596
AXPQ20 PGUM 220441 AAA
TWDPQ
TROPICAL WEATHER DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE TIYAN GU
241 PM CHST TUE SEP 22 2026
TROPICAL WEATHER DISCUSSION FOR THE WESTERN NORTH PACIFIC BETWEEN
THE EQUATOR AND 25N FROM 130E TO 180. THE FOLLOWING INFORMATION IS
BASED ON RECENT SATELLITE IMAGERY/DATA, WEATHER OBSERVATIONS, RADAR,
AND METEOROLOGICAL ANALYSIS.
..SPECIAL FEATURES
UPDATED FOR ISSUANCE OF TCFA FOR INVEST 91W.
TROPICAL AND MONSOON DISTURBANCES...
UPDATE: INVEST 91W HAS CONTINUED TO ORGANIZE THROUGH THE DAY. THIS
MORNING SCATTEROMETRY SHOWED A TIGHTENING LOW-LEVEL CIRCULATION
SURROUNDED BY CONVECTION IN ALL QUADRANTS. BASED ON THESE TRENDS, THE
JOINT TYPHOON WARNING CENTER UPGRADED INVEST 91W FROM MEDIUM TO HIGH,
ISSUING A TROPICAL CYCLONE FORMATION ALERT. A TCFA MEANS THAT
DEVELOPMENT INTO A SIGNIFICANT TROPICAL CYCLONE IS EXPECTED WITHIN 24
HOURS.
PREVIOUS: THE JOINT TYPHOON WARNING CENTER'S INVEST 91W IS CURRENTLY
LOCATED NEAR 12N143E. THE JTWC HAS UPGRADED INVEST 91W TO MEDIUM,
WHICH MEANS DEVELOPMENT INTO A SIGNIFICANT TROPICAL CYCLONE IS NOT
EXPECTED WITHIN 24 HOURS, BUT IS LIKELY WITHIN THE NEXT FEW DAYS.
INVEST 91W HAS VASTLY IMPROVED IN STRUCTURE OVERNIGHT AND IS
BEGINNING TO CONSOLIDATE. INVEST 91W IS EXPECTED TO MOVE NORTHWEST
AWAY FROM BOTH THE MARIANAS AND YAP OVER THE NEXT COUPLE OF DAYS.
FOR MORE INFORMATION ON INVEST 91W, SEE BULLETINS ISSUED BY JTWC
UNDER WMO HEADER ABPW10 PGTW.
..OTHER WEATHER SYSTEMS
MONSOON TROUGH...
THE MONSOON TROUGH ENTERS THE REGION AT 14N130E AND EXTENDS EAST-
SOUTHEAST WHERE IT INTERSECTS INVEST 91W AT 12N143E. THE TROUGH THEN
EXTENDS NORTHEAST TO 15N148E WHERE IT MEETS A COL. SCATTERED TO
NUMEROUS SHOWERS AND ISOLATED THUNDERSTORMS ARE SEEN ALONG THE
MONSOON TROUGH. THE MONSOON TROUGH WILL SHIFT NORTHWARD OVER THE
COMING DAYS BRINGING SHOWERS AND THUNDERSTORMS TO THE MARIANAS LATER
THIS WEEK.
SURFACE TROUGHS...
A SURFACE TROUGH EXTENDS FROM THE RIGHT SIDE OF A COL AT 14N155E AND
EXTENDS EASTWARD INTO A BROAD CIRCULATION CENTERED NEAR 13N165E. THE
TROUGH EXTENDS SOUTHEASTWARD UNTIL IT REACHES A SECOND COL AT
10N180. SCATTERED TO NUMEROUS SHOWERS AND ISOLATED THUNDERSTORMS ARE
SEEN WHERE THE TROUGH INTERACTS WITH THE BROAD CIRCULATION.
ELSEWHERE, ISOLATED SHOWERS ARE SEEN ACROSS THE TROUGH. THIS TROUGH
WILL REMAIN NEARLY STATIONARY OVER THE COMING DAYS.
A SECOND TROUGH EXTENDS NORTH OF THE CIRCULATION AT 13N165E TO
24N170E. SCATTERED TO WIDESPREAD SHOWERS AND ISOLATED THUNDERSTORMS
ARE SEEN ALONG THE TROUGH AXIS. THIS TROUGH WILL MOVE WEST OVER THE
NEXT FEW DAYS.
TUTT...
A TUTT ENTERS THE REGION AT 25N170E AND EXTENDS WEST-SOUTHWEST INTO
A TUTT CELL NEAR 20N143E. LITTLE TO NO SHOWER ACTIVITY IS SEEN ALONG
THE TUTT. HOWEVER, THE TUTT APPEARS TO BE HELPING VENTILATE INVEST
91W AND THE WEAK CIRCULATION AT 13N165E. THE TUTT WILL CONTINUE TO
MOVE WESTWARD AND INTENSIFY OVER THE NEXT DAY OR TWO.
WILLIAMS
CLICK HERE TO GO TO PREVIOUS BULLETINS.
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