[Tropical] Tropical Weather Discussion

[EMWIN Server]

AXNT20 KNHC 211734
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
205 PM EDT THU JUN 21 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.

...TROPICAL WAVES...

A TROPICAL WAVE IS ALONG 29W S OF 12N MOVING W NEAR 20 KT. THIS
WAVE IS LESS DEFINED THAN THE PAST FEW WHEN IN THIS VICINITY.
SATELLITE IMAGES SHOW ONLY SLIGHT TURNING IN THE LOW-MID LEVELS
ABOUT THE WAVE AXIS. ASSOCIATED SHOWER ACTIVITY IS MINIMAL AND
MOSTLY AHEAD OF THE WAVE EMBEDDED IN THE ITCZ.

A TROPICAL WAVE IS ALONG 43W S OF 12N MOVING W 15-20 KT. THIS
WAVE HAS BECOME MORE CHALLENGING TO TRACK TODAY WITH THE
CLOUDS/CONVECTION TAKING A LINEAR SHAPE SHUNTED BY LOW-LEVEL
NELY FLOW AND ABSORBED BY THE ITCZ.

A TROPICAL WAVE IS IN THE CENTRAL CARIBBEAN TITLED ALONG 71W/72W
S OF 21N MOVING W NEAR 15 KT. MUCH OF THIS WAVE'S MOISTURE FIELD
HAS BEING DRIVEN FAR TO THE NE ACROSS THE DOMINICAN REPUBLIC AND
INTO THE ATLANTIC SHEARED BY STRONG MID-UPPER SWLY FLOW AHEAD OF
A TROUGH. SIMILARLY TO THE WAVE IN THE CENTRAL ATLC...THIS
FEATURE HAS BECOME LESS DEFINED TODAY WITH THE CURRENT PSN BASED
MOSTLY ON FORWARD CONTINUITY.

...THE ITCZ...

ITCZ AXIS IS CENTERED ALONG 8N13W 7N22W 8N27W 7N37W 5N52W.
SCATTERED MODERATE CONVECTION IS WITHIN 150 NM N OF THE AXIS
BETWEEN 34W-43W. ISOLATED MODERATE IS WITHIN 90 NM S OF THE AXIS
BETWEEN 19W-22W AND WITHIN 60 NM N E OF 15W.

...DISCUSSION...

THE GULF OF MEXICO...
WEAK LOW PRES TROUGHING COVERS THE E GULF ASSOCIATED WITH A SLOW
MOVING 1013 MB LOW CENTERED OVER NE FLORIDA. ISOLATED SHOWERS
AND TSTMS ARE STARTING TO FIRE UP OVER THE FL PENINSULA
SUPPORTED BY THIS LOW-LEVEL TROUGH. MODEST RIDGING EXTENDS SW
FROM A 1021 MB CENTER IN THE MIDWEST TOWARD THE BAY OF CAMPECHE.
THIS OVERALL WEAK PRES PATTERN IS PROVIDING THE AREA WITH LIGHT
WINDS AND LOW SEAS. ALOFT...THE FLOW IS PRIMARILY NLY ON THE WRN
PERIPHERY OF A HIGH CENTERED OVER SRN MEXICO NEAR 20N99W. A WEAK
INVERTED TROUGH ALONG 87W/88W IS INTERRUPTING THE RIDGING
ALLOWING MOST OF THE UPPER FLOW TO BE LIGHT IN ITS VICINITY.
THIS UPPER PATTERN IS NOT GENERATING MUCH MOISTURE WITH ONLY A
MID-HIGH LEVEL CLOUD DECK AND EMBEDDED ISOLATED SHOWER/TSTM
ACTIVITY W OF 93W. LOOKING AHEAD...NWP MODELS GENERALLY SHOW
LITTLE MOVEMENT OF THE LOW OR REMNANT TROUGH. THIS WILL ALLOW
THE SFC FLOW TO REMAIN LIGHT FOR ANOTHER DAY OR SO.
THEREAFTER...SFC WINDS AND MOISTURE MAY INCREASE ACROSS THE SRN
WATERS AS THE NRN EXTENSION OF THE CARIB TROPICAL WAVE
APPROACHES.

THE CARIBBEAN SEA...
ACTIVE WEATHER IS IN THE SW CARIB WHERE LARGE CLUSTERS OF
NUMEROUS MODERATE/SCATTERED STRONG CONVECTION IS S OF 16N W OF
79W. THERE APPEARS TO BE SEVERAL ELEMENTS CONTRIBUTING TO THIS
STRONG ACTIVITY. ONE FACTOR IS UPPER DIFFLUENCE BETWEEN AN UPPER
HIGH CENTERED OVER SRN MEXICO AND ANOTHER CENTER OVER THE
WINDWARD ISLANDS. ANOTHER FACTOR IS FORCING IN THE LOW TO MID
LEVELS. WHILE THE ITCZ IS PROVIDING SOME OF THIS FORCING...I AM
A LITTLE MORE CONVINCED THAT THERE IS A TROPICAL WAVE PROVIDING
SUPPORT FOR MAINTAINING THIS WWD PROPAGATION OF CONVECTION. THIS
WILL BE FURTHER ANALYZED AND POSSIBLY ADDED TO THE 18Z ANALYSIS.
ELSEWHERE...SKIES ARE MOSTLY FAIR BESIDES FOR SHEARED LIGHT
SHOWER ACTIVITY OVER THE DOMINICAN REPUBLIC AND WINDWARD
PASSAGE...ASSOCIATED WITH THE CENTRAL CARIB TROPICAL WAVE. TRADE
WINDS REMAIN ON THE STRONG SIDE...20 TO 30 KT...IN THE CENTRAL
CARIB AS INDICATED BY A 1022 UTC QSCAT PASS. THESE STRONG WINDS
ARE ANTICIPATED TO PERSIST AND EXPAND WWD SLIGHTLY OVER THE NEXT
COUPLE DAYS.

THE ATLANTIC OCEAN...
INTERESTING AREA OF LOW PRES...ANALYZED 1013 MB...HAS BROKEN OFF
THE TAIL END OF AN ATLC FRONT CENTERED JUST S OF ST AUGUSTINE
FLA. 88-D DATA FROM JAX SHOWS SCATTERED SHOWERS AND TSTMS
FLARING UP A BIT ON THE E SIDE OF THE CIRCULATION N OF 29N
BETWEEN 77W-80W. IN GENERAL...NWP MODELS FORECAST LITTLE
MOVEMENT OR DEVELOPMENT OF THIS SYSTEM. FARTHER E...AN UPPER
TROUGH CUTS ACROSS THE AREA FROM 32N62W SW ACROSS THE SE
BAHAMAS. DIFFLUENCE AND SWLY FLOW E OF THE TROUGH AXIS IS
SHEARING THE TROPICAL WAVE IN THE CENTRAL CARIB AND GENERATING
MOISTURE...MOSTLY SCATTERED SHOWERS...S OF 25N BETWEEN 52W-70W.

OTHERWISE...A SFC HIGH PRES RIDGE IS IN CONTROL RUNNING FROM A
1029 MB HIGH S OF THE AZORES NEAR 35N24W TO A 1022 MB CENTER
NEAR 27N62W. THIS NARROW RATHER LOW-LATITUDE RIDGE IS ALLOWING
WINDS TO BE LIGHT TO MODERATE ACROSS MOST OF THE ATLC DISCUSSION
AREA. THE EXCEPTION IS NEAR THE AFRICAN COAST WHERE THE PRES
GRADIENT IS TIGHTENED BETWEEN THE AZORES HIGH AND INVERTED
TROUGHING OVER THE CONTINENT. THE COMBINATION OF THIS HIGH PRES
ALONG WITH DRY STABLE AIR ALOFT ASSOCIATED WITH AN UPPER RIDGE
ALONG 24W/25W IS PROVIDING TRANQUIL CONDITIONS ACROSS THE E AND
MOST OF THE TROPICAL ATLC. ENHANCING STABILITY FURTHER IS A
PLUME OF SAHARAN DUST LOCATED BEHIND THE TROPICAL WAVE ALONG
29W.

$$
CANGIALOSI




This weather bulletin was brought to you by:
www.nashvilleweather.net