textproduct: Tiyan

Marianas Synopsis

Satellite imagery shows partly cloudy skies, while radar imagery shows isolated showers over the region. Altimetry shows about 7 foot combined seas, while buoy data shows 4 to 5 foot swells at 16 to 17 seconds. A High Surf Advisory (HSA) and a High Risk of Rip Currents statement (HRRC) are in effect.

Discussion

A seasonal trade-wind pattern has set up over the region. A trade- wind trough is expected to move through the Marianas Saturday. This trough may bring low-end scattered showers with it. Over the next several days, the main concern remains the elevated winds. Winds are anticipated to become breezy by Saturday night, however, these winds may increase sooner. Overall pleasant but windier weather is in store for the Marianas.

Marine/Surf

The main concerns are the seas and surf. Seas are expected to build due to the combination of a midlatitude high pressure system and the trades. Combined seas are currently 7 feet and they are expected to build up to 12 ft around the beginning of next week. Winds will also build up to strong over the next few days. For these reasons, a Small Craft Advisory (SCA) was issued for Saturday night through Sunday. Surf is also expected to rise as the seas rise and may cause the risk of rip currents be elevated to dangerous. Seas and surf may start tapering down around Tuesday.

Eastern Micronesia

The main item of interest continues to be seas and surf. The winds have dropped below 22 knots and seas have fallen below 10 feet at Pohnpei, allowing the advisory to be cancelled. However, altimetry shows seas of 9 feet just outside the area and poised to continue moving south to southeast towards Kosrae. As such, we maintained the High Surf Advisories. However, today's model trends are allowing surf to subside sufficiently to possibly allow these advisories to expire early. We'll give it another forecast cycle or two to see if this trend continues.

Otherwise, mainly gentle to moderate winds will continue the next few days, with strong wind possible from time to time. These winds will subside some during the first half of next week. Aside from that, embedded disturbances in the flow will bring periodic increases in shower coverage the next several days.

Western Micronesia

The latest satellite data shows mostly cloudy skies with numerous showers and isolated thunderstorms across Palau. Yap is seeing a dry pattern, with spotty clouds and showers. Numerous showers are seen to the south of Chuuk with scattered showers seen across the southern waters. Altimetry shows seas between 6 and 8 feet across the region.

For Palau, the Near-Equatorial Trough (NET), seen to the south, is interacting with a couple of weak trade-wind troughs moving through the region, generating numerous showers and isolated thunderstorms across the Republic. This looks to continue through Saturday before convection winds down a bit Saturday night into Sunday as the NET drifts west-southwest. By Sunday night, a much drier pattern is expected to move into the region. Yap can expect a dry trade-wind pattern to continue through the next several days.

For Chuuk, numerous showers and isolated thunderstorms are seen south of Weno along the far western end of the Inter-Tropical Convergence Zone (ITCZ). Most of the convection will remain south of Weno, however, scattered showers are expected to be over the southern half of the coastal waters through Saturday afternoon, with showers becoming isolated by Saturday night as the convergence along the ITCZ weakens. Early next week, a couple of trade-wind troughs look to move into Chuuk and invigorate the convergence over the State. This will result in increased convection for the first couple of days of next week.

For the marine forecast, a Small Craft Advisory (SCA) remains in effect for Yap and Palau. The SCA was extended by 12 hours for Yap due to continued strong gusts reported at Yap Proper. The latest ASCAT analysis does show weaker winds moving into Yap, so winds should fall below SCA levels early Saturday morning. For Palau, the SCA remains in effect. The latest ASCAT analysis shows winds of 20+ knots mainly over the northern portion of the coastal waters. This is verified by Kayangel observations showing sustained winds of 22 to 25 knots this afternoon and evening. Winds will likely subside a bit earlier than previously expected, allowing the SCA to be cancelled a little early. Combined seas of 6 to 8 feet at Yap and Palau will also slowly subside over the next few days, before building again early next week as a increasing trade-wind swell moves into the region.

For Chuuk, mostly moderate to fresh winds are expected through the weekend becoming gentle to moderate around Tuesday next week. Combined seas of 6 to 8 feet will subside a bit Sunday night into Monday. However, a building trade-wind swell is expected to return around Tuesday next week. Seas could reach as high as 10 feet Tuesday, though seas are currently forecast to remain below SCA levels.

GUM WATCHES/WARNINGS/ADVISORIES

GU...High Rip Current Risk through late Sunday night for GUZ001.

High Surf Advisory until 6 AM ChST Monday for GUZ001.

MP...High Rip Current Risk through late Sunday night for MPZ001>003.

High Surf Advisory until 6 AM ChST Monday for MPZ001>003.

Marianas Waters...None.