000
AXPZ20 KNHC 270950
TWDEP 

TROPICAL WEATHER DISCUSSION   
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
1005 UTC FRI OCT 27 2006

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 0600 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 
0845 UTC.

...SPECIAL FEATURE...
.TROPICAL DEPRESSION EIGHTEEN E NEAR 16.6N 106.4W 1007 MB AT 
0900 UTC OCT 27 MOVING W OR 265 DEG AT 8 KT. MAXIMUM SUSTAINED 
WINDS 25 KT GUSTS 35 KT. FORECAST/ADVISORIES ON TROPICAL 
DEPRESSION EIGHTEEN-E ARE ISSUED UNDER WMO HEADER WTPZ23 KNHC 
AND UNDER AWIPS HEADER MIATCMEP3. CLUSTER OF MODERATE TO STRONG 
CONVECTION WITHIN 60 NM OVER THE E QUADRANT. 

...ITCZ...

ITCZ AXIS IS CENTERED ALONG 8N78W 9N95W 11N116W 10N127W 14N137W.
SCATTERED MODERATE CONVECTION NEAR 6N79W 6N81W 6N85W AND 
13N109W. SCATTERED MODERATE WITHIN 60 NM OF 16N133W AND ISOLATED 
MODERATE NEAR 14N140W.

...DISCUSSION...

THE REGION IS DOMINATED BY A MID LEVEL RIDGE ALONG 20N THAT 
EXTENDS W TO 124W. AN OLD CUTOFF MID LEVEL LOW OVER THE NW 
PORTION OF THE REGION THAT HAS OPENED UP AND EXTENDS FROM 
30N120W SW TO 22N140W. AN IMPRESSIVE SHORTWAVE IS DIGGING S OVER 
THE SRN PLAINS TONIGHT AND IS LOWERING MID LEVEL HEIGHTS OVER 
NRN MEXICO. ON THE SURFACE TONIGHT TROPICAL DEPRESSION 18 HAS 
FORMED IN THE ERN PACIFIC AND IS BEING STIRRED BY THE MID LEVEL 
RIDGE ALONG 20N..THUS IT'S WWD MOVEMENT. A LOW LEVEL TROUGH 
ALONG 135W IS MOVING W ON THE SRN SIDE OF THE PACIFIC HIGH. THE 
GRADIENT BETWEEN THE RIDGE AND THE TROUGH HAS ENHANCED THE NE 
TRADES W OF 120W AND S OF 22N TO 25 KT.

LATER DAY 1 LOOK FOR THE MID LEVEL RIDGE OVER MEXICO TO SLIDE 
WWD AND CENTER ITSELF NEAR 20N110W. ON THE BACK SIDE OF THE 
STRONG SHORTWAVE A NLY MID LEVEL FLOW WILL MOVE INTO NRN MEXICO. 
THE ELONGATED MID LEVEL TROUGH OVER THE NW PORTION OF THE REGION 
WILL CHANGE LITTLE. ON THE SURFACE LATER DAY 1 THE TROPICAL 
DEPRESSION IS FORECAST TO STRENGTHEN TO A TROPICAL STORM WHILE 
CONTINUING TO MOVE WWD. THE STORM IS MOVING W ON THE S SIDE OF 
THE MID LEVEL RIDGE. THE TROUGH ALONG 135W MOVES TO NEAR 138W 
AND THE GRADIENT BEGINS TO WEAKEN W OF 130W. GAP WINDS REMAIN 
LIGHT WHILE CROSS EQUATORIAL SLY WINDS INCREASE S OF 5N E OF 
100W TO 20 KT. W OF 100W WINDS ARE MOSTLY SELY TO 20 KT.

FOR DAY 2 THE MID LEVEL RIDGE ENLARGES AND BECOMES THE DOMINATE 
FEATURE OVER THE REGION. THE RIDGE WILL BE CENTERED NAER 20N115W 
AND BUILDS NWD ALONG 110W AS HEIGHTS RISE OVER THE SW US WITH 
THE DEPARTING SHORTWAVE. A NEW TROUGH MOVES TOWARD THE REGION 
FROM THE NW AND BEGINS TO KICK OUT THE ELONGATED TROUGH THAT HAS 
BEEN STATIONARY OVER THE NW PORTION. THE MID LEVEL FLOW BECOMES 
MORE SWLY AND INCREASES WITH THE TROUGH LIFTING NE AWAY FROM THE 
AREA. ON THE SURFACE DAY 2 THE TROPICAL STORM IS FORECAST TO 
CONTINUE MOVING W ALONG 16N WITH LITTLE STRENGTHENING. THE 
PACIFIC RIDGE IS FORECAST TO WEAKEN DUE TO THE MID LEVEL TROUGH 
MOVING OVER THAT REGION.  THE LOW LEVEL TROUGH MOVES W OF THE 
REGION AND THE TRADES DECREASE TO 10 TO 15 KT. GAP WINDS THROUGH 
TEHUANTEPEC INCREASE TO GALE FORCE AS HIGH PRESSURE BUILDS OVER 
THE SW GULF. CROSS EQUATORIAL SLY WINDS REMAIN 20 KT AND GUSTY S 
OF 5N AND E OF 100W. 

$$
RRG