[Tropical] Tropical Weather Discussion

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AXNT20 KNHC 140539
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
205 AM EDT FRI SEP 14 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 0000 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH
0515 UTC.

...SPECIAL FEATURES...

THE NINTH STORM OF THE YEAR...TROPICAL STORM INGRID...FORMS TO
THE E OF THE LESSER ANTILLES. INGRID IS CENTERED NEAR 14.7N
48.7W AT 14/0300 UTC OR ABOUT 735 NM EAST OF THE LESSER ANTILLES
MOVING WEST-NORTHWEST AT 5 KT. ESTIMATED MINIMUM CENTRAL
PRESSURE IS 1002 MB. MAXIMUM SUSTAINED WIND SPEED IS 35 KT WITH
GUSTS TO 45 KT. SEE LATEST NHC FORECAST/ADVISORY UNDER AWIPS/WMO
HEADERS MIATCMAT3/WTNT23 KNHC FOR MORE DETAILS. NIGHT CHANNEL
VIS IMAGES SHOW AN OVERALL SLIGHT IMPROVED STRUCTURE OF INGRID
WITH THE LOW-LEVEL CENTER POSITIONED BETWEEN WEAK BANDS TO THE N
AND W OF THE CENTER AND VERY NEAR THE PRIMARY CONVECTIVE AREA.
HOWEVER...MODERATE WESTERLY SHEAR CONTINUES TO AFFECT THE
CIRCULATION. IR IMAGERY SHOWS NUMEROUS MODERATE CONVECTION
...OVAL-LIKE SHAPED...FROM 13.5N-15.5N BETWEEN 48W-49W. GIVEN
THE MODERATE SHEAR ENVIRONMENT ONLY SLIGHT INTENSIFICATION IS
FORECAST IN THE SHORT TERM. THEREAFTER STEADY STATE OR WEAKENING
IS LIKELY AS WESTERLY SHEAR INCREASES.

...TROPICAL WAVES...

TROPICAL WAVE IS NEAR THE CAPE VERDE ISLANDS ALONG 23W S OF 18N
MOVING W 10-15 KT. A 1010 MB LOW IS ANALYZED ALONG THE WAVE AXIS
NEAR 10N...CONFIRMED BY A BROAD AREA OF CYCLONIC TURNING IN AN
EARLIER QSCAT PASS. OVERALL...THIS WAVE HAS BECOME A LITTLE LESS
DEFINED THAN 24 HOURS AGO WITH CONVECTION MINIMAL NEAR THIS
FEATURE. THE UW-CIMSS TPW ANIMATION SHOWS A WELL DEFINED
MOISTURE PLUME ASSOCIATED WITH THIS WAVE...MAKING IT EASY TO
TRACK.

HIGH AMPLITUDE TROPICAL WAVE IS ALONG 40W S OF 21N MOVING W 5 TO
10 KT. THE NRN PART OF THE WAVE HAS FRACTURED BASED ON THE
POLEWARD MOVEMENT OF MOISTURE SEEN ON SATELLITE IMAGES AND THE
UW CIMSS TPW ANIMATION. A SLOPING TROUGH WAS ANALYZED TO REFLECT
THIS RUNNING FROM 22N40W TO 27N37W. THIS SPLIT IS BEING
INDUCED BY A DEEP LAYER TROUGH ASSOCIATED WITH A LOW PRES SYSTEM
WELL N OF THE REGION. THE NRN PART...TROUGH...CURRENTLY LIES IN
AN UPPER DIFFLUENT ZONE WHICH HAS FUELED SCATTERED MODERATE
CONVECTION WITHIN 180 NM E OF THE ANALYZED AXIS. THE SRN PORTION
OF THE WAVE IS MUCH LESS DEFINED THAN PREVIOUS DAYS WITH LITTLE
SIGNIFICANT SHOWER ACTIVITY.

TROPICAL WAVE IS IN THE W CARIBBEAN ALONG 82W S OF 22N MOVING W
15 KT. THE NARROW MOISTURE SWATH...USED TO TRACK THIS WAVE ON
THE TPW ANIMATION OVER THE PAST FEW DAYS...HAS BECOME MORE
COMPLEX DUE TO THE UPPER FEATURES AFFECTING THE MOISTURE
PATTERN. HOWEVER...IT APPEARS AS IF THIS WAVE COULD BE A LITTLE
FURTHER W AND WILL REEVALUATE AT 06Z. THE INTERACTION BETWEEN
THIS WAVE...THE ITCZ...AND DIFFLUENCE ALOFT...IS MAINTAINING
CLUSTERS OF SCATTERED MODERATE CONVECTION ACROSS THE SW CARIB
ROUGHLY S OF 15N W OF 75W.

...THE ITCZ...
ITCZ AXIS IS CENTERED ALONG 13N17W 9N29W 13N39W 11N54W 10N63W.
BESIDES FOR THE CONVECTION ASSOCIATED WITH THE TROPICAL WAVES
AND RECENTLY UPGRADED T.S. INGRID...SCATTERED MODERATE
CONVECTION IS FROM 4N-8N BETWEEN 36W-42W.

DISCUSSION...

THE GULF OF MEXICO...
THE WEATHER ACROSS THE NRN GULF HAS GREATLY CALMED DOWN AS
HUMBERTO HAS TRACKED WELL INLAND AND WEAKENED TO A DEPRESSION.
CURRENTLY...THE MOISTURE PATTERN IN THE REGION IS MAINLY
GOVERNED BY UPPER LEVEL FEATURES. THE PREDOMINANT SYSTEM IS AN
NE-SW ELONGATED UPPER HIGH CENTERED NEAR 28N90W. A FAIR AMOUNT
OF CLOUDINESS AND ISOLATED SHOWERS ARE LOCKED WITHIN THE
RIDGE...ROUGHLY N OF 26N. A WEDGE OF DRY AIR IS EVIDENT ON WATER
VAPOR IMAGERY BETWEEN 24N-26N DUE TO A SLIGHTLY CONFLUENT
PATTERN BETWEEN THE RIDGE AND TROUGHING TO THE S AND E. MOISTURE
INCREASES AGAIN S OF 24N CLOSER TO THE PROXIMITY OF THE
TROUGHING. THE ONLY AREA OF NOTABLE CONVECTION AT THE MOMENT IS
IN THE BAY OF CAMPECHE E OF 94W ASSOCIATED WITH AN UPPER LOW
OVER GUATEMALA. SFC WINDS ARE MOSTLY LIGHT OUT OF THE S TO
SE...EXCEPT SWLY BEHIND THE TRAILING TROUGH ASSOCIATED WITH
HUMBERTO.

THE CARIBBEAN SEA...
CLUSTERS OF SCATTERED MODERATE CONVECTION HAVE FIRED UP OVER THE
SW CARIB THIS EARLY MORNING ROUGHLY S OF 15N W OF 75W. THE
CONTRIBUTING LOW-LEVEL SYSTEMS INCLUDE A WEAK TROPICAL WAVE
ALONG 82W AND THE ITCZ WHICH BASED ON QSCAT DATA APPEARS TO RUN
ALONG 10N-11N. CONVERGENCE ALONG THESE BOUNDARIES COUPLED WITH
INSTABILITY AND DIFFLUENCE ALOFT ARE THE MAIN CONTRIBUTORS.
FAIRLY STRONG UPPER WLY FLOW IS OBSERVED ACROSS THE MAJORITY OF
THE CARIB SET UP BETWEEN AN UPPER HIGH OVER COLOMBIA AND UPPER
TROUGHING OVER CUBA. THIS FLOW IS TRANSPORTING DEBRIS HIGH LEVEL
CLOUDINESS ACROSS THE AREA CONTAINED W OF 75W. THE AIR GREATLY
DRIES OUT E OF 75W...THOUGH THERE ARE A COUPLE OF EXCEPTIONS.
INSTABILITY ASSOCIATED WITH DEEP LAYERED TROUGHING N OF THE ERN
CARIB IS PRODUCING SCATTERED SHOWERS AND ISOLATED TSTMS ACROSS
PUERTO RICO AND THE VIRGIN ISLANDS. SIMILAR WEATHER IS LIKELY
OVER THE SRN WINDWARD ISLANDS ASSOCIATED WITH ITCZ ENERGY.

THE ATLANTIC OCEAN...
RECENTLY UPGRADED TROPICAL STORM INGRID IS THE MAIN FEATURE OF
INTEREST ACROSS THE TROPICAL AND SUBTROPICAL ATLC DISCUSSION
ZONE. FOR DETAILS AND REFERENCES REFER TO THE SPECIAL FEATURE
SECTION ABOVE. ONE OTHER AREA OF ACTIVE WEATHER IS IN THE
CENTRAL ATLC ASSOCIATED WITH THE NRN EXTENSION OF A TROPICAL
WAVE. FOR DETAILS SEE ABOVE. THE REMAINDER OF THE SFC PATTERN IS
DOMINATED BY TYPICAL SUBTROPICAL RIDGING. THERE REMAINS A FAIRLY
PRONOUNCED WEAKNESS IN THIS RIDGE BETWEEN 35W-45W INDUCED BY A
PERSISTENT BUT WEAKENING AREA OF LOW PRES WELL N OF THE AREA.

ALOFT...A COMPLEX PATTERN REMAINS IN PLACE ACROSS THE CENTRAL
AND W ATLC. THE LARGE SCALE FEATURES CONSIST OF THE ERN
PERIPHERY OF A GULF OF MEXICO HIGH...ANOTHER UPPER HIGH LOCATED
NE OF BERMUDA NEAR 36N52W...AN UPPER LOW S OF BERMUDA NEAR
27N64W AND ANOTHER UPPER LOW CENTERED NEAR 25N50W. THE ONLY
SYSTEM CURRENTLY PRODUCING ANY SENSIBLE WEATHER IS THE UPPER LOW
S OF BERMUDA...WHICH APPEARS TO HAVE A RELATED LOW-LEVEL
TROUGH...PRODUCING SCATTERED SHOWERS FROM 22N-26N BETWEEN
60W-67W. FARTHER E...THE PERSISTENT DEEP LAYER TROUGH MENTIONED
ABOVE COMBINED WITH VERY LARGE UPPER LOW OVER SRN SPAIN HAS
CREATED QUITE A BIT OF TROUGHING ACROSS THE N PART OF THE E ATLC
DISCUSSION AREA. THE TROPICAL E AND CENTRAL ATLC IS STILL
DOMINATED BY AN E-W RIDGE COVERING THE AREA FROM THE LESSER
ANTILLES EWD WITH A MEAN AXIS ALONG 17N WITH SEVERAL EMBEDDED
ANTICYCLONES.

$$
CANGIALOSI




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