First published Oct 18, 2026, 8:47:15 AM UTC · Last updated Oct 18, 2026, 8:47:15 AM UTC

Special Marine Warning issued October 18 at 6:26PM ChST until October 18 at 6:45PM ChST by NWS Tiyan GU

Reported by U.S. National Weather Service Alerts NWS

The National Weather Service reported a severe thunderstorm producing waterspouts southeast of Guam, moving north at 30 knots. Boaters were told to move to safe harbor until the hazardous weather passes.

At a glance

Affected location: Southeastern Guam coastal waters
Boaters were told to move to safe harbor until the hazardous weather passes.

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Why it matters

The warning describes waterspouts that can overturn boats and directs people on the water to seek safe harbor.

Location

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Generated scores

Scores are based on the cited reporting and use a 1–10 scale. Read the methodology.

Confidence: 8/10How certain the assessment is based on the clarity and evidence in the cited reporting.
Geographic reach: 2/10How widely the event reaches, from a local area (1) to worldwide impact (10).
Global importance: 2/10The event's broader significance, from limited importance (1) to major global importance (10).
Impact magnitude: 3/10The scale or severity of the real-world impact, from minor (1) to extreme (10).
Urgency: 9/10How time-sensitive the event is, from low urgency (1) to immediate attention needed (10).

Primary official sources

U.S. National Weather Service Alerts NWS Special Marine Warning issued October 18 at 6:26PM ChST until October 18 at 6:45PM ChST by NWS Tiyan GU

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Related developments reported in the last 30 days. These are not necessarily ongoing incidents.

Nearby · within 200 km
Special Marine Warning issued October 19 at 11:57AM ChST until October 19 at 12:45PM ChST by NWS Tiyan GUOct 19, 2026, 2:00 AM UTC
Strong thunderstorms threatened Guam and Rota coastal waters with gusts of at least 34 knots and higher waves. Mariners were told to seek safe harbor immediately until the hazardous weather passed.
Nearby · within 200 km
NWS Tiyan issues Special Marine Warning for Guam and Rota Coastal WatersOct 19, 2026, 12:41 AM UTC
The warning reported severe thunderstorms capable of producing gusts near 50 knots, frequent lightning, and possible waterspouts over Rota Coastal Waters. It instructed mariners to move to safe harbor immediately.
Nearby · within 200 km
NWS Tiyan issues Special Marine Warning for Guam Coastal Waters as severe thunderstorm brings waterspout riskOct 18, 2026, 11:48 PM UTC
The National Weather Service in Tiyan issued a Special Marine Warning for Guam Coastal Waters through 10:30 a.m. ChST, citing a severe thunderstorm, strong wind gusts, frequent lightning, and possible waterspouts.
Nearby · within 200 km
NWS Tiyan issues Special Marine Warning for Guam coastal waters amid waterspout threatOct 18, 2026, 9:04 AM UTC
NWS Tiyan issued a warning for Guam coastal waters until 7:30 p.m. ChST after a shower capable of producing waterspouts was located over eastern Guam waters. The warning instructed boaters to seek safe harbor immediately.
Nearby · within 200 km
Extreme Wind Warning issued October 18 at 3:26AM ChST until October 18 at 5:30AM ChST by NWS Tiyan GUOct 17, 2026, 5:52 PM UTC
The National Weather Service in Tiyan issued an observed extreme wind warning for southern Guam until 5:30 AM ChST. The alert reported destructive winds of 115 to 135 mph and instructed people to take cover immediately.
Nearby · within 200 km
Flash Flood Warning issued October 17 at 7:28PM ChST until October 18 at 3:30AM ChST by NWS Tiyan GUOct 17, 2026, 9:28 AM UTC
The National Weather Service extended a flash-flood alert for Guam through 7:30 a.m. ChST on October 18, reporting heavy rain and flooding ongoing or expected shortly. The notice warns of flooding in urban and low-lying areas and advises avoiding flooded roads.

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