[Tropical] Tropical Weather Discussion

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AXNT20 KNHC 270553
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
205 AM EDT THU JUL 27 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 0000 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH
0530 UTC.

...TROPICAL WAVES...

BASED UPON SATELLITE IMAGERY AND THE AVAILABLE DATA...THE
TROPICAL WAVE IN THE EASTERN ATLANTIC PREVIOUSLY ALONG 31W HAS
BEEN DROPPED FROM THE SURFACE ANALYSIS. THIS FEATURE DOES NOT
APPEAR TO HAVE BEEN A TROPICAL WAVE BUT RATHER SOME INSTABILITY
LEFT BEHIND FROM THE BROAD HIGH AMPLITUDE WAVE 600 NM TO ITS
WEST.

A HIGH AMPLITUDE TROPICAL WAVE IS ALONG 44W SOUTH OF 21N MOVING
WEST 15-20 KT. THIS WAVE IS VERY BROAD YET WELL DEFINED WITH
CLEAR LOW-MID LEVEL TURNING EVIDENT ON SATELLITE IMAGERY.
THE WAVE IS ENHANCING CONVECTION EMBEDDED WITHIN THE ITCZ FROM
5N-12N BETWEEN 35W-53W. THE NORTHERN EXTENSION OF THE WAVE HAS
LIMITED SHOWER ACTIVITY AS IT IS EMBEDDED IN A DRY/STABLE
ENVIRONMENT LIKELY DUE TO SAHARAN DUST.

A HIGH AMPLITUDE TROPICAL WAVE IS IN THE EASTERN CARIBBEAN ALONG
65W SOUTH OF 22N MOVING WEST NEAR 20 KT. THIS WAVE HAS BEEN
WELL-DEFINED OVER THE PAST SEVERAL DAYS. SHOWER AND TSTM
ACTIVITY HAS INCREASED TODAY WITH PATCHES OF SCATTERED MODERATE
CONVECTION MAINLY BEHIND THE WAVE AXIS ACROSS THE VIRGIN
ISLANDS...LEEWARD AND WINDWARD ISLANDS FROM 12-21N BETWEEN
58W-66W. AN INCREASE IN WINDS IS EVIDENT BEHIND THE WAVE AXIS
BASED ON AN EARLIER QUIKSCAT PASS AND BUOY/SHIP OBS. FURTHER
DEVELOPMENT IS NOT LIKELY TO OCCUR AS UPPER LEVEL WINDS ARE
UNFAVORABLE.

A WESTERN CARIBBEAN SEA TROPICAL WAVE IS ALONG 82W SOUTH OF 18N
MOVING WEST NEAR 15 KT. VERY LITTLE WAVE SIGNATURE IS NOTED ON
SATELLITE IMAGERY. HOWEVER...THIS WAVE MAY BE AIDING IN
TRIGGERING CLUSTERS OF MODERATE/STRONG CONVECTION EMBEDDED IN
THE ITCZ ACROSS THE SOUTHERN CARIBBEAN FROM 5N-11N BETWEEN
73W-82W.

...ITCZ...
ITCZ AXIS IS CENTERED ALONG 11N15W 10N30W 9N42W TO INLAND OVER
SOUTH AMERICA NEAR 9N62W TO PANAMA NEAR 9N82W. BESIDES FOR THE
CONVECTION ENHANCED BY THE TROPICAL WAVES...CLUSTERS OF
SCATTERED MODERATE CONVECTION EXISTS EAST OF 30W WITHIN 240 NM
EITHER SIDE OF THE AXIS. THIS ACTIVITY MAY BE ASSOCIATED WITH
ANOTHER TROPICAL WAVE APPROACHING 20W.

...DISCUSSION...
GULF OF MEXICO...
THE MOST ACTIVE WEATHER IN THE REGION CONTINUES TO BE IN THE NW
GULF. THE SURFACE LOW THAT HAS BEEN MOVING NORTHWARD ALONG THE
MEXICO/TEXAS COAST OVER THE PAST FEW DAYS APPEARS TO HAVE
DISSIPATED. HOWEVER...PATCHES OF MODERATE CONVECTION CONTINUES
ACROSS PORTIONS OF NRN MEXICO...SOUTH TEXAS...WRN LOUISIANA AND
THE COASTAL WATERS FROM 24N-30N W OF 93W...CAUSED BY LOW LEVEL
CONVERGENCE AND UPPER DIFFLUENCE BETWEEN AN UPPER HIGH IN THE
CENTRAL GULF AND AN UPPER LOW OVER NRN MEXICO. THE UPPER HIGH IS
ADVECTING SOME OF THE MOISTURE FROM THE W GULF ACROSS THE SE
U.S. AND NRN GULF...HOWEVER MUCH OF IT IS MAINLY IN THE UPPER
LEVELS. MOISTURE IS SLIGHTLY DEEPER WITH EMBEDDED SCATTERED
SHOWERS/TSTMS ACROSS FLORIDA AND THE SE GULF AS UPPER DIFFLUENCE
IS STRONGER BETWEEN THE GULF OF MEXICO HIGH AND A TROUGH OFF THE
SE U.S. AT THE SURFACE...RIDGING HAS BUILT ACROSS THE REGION
FROM THE BERMUDA-AZORES HIGH TO A 1018 MB HIGH CENTER OVER THE
FL/GA BORDER. SFC FLOW IS LIGHT ACROSS FLORIDA AND THE E
GULF...STRONGER W OF 87W WHERE SE WINDS OF 15-20 KT ARE COMMON.
THE MOISTURE IN THE W GULF WILL CONTINUE TO DRIFT NWD AND SLOWLY
WEAKEN. LITTLE CHANGE IN THE SURFACE PATTERN IS EXPECTED OVER
THE NEXT FEW DAYS AS SFC RIDGING IS LIKELY TO REMAIN
ESTABLISHED.

CARIBBEAN SEA...
TWO TROPICAL WAVES ARE IN THE CARIBBEAN SEA THIS EARLY MORNING.
THE WESTERN-MOST WAVE IS ALONG 82W ENHANCING CONVECTIVE ACTIVITY
IN THE ITCZ ACROSS THE SOUTHERN CARIBBEAN. SEE THE TROPICAL
WAVES SECTION FOR MORE DETAILS. THE OTHER WAVE...ALONG 65W...IS
MORE IMPRESSIVE INTERACTING WITH AN UPPER LEVEL LOW IN THE ATLC
TO PRODUCE A RATHER WIDE AREA OF SHOWERS AND TSTMS ACROSS THE
LESSER ANTILLES NOW MOVING OVER PUERTO RICO FROM 12N-21N BETWEEN
58W-67W. PUERTO RICO DOPPLER RADAR SHOWS NARROW BANDS OF SHOWERS
AND TSTMS MOVING WWD ACROSS THE ISLAND WITH A MUCH LARGER
SHIELD OF MODERATE TO HEAVY RAIN OVER THE VIRGIN ISLANDS. THIS
WAVE WILL CONTINUE TO MOVE QUICKLY TO THE WEST...STEERED BY THE
STRONG SFC HIGH...SPREADING MOISTURE ACROSS THE CENTRAL
CARIBBEAN LATER TODAY. AN UPPER LOW IS MOVING TO THE WSW IN THE
WRN CARIBBEAN CENTERED NEAR 19N85W. WEAK UPPER DIFFLUENCE
BETWEEN THIS UPPER LOW AND THE GULF OF MEXICO UPPER HIGH IS
TRIGGERING SCATTERED SHOWERS/ISOLATED TSTMS OVER SOUTH CUBA AND
THE CAYMAN ISLANDS FROM 20N-22N BETWEEN 78W-84W. TRADE WINDS ARE
GENERALLY IN THE 15-20 KT RANGE WITH SOME SLIGHTER STRONGER
WINDS OFF THE COAST OF COLOMBIA AND POSSIBLY IN THE CONVECTION
ACROSS THE LESSER ANTILLES.

THE ATLANTIC OCEAN...
A BERMUDA-AZORES SURFACE RIDGE RUNS FROM A 1027 MB HIGH
PRESSURE CENTER OVER THE AZORES TO A 1029 MB HIGH IN THE CENTRAL
ATLC NEAR 36N49W ACROSS BERMUDA INTO THE CENTRAL GULF OF MEXICO.
A WEAK RATHER BENIGN 1020 MB SURFACE LOW PRESSURE CENTER IS
CONTAMINATING THE RIDGE NEAR 32N30W. IN THE UPPER LEVELS...A
TROUGH OFF THE SE U.S. INTERACTING WITH AN UPPER HIGH IN THE
GULF IS PRODUCING A CONSIDERABLE AMOUNT OF UPPER LEVEL MOISTURE
W OF 72W N OF 24N. ONLY SCATTERED SHOWERS AND ISOLATED TSTMS
ARE EMBEDDED IN THIS MOISTURE PLUME. A WELL-DEFINED UPPER LOW IS
CENTERED NEAR 26N65W. THIS UPPER LOW IS INTERACTING WITH THE
EASTERN CARIBBEAN TROPICAL WAVE TO PRODUCE SCATTERED MODERATE
CONVECTION. SEE THE CARIBBEAN SECTION FOR MORE DETAILS. A VERY
WEAK DRY UPPER LOW IS MOVING NWD OUT OF THE DISCUSSION AREA NEAR
31N55W. A BROAD UPPER RIDGE COVERS A LARGE PORTION OF THE ATLC
N OF 10N BETWEEN 18W AND 54W. MIDDLE TO UPPER LEVEL DRY/STABLE
AIR IS NORTH OF 14N BETWEEN 25W AND 55W. AN UPPER TROUGH CLIPS
THE AREA E OF 18W N OF 27N. A WIDESPREAD AREA OF DENSE SAHARAN
DUST EXTENDS OUT TO ABOUT 65W...BEHIND THE E CARIBBEAN TROPICAL
WAVE. THE COMBINATION OF THE DRY/STABLE ATMOSPHERE FROM THE
SAHARAN DUST AND SUBSIDENCE FROM UPPER RIDGING IS SUPPRESSING
ANY SIGNIFICANT CONVECTION IN THE ATLC N OF THE ITCZ.

$$
CANGIALOSI


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