[Tropical] Tropical Weather Discussion

[EMWIN Server]

AXNT20 KNHC 072350
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
805 PM EDT SUN OCT 07 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 1800 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH
2315 UTC.

...SPECIAL FEATURE...

A BROAD 1003 MB LOW PRESSURE AREA IS OVER THE NW CARIBBEAN NEAR
17N85W. THIS SYSTEM IS GENERATING SCATTERED SHOWERS AND TSTMS
BETWEEN BELIZE...HONDURAS...AND THE CAYMAN ISLANDS. SURFACE
PRESSURES CONTINUE TO FALL IN THE AREA...BUT THERE IS NO
WELL-DEFINED CIRCULATION CENTER. UPPER-LEVEL WINDS ARE GRADUALLY
BECOMING MORE FAVORABLE AND SLOW DEVELOPMENT OF THIS SYSTEM IS
POSSIBLE OVER THE NEXT FEW DAYS AS THE LOW REMAINS NEARLY
STATIONARY. ANOTHER AIR FORCE HURRICANE HUNTER MISSION IS
SCHEDULED TO INVESTIGATE THE AREA ON MONDAY...IF NECESSARY.

...TROPICAL WAVES...

TROPICAL WAVE IS ALONG 55W S OF 20N MOVING W TO NW NEAR 10 KT. A
1010 MB LOW IS LOCATED ALONG THE WAVE AXIS NEAR 17N. THE
CIRCULATION REMAINS AN EXPOSED LOW LEVEL SWIRL...WITH MOST OF
THE LIMITED SHOWER/TSTM ACTIVITY E OF THE CENTER FROM 15N-18N
BETWEEN 50W-54W. DEVELOPMENT OF THIS SYSTEM IS NOT ANTICIPATED
DUE TO UNFAVORABLE UPPER LEVEL WINDS. THE SOUTHERN END OF THE
WAVE IS ENHANCING SOME SHOWER/TSTM ACTIVITY OVER FRENCH GUIANA
AND SURINAME.

...THE ITCZ...
ITCZ AXIS IS CENTERED ALONG 11N14W 6N30W 8N40W 10N52W. THE ITCZ
REMAINS FAIRLY ACTIVE THIS EVENING. SCATTERED MODERATE TO
ISOLATED STRONG CONVECTION IS OVER THE TROPICAL ATLANTIC FROM
3N-11N BETWEEN 23W-50W. THE UW-CIMSS TPW PRODUCT SUGGESTS THAT A
WEAK TROPICAL WAVE IS PROBABLY NEAR 36W WHERE THERE IS A SMALL
BULGE OF MOISTENED AIR. THIS TROPICAL WAVE MAY BE ADDED TO THE
0000 UTC SURFACE MAP.

DISCUSSION...

THE GULF OF MEXICO...
A SFC RIDGE DOMINATES THE SE U.S. AND THE NORTHERN GULF WATERS.
PRES GRADIENT BETWEEN THIS RIDGE AND A SFC LOW OVER THE NW
CARIBBEAN CONTINUES TO PRODUCE MODERATE TO FRESH ELY SFC WINDS
OVER FLORIDA AND THE NE QUADRANT OF THE GULF. THESE WINDS ARE
ADVECTING MOSTLY SHALLOW SHOWERS FROM THE ATLC ACROSS FLORIDA
AND INTO THE E GULF WATERS. SCATTERED SHOWERS AND TSTMS ARE A
LITTLE MORE CONCENTRATED BETWEEN THE YUCATAN PENINSULA AND WRN
LOUISIANA. THIS ACTIVITY IS ASSOCIATED WITH DEEP LAYER INVERTED
TROUGH WHICH EXTENDS NWD FROM THE LOW IN THE NW CARIBBEAN
THROUGH THE YUCATAN PENINSULA INTO THE GULF TO 29N95W. THE
TROUGH IS WELL DEFINED IN THE WIND SHIELD. A LARGE CLUSTER OF
MODERATE TO STRONG CONVECTION HAS DEVELOPED OVER THE YUCATAN
PENINSULA. W OF TROUGH...MOSTLY CLEAR SKIES PREVAIL UNDER THE
INFLUENCE OF A MODERATE SUBSIDENT ENVIRONMENT SUPPORTED BY AN
UPPER HIGH LOCATED OVER CENTRAL MEXICO. MODERATE TO FRESH ELY
WINDS WILL CONTINUE TO BLOW ACROSS THE E AND CENTRAL GULF OVER
THE NEXT DAY OR SO.

THE CARIBBEAN SEA...
THE BROAD AREA OF LOW PRESSURE CENTERED BETWEEN BELIZE...
HONDURAS...AND THE CAYMAN ISLANDS REMAINS THE MAIN FEATURE OF
INTEREST ACROSS THE BASIN. THIS SYSTEM IS BEING MONITORED FOR
SLOW DEVELOPMENT. SEE SPECIAL FEATURE FOR MORE DETAILS. SHOWERS
AND TSTMS HAVE DEVELOPED AGAIN ACROSS CUBA. ACCORDING TO
LIGHTNING DATA...TSTMS ARE MORE CONCENTRATED OVER THE WESTERN
PART OF THE ISLAND. SIMILAR ACTIVITY IS SEEN OVER JAMAICA. A
MOIST AND UNSTABLE SLY FLOW ON THE E SIDE OF THE BROAD AREA OF
LOW PRESSURE CENTERED OVER THE NW CARIBBEAN IS ENHANCING THIS
CONVECTIVE ACTIVITY. UPPER-LEVEL FLOW IS ALSO DIFFLUENT OVER
THIS REGION BETWEEN TROUGHING OVER THE BAHAMAS AND RIDGING OVER
THE CENTRAL CARIBBEAN. THE TRADE WINDS ARE EXPECTED TO REMAIN
INTERRUPTED OVER THE WESTERN CARIBBEAN...W OF 70W DURING THE
NEXT FEW DAYS. LIGHT TO MODERATE ELY WINDS ARE BLOWING ACROSS
THE REMAINDER OF THE AREA.

THE ATLANTIC OCEAN...
AN ELONGATED SFC TROUGH PERSISTS ACROSS MUCH OF THE WEST AND
CENTRAL ATLC EXTENDING FROM THE SE BAHAMAS ALONG 24N60W TO
29N42W. AN UPPER-LEVEL TROUGH WITH A SERIES OF EMBEDDED UPPER
LOW IS SUPPORTING THIS SURFACE FEATURE. THERE ARE A COUPLE OF
AREAS ALONG THE TROUGHING WHERE LOW LEVEL VORTICITY APPEARS TO
BE MAXIMIZED. ONE IS LOCATED SEVERAL HUNDRED MILES
NORTH-NORTHWEST OF PUERTO RICO NEAR 23N69W...WHERE THERE IS A
DISORGANIZED AREA OF SHOWERS AND TSTMS. THE SECOND ONE IS NEAR
28N50W AND IS ALSO GENERATING SCATTERED MODERATE CONVECTION.
UPPER-LEVEL WINDS REMAIN STRONG ENOUGH TO INHIBIT ANY TROPICAL
DEVELOPMENT OF THESE SYSTEMS. ELY WINDS REMAINS MODERATE TO
FRESH N OF THE TROUGHING DUE TO THE TIGHTENED GRADIENT BETWEEN
THE TROUGH AND HIGH PRES OVER THE MID ATLC COAST. AS IS USUAL
FOR THIS TIME OF THE YEAR...COMPUTER MODELS DEVELOP A SERIES OF
LOW PRES AREAS ALONG THE TROUGHING OVER THE NEXT SEVERAL DAYS
THAT MOVE MAINLY NE ALONG THE BOUNDARY...BUT CURRENTLY HAVE LOW
CONFIDENCE IN THESE LOWS WITH FAIRLY WIDE DIVERGENCE BETWEEN THE
GLOBAL MODELS. MUCH QUIETER WEATHER EXISTS E OF 40W UNDER THE
INFLUENCE OF A SFC RIDGE WITH A 1022 MB HIGH NEAR 31N30W. THIS
IS KEEPING WINDS LIGHT IN THE SUBTROPICS AND MODERATE IN THE
TROPICS... EXCEPT SLIGHTLY STRONGER 20-25 KT NLY WINDS OFF THE
COAST OF NW AFRICA WHERE THE GRADIENT REMAINS TIGHTER PER USUAL.
THE MAIN MID TO UPPER LEVEL FEATURE OVER THE TROPICS IS AN UPPER
HIGH LOCATED NEAR 12N37W. THE UPPER-LEVEL FLOW IS QUITE STRONG
OUT OF THE W TO SW ON THE NORTHERN SIDE OF THE TROPICAL RIDGE.
UPPER DIFFLUENCE BETWEEN THE AFOREMENTIONED UPPER-LEVEL TROUGH
AND THIS RIDGE IS SUPPORTING THE SHOWER/TSTM ACTIVITY OVER THE
CENTRAL ATLC NEAR 28N50W.

$$
GR




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