000
AXPZ20 KNHC 240959
TWDEP 

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
1005 UTC SUN AUG 24 2008

TROPICAL WEATHER DISCUSSION FOR THE EASTERN PACIFIC OCEAN FROM 
THE EQUATOR TO 32N...EAST OF 140W. 

BASED ON 0000 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 
0315 UTC.

...SPECIAL FEATURE...

TROPICAL STORM JULIO CENTERED NEAR 21.5N 109.6W AT 24/0900 UTC 
MOVING NNW OR 330 DEG AT 12 KT. ESTIMATED MINIMUM CENTRAL 
PRESSURE IS 1005 MB. MAXIMUM SUSTAINED WIND SPEED IS 35 KT WITH 
GUSTS TO 45 KT. SATELLITE IMAGERY REVEALS A SINGLE CLUSTER OF 
DEEP CONVECTION WITH CLOUD TOP TEMPERATURES TO -80C NEARLY 30 NM 
W OF BUT NOT OVER THE CENTER. THE CONVECTION HAS A WEDGE-LIKE 
SHAPE...MOST NARROW CLOSEST TO THE CENTER AND MOST EXPANSIVE 
FARTHER W...EXTENDING OUTWARD UP TO 150 NM OVER THE W 
SEMICIRCLE. NIGHTTIME VISIBLE IMAGERY ELUCIDATES THE LOW-LEVEL 
CENTER FARTHER E...ENTIRELY DEVOID OF CONVECTION EXCEPT FOR ONE 
THUNDERSTORM CELL WHICH HAS SPROUTED UP IMMEDIATELY TO THE SE. 
THE CONVECTIVE STRUCTURE OF THE STORM CONCEPTUALLY MATCHES A 
TROPICAL CYCLONE EMBEDDED IN A STRONG EASTERLY SHEARED 
ENVIRONMENT. SEE LATEST NHC FORECAST/ADVISORY UNDER AWIPS/WMO 
HEADERS MIATCMEP1/WTPZ21 KNHC FOR MORE DETAILS.

...TROPICAL LOWS...

AN EVENING QUIKSCAT PASS FROM YESTERDAY INDICATED A WEAK SURFACE 
LOW NEAR 08N88W ALONG THE ITCZ...POSSIBLY ASSOCIATED WITH A 
TROPICAL WAVE WHICH MARCHED THROUGH THE CARIBBEAN BASIN LATE 
THIS PAST WEEK. TWO SHIP REPORTS NEAR THIS AREA SUGGEST THAT THE 
LOW HAS BEEN DRIFTING WNW TO NW OVERNIGHT...AND GLOBAL MODELS 
AGREE WITH THIS TYPE OF MOTION OVER THE NEXT DAY OR SO. 
SCATTERED MODERATE CONVECTION IS NOTED WELL TO THE W AND NW OF 
THE SURFACE LOW...AND IT IS NOT CLEAR WHETHER IT IS ASSOCIATED 
WITH THIS FEATURE OR NOT.

IN RESPONSE TO THE FORMATION OF TROPICAL STORM JULIO TO THE S OF 
THE BAJA PENINSULA...THE ITCZ HAS RISEN FAR TO THE N AND EXTENDS 
FROM JULIO WELL TO THE WSW TO BROAD 1010 MB SURFACE LOW LOCATED 
NEAR 13N126W. THIS SURFACE LOW IS ASSOCIATED WITH THE REMNANTS 
OF FORMER TROPICAL STORM ISELLE AND IS FORECAST BY THE GLOBAL 
MODELS TO REMAIN NEARLY STATIONARY FOR THE NEXT 48 HOURS BEFORE 
SLOWLY WEAKENING. 

...ITCZ...

INTERTROPICAL CONVERGENCE ZONE AXIS 08N78W TO 07N100W THEN FROM 
T.S. JULIO TO 13N126W TO 08N140W. SCATTERED MODERATE CONVECTION 
WITHIN 300 NM S AND 90 NM N OF AXIS FROM 111W TO 130W. NUMEROUS 
STRONG CONVECTION WITHIN 60 NM EITHER SIDE OF 13N BETWEEN 125W 
AND 129W.  

WIDELY SCATTERED MODERATE ISOLATED STRONG CONVECTION FROM 07N TO 
16N BETWEEN 90W AND 95W.

...DISCUSSION...

THE EASTERN END OF THE ITCZ RUNS FROM SOUTHERN CENTRAL AMERICA 
TO AROUND 07N100W....WHERE IT BECOMES DISCONTINUOUS. AS NOTED... 
A WEAK SURFACE LOW IS ANALYZED ALONG THE WAVE NEAR 08N88W AND IS 
DRIFTING SLOWLY WNW TO NW. N OF THE LOW...TWO QUIKSCAT PASSES 
FROM YESTERDAY REVEALED UP TO 20 KT OF NE OR E FLOW BEING 
FUNNELED THROUGH THE GULF OF PAPAGAYO...WITHIN ABOUT 30 NM OF 
11N E OF 87W. THESE WINDS ARE EXPECTED TO PERSIST INTO THIS 
AFTERNOON OR TONIGHT BEFORE LOW PRESSURE MOVES FARTHER 
NW...CAUSING THE LOW-LEVEL FLOW TO VEER SE.

FARTHER W...THE WESTERN END OF THE ITCZ RUNS FROM TROPICAL STORM 
JULIO WELL WSW TO 07N140W.  A NEARLY STATIONARY AND WEAK SURFACE 
LOW WITHIN THE ITCZ WAS NOTED NEAR 14.5N114W IN HIGH RESOLUTION 
QUIKSCAT IMAGERY LATE YESTERDAY. THE SAME QUIKSCAT IMAGERY ALSO 
INDICATED SW TO W 20 TO 30 KT WINDS WITHIN 360 NM SE SEMICIRCLE 
OF THE LOW...WHICH SEEM TO BE PART OF WHAT HAS BEEN AN ENHANCED 
CROSS-EQUATORIAL FLOW OBSERVED THE LAST COUPLE OF DAYS. GLOBAL 
MODELS AND THEIR COMPANION OCEAN MODELS HAVE NOT INITIALIZED 
THESE CONDITIONS WELL. AS A RESULT...NOAA WAVEWATCH III GUIDANCE 
HAS SEVERELY UNDERESTIMATED WAVE HEIGHTS IN THE VICINITY OF THE 
STRONG WINDS. IN FACT...WAVE HEIGHTS ARE ESTIMATED TO PEAK 
AROUND 11 FT WITHIN THIS AREA.

ELSEWHERE...THE REMNANTS OF WHAT WAS TROPICAL STORM ISELLE NEAR 
13N125W HAVE BECOME ASSIMILATED WITHIN THE ITCZ WITHIN THE LAST 
DAY OR TWO. AS HAS BEEN THE CASE THE LAST SEVERAL DAYS...WITHIN 
360 NM SE SEMICIRCLE OF THE LOW SW TO W WINDS OF 20 TO 25 KT ARE 
NOTED...WITH NE WINDS TO 20 KT WITHIN 420 NM NW SEMICIRCLE. PEAK 
SEAS ARE LIKELY UP TO 10 TO 11 FT OVER THE SE SEMICIRCLE AND UP 
TO 8 OR 9 FT OVER THE NW SEMICIRCLE.

FINALLY...LONG PERIOD SE SWELL COMING OUT OF THE SOUTHERN 
HEMISPHERE ARE GRADUALLY SUBSIDING S OF ABOUT 10N BETWEEN 95W 
AND 125W. HOWEVER...A NEW SWELL TRAIN FROM THE SW SHOULD BEGIN 
TO ARRIVE OVER THESE FAR SOUTHERN WATERS LATER MON AND 
TUE...WITH SOME OF THE SWELL LIKELY REACHING THE MEXICAN COAST 
BY LATE TUE. MARINERS CAN EXPECT PEAK SEAS OF UP TO 9 TO 10 FT 
MON AND TUE AS THE SWELL ARRIVE.

$$
KIMBERLAIN