[Tropical] Tropical Weather Discussion

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AXNT20 KNHC 121742
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
205 PM EDT SUN AUG 12 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.

...SPECIAL FEATURE...

A 1008 MB LOW...ASSOCIATED WITH A VIGOROUS TROPICAL WAVE...IS
LOCATED OVER THE FAR EASTERN ATLANTIC OCEAN ABOUT 150 NM SOUTH
OF THE SOUTHERNMOST CAPE VERDE ISLANDS NEAR 12.5N25W. VISIBLE
IMAGERY SHOWS THE LOW-LEVEL CIRCULATION PARTIALLY EXPOSED TO THE
E OF A CONVECTIVE MASS FROM 10N-14N BETWEEN 25W-30W.
OVERALL...THIS SYSTEM HAS IMPROVED IN ORGANIZATION OVER THE PAST
24 HOURS AND A TROPICAL DEPRESSION COULD FORM LATER TODAY OR
TOMORROW AS THE LOW MOVES WESTWARD AT 15-20 KT.

. ...TROPICAL WAVES...

TROPICAL WAVE IS ALONG 35W/36W S OF 14N MOVING W 10-15 KT. A
SMALL LOW-LEVEL CLOUD SWIRL HAS DEVELOPED...OR PULLED OUT OF THE
ITCZ CONVECTION...LIKELY ASSOCIATED WITH THIS FEATURE. THE
UW-CIMSS TPW PRODUCT DOES NOT SHOW MUCH OF A MOISTURE SURGE BUT
IT'S NOT SURPRISING GIVEN THE WAVE'S LOW AMPLITUDE AND CLOSE
PROXIMITY TO THE MUCH LARGER WAVE/LOW (SPECIAL FEATURE) TO THE E.

TROPICAL WAVE IS RELOCATED E ALONG 43W S OF 14N MOVING W NEAR 10
KT. THIS RELOCATION IS BASED ON THE IMPROVED SATELLITE SIGNATURE
WHICH SHOWS AN INVERTED V-SHAPE TO IT'S CLOUD FIELD AND THE
SURROUNDING STRATOCUMULUS. MID-LEVEL ROTATION HAS ALSO BECOME
EVIDENT ALONG THE AXIS WITHIN THE ITCZ. AT FIRST...IT WAS
THOUGHT THAT THIS COULD HAVE BEEN A MISSED FEATURE RATHER THAN
THE WAVE ALREADY ON THE ANALYSIS...BUT FURTHER INVESTIGATION
SUGGESTS OTHERWISE. MET-9 SATELLITE HOVMOLLER DIAGRAMS DISPLAY A
TRACEABLE SLOW MOVING FEATURE LIKELY ASSOCIATED WITH THIS WAVE.
IN ADDITION...THE UW-CIMSS TPW PRODUCT INDICATES A SLOW MOVING
SLIGHT MOISTURE RIDGE WHICH MATCHES UP WELL WITH THE HOVMOLLER
DIAGRAMS. SCATTRED SHOWERS AND ISOLATED TSTMS ARE CURRENTLY
CONFINED NEAR THE INTERSECTION OF THE ITCZ FROM 7N-11N BETWEEN
39W-45W.

TROPICAL WAVE IS IN THE CENTRAL/WRN CARIB ALONG 76W/77W S OF
23N. EARLIER SATELLITE IMAGERY WAS NOT MUCH HELP IN FINDING THE
LOCATION OF THE WAVE WITH ABUNDANT CIRRUS MASKING THE LOWER
LEVEL CLOUDS. THE TOOL MOST RELIED ON IS THE UW-CIMSS TPW
PRODUCT WHICH CLEARLY SHOWS A WWD MOVING SHARP MOISTURE
GRADIENT...OR SURGE. ALTHOUGH MOST OF THE DRYING IS ASSOCIATED
WITH NLY FLOW ON THE W SIDE OF AN UPPER LOW OVER THE ERN CARIB
WATERS...PART OF IT MAY BE RELATED TO THIS THIS WAVE AS IT HAS
HAD A SURGE-LIKE HISTORY. THE INTERACTION BETWEEN THIS WAVE AND
THE UPPER LOW NEAR THE FLORIDA KEYS IS PRODUCING SCATTERED
SHOWERS AND TSTMS ACROSS A GOOD PORTION OF THE W CARIB AND IN
THE BAHAMAS. DEVELOPMENT OF THIS SYSTEM...IF ANY...IS EXPECTED
TO BE SLOW TO OCCUR AS THE NRN PORTION MOVES NW TOWARD THE
SOUTHERN GULF OF MEXICO AT 5-10 KT.

TROPICAL WAVE IS ALONG 86W/87W S OF 22N MOVING W NEAR 15 KT.
THIS WAVE IS EMBEDDED IN A MOIST UPPER ENVIRONMENT WHICH IS
HELPING TO SUSTAIN SCATTERED MODERATE CONVECTION WITHIN 240 NM
EITHER SIDE OF THE WAVE AXIS.

...THE ITCZ...
THE ITCZ AXIS IS CENTERED ALONG 16N17W 11N26W 9N35W 10N42W
10N61W.  BESIDES THE CONVECTION DISCUSSED ABOVE...ISOLATED
MODERATE IS ALONG THE AFRICAN COAST FROM 12N-16N E OF 18W
ASSOCIATED WITH THE NEXT TROPICAL WAVE.

DISCUSSION...

GULF OF MEXICO...
AN UPPER LOW SPINNING NEAR THE LOWER FLORIDA KEYS IS PRODUCING
AN AREA OF CLOUDINESS AND SCATTERED SHOWERS/TSTMS ACROSS THE SRN
GULF...ESPECIALLY NEAR THE UPPER LOW CENTER. MUCH DEEPER
MOISTURE IS FURTHER S IN THE NW CARIB WHERE A TROPICAL WAVE IS
ADDING A LIFTING MECHANISM. THIS UPPER FEATURE DOES HAVE A WEAK
ILL-DEFINED SFC TROUGH ANALYZED FROM 24N86W 28N84W. THIS TROUGH
ALONG WITH ANOTHER LOW-LEVEL BOUNDARY ACROSS THE N GULF COAST IS
KEEPING A VERY WEAK PRES GRADIENT IN THE REGION WHICH HAS
ALLOWED WINDS TO BE LIGHT AND SOMEWHAT VARIABLE. DRIER
CONDITIONS ARE OBSERVED IN THE NW GULF STILL UNDER THE INFLUENCE
OF ELY UPPER FLOW ON THE S PERIPHERY OF A STRONG UPPER RIDGE
CENTERED OVER THE TEXAS PANHANDLE. MOISTURE IS ANTICIPATED TO BE
ON THE INCREASE OVER THE NEXT COUPLE OF DAYS AS THE UPPER
LOW/TROPICAL WAVE TRACK NWWD DRAWING THE DEEPER MOISTURE INTO
THE SRN HALF OF THE REGION.

CARIBBEAN SEA...
A CONSIDERABLE AMOUNT OF MOISTURE REMAINS ACROSS THE AREA W OF
75W. THE CONTRIBUTING LOW-LEVEL FEATURES CONSIST OF A PAIR OF
TROPICAL WAVES. LIFT NEAR THESE BOUNDARIES ALONG WITH DIFFLUENCE
ALOFT IS SUSTAINING SCATTERED SHOWERS AND TSTMS FROM 12N-22N
BETWEEN 77W-90W. VISIBLE IMAGERY SHOWS SOME TURNING NEAR SW
CUBA...WHICH IS COINCIDENTALLY BETWEEN THE ANALYZED WAVE PSNS.
FOR MORE DETAILS REFER TO THE TROPICAL WAVES SECTION ABOVE. A
LARGE UPPER LOW CENTERED OVER THE NRN LEEWARD ISLANDS IS DRAWING
MUCH DRIER AIR FROM THE N AND SPREADING IT ACROSS THE E CARIB
WATERS...ROUGHLY N OF 14N E OF 70W. SCATTERED SHOWERS AND TSTMS
EXIST NEAR THE BASE OF THE UPPER LOW AND THE ASSOCIATED SELY JET
S OF 14N E OF 67W...WHICH INCLUDES THE SRN WINDWARDS. AN 11Z
QSCAT PASS SHOWS A LARGE AREA OF FRESH TO STRONG TRADES ACROSS
THE E AND CENTRAL CARIB. THESE WINDS ARE EXPECTED TO INCREASE
SLIGHTLY AND SPREAD W TOMORROW BEFORE DECREASING ON TUE AND WED.

THE ATLANTIC OCEAN...
UPPER DIFFLUENCE BETWEEN THE AFOREMENTIONED UPPER LOW LOCATED
NEAR THE LOWER FLORIDA KEYS AND WEAK UPPER RIDGING NEAR 30N75W
IS SUPPORTING CLOUDINESS AND SCATTERED SHOWERS AND TSTMS ACROSS
THE BAHAMAS AND OFFSHORE WATERS. SLIGHTLY LIGHTER ACTIVITY IS
STRUNG OUT ALONG 32N/33N ASSOCIATED WITH A STALLED FRONTAL
BOUNDARY WHICH RUNS E-W FROM THE SE U.S. COAST TO BEYOND
BERMUDA. ELONGATED UPPER TROUGHING LIES FURTHER E WITH TWO
EMBEDDED UPPER LOWS ONE NEAR 25N50W AND THE OTHER OVER THE NRN
LEEWARD ISLANDS. DEBRIS CIRRUS ARE BEING ADVECTED BY A SELY JET
NEAR THE SRN UPPER LOW CONTAINED S OF 20N BETWEEN 51W-61W AND W
OF THE NRN UPPER LOW FROM 25N-28N BETWEEN 56W-61W. UPPER RIDGING
DOMINATES THE PATTERN E OF THE TROUGH WITH AN ANTICYCLONE PARKED
NEAR 23N30W. ABUNDANT DRY AIR ALOFT COVERS MUCH OF THE
ATLC...ESPECIALLY IN THE SUBTROPICS WHERE THE FLOW IS CONFLUENT
BETWEEN THE RIDGE AND A TROUGH N OF THE REGION.

AT THE SFC...THE MAIN WEATHER FEATURE IS A STATIONARY 1026 MB
HIGH CENTERED S OF THE AZORES NEAR 34N30W. THIS MODEST HIGH PRES
SYSTEM IS PRODUCING WIDESPREAD LIGHT TO MODERATE WINDS ACROSS
THE BULK OF THE ATLC BASIN...EXCEPT IN THE TYPICAL STRONGER
AREAS NEAR THE AFRICAN COAST AND THE CARIB ISLANDS WHERE THE
GRADIENT IS SLIGHTLY TIGHTER.

$$
CANGIALOSI




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