000
AXPZ20 KNHC 042128
TWDEP 

TROPICAL WEATHER DISCUSSION    
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
2205 UTC FRI MAY 04 2007

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 
2130 UTC.

...ITCZ...
AXIS ALONG 7N78W 10N94W 7N110W 9N120W 4N140W. SCATTERED MODERATE 
TO STRONG WITHIN 120-180 NM EITHER SIDE OF AXIS BETWEEN 108W AND 
120W. SCATTERED MODERATE WITHIN 60 NM EITHER SIDE OF AXIS 
BETWEEN 123W AND 126W...AND WITHIN 90 NM OF THE AXIS BETWEEN 83W 
AND 85W.

...DISCUSSION...
N OF 20N...HIGHLY AMPLIFIED PATTERN IN PLACE WITH REX BLOCK 
FEATURE JUST W OF DISCUSSION AREA ALONG 145W CONSISTING OF A DRY 
MID/UPPER LOW CYCLONIC CIRCULATION NEAR 26N145W...AND UPPER 
RIDGE TO THE N. ASSOCIATED 1031 MB SFC HIGH IS CENTERED NEAR 
33N143W. AFTERNOON SHIP OBSERVATIONS SHOW A CONTINUATION OF 
FRESH TO STRONG TRADES ON THE SOUTHERN PERIPHERY OF THE HIGH AS 
FAR S AS 8N. TO THE EAST OF THE UPPER RIDGE...A BROAD MID TO 
UPPER LEVEL TROUGH DIGGING INTO THE NORTHERN ROCKIES IS 
PROVIDING UPPER SUPPORT TO A 1010 MB SURFACE LOW PRESSURE SYSTEM 
AND ASSOCIATED COLD FRONT MOVING FROM THE CENTRAL CALIFORNIA 
COAST INTO SOUTHERN CALIFORNIA. THE TIGHT GRADIENT BETWEEN THE 
SURFACE HIGH PRES TO THE W AND THE LOW OFF THE CALIFORNIA COAST 
HAS SET UP GOOD NW FETCH PROMOTING LARGE NLY SWELLS OF UP TO 13 
FT ACROSS THE AREA.  

FRESH TO STRONG NWLY WINDS ARE ALSO EVIDENT OFF THE BAJA COAST 
ON THE WESTERN EDGE OF THE HIGH PRES. LITTLE CHANGE IS EXPECTED 
IN CONDITIONS THROUGH SAT AS THE RIDGE REMAINS IN PLACE. 
HOWEVER...THE UPPER RIDGE WILL WEAKEN BY LATE SAT...AHEAD OF A 
DEEP UPPER TROUGH ADVANCING THROUGH THE CENTRAL 
PACIFIC...ALLOWING THE SURFACE RIDGE TO WEAKEN SLIGHTLY. THE NW 
FLOW OFF OF BAJA WILL SUBSEQUENTLY DIMINISH ON SUN...AS WILL 
TRADE FLOW S OF THE RIDGE ON SUN.

S OF 20N...UPPER TROUGH EXTENDS OFF THE SE CONUS THROUGH THE WRN 
BAHAMAS...W CARIBBEAN TO THE EAST PACIFIC NEAR 10N90W. FAIRLY 
DRY MID LEVEL AIR ASSOCIATED WITH THE UPPER TROUGH IS 
SUPPRESSING CONVECTION OVER THE EAST PACIFIC. HOWEVER...UPPER 
DIVERGENCE E OF THE UPPER TROUGH IS ENHANCING CONVECTION OFF THE 
COLOMBIAN COAST AND GULF OF PANAMA. FURTHER W...UPPER LEVEL 
ANTICYCLONE CENTERED NEAR 11N120W IS SIMILARLY AIDING CONVECTION 
ALONG AND N OF THE ITCZ BETWEEN 108W AND 119W.

$$
COBB