Special Weather Statement

Updated to include Tropical Cyclone Formation Alert.

...TROPICAL CYCLONE FORMATION ALERT HAS BEEN ISSUED... ...POTENTIAL FOR HEAVIER SHOWERS AND GUSTY WINDS THROUGH TUESDAY NIGHT...

A developing tropical disturbance known as Invest 94W by the Joint Typhoon Warning Center (JTWC) continues to close in on the Marianas, centered near 14.2N 147.7E as indicated in latest Guam radar imagery. Its current motion is roughly W to WNW at around 15 kt (17 mph). As of 1100 UTC, 9 PM ChST, JTWC has upgraded Invest 94W's rating to HIGH with a Tropical Cyclone Formation Alert, meaning it is expected to develop into a significant tropical cyclone (a Tropical Depression) within the next 24 hours. Currently, lines of patchy showers are rotating slowly through the Marianas, moving south-southwest over the coastal waters with the heaviest showers seen east of Tinian and Saipan.

Model guidance shows 94W crossing the Marianas anywhere between Rota to N of Saipan. Currently, the heaviest showers and gusty winds are found near and east to northeast of center. Therefore, a more northward track would cause islands south of the center to see a lower potential for these impacts. If the center passes near Tinian and Saipan, then these islands will see heavy showers and gusty winds. If the track ends up north of Saipan, this risk would be highest for the northern Mariana Islands, with an overall reduction for Guam, Rota, Tinian and Saipan. Based on current model trends, the overall motion looks to favor a passage near Saipan.

Rainfall totals could reach between 0.5 to 1.5 inches along with gusts around 25 to 30 mph or higher within the heaviest showers. However, due to 94W's disorganized nature, these totals may not be widespread and will vary from island to island. Additionally, locally higher amounts will be possible.

For more information on Invest 94W, please refer to the Tropical Cyclone Formation Alert issued by the Joint Typhoon Warning Center under WMO header WTPN21 PGTW.