A monsoon trough, extending across the Philippines and into the Mariana Islands, brought periods of heavy rain to Guam leading to flooding during the morning of October 11th. Central and southern portions of Guam received on average 4 to 7 inches of rain between 0130ChST and 1400ChST, while northern portions of Guam received 1 to 3  inches of rain between 0300ChST and 1300ChST. The peak of the heavy rainfall was between 0300ChST and 0600ChST, with an automated rain gage in southern Guam (near the village of Umatac) recording 0.72 inches in 15 minutes or an hourly rain rate of 2.88 inches.

Flood in GUAM, GUAM
From 11-OCT-22 03:00:00 to 11-OCT-22 10:00:00 (GST10)
Location: MERIZO
Flood cause: Heavy Rain
Property damage: 0.50K
Crop damage: 0.00K
Reported by: Public

Heavy rainfall across central and southern portions of Guam caused ponding on roadways. Rain gages across southern Guam showed about 4 to 7 inches fell during the morning hours. A bridge located where Joutan Lane meets up with Route 4 had water over the road and debris was piled up along the side of the bridge and road. Removal of debris is estimated to cost about $500.

Flash Flood in GUAM, GUAM
From 11-OCT-22 02:50:00 to 11-OCT-22 07:40:00 (GST10)
Location: YONA
Flood cause: Heavy Rain
Property damage: 0.00K
Crop damage: 0.00K
Reported by: River/Stream Gage

Heavy rainfall across central and southern portions of Guam caused ponding on roadways. Estimates of 4 to 6 inches fell across the Pago watershed. The Pago River gage showed Pago river starting at a height around 2 feet at 0250ChST quickly climbing to over 5 feet at 0315ChST, and peaking at 14.28 feet at 0505ChST before slowly decreasing and not dropping below 5 feet until 0740ChST. Route 4 near Pago Bay (located just north of the Pago River crossing) had reports of water over the road, and though it never officially closed, traffic stopped for a time as people felt passage was unsafe.

Flood in GUAM, GUAM
From 11-OCT-22 07:40:00 to 11-OCT-22 11:36:00 (GST10)
Location: YONA
Flood cause: Heavy Rain
Property damage: 0.00K
Crop damage: 0.00K
Reported by: River/Stream Gage

Heavy rainfall across central and southern portions of Guam caused ponding on roadways. Estimates of 4 to 6 inches fell across the Pago watershed. The Pago River gage showed Pago river starting at a height around 2 feet at 0250ChST quickly climbing to over 5 feet at 0315ChST, and peaking at 14.28 feet at 0505ChST before slowly decreasing and not dropping below 5 feet until 0740ChST. Route 4 near Pago Bay (located just north of the Pago River crossing) had reports of water over the road, and though it never officially closed, traffic stopped for a time as people felt passage was unsafe. Moderate rainfall then kept Pago river between 4 and 5 feet from 0740ChST to 1135ChST as the Route 4 near Pago Bay still had ponding on the road, but traffic was moving and improving at this time.

Flood in GUAM, GUAM
From 11-OCT-22 03:00:00 to 11-OCT-22 10:00:00 (GST10)
Location: APRA HARBOR
Flood cause: Heavy Rain
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Public

Heavy rainfall across central and southern portions of Guam caused ponding on roadways. Via group chats and social media, the office received reports of water covering the northbound lanes of Route 1 (called locally as Marine Corps Drive) near Polaris Point, located south of the village of Piti. The Mount Chachao rain gage near Piti reported a total of 4.69 inches with 2.89 inches falling between 0245ChST and 0530ChST.