000
AXPZ20 KNHC 171555
TWDEP 

TROPICAL WEATHER DISCUSSION   
NWS NATIONAL HURRICANE CENTER MIAMI FL
1605 UTC TUE JAN 17 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 1200 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 
1500 UTC.

...INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH...
MONSOON TROUGH EXTENDS FROM 08N76W TO 04.5N79W TO 03N91W TO 
04N94W...WHERE IT TRANSITIONS TO ITCZ...CONTINUING ON TO 06N110W 
TO 06.5N124W TO BEYOND 05N140W. SCATTERED MODERATE TO STRONG 
CONVECTION NOTED FROM NEAR THE EQUATOR N TO TROUGH E OF 83W. 
SCATTERED MODERATE TO STRONG CONVECTION NOTED WITHIN 180 NM N OF 
TROUGH BETWEEN 87W AND 92W. SCATTERED MODERATE TO STRONG 
CONVECTION NOTED WITHIN 120 NM N OF AXIS BETWEEN 108W AND 123W. 

...DISCUSSION...
SHARP MIDDLE TO UPPER LEVEL SOUTHERN STREAM TROUGH EXTENDS FROM 
32N130W TO 13N133W THEN TO BROAD BASE NEAR 05N138W. TROUGH HAS 
BEEN PROGRESSING EWD PAST 24 HOURS...AND IS LARGELY IN PHASE 
WITH A SHORTWAVE TROUGH IN SW QUADRANT OF BROAD UPPER TROUGH 
ACROSS NW N AMERICA. A BROAD UPPER LEVEL RIDGE IS N OF 08N-10N E 
OF THE TROUGH WITH MAIN AXIS ALONG 97W/98W ACROSS SE MEXICO. 
THIS RIDGE FORECAST TO REMAIN IN PLACE NEXT FEW DAYS AND HALT 
FOREWORD PROGRESS OF SOUTHERN STREAM UPPER TROUGH...FORCING 
DECOUPLING FROM PROGRESSIVE SHORTWAVE WITHIN BROAD N AMERICAN 
TROUGH...WITH A MID TO UPPER CYCLONE FORECAST TO PINCH OF AND BE 
LEFT BEHIND NEAR 25N128W BY WED EVENING. A 65-85 KT JETSTREAM IS 
MOVING THROUGH THE BASE OF THE SOUTHERN STREAM TROUGH AND OVER W 
PORTIONS OF THE RIDGE...AND ACTING TO ENHANCE CONVECTION N OF 
THE ITCZ AND TO THE E OF TROUGH WITH JET DYNAMICS AND BROAD 
DIFFLUENT FLOW...WHILE THE NARROW ZONE OF DEEP CONVECTION NOTED 
ABOVE IS FURTHER DIVERTING THE UPPER LEVEL FLOW ALOFT. 

EPAC HIGH PRES RIDGE EXTENDS FROM A 1029 MB HIGH NEAR 34N130W SE 
TO THE BAJA CALIFORNIA PENINSULA NEAR 28N114W...AND S TO LOW 
PRES ALONG THE ITCZ. THE PRES GRADIENT TO THE S OF THE RIDGE IS 
PRODUCING AN AREA OF FRESH TRADEWINDS FROM 06N TO 17N W OF 
128W...WHERE COMBINED SEAS ARE GENERALLY 8 TO 9 FT IN MIXED N 
AND NE SWELL. THE PRES GRADIENT BETWEEN THE HIGH AND LOWER PRES 
ACROSS NW MEXICO AND THE BAJA PENINSULA IS ALSO PRODUCING A 
SMALL AREA OF FRESH N-NW WINDS N OF 29N E OF 118W...WHERE 
OBSERVATIONS SUGGEST SEAS TO 9 FT IN MIXED NW SWELL. THE HIGH 
WILL BE FORCED SLIGHTLY SE DURING THE NEXT 12-36 HOURS...AND 
INCREASE THE PRES GRADIENT INSIDE THE GULF OF CALIFORNIA... 
LEADING TO FRESHENING NWLY WINDS THIS EVENING THROUGH WED.

...GAP WINDS...
TIGHT PRES GRADIENT OVER SOUTHERN MEXICO IS WEAKENING SLIGHTLY 
ALLOWING FOR NOCTURNAL DRAINAGE FLOW TO ENHANCE THE GAP WIND 
FLOW SPILLING INTO THE GULF OF TEHUANTEPEC...PRODUCING NLY WINDS 
20-25 KT AND SEAS TO 8 FT. THIS FLOW IS EXPECTED TO DIMINISH TO 
AROUND 20 KT THIS AFTERNOON...POSSIBLY BRIEFLY FALLING BELOW 20 
KT THIS EVENING...BEFORE NOCTURNAL DRAINAGE FLOW YIELDS NLY 
WINDS 20-25 KT LATE TONIGHT THROUGH WED MORNING. HIGH PRES 
BEHIND A WEAK COLD FRONT EXPECTED ACROSS THE NE GULF WED IS 
EXPECTED TO INCREASE THE GRADIENT WIND FLOW THROUGH THE GULF OF 
TEHUANTEPEC TO NEAR 30 KT BY WED EVENING. 

NELY WINDS 20-25 KT ARE BLOWING THROUGH THE GULF OF PAPAGAYO AND 
DOWNSTREAM TO ABOUT 92W THIS MORNING...AND WILL GENERALLY 
PERSIST IN THIS MANNER THROUGH THU. MEANWHILE NLY WINDS AROUND 
20 KT BLOWING THROUGH THE GULF OF PANAMA ARE ALSO EXPECTED TO 
CONTINUE THROUGH THE NEXT 48 HOURS.

$$
STRIPLING