000
AXPZ20 KNHC 201006
TWDEP 

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
1005 UTC TUE MAY 20 2008

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 
0945 UTC.

...TROPICAL WAVES...

A TROPICAL WAVE WAS PREVIOUSLY ANALYZED FROM 03N TO 13N ALONG 
94W BUT IS CURRENTLY VERY DIFFICULT TO LOCATE. ONLY A FEW 
SHOWERS ARE NOTED ALONG THE ESTIMATED AXIS POSITION...AND SHIP 
REPORTS ARE IN THE 5 TO 10 KT RANGE. THE UPPER ENVIRONMENT 
BECOMES EVEN LESS FAVORABLE FOR THE CONVECTION IN ABOUT 30 HOURS 
SO WAVE POSITIONS ARE NOT DEPICTED ON MARINE GRAPHICS. 

...ITCZ...

THE ITCZ AXIS IS ALONG LINE 09N84W TO 07N93W TO 11N106W TO 
04N140W. SCATTERED MODERATE ISOLATED STRONG CONVECTION IS MOVING 
OFF THE COAST OF COLOMBIA TO THE N OF 03N AND E OF 80W. SIMILAR 
CONVECTION IS ALSO NOTED WITHIN 150 NM EITHER SIDE OF LINE FROM 
12110W TO 07N123W. SCATTERED MODERATE CONVECTION WITH A FEW 
TSTMS IS OBSERVED WITHIN 30 NM EITHER SIDE OF LINE FROM 08N95W 
TO 16N100W AND ALSO IN THE GULF OF TEHUANTEPEC.

...DISCUSSION...

A STATIONARY UPPER LEVEL CYCLONE IS CENTERED AT 24N139W WITH A 
TROUGH SW TO NEAR 14N140W. DRY UPPER AIR CIRCLES THE CYCLONE 
WITHIN ABOUT 120 NM N AND WITHIN 180 NM S SEMICIRCLES OF THE  
CENTER. AN UPPER CYCLONE HAS CUT OFF OVER CENTRAL OLD MEXICO 
NEAR 24N107W WITH AN UPPER TROUGH EXTENDING S TO 17N110W. A
LARGE AREA OF DRY UPPER AIR IS INDICATED OVER THE W SEMICIRCLE 
OF THE CYCLONE...ROUGHLY WITHIN 360 NM EITHER SIDE OF LINE FROM 
16N105W TO 23N118W TO 34N122W.

AN UPPER ANTICYCLONE IS OVER THE CARIBBEAN NEAR 17N82W WITH A 
RIDGE EXTENDING SW TO ANOTHER UPPER ANTICYCLONE NEAR 11N115W... 
WITH A RIDGE EXTENDING NW ALONG 25N125W TO A CREST AT 35N122W
SEPARATING THE FLOW ASSOCIATED WITH THE UPPER CYCLONES DESCRIBED 
ABOVE. 

UPPER DIFFLUENCE ENHANCED CONVECTION YESTERDAY ALONG THE ITCZ 
BETWEEN 132W AND 148W WITH THE RESULTANT DEBRIS MOISTURE STILL 
SPREADING N AS A NARROW PLUME WITHIN 120 NM EITHER SIDE OF LINE 
08N140W TO 20N130W TO 30N132W WHERE THE MOISTURE FANS OUT WITH 
SOME TURNING CYCLONICALLY W IN RESPONSE TO THE CYCLONE AT 
24N139W. ANOTHER BRANCH OF THIS TROPICAL PLUME TURNS NE ALONG 
THE UPPER RIDGE AND EVENTUALLY ACROSS CALIFORNIA.   

UPPER DIFFLUENCE IS ALSO ENHANCING CONVECTION ALONG THE ITCZ 
BETWEEN 98W AND 128W. THE ASSOCIATED UPPER DEBRIS MOISTURE IS 
ADVECTED NE ACROSS CENTRAL AMERICA BETWEEN 103W AND 93W...WITH 
THE TROPICAL PLUME CONTINUING ENE ACROSS THE SE GULF OF MEXICO 
AND SOMEWHAT EVAPORATING AS IT CROSSES FLORIDA S OF 27N.  

DEBRIS MOISTURE OVER CENTRAL AMERICA E OF 93W APPEARS TO 
EVAPORATE IN DRY AIR ALOFT OVER THE W CARIBBEAN. HOWEVER THE 
WESTERN EXTENT OF THIS CARIBBEAN DRY AIR HAS BEEN SHIFTING E 
AWAY FROM CENTRAL AMERICA FOR THE PAST DAY OR SO. PERHAPS THIS 
WILL ALLOW DEBRIS MOISTURE FROM E PAC ITCZ CONVECTION TO 
EVENTUALLY REACH THE SE CONUS AND HELP IGNITE SOME MUCH NEEDED 
CONVECTION.

AT THE SURFACE...HIGH PRESSURE IS NEARLY STATIONARY NEAR 30N140W 
WITH A RIDGE EXTENDING SE TO NEAR 18N110W. THE LOW LEVEL 
EASTERLY TRADES SW OF THIS RIDGE ARE MOSTLY IN THE 15 KT RANGE.
SOUTHERLY SWELL TO 8 FT HAS BEEN CROSSING THE EQUATOR OVER THE 
WATERS S OF 20N W OF 105W VERIFIED BY ALTIMETER DATA. 
NW WINDS AND NW SWELL ARE INCREASING ALONG THE NORTHERN BAJA 
PENINSULA AND ARE EXPECTED TO FURTHER INCREASE AS A SERIES OF 
FRONT S SWEEP INTO AREA THE NEXT 3 DAYS. EXPECTING 20 TO 30 KT 
WED NIGHT AND THU WITH SEAS 10 TO 15 FT OVER WATERS N OF 26N E 
OF 127W. 

$$
NELSON