[Tropical] Tropical Weather Discussion

[EMWIN Server]

AXNT20 KNHC 211740
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
205 PM EDT WED MAY 21 2008

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 20W/21W S OF 12N MOVING W 10 KT.
VISIBLE IMAGES SHOW A WELL DEFINED BUT BROAD AREA OF LOW-LEVEL
CYCLONIC TURNING CENTERED NEAR 6N. SCATTERED SHOWERS AND TSTMS
ARE MAINLY WITHIN 300 NM E OF THE AXIS S OF 8N.

A TROPICAL WAVE IS ALONG 52W S OF 10N MOVING W 10-15 KT. VISIBLE
IMAGERY REVEALS MODERATE LOW-LEVEL CYCLONIC TURNING ALONG THE
WAVE AXIS. HOWEVER...MOST OF ITS DEEP CLOUDINESS HAS BEEN
ABSORBED BY A HIGH AMPLITUDE UPPER TROUGH WHICH IS NOW E OF THE
WAVE.

TROPICAL WAVE IS ALONG 77W S OF 13N MOVING W 10-15 KT. THIS WAVE
IS MAINLY INLAND OVER W COLOMBIA. WHILE ONLY A WEAK SIGNATURE OF
THIS WAVE IS APPARENT ON SATELLITE IMAGERY...THE MIMIC TPW
ANIMATION DOES SHOW FAIRLY GOOD CONTINUITY OF THIS FEATURE. THIS
WAVE MAY BE ENHANCING CONVECTION OVER THE SW CARIBBEAN. SEE
CARIBBEAN DISCUSSION FOR MORE DETAILS.

..THE ITCZ...
ITCZ AXIS IS CENTERED ALONG 8N13W 5N22W 3N30W 2N37W 4N50W.
SCATTERED MODERATE TO STRONG CONVECTION IS WITHIN 30 NM EITHER
SIDE OF THE AXIS BETWEEN 29W-31W. ISOLATED MODERATE CONVECTION
IS S OF 3N W OF 47W.

...DISCUSSION...

GULF OF MEXICO...
A STRONG SW TO W UPPER FLOW REGIME CONTINUES OVER THE REGION
KEEPING THE MID AND UPPER LEVELS FAIRLY MOIST. HOWEVER...UNLIKE
YESTERDAY THERE IS NOT A SYNOPTIC SCALE LOW-LEVEL BOUNDARY TO
PROVIDE ENHANCED LIFT. THEREFORE...SHOWER AND TSTM ACTIVITY IS
FAIRLY LIMITED. IR IMAGES SHOW THE THICKEST CLOUDINESS OVER THE
W GULF FROM 20N-27N BETWEEN 87W-96W. LIGHTNING DATA HAS RECENTLY
DETECTED A FEW FLASHES IN THIS CLOUDINESS...SO ISOLATED
ACTIVITY SEEMS LIKELY IN THE OUTLINED AREA.  OTHERWISE...THE
REGION LIES ON THE W PERIPHERY OF A CENTRAL ATLC SFC RIDGE
PROVIDING MAINLY 10-15 KT S TO SW FLOW AND WARM/HUMID
CONDITIONS. SLY WINDS ARE EXPECTED TO INCREASE OVER THE W WATERS
LATER TONIGHT AND THU AS LOW PRES DEEPENS OVER THE ROCKIES.

CARIBBEAN SEA...
IR IMAGERY AND LIGHTNING DATA INDICATE SCATTERED SHOWERS AND
TSTMS OVER THE SW WATERS MAINLY S OF 15N W OF 77W. THIS ACTIVITY
IS ASSOCIATED WITH AN UPPER DIFFLUENT PATTERN ON THE SW SIDE OF
A BROAD UPPER RIDGE WITH SOME POSSIBLE ENHANCEMENT FROM A NEARBY
TROPICAL WAVE. OTHERWISE...A SUBSIDENT ENVIRONMENT IS IN PLACE
CAPPING THE TYPICAL STREAMS OF LOW-LEVEL CLOUDS AND ALLOWING
MAINLY FAIR WEATHER TO DOMINATE. ELY TRADES ARE STRONGEST...NEAR
20 KT...OVER THE S CENTRAL WATERS WITH MAINLY 10-15 KT SE TO S
WINDS OBSERVED ELSEWHERE.

ATLANTIC OCEAN...
BROAD MID-UPPER RIDGING COVERS THE W ATLC WITH STRONG ZONAL FLOW
LYING ON ITS N PERIPHERY OVER THE N PORTION OF THE DISCUSSION
ZONE. THIS STRONG UPPER FLOW IS TRANSPORTING HIGH LEVEL CLOUDS N
OF 28N W OF 50W AND IS GENERATING ISOLATED TSTMS OVER THE NW
BAHAMAS...AS NOTED IN LIGHTING DATA. ELSEWHERE...LIKE THE
CARIBBEAN...DRY STABLE AIR IS EMBEDDED IN THE CORE OF THE RIDGE
PROVIDING MAINLY FAIR WEATHER W OF 50W. A HIGH AMPLITUDE
LONGWAVE TROUGH LIES TO THE E OF THE RIDGE ANCHORED BY AN UPPER
LOW NEAR 27N33W AND EXTENDS SW ALONG 18N34W 6N48W. UPPER
DIFFLUENCE AND STRONG SW FLOW ALOFT E OF THE TROUGH AXIS ARE
GENERATING A SWATH OF CLOUDINESS...WITH EMBEDDED SCATTERED
SHOWERS AND TSTMS...WITHIN 180 NM E OF THE TROUGH AXIS S OF 18N.
A LARGE SCALE MID-UPPER RIDGE IS SITUATED OVER W AFRICA AND IS
LIKELY ENHANCING CONVECTION WITHIN THE ITCZ.

AT THE SFC...A 1024 MB HIGH CENTERED NEAR 29N44W IS PROVIDING
MODERATE NE/E TRADES ACROSS THE TROPICS AND MAINLY LIGHT WINDS
ACROSS THE SUBTROPICS. HOWEVER...THE EXCEPTION TO THIS IS OVER
THE W ATLC N OF 26N W OF 62W WHERE STRONG SW WINDS EXIST IN
RESPONSE TO A LOW PRES SYSTEM OVER THE N ATLC.

$$
CANGIALOSI/BELL


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