FXPQ50 PGUM 152015 AFDGUM Area Forecast Discussion National Weather Service Tiyan GU 615 AM ChST Fri Oct 16 2026 .Marianas Update... Tropical Storm Champi continues to approach. Most models now take it close to Guam, so they appear to be converging on a solution. It's satellite presentation has been improving, therefore it either is already intensifying, or will soon begin to. A lightning burst near the center could be another sign in that direction. So went ahead and worded the recent TCP that this general track would take it close to Guam. This will be one to keep a close eye on. && .Hydrology Update... GEFS gives Guam especially about 6 inches of rain. Considering the averaging of the ensemble members and the fairly low resolution of 55 km, the amounts (especially localized amounts) could be much higher. Therefore, went ahead and issued a Flood Watch for Guam, Rota, Tinian and Saipan. Also coordinated with the National Water Center to update the Flood Hazard Outlook, maintaining Tinian and Saipan as Limited, but making Guam and Rota be Considerable. Watch for Flash Flood Warnings possibly starting on Sunday. && .Tropical Systems Update... 29W has been upgraded from a tropical depression to Tropical Storm Champi. The latest Joint Typhoon Warning Center Advisory showed Champi with maximum sustained winds of 40 mph. The latest satellite fix gives a location at 11.6N, 156.5E, which is about 340 miles north- northwest of Pohnpei and 800 miles east of Guam. Champi is currently moving west at 12 mph towards the Marianas. It is expected to maintain this general course towards the Marianas with a slight increase in forward speed through Saturday. Champi is visibly intensifying this morning as large convective bursts with significant lightning are visible near the center. A large outer band of numerous to widespread showers and isolated thunderstorms has grown along the western half of Champi. Scattered showers and isolated thunderstorms are on the eastern half but beginning to fill in as wind shear has decreased. Deterministic and ensemble model guidance are now showing the center passing over the Marianas passage sometime Sunday morning. Most tracks take the developing cyclone directly through the southern Marianas, though individual model tracks range from passing to the south of Guam, to as far north as Saipan, potentially as a well-developed typhoon (sustained winds 74+ mph). Uncertainty is decreasing in the eventual track and but remains high, particularly with the intensity upon passage through the Marianas. Residents of the Marianas are urged to begin making preparations, stay informed, and monitor for updates from the National Weather Service in Tiyan, Guam, as well as local emergency management. For more information on TD Champi, see bulletins issued by JTWC under WMO header WTPN32 PGTW and by the NWS under WMO headers WTPQ32 PGUM and WTPQ82 PGUM. && .Eastern Micronesia Update... For Majuro no significant updates were needed. For Kosrae, the Small Craft Advisory was expired due to ASCAT, and weather station data both showed winds below thresholds. For Pohnpei, model guidance suggested slightly higher winds than previously forecasted. Otherwise, the forecast packages remains in good shape. && .Western Micronesia Update... Palau, Yap, and Chuuk remain in good shape. Drier conditions are expected for Palau and Yap. TS Champi has been producing a mostly cloudy skies and light shower at Chuuk, this is expected to continue to degrade as the day passes. Otherwise, the forecast packages remains in good shape. A Small Craft Advisory is in effect for tonight through Sunday for Chuuk. && .Prev discussion... /issued 734 PM ChST Thu Oct 15 2026/ Marianas Synopsis... Gentle northeasterlies prevail across the Marianas, with mostly clear skies observed on satellite imagery. Tropical Depression Champi (29W) begins its movement toward the Marianas. Discussion... A mostly drier regime is expected to continue across the Marianas through Friday night, followed by quickly deteriorating conditions thereafter as Tropical Depression Champi (29W) continues to intensify and potentially develop into a typhoon prior to making its way across the region. The onset of tropical storm conditions is expected beginning late Saturday night or early Sunday morning, with potential onset of typhoon conditions later on Sunday. It continues to remain possible for said conditions to develop anywhere in the southern Marianas between Guam and Saipan. 15 to 25 mph northeast winds are expected to increase considerably beginning Saturday evening, with west tropical storm force winds of 60 to 70 mph with gusts to 100 mph possible come Sunday. The system is not expected to linger in the general area for too long, as its forward speed is expected to allow winds and showers to begin tapering down beginning Sunday night, with a chance for winds to fall below damaging levels as early as Monday. After, a ridge along the leeside of passing Champi is expected to move in, with a return of low-end patchy showers expected through the first half of next week. Marine... A Typhoon Watch is in effect for Guam, Rota, and Tinian and Saipan waters. Gentle to moderate northeasterlies will prevail across the Marianas tonight through Friday night, followed by quickly deteriorating sea and surf conditions as TD Champi makes its way across the Marianas, potentially as a Typhoon Saturday night through Sunday night. As such, seas are expected to quickly rise above 20 feet during closest passage of 29W, producing dangerous seas possibly into Monday. Surf conditions are also expected to become hazardous, then quickly becoming dangerous and life threatening beginning Saturday night. Depending on the exact location of 29W as it moves through the Marianas, inundation of 2 to 4 feet, possibly higher, is possible along most reefs of the Marianas. Hydrology... As Tropical Depression Champi makes its way across the Marianas, it is expected to produce 5 to 8 inches of rainfall between Saturday and Monday, with localized amounts upwards of 12 inches possible near the center. As the rain forecast has remained quite consistent, and such rainfall amounts posing a flash flood threat, a Flood Watch is likely to be issued over the next day or so for Guam, Rota, Tinian and Saipan. Tropical Systems... At 4 PM, Tropical Depression Champi (29W) was centered 945 miles east of Guam, 925 miles east-southeast of Rota, 915 miles east-southeast of Tinian, and 910 miles east-southeast of Saipan. Champi was moving west-northwest at 13 mph. It is expected to make a turn toward the west, or possibly, west-southwest over the next couple of days as it strengthens. Champi is expected to approach the Marianas over the weekend, with tropical storm force winds possible as early as Saturday evening. Typhoon force winds are possible Sunday morning. As TD Champi continues to strengthen, the expected movement and intensity as it approaches the Marianas will become more clear. The latest forecast track takes Champi through the Rota channel, just north of Andersen AFB. It needs to be emphasized, this is a preliminary track, and definitely subject to change as time progresses. Based on the uncertainty with actual track, a Typhoon Watch was issued for the Marianas. Residents of the Mariana Islands should continue to monitor forecast for any changes in expected track and/or intensity as Champi approaches. For more information on TD Champi, see bulletins issued by JTWC under WMO header WTPN32 PGTW and by the NWS under WMO headers WTPQ32 PGUM and WTPQ82 PGUM. Tropical Depression 28W is centered 625 milesnorthwest of Saipan near 23N140E, moving west at 7 mph. 28W continues to slowly weaken and is expected to dissipate as a significant tropical cyclone within the next 24 hours. For more information on TD 28W, see bulletins issued by the Joint Typhoon Warning Center (JTWC) under WMO header WTPN31 PGTW, and by the National Weather Service (NWS) under WMO header WTPQ31 PGUM. Eastern Micronesia... Kosrae: Tropical Depression Champi (29W) is still having impacts on the weather at Pohnpei and Kosrae. For Kosrae, although the heavier showers have moved off to the northwest, the overnight altimetry pass showed 15 to 20 knot winds just east-northeast of Kosrae. Given that 29W continues to organize and strengthen, sustained winds just under 22 knots are likely with frequent gusts above that. Therefore, we extended the Small craft Advisory through 3 PM Friday. Seas of 6 to 8 feet and gentle to fresh winds will continue through this time, before gradually subsiding. Pohnpei: The heavier rainfall has moved off to your north and west, but scattered showers remain possible through Friday. Similar to Kosrae, frequent gusts to 30 knots remain likely. As such, your Small Craft Advisory also remains in effect through 3 PM Friday. Seas of 7 to 9 feet and gentle to fresh winds will continue through this time, before gradually subsiding. Majuro: Although you have no headlines in place, the monsoon trough located just north of you continues to produce scattered showers. This looks to continue through Friday night, before shower coverage decreases to isolated for the weekend. Winds will be light to gentle with seas of 4 to 6 feet. Western Micronesia... Chuuk: The main changes to the forecast were to hoist a Small Craft Advisory at Chuuk, beginning 5 PM Friday and continuing through 5 PM Sunday. As Tropical Depression Champi (29W) continues to strengthen into a tropical storm over the next 12 to 24 hours, an expanding wind field will commence. Sustained gentle to moderate winds will become moderate to fresh on Saturday. For now, we have frequent gusts to 30 kt as a start, but depending how the monsoon inflow band sets up, and how Champi evolves, this may need to be revisited. An increasing northeast to north swell meeting the southwest swell will add a layer of chop to the seas by early next week. Intra-island travel is highly discouraged from late Friday afternoon into early next week to account for this. As for precipitation, scattered showers will continue through at least the first part of the weekend, becoming isolated by early next week. Palau: Light to gentle winds will become gentle to moderate by Tuesday, with seas and surf building for the latter half of the week. Scattered oragraphically-induced showers may need to be added to the forecast Friday into Saturday, but for now we didn't include this as we want to see how the pattern reorientates as TD Champi (29W) evolved as it approaches the Marianas. Otherwise, isolated showers remain possible. Yap: The main story here is a northeast swell looks to arrive for the early to middle portion of next week, as Tropical Depression Champi (29W) continues to strengthen as it passes through and west of the Marianas. Otherwise, isolated showers remain possible. && .GUM WATCHES/WARNINGS/ADVISORIES... GU...Flood Watch through Sunday afternoon for GUZ001. Typhoon Watch for GUZ001. MP...Flood Watch through Sunday afternoon for MPZ001>003. Typhoon Watch for MPZ001>003. Marianas Waters...Typhoon Watch for PMZ151>154. && $$ East and West Micronesia Update: Bowsher Marianas Update: Stanko Tropical Update: Ogle/stanko Marianas/Tropical: Montvila/Mesa East/West Micronesia: Doll Tropical: Kleeschulte