000
AXPZ20 KNHC 191010
TWDEP 

TROPICAL WEATHER DISCUSSION 
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
1005 UTC TUE MAY 19 2009

TROPICAL WEATHER DISCUSSION FOR THE EASTERN PACIFIC OCEAN FROM 
THE EQUATOR TO 32N...EAST OF 140W. 

BASED ON 0600 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 
0900 UTC.

...ITCZ...

THE ITCZ AXIS WAS ALONG 07N78W TO 08N90W TO 09N104W TO 12N118W 
TO 06N130W TO 07N140W. SCATTERED TO NUMEROUS MODERATE WITH 
ISOLATED STRONG CONVECTION WAS WITHIN 240 NM OF AXIS BETWEEN 
117W AND 97W. SCATTERED MODERATE CONVECTION WAS WITHIN 120 NM OF 
AXIS BETWEEN 123W AND 119W...AND ALSO E OF 92W. 

...DISCUSSION...

ALOFT...A DEEP LAYERED CYCLONE HAS CUT OFF NEAR 29N124W. AN 
UPPER TROUGH EXTENDS SE TO 16N112W AND IS SWINGING SLOWLY NE 
WITH TIME. AN UPPER LEVEL ANTICYCLONE IS CENTERED AT 10N135W 
WITH A SHORTWAVE RIDGE EXTENDING N WITH ITS CREST FROM 26N137W 
TO A SHARP CREST AT 12N122W. SOME UPPER MOISTURE IS SPREADING 
INTO THE AREA NEAR 19N135W. OTHERWISE THESE UPPER FEATURES 
COMBINE TO DRY OUT THE UPPER LEVELS W OF 128W AND N OF 12N 
BETWEEN 128W AND 117W.

A QUASI STATIONARY UPPER ANTICYCLONE IS CENTERED NEAR 11N101W 
WITH A SHORTWAVE RIDGE AMPLIFYING N TO A CREST OVER SOUTHERN NEW 
MEXICO. UPPER DIFFLUENCE UNDER THIS BROAD RIDGE HAS BEEN 
ENHANCING CONVECTION ALONG AND TO THE N OF THE ITCZ BETWEEN 90W 
AND 120W...WITH MOST OF THE DEBRIS MOISTURE SPREADING N OVER THE 
ENTIRE UPPER LEVELS OF OLD MEXICO...WITH SOME OF THE MOISTURE 
SPILLING SE OVER THE GULF OF MEXICO AND THE W CARIBBEAN.

A STATIONARY UPPER RIDGE EXTENDS W ACROSS NORTHERN VENEZUELA TO 
A CREST OVER W COLOMBIA. AN UPPER TROUGH EXTENDS S ALONG 73W 
ACROSS THE PANAMA AND COLOMBIA BORDER. THIS MID TO UPPER TROUGH 
SEPARATES THE FLOW ASSOCIATED WITH THE S AMERICAN RIDGE FROM THE 
TROPICAL E PACIFIC RIDGE DESCRIBED ABOVE. E PACIFIC ITCZ 
CONVECTION IS ENHANCED BETWEEN 83W AND 77W WITH SOME OF THE 
RESULTANT DEBRIS MOISTURE ADVECTED NE ACROSS THE E CARIBBEAN 
INTO THE SUBTROPICAL CENTRAL N ATLC.
     
AT THE LOW LEVELS...A RIDGE EXTENDS OVER THE AREA N OF 20N W OF 
132W. A LOW LEVEL TROUGH EXTENDS ALONG 30N126W TO 22N127W...AND
IS DRIFTING W WITH TIME. THE GRADIENT BETWEEN THIS TROUGH AND 
RIDGE IS SUPPORTING NE WINDS TO 20 KT AND SEAS TO 8 FT A FEW 
DEGREES TO THE W OF THE TROUGH. THE TROUGH IS EXPECTED TO 
CONTINUE DRIFTING W BUT GRADUALLY FILL TUE NIGHT. A 1016 MB HIGH 
PRES HAS FORMED E OF THE TROUGH NEAR 25N123W...INCREASING THE 
GRADIENT ALONG THE W COAST OF THE BAJA PENINSULA N OF 22N WITH 
SURGES OF NW WINDS TO 20 KT. THESE CONDITIONS ARE EXPECTED TO 
CONTINUE THROUGH WED.

AN EARLY SEASON TROPICAL WAVE HAS MOVED ACROSS NRN S AMERICA 
DURING THE PAST COUPLE OF DAYS AND HAS LIKELY CROSSED 70W 
TONIGHT. THIS WAVE IS A LOW LEVEL FEATURE...WITH LITTLE ENERGY 
EXPECTED TO EMERGE OVER THE EPAC DURING THE NEXT 36 HOURS AS THE 
WAVE MOVES W ACROSS THE MOUNTAIN RANGES OF COLOMBIA. 

SEVERAL WEAK CYCLONIC CURLS AND SWIRLS ARE NOTED EMBEDDED ALONG 
THE ITCZ TONIGHT...WITH THE TWO MOST WELL DEFINED LOWS ALONG 
102W AND 118W...BOTH WITH VERY ACTIVE CONVECTION ON THEIR ERN 
SEMICIRCLES. WINDS AROUND 20 KT ARE LIKELY FOUND IN THE WRN HALF 
OF THE LOW ALONG 118W.

GAP WINDS...HIGH PRESSURE OVER THE GULF OF MEXICO WILL CONTINUE 
TO DRIVE NLY WINDS AT 20 TO 30 KT THROUGH THE GULF OF 
TEHUANTEPEC AND THEN ARCHING SW AND DOWNWIND TO NEAR 100W FOR 
THE NEXT 24 HOURS...BEFORE WINDS BEGIN TO DIMINISH TO AROUND 20 
KT BY 48 HOURS. AN EVENING QUIKSCAT PASS REVEALED GALE FORCE 
WINDS THROUGH THE GULF AND DOWNSTREAM FOR ABOUT 2 DEGREES...AND 
A GALE WARNING HAS BEEN ISSUED. THESE WINDS ARE EXPECTED TO 
WEAKEN SLIGHTLY TO 20 TO 30 KT BY 18Z THIS AFTERNOON...WITH 
MODEL GUIDANCE SUGGESTING A POSSIBLE PULSE OF NEAR GALE FORCE 
WINDS AGAIN TONIGHT.

$$
STRIPLING