Area Forecast Discussion

Marianas Synopsis

Typhoon Champi continues to strengthen, and is now a category 4 typhoon. It looks to pass over the southern tip of Guam, or just south of there Sunday morning, possibly as a dangerous super typhoon. This is a dangerous and potentially life threatening storm.

Discussion

The main focus continues to be on Typhoon Champi, which continues to strengthen. Champi began Rapid Intensification earlier this morning, and appears like it could be going through an Eyewall Replacement Cycle, as there's been a couple of expansions and contractions where the eye's Central Dense Overcast (CDO), allowing the eye to become more opaque. This has been preceded by many lightning bursts that have mainly been confined to the southern flank of the eyewall, as one would expect.

Guam: The Typhoon Warning remains in effect. Maximum sustained winds have increased to 100 mph near the center, and it's forecast to continue strengthening, with sustained winds of 115 mph probable late this evening. At this time, Champi looks to pass over the southern tip of Guam or just south between 4 AM and 6 AM, which will allow the storm to continue to intensify as it moves through. The worst conditions look to occur over the southern half of the island, where peak sustained winds of 110 to 130 mph, with gusts to 160 mph, will be possible. Winds will increase this evening, becoming strong tropical storm force. Typhoon force winds are expected early Sunday morning. These winds will continue to veer to the southwest, decreasing through the afternoon. Damaging winds will continue into Sunday night.

Significant coastal flooding of up to 7 feet is expected, with landslides possibly causing road closures, especially south of Cross Island Road.

Rota: Sustained tropical storm force winds will move into the area this evening, becoming strong tropical storm force by morning. However, if the typhoon "wobbles" far enough north, typhoon winds would potentially occur. As such, the Typhoon Warning remains in effect.

Tinian and Saipan: Sustained tropical storm force winds are anticipated later tonight. These winds will develop after 7 PM, peaking between 3 AM and 9 Am when they become east- southeasterly. During this time, sustained withs of 40 to 50 mph, with gusts to 70 mph.

For more information, please reference our Zone Forecast package and Typhoon Local Statement.

As TY Champi departs the region, a dry pattern looks to move in, with POPs (Probability of Precipitation) dropping to around 20 percent and staying at these levels at least into next weekend.

Marine/Coastal

Numerous roads may be closed. Low-lying property including homes, businesses, and some critical infrastructure will be inundated. Shoreline erosion will occur. Breaking waves can sweep people off their feet, and into dangerous seas. Life- threatening swimming conditions and significant beach erosion can be expected. Coastal inundation of 5 to 7 feet for Guam, 2 to 4 feet for Rota and 1 to 3 feet for Tinian and Saipan is possible along with coastal flooding and beach erosion.

Surf is expected to rise rapidly to dangerous levels tonight. Coastal impacts to the western coasts of Guam and Rota are highly dependent on the final track of Champi; passage south of Guam would be reduced impacts whereas passage over Guam would result in larger coastal inundation.

For more information please refer to the Hurricane Local Statement and Coastal Flood Warning.

Hydrology

Typhoon Champi will produce locally heavy rainfall late tonight and Sunday. Although an unexpected southward shift in track will reduce these somewhat. Tinian and Saipan will see around 3 to 5 inches, Rota could receive 5 to 8 inches, and Guam might get 8 to 14 inches. For more information please see the Flood Watch.

Tropical Systems

As of 6:00 PM ChST, Typhoon Champi (29W) has rapidly intensified to Category 4 with maximum sustained wind speeds of 130 MPH according to the Joint Typhoon Warning Center (JTWC). Its center was located around 12.5N 147.0E which was about 160 miles east-southeast of Guam's radar and 200 miles south-southeast of Saipan airport. Champi has slowed to 9 MPH heading west-northwest, with a forecast track remaining south of Guam early Sunday morning as it intensifies further to a Super Typhoon within the next 12 hours. Environmental conditions will be favorable for such strengthening characterized by weak wind shear, warm sea surface temperatures, and exceptional polar outflow. Over the past several hours, Champi has shifted its forward motion from west to west-northwest and slowed from 16 MPH to 9 MPH while increasing from Category 2 to Category 4 strength. Typhoon-force winds are forecast to encompass all of Guam, with the strongest impacts concentrated over southern Guam. However, should the actual track shift more north, central and northern Guam could see worse conditions. The onset of tropical-storm-force winds for all of the Marianas is expected to occur imminently. Remain in sturdy shelter and do NOT venture out.

For more information, please refer to the bulletins issued by the Joint Typhoon Warning Center under WMO header WTPN32 PGTW, and by the National Weather Service in Tiyan, Guam under WMO header WTPQ32 PGUM.

Eastern Micronesia

The main feature of interest is a surface trough that bi-sects Majuro, where it links up with the monsoon trough. Here, scattered showers will continue the next few days. We may need to increase showers in later forecasts as a circulation just east of the Date Line potentially heads towards Majuro in a couple days. With that said, satellite imagery shows scattered showers sow e stuck with that for now. Further west for Pohnpei and Kosrae, as the surface trough heads west, it'll briefly bring increasing shower potential towards the middle of the week.

For our mariners. look for light to gentle winds to prevail with seas in the 4 to 6 foot range.

Western Micronesia

Chuuk: Typhoon Champi continues to head west-northwest towards Guam, taking it's stronger winds west of Chuuk. The latest scatterometer data shows winds near 15 knots, which lines up with the airport observations. As such, the Small Craft Advisory has been cancelled. The weakening winds will also decrease surface convergence, with just isolated showers anticipated.

At Palau and Yap, the main focus was on precipitation potential, winds, and seas. Yap looks to get the benefit of the southwest monsoon trough inflow into Champi, with scattered showers developing over the next few days. The trough will also allow the current light to gentle winds to increase into the gentle to fresh range starting Monday and continuing through the middle of the week. Champi will also send a northerly swell towards the region for the first half of the week, potentially longer.

GUM WATCHES / WARNINGS / ADVISORIES

GU...Flood Watch through Sunday afternoon for GUZ001.

Typhoon Warning for GUZ001.

Coastal Flood Warning until 4 AM ChST Monday for GUZ001.

High Surf Warning until 4 AM ChST Monday for GUZ001.

MP...Flood Watch through Sunday afternoon for MPZ001>003.

Typhoon Warning for MPZ001.

Coastal Flood Warning until 4 AM ChST Monday for MPZ001>003.

High Surf Warning until 4 AM ChST Monday for MPZ001>003.

Tropical Storm Warning for MPZ002-003.

Typhoon Watch for MPZ002-003.

Marianas Waters...Typhoon Warning for PMZ151-152.

Tropical Storm Warning for PMZ153-154.

Typhoon Watch for PMZ153-154.