000
AXPZ20 KNHC 182205
TWDEP 

TROPICAL WEATHER DISCUSSION
NWS NATIONAL HURRICANE CENTER MIAMI FL
2205 UTC TUE SEP 18 2012

TROPICAL WEATHER DISCUSSION FOR THE EASTERN PACIFIC OCEAN FROM 
THE EQUATOR TO 32N...EAST OF 140W. THE FOLLOWING INFORMATION IS 
BASED ON SATELLITE IMAGERY...WEATHER OBSERVATIONS...RADAR...AND 
METEOROLOGICAL ANALYSIS.

BASED ON 1800 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 
2100 UTC.

...SPECIAL FEATURE...
TROPICAL STORM LANE AT 20.6N 129.4W AT 2100 UTC MOVING NW OR 320 
DEG AT 7 KT.  MAXIMUM SUSTAINED WIND 45 GUSTS TO 55 KT AND PRES 
OF 999 MB.  SCATTERED MODERATE ISOLATED STRONG CONVECTION WITHIN 
45 NM N QUADRANT OF CENTER.  LANE QUICKLY WEAKENED AS IT MOVED 
OVER COOLER WATERS AND FACES INCREASED S WIND SHEAR.  IT IS 
EXPECTED TO DOWNGRADE TO TROPICAL DEPRESSION LATE TUE AND A 
REMNANT LOW PRES CENTER WED.  SEE LATEST NHC FORECAST/ADVISORY 
UNDER AWIPS/WMO HEADERS MIATCMEP2/WTPZ22 KNHC FOR ADDITIONAL 
DETAILS.

...INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH...
MONSOON TROUGH FROM 10N86W TO 13N92W TO 08N113W THEN ITCZ AXIS 
TO 10N119W THEN RESUME FROM 09N123W TO 08N127W TO 12N136W TO 
BEYOND 11N140W.  SCATTERED MODERATE ISOLATED STRONG CONVECTION 
WITHIN 180 NM S OF AXIS FROM 94W TO 110W.  SCATTERED MODERATE 
CONVECTION WITHIN 150 NM S OF AXIS E OF 88W.
 
...DISCUSSION...
DEEP LAYER TROUGH EXTEND FROM UPPER LEVEL CYCLONE AT 38N137W TO 
18N140W MAINTAINS VERY DRY AIR MASS N OF 15N W OF 120W.  BROAD 
UPPER LEVEL ANTICYCLONE OVER SOUTHERN PART OF GULF OF CALIFORNIA 
DOES ALSO KEEP DRY AIR MASS N OF 20N E OF 115W.  STRONG 
SOUTHERLY WINDS BETWEEN BOTH FEATURES ADVECT TROPICAL MOISTURE 
FROM T.S. LANE NORTHWARD...BUT THE STRONG SHEAR AND COOL SEA 
SURFACE TEMPERATURES HAVE SIGNIFICANTLY WEAKENED LANE. 

HIGH PRES AT 33N131W EXTENDS RIDGE E-SE INTO NW PORTION OF BASIN 
EXPECTED TO SHIFT S OVER NEXT FEW DAYS TIGHTENING PRES GRADIENT 
N OF CONVERGENCE ZONE AND INCREASING NE TRADES TO A FRESH BREEZE 
W OF 125W BY LATE WED.  LIGHT TO MODERATE WINDS AND SEAS TO 5-7 
FT EXPECTED TO PREVAIL ELSEWHERE ACROSS BASIN THROUGH WED.

GAP WINDS...BUILDING HIGH PRES BEHIND GULF OF MEXICO COLD FRONT 
WILL FORCE STRONG N WINDS THROUGH ISTHMUS LATE TONIGHT INTO GULF 
OF TEHUANTEPEC BY EARLY WED.  DRAINAGE WINDS INCREASE MAY 
ENHANCE GUSTS TO REACH NEAR GALE FORCE. 

$$
WALLY BARNES