. A COLD FRONT MAY DIG AS FAR SOUTH AS THE N
GULF ON SUN.

CARIBBEAN SEA...
A TROPICAL WAVE ACROSS THE YUCATAN PENINSULA INTERACTING WITH A
BROAD UPPER RIDGE EXTENDING FROM S MEXICO INTO THE W CARIBBEAN
AND AN UPPER LOW IN THE SE GULF IS PRODUCING SCATTERED MODERATE
CONVECTION OVER THE NW CARIBBEAN W OF 83W. AN UPPER TROUGH
COVERS THE REMAINDER OF THE CARIBBEAN WITH MODERATE SUBSIDENCE
ACCOMPANYING THE TROUGH. FAIR WEATHER COVERS THE REMAINDER OF
THE CARIBBEAN E OF 83W EXCEPT FOR SCATTERED SHOWERS AND TSTMS
OVER THE LANDMASSES OF PUERTO RICO...HISPANIOLA AND CUBA
ENHANCED BY LOCAL SEA-BREEZES AND TOPOGRAPHIC LIFT AND A NARROW
BAND OF SHOWERS NORTH OF THE ABC ISLANDS DRIVEN BY SOUTHERLY
UPPER LEVEL WINDS. THE TROPICAL WAVE IN THE LESSER ANTILLES IS
CAUSING VERY LITTLE SHOWER ACTIVITY AS IT IS EMBEDDED IN A
DRY/STABLE ENVIRONMENT. TRADE WINDS ARE MODERATE TODAY AND THEY
WILL LIKELY REMAIN THAT WAY TOMORROW. AN INCREASE IN WIND SPEEDS
ARE EXPECTED LATE THIS WEEKEND AND MONDAY.

ATLANTIC OCEAN...
THE MAIN FEATURE IN THE WESTERN ATLANTIC IS AN UPPER TROUGH
WHICH EXTENDS FROM THE EXTRA-TROPICAL CYCLONE BERYL TO AN UPPER
LOW NEAR 34N70W TO CENTRAL FLORIDA. UPPER DIFFLUENCE ON THE
MOIST EAST SIDE OF THE TROUGH AXIS IS GENERATING AN ABUNDANT
AMOUNT OF MOISTURE W OF 65W. NUMEROUS SHOWERS AND TSTMS ARE
SPREAD OUT ACROSS SOUTH FLORIDA AND THE W BAHAMAS BECOMING MORE
SCATTERED FURTHER EAST OUT TO 69W. AN ILL-DEFINED SFC TROUGH IS
ALONG 66W FROM 23N-36N. THIS TROUGH MARKS AS A VERY PRONOUNCED
MOISTURE BOUNDARY WITH STRONG SUBSIDENCE WIDESPREAD TO IT'S
EAST. THE REMAINDER OF THE ATLANTIC...E OF 65W...IS UNDER BROAD
UPPER RIDGING. THERE IS AN UPPER LOW EMBEDDED IN THIS AREA NEAR
28N46W GENERATING A FEW SHOWERS TO THE EAST OF THE ITS CENTER
BUT FAIR WEATHER IS THE DOMINATE THEME. THE LEADING EDGE OF
DENSE SAHARAN DUST HAS PROGRESSED TO NEAR 50W.

$$
CANGIALOSI


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