Subject: Pacific-EN: Tropical Weather Discussion

From: SIU Weather Processor <[email-masked]>
Date: Wed, 12 Jan 2005 03:21:40 -0600

AXPZ20 KNHC 120921
TWDEP

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
1005 UTC WED JAN 12 2005

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
0900 UTC.

..ITCZ...
INTERTROPICAL CONVERGENCE ZONE AXIS IS ALONG LINE 4N77W 4N90W
5N120W 10N140W.  SCATTERED MODERATE CONVECTION IS WITHIN 75 NM
EITHER SIDE OF AXIS WEST OF 130W.

..DISCUSSION...
N OF 20N...
BROAD MID/UPPER LEVEL RIDGE WITH AXIS FROM 32N130W TO BEYOND
20N130W SITS BETWEEN A LARGE DEEP LAYERED LOW W OF AREA NEAR
150W...AND ANOTHER POWERFUL LOW PRESSURE SYSTEM INLAND OVER
UTAH. DESPITE THE RIDGING OVER AREA...SW FLOW IS VERY STRONG
WITH A JET STREAM OF 110-130 KT OVER FAR NW CORNER OF AREA.
DOWNSTREAM OF THE RIDGE AXIS AND S OF THE SW UNITED STATES
LOW...A STRONGER NW JET STREAM OF 130-150 KT EXTENDS FROM
32N122W TO OVER NORTHERN BAJA CALIFORNIA PENINSULA AND NW
MEXICO.  OVER MAINLAND MEXICO...STRONG SW-W FLOW IS MAINLY N OF
27N...WITH MUCH LIGHTER WINDS S OF 27N. A SURFACE COLD FRONT
EXTENDS FROM SE ARIZONA ACROSS THE NORTHERN PORTIONS OF THE SEA
OF CORTEZ AND BAJA CALIFORNIA TO 25N120W.  WIDELY SCATTERED
SHOWERS ARE ALONG THE FRONT. MOST OF THE SIGNIFICANT CLOUDINESS
IS W OF 130W WHERE DEEP TROPICAL MOISTURE IS BEING PULLED
NORTHWARD BY STRONG LOW NEAR 150W. THIS AREA WILL BE THE FOCUS
FOR INCREASING CONVECTION AND SCATTERED THUNDERSTORMS OVER THE
NEXT 24 HOURS AS THE LOW MOVES SLOWLY EASTWARD. THE RIDGE OVER
THE AREA WILL AMPLIFY ALONG 128W DURING THE NEXT 24 HOURS AS THE
SW UNITED STATES LOW DIGS SOUTHWARD OVER THE SOUTHERN ROCKIES
AND NORTHERN MEXICO. AS A RESULT...STRONG UPPER LEVEL NW WINDS
WILL PUSH SOUTHWARD BEHIND THE LOW OVER NORTHERN HALF OF
MEXICO.

S OF 20N W OF 100W...
RELATIVELY TRANQUIL CONDITIONS PREVAIL AS TWO HIGHS CONTROL THE
FLOW IN THIS AREA. THE RIDGE MENTIONED IN SECTION N OF 20N IS
ANCHORED BY A HIGH CENTERED NEAR 12N132W...WITH ANOTHER SMALLER
HIGH LOCATED NEAR 9N110W. AS A RESULT...ANTICYCLONIC UPPER LEVEL
FLOW AND ASSOCIATED MODERATE TO LOCALLY STRONG SUBSIDENCE IS
OBSERVED OVER MOST OF AREA. THE EXCEPTION TO THIS IS A WEAK
NE-SW MID/UPPER TROUGH WHICH SPLITS THE HIGHS...EXTENDING FROM
WESTERN MEXICO NEAR 20N100W TO 5N125W. NARROW BAND OF MOISTURE
LIES ALONG THE TROUGH. SCATTERED MODERATE ITCZ CONVECTION W OF
130W IS BEING ENHANCED BY WEAK WESTWARD-MOVING LOW LEVEL
CIRCULATION MOVING ALONG ITCZ NEAR 134W. THE MID/UPPER TROUGH
WILL MOVE SE ACROSS SOUTHERN MEXICO OVER THE NEXT 24 HOURS...
LEAVING AREA UNDER PREDOMINANT HIGH ALOFT.

S OF 20N E OF 100W...
NEARLY STATIONARY MID/UPPER TROUGH CONTINUES OVER CENTRAL
AMERICA FROM HONDURAS AND EL SALVADOR SW TO NEAR 2N100W. SHARP
MOISTURE GRADIENT EXISTS ON EITHER SIDE OF THE TROUGH...WITH
WIDELY SCATTERED MODERATE CONVECTION E OF THE TROUGH FROM THE
ITCZ NORTH TO COSTA RICA AND MAINLY DRY CONDITIONS W OF TROUGH.
THIS GENERAL PATTERN IS EXPECTED TO PERSIST...WITH ONLY CHANGE
BEING A MID/UPPER TROUGH MOVING ACROSS SE MEXICO DURING THE NEXT
24 HOURS. ONLY A SLIGHT INCREASE IN MOISTURE IS EXPECTED OVER SE
MEXICO WITH THE PASSAGE OF THE TROUGH.

LIGHT SURFACE WINDS ARE EXPECTED OVER THE GULF OF TEHUANTEPEC
REGION OVER THE NEXT 42 HOURS THEN AN INCREASE IN NORTHERLY WIND
WILL BEGIN...WHILE WIND OVER THE GULF OF PAPAGAYO WILL BE
DIMINISHING TO LESS THAN 20 KT WITHIN 6 HOURS.

$$
LL

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