597
AXPQ20 PGUM 010103
TWDPQ
TROPICAL WEATHER DISCUSSION
NATIONAL WEATHER SERVICE TIYAN GU
1103 AM CHST FRI MAY 1 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
TROPICAL AND MONSOON DISTURBANCES...
THE JOINT TYPHOON WARNING CENTER CLOSED INVEST 91W YESTERDAY EVENING
AS THE WEAK CIRCULATION SOUTHWEST OF CHUUK LAGOON, LOCATED NEAR
6N150E, WAS ELONGATING AND BECOMING MORE EMBEDDED WITHIN THE NEAR-
EQUATORIAL TROUGH TO THE WEST AND AN ACTIVE ITCZ ACROSS EASTERN
MICRONESIA (BOTH DISCUSSED IN MORE DETAIL BELOW). LONG-RANGE GUIDANCE
SHOWS AN OVERALL BACKGROUND PATTERN SUPPORTIVE FOR TROPICAL CYCLONE
DEVELOPMENT, ESPECIALLY AS CROSS-EQUATORIAL FLOW IS STARTING TO
INCREASE SOUTH OF CHUUK AND KOSRAE STATES, BUT IN THE SHORT-TERM THIS
POTENTIAL IS CURRENTLY LOW DUE TO LACK OF A DISTINCT AND ORGANIZED
SURFACE CIRCULATION.
..OTHER WEATHER SYSTEMS
NEAR-EQUATORIAL TROUGH...
A NEAR-EQUATORIAL TROUGH (NET) EXTENDS EASTWARD INTO THE REGION
FROM NEAR 5N130E, PASSING TO THE SOUTH OF THE MAIN ISLANDS OF PALAU
AND SOUTHERN YAP STATE AS IT CONTINUES THROUGH AN ELONGATED
CIRCULATION SOUTHWEST OF CHUUK LAGOON NEAR 6N150E. THE NET THEN
ENDS NEAR POHNPEI, AROUND 6N160E, AS IT MERGES WITH THE ITCZ THAT
EXTENDS FROM ACROSS THE DATE LINE TO EASTERN POHNPEI STATE. FROM
130E TO WESTERN CHUUK STATE, SHOWERS ARE FAIRLY SPOTTY ALONG THE
NET, FOUND MAINLY ALONG WEAK CONVERGENCE ALONG THE NORTHERN EDGE
OF THE NET THAT EXTENDS ACROSS PALAU, AND ALONG THE EQUATOR WHERE A
SOME ISOLATED THUNDERSTORMS ARE ALSO BEING DETECTED BY THE GLOBAL
LIGHTNING DETECTION (GLD) NETWORK. SHOWERS BECOME MORE SCATTERED IN
COVERAGE AROUND THE ELONGATED CIRCULATION SOUTHWEST OF WENO,
ESPECIALLY ALONG THE SOUTHERN TO NORTHEASTERN FLANK WHERE CROSS-
EQUATORIAL, CONVERGENT FLOW IS WRAPPING ALONG THE EASTERN SIDE OF
THE CIRCULATION, SUPPORTING SCATTERED SHOWERS AND ISOLATED
THUNDERSTORMS. THEN, WHERE THE NET MERGES WITH THE ITCZ, SHOWERS
BECOME MUCH MORE NUMEROUS TO WIDESPREAD IN COVERAGE, WITH ISOLATED
THUNDERSTORMS EMBEDDED IN THE HEAVIER SHOWERS, ESPECIALLY JUST EAST
OF POHNPEI AND EXTENDING INTO KOSRAE. THE NET IS EXPECTED TO LINGER
AROUND PALAU AND YAP OVER THE NEXT COUPLE OF DAYS, SUPPORTING PERIODS
OF SCATTERED SHOWERS AND ISOLATED THUNDERSTORMS ACROSS WESTERN
MICRONESIA. THE NET IS EXPECTED TO SHIFT NORTHWARD SLIGHTLY OVER THE
NEXT FEW DAYS AS IT CONTINUES TO INTERACT WITH THE ITCZ AND WEAK
VORTICITY FEATURES DEVELOP WITHIN THE NET. THIS WILL CONTINUE TO
SUPPORT PERIODS OF SCATTERED SHOWERS AND ISOLATED THUNDERSTORMS IN
THE VICINITY OF PALAU THAT WILL THEN LIFT INTO YAP STATE. THE
POTENTIAL FOR HEAVIER RAINFALL WILL CONTINUE NEAR POHNPEI AND
POTENTIALLY EXTENDING WESTWARD INTO CHUUK STATE AS THE NET AND ITCZ
INTERACT.
TRADE-WIND TROUGHS...
BETWEEN 10N AND 25N A MODERATE TO FRESH TRADE-WIND PATTERN EXTENDS
ACROSS THE REGION. SPOTTY SHOWERS ASSOCIATED WITH WEAK, WESTWARD
MOVING TRADE-WIND TROUGHS CAN BE FOUND EAST OF THE MARIANAS NEAR 150E
AND AROUND WAKE ISLAND. A MORE NOTABLE TRADE-WIND TROUGH IN THE
PHILIPPINE SEA AND WELL NORTHWEST OF YAP PROPER IS PRODUCING A
CLUSTER SCATTERED SHOWERS AND ISOLATED THUNDERSTORMS, CENTERED NEAR
13N134E AND ALSO STEADILY DRIFTING WESTWARD. THE MARIANAS AND WAKE
ISLAND MAY SEE BRIEF UPTICKS IN SPOTTY SHOWERS AS THESE TROUGHS PASS
NEAR THE ISLANDS.
OTHER SYSTEMS...
A COLD FRONT IS CLIPPING THE NORTHWESTERN EDGE OF THE REGION,
ENTERING THE REGION AT 25N134E AND THEN EXITING THE REGION AT
22N130E. ALONG THE LEADING EDGE OF THE COLD FRONT, A BROKEN LINE OF
SCATTERED SHOWERS AND ISOLATED THUNDERSTORMS ARE FOUND, WITH A
BROKEN TO OVERCAST BAND OF CLOUDS, POTENTIALLY PRODUCING LIGHT RAIN,
EXTENDS UP TO 300 MILES BEHIND (NORTHWEST) OF THE COLD FRONT. THE
COLD FRONT IS EXPECTED TO SHIFT EAST-SOUTHEAST OVER THE NEXT FEW DAYS
BUT NOT EXPECTED HAVE MUCH OF AN IMPACT ON THE ISLANDS IN THE
MARIANAS OR MICRONESIA AS REMAINS IN THE NORTHERN EDGE OF THE REGION.
..ITCZ
THE CONVECTION ALONG ITCZ HAS BECOME MORE COHERENT AS THE ITCZ
HAS STRENGTHENED AS CROSS-EQUATORIAL FLOW HAS INCREASED SOUTH OF
KOSRAE AND SOUTH OF THE MARSHALL ISLANDS AND IS MEETING THE
MODERATE TO FRESH TRADE-WIND FLOW EXTENDING ACROSS THE REGION. THE
MAIN AXIS OF THE ITCZ EXTENDS FROM THE CENTRAL PACIFIC, ENTERING
THE REGION NEAR 7N180 AND ENDS NEAR 6N160E WHERE IT IS INTERACTING
WITHE NET NEAR POHNPEI. NUMEROUS TO WIDESPREAD SHOWERS AND
ISOLATED THUNDERSTORMS EXTEND ALONG THE ITCZ, SPREADING ACROSS THE
MARSHALL ISLANDS NEAR AND SOUTH OF MAJURO, ACROSS KOSRAE, AND
MOST OF EASTERN POHNPEI STATE, WITH THE MOST OF THE CONVECTION
CURRENTLY JUST EAST OF POHNPEI. SOME OF THE SHOWERS AND
THUNDERSTORMS ARE PRODUCING VERY HEAVY AND LOCALIZED RAINFALL,
CAPABLE OF PRODUCING STRONG GUSTY WINDS AND CHOPPY SEAS. THE ITCZ
IS EXPECTED TO SHIFT WEST-NORTHWEST AS IT PUSHES AGAINST THE NET
OVER THE NEXT COUPLE OF DAYS, LIKELY MOVING THE AREA OF NUMEROUS
TO WIDESPREAD, LOCALLY HEAVY SHOWERS OVER POHNPEI, AND TOWARD
MAJURO AND KWAJALEIN IN THE MARSHALL ISLANDS, WHILE KOSRAE WILL BE
CLOSER TO THE SOUTHERN EDGE OF THIS CONVECTION. LOOKING TOWARD
THE UPCOMING WEEK, MODEL GUIDANCE SHOWS THE ITCZ MAY START TO
FRAGMENT AS A TROUGH OR POTENTIALLY A CIRCULATION STARTS TO
DEVELOP ALONG THE LEADING EDGE OF THE ITCZ THAT IS INTERACTING
WITH THE NET.
SCHANK
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