000
AXPZ20 KNHC 280940
TWDEP 

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
1005 UTC SAT NOV 28 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...
AXIS ALONG 07N80W TO 07N97W TO 06N104W TO 11N120W TO 09N130W TO 
10N137W TO 09N140W.  SCATTERED MODERATE CONVECTION WITHIN 75 NM 
OF AXIS E OF 102W. SCATTERED MODERATE ISOLATED STRONG CONVECTION 
WITHIN 240 NM S OF AXIS FROM 115W-136W. 

...DISCUSSION...
UPPER LEVEL TROUGH EXTENDS FROM CENTRAL TEXAS THROUGH MEXICO TO 
15N115W WITH VERY DRY AIR MASS WITHIN 10 DEGREES NW OF AXIS.  
TROPICAL MOISTURE ADVECTED NE BY 75 KT SW JET CORE INTO SRN 
MEXICO.  BROAD UPSTREAM RIDGE CENTERED AT 10N131W MAINTAINS 
ANTICYCLONIC FLOW ACROSS REMAINDER BASIN W OF 115W.  RIDGE CREST 
FLATTENED BY DEEP LAYER LARGE AMPLITUDE TROUGH SKIRTING NW 
PORTION OF BASIN.  JET STREAM 120 KT ROTATING AROUND TROUGH BASE 
IS ADVECTING LARGE AMOUNTS OF MOISTURE INTO CALIFORNIA JUST N OF 
E PAC BORDER. 
 
AT THE SURFACE...
HEALTHY HIGH PRES 1036 MB AT 38N136W WITH RIDGE EXTENDING TO 
20N118W TIGHTENS GRADIENT WITH TROUGH RIDING ITCZ ALONG 121W AND 
WEAK LOW PRES 1008 MB AT 06N100W.  TROUGH UNDER STRONG N SHEAR 
MOVE W INTO SLIGHTLY MORE FAVORABLE CONDITIONS ALOFT AND 
ABUNDANT TROPICAL MOISTURE ALONG ITCZ TO FEED CONTINUED 
CONVECTION.  FURTHER E...LOW PRES REMAIN AT EDGE OF CARIBBEAN 
UPPER LEVEL RIDGE NEXT 24 HRS BUT THEN DRIFT W INTO STRONGLY 
HOSTILE SW WINDS ALOFT AND DRY AIR MASS EXPECTED TO WEAKEN IT.   

RIDGE ALSO PRODUCING LARGE LONG PERIOD NW SWELL UP TO 16 FT 
WHICH PROPAGATE SE ACROSS E PAC W OF 100W.

...GAP WINDS...
HIGH PRES IN GULF OF MEXICO WEAKENED TO 1023 MB AND DRIFTED E 
VEERING WINDS EFFECTIVELY CUTTING OFF AIR FLOW ACROSS ISTHMUS OF 
TEHUANTEPEC.  GALE FORCE WINDS DIMINISH TO LESS THAN GALE FORCE 
WITHIN NEXT 6 HRS AND BELOW 20 KT WITHIN 30 HRS.

EASTERLY TRADES IN W CARIBBEAN CONTINUE TO FUNNEL WINDS THROUGH 
GULF OF PAPAGAYO AND DOWNSTREAM WATERS TO NEAR 91W THROUGH SUN 
TO MAINTAIN FRESH TO STRONG BREEZE. 

$$
WALLY BARNES