27/05/2026
Weekly Regional Weather Outlook
Tuesday, May 26, 2026
Valid at 10:45 AM ChST
REGIONAL OVERVIEW:
Moderate to fresh trades prevail across the Marianas with a mix of sun and spotty showers. A developing disturbance near Yap, Invest 99W, will keep well southwest and west of the Marianas. However, steady trades converging into the eastern periphery of the broader wind field around 99W will keep a showery pattern in place across the Marianas this week. Combined seas of 3 to 5 feet will build to around 6 to 8 feet by the end of the week as a long-period north swell, and southwest swell reach the Marianas.
A wet pattern will prevail this week across Yap and Palau as Invest 99W takes shape nearby. 99W will lift north-northwest over Yap into the Philippine Sea by Wednesday. As it does, it’ll pull the showery monsoon over both locations, keeping strong, gusty southwest to west winds, showers, thunderstorms and choppy seas in place through the week. A Special Weather Statement has been issued for western Micronesia to provide more details.
Farther east, variable winds and a few showers are found near Chuuk, while the ITCZ is generating showers and thunderstorms near Pohnpei and Kosrae. Drier weather prevails near and north of Majuro. Significant weather is not expected across the eastern region through the weekend, but passing surface troughs will bring periods of scattered showers. Otherwise, expect light to moderate winds and combined seas of 4 to 6 feet across Chuuk, Pohnpei and Kosrae, and moderate trades with seas up to 7 feet across Majuro.
TC POTENTIAL/HAZARDS:
A tropical disturbance, Invest 99W, tracked slowly westward across Yap State the last several days. Now located near 8.4N 138.8E, it has been upgraded to medium for development by the Joint Typhoon Warning Center. This means that tropical cyclone (TC) development is likely, but beyond 24 hours. In other words, 99W is likely to be upgraded to a tropical depression on Wednesday.
99W will move toward the NNW into the Philippine Sea as it continues to develop. Showers, thunderstorms, locally heavy rainfall and gusty west to southwest winds will encompass much of the region the next few days south of 99W, the associated trough and a second circulation to the west. This will include Palau and Yap State. 99W does not pose a threat to Guam or the CNMI, and will keep well to the west.
Elsewhere across the NWS Guam AOR, there are no suspect areas for TC development through the weekend.
DROUGHT OUTLOOK:
No drought concerns at this time. Regional rainfall patterns remain sufficient to meet needs. However, a drier trend will take shape across western Micronesia the next few weeks into at least mid-June, with below-normal rainfall anticipated for islands across Palau and Yap State. Expect near-normal rainfall elsewhere.
TROPICAL DISTURBANCE VS TROPICAL CYCLONE:
A tropical disturbance is an area of disturbed weather, such as a broad area of showers, thunderstorms, and gusty winds with some degree of organization. It may or may not have a closed circulation and it may or may not develop. On a weather map, it is labeled with a number between 90 and 99, and followed by "W", denoted the western North Pacific basin.
A tropical cyclone is a term that includes tropical depressions, tropical storms, typhoons (or hurricanes/cyclones, depending on the ocean basin) and super typhoons. All tropical cyclones begin as a disturbance, but not all disturbances become tropical cyclones. Once upgraded from a tropical disturbance, tropical cyclones receive a new number. In our present case, if Invest 99W becomes a tropical depression, it'll be assigned the number "06W", indicating it is the 6th tropical cyclone in 2026. The "W" denotes the western North Pacific basin.
FOR MORE INFORMATION:
NWS Guam:
weather.gov/gum
Climate Prediction Center
www.cpc.ncep.noaa.gov/
Joint Typhoon Warning Center
www.metoc.navy.mil/jtwc/jtwc.html
