000
AXPZ20 KNHC 210947
TWDEP 

TROPICAL WEATHER DISCUSSION    
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
1005 UTC MON MAY 21 2007

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 
0845 UTC.

...ITCZ...
INTERTROPICAL CONVERGENCE ZONE AXIS ALONG 6N77W 8N90W 9N102W 
7N112W 7N121W 6N140W. SCATTERED STRONG CONVECTION FROM 6N TO 12N 
BETWEEN 90W AND 109W. SCATTERED MODERATE AND STRONG WITHIN 60 NM 
OF A LINE FROM 7N112W TO 7N140W.

SCATTERED STRONG CONVECTION WITHIN 90 NM OF THE COAST FROM 4N78W 
TO 7N80W TO 9N85W TO 11N89W TO 13N89W TO 14N92W.

...DISCUSSION...

GRADUAL EROSION OF THE MID LEVEL RIDGE OVER NRN MEXICO/SW CONUS 
TONIGHT WILL ALLOW THE PERSISTENT SHORTWAVE ALONG 114W TO 
FINALLY MOVE E. MID LEVEL RIDGING CONTINUES TO STRENGTHEN 
BETWEEN 130W AND 140W. WATER VAPOR IMAGERY SHOWS THIS RIDGE 
BUILDING RAPIDLY NWD ALONG 150W AHEAD OF A VERY STRONG UPPER LOW 
OVER THE MID PACIFIC. SRN BRANCH OF THE WESTERLIES CONTINUE TO 
WORK THEIR WAY S OF THE RIDGE ALONG 20N WITH WEAK IMPULSES 
EMBEDDED..ONE OF WHICH IS ALONG 135W. ON THE SURFACE TONIGHT A 
1028 MB HIGH ANCHORES THE PACIFIC RIDGE. THE HIGH RIDGES SE TO 
15N106W AND IS PRODUCING NE TRADES 20 TO 25 KT W OF 130W. WINDS 
ALONG THE BAJA COAST ARE MOSTLY 10 TO 15 KT WITH NW SWELL TO 8 
FT. BACK N OF 27N BETWEEN 119W AND 125W NW WINDS INCREASE TO 25 
KT WITH SWELL TO 12 FT. GAP WINDS ARE MOSTLY LIGHT WHILE SW 
WINDS TO 20 KT ARE EVIDENT S OF 4N E OF 95W. CONVECTION IS 
FLARING UP ALONG THE ITCZ E OF 100W TONIGHT IN WHATS CALLED THE 
MONSOONAL TROUGH. IT'S ACTS AS AN INCUBATOR FOR TROPICAL 
DISTURBANCES WHICH MIGRATE WNW AND OCCASIONALLY DEVELOP. 

LATER DAY 1 WHILE THE MID LEVEL RIDGE OVER NRN MEXICO WEAKENS 
WHICH SHOULD ALLOW THE SHORTWAVE TO MOVE EWD..MID LEVEL HEIGHTS 
BEGIN FALLING OVER THE WRN CONUS WHICH SLOWS THE MOVEMENT OF THE 
SHORTWAVE. A STRONG MID LEVEL RIDGE HOLDS FIRM BETWEEN 130W AND 
140W WITH LITTLE CHANGE TO THE SRN BRANCH ALONG 20N. ON THE 
SURFACE LATER DAY 1 EVERYTHING REMAINS STATUS QUO WITH NO 
APPRECIABLE CHANGES. 

FOR DAY 2 WHATS LEFT OF THE SHORTWAVE MOVES E TO 95W. MID LEVEL 
HEIGHTS FALL SLOWLY ALONG 110W AS AN UPPER TROUGH DEVELOPS OVER 
THE WRN CONUS. THE MID LEVEL RIDGE BETWEEN 130W AND 140W SHOWS 
SIGNS OF WEAKENING AS THE MID LEVEL FLOW W OF THE RIDGE BECOMES 
MORE WLY. SRN BRANCH OF THE WESTERLIES WEAKENS DAY 2. A WEAK 
IMPULSE MOVING SLOWLY E TO NEAR 118W. ON THE SURFACE DAY 2 THE 
PACIFIC RIDGE WITH IT'S 1027 MB CENTER NEAR 32N136W SHOWS SIGNS 
OF RE-ORIENTING ITSELF MORE N/S. THIS WILL MAINTAIN MODERATE NLY 
WINDS N OF 27N BETWEEN 120W AND 130W BUT NE TRADES RELAX SOME TO 
20 KT AND MAINLY W OF 128W. GAP WINDS REMAIN LIGHT AS DO NW 
WINDS ALONG THE BAJA COAST. MODERATE SW WINDS TO 20 KT CONTINUES 
S OF 5N E OF 95W AS MONSOONAL PRESSURE FALLS SLIGHTLY. 

$$
RRG