000
AXPZ20 KNHC 010948
TWDEP 

TROPICAL WEATHER DISCUSSION 
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
1005 UTC FRI MAY 01 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 
0915 UTC.

...ITCZ...

ITCZ AXIS IS ALONG 04N77W TO 08N91W TO 05N101W TO 11N113W TO 
05N140W. SCATTERED MODERATE ISOLATED STRONG CONVECTION IS NOTED 
WITHIN 60 NM OF 03N110W AND 07N112W AND 07N118W. 

...DISCUSSION...

ALOFT...AN UPPER TROUGH OVER THE N PACIFIC ENTERS THE DISCUSSION 
AREA ALONG 32N134W TO 15N139W. AN UPPER ANTICYCLONE IS CENTERED 
AT 11N120W WITH A RIDGE EXTENDING N TO WELL BEYOND 32N116W. 
UPPER DEBRIS MOISTURE IS DIVING SE INTO THE TROUGH TO THE N OF 
20N...WHILE DRY UPPER AIR IS INDICATED ALONG THE TROUGH AXIS TO 
THE S OF 20N. UPPER DIFFLUENCE UNDER THE RIDGE IS ENHANCING 
CONVECTION ALONG THE ITCZ BETWEEN 118W AND 142W...WITH THE 
DEBRIS MOISTURE ADVECTED NE AS A DENSE TROPICAL PLUME WITHIN THE 
UPPER RIDGE...AND NOW SPILLING OVER THE MOST OF THE WESTERN 
CONUS.  

A SECOND UPPER TROUGH OVER CENTRAL N AMERICA HAS ITS MEAN AXIS 
ALONG 32N93W TO 21N98W THROUGH A DEEP LAYERED CYCLONE AT 16N96W 
AND INTO A SECOND MID TO UPPER CYCLONE AT 09N100W...WITH THE 
TROUGH CONTINUING S ACROSS THE EQUATOR TO A BASE AT 02S102W. A 
STATIONARY UPPER RIDGE EXTENDS W ACROSS COLOMBIA AND THE NW 
CARIBBEAN CRESTING OVER THE BAY OF CAMPECHE. UPPER DIFFLUENCE E
OF THIS UPPER TROUGH IS ENHANCING SOME CONVECTION OVER MEXICO 
WITHIN 120 NM OF A DEVELOPING 1012 MB SURFACE LOW AT 16N97W. 
LIKEWISE UPPER DIFFLUENCE ENHANCED A FEW SHOWERS OVER THE E 
SEMICIRCLE OF THE UPPER CYCLONE AT 09N100W. RESULTANT UPPER 
DEBRIS MOISTURE IS NOTED WITHIN 420 NM EITHER SIDE OF LINE FROM 
01N79W TO 19N95W. OTHERWISE DRY UPPER AIR IS OBSERVED WITHIN THE 
TROUGH...OVER THE AREA N OF 09N BETWEEN 110W AND 100W...AND ALSO 
OVER THE DEEP TROPICS S OF 06N BETWEEN 103W AND 81W AND 
SUPPRESSING ITCZ CONVECTION.

AT THE SURFACE...1022 MB HIGH PRES IS CENTERED NEAR 27N127W WITH 
A RIDGE EXTENDING SW TO BEYOND 21N140W AND A RIDGE ALSO EXTENDS 
SE TO NEAR 13N103W. SOUTHERLY SURFACE WINDS TO THE NW OF THE 
RIDGE ARE IN THE 20 KT RANGE IN ADVANCE OF A SERIES OF WEAK COLD 
FRONTS THAT WILL SWEEP THROUGH THE AREA N OF THE RIDGE OVER THE 
NEXT FEW DAYS. NORTHERLY WINDS TO 20 KT ALONG THE PACIFIC COAST 
OF BAJA WILL RETRACT N TODAY AND SAT THEN INCREASE WHILE 
SPREADING S ALONG THE ENTIRE BAJA PENINSULA SUN.  

$$
NELSON