Tropical Disturbance South of Guam

Tropical Disturbance South of Guam

The National Weather Service (NWS) Weather Forecast Office Guam has announced of a tropical disturbance (Invest Area 99W) located about 220 miles south-southwest of Guam.  99W will pass south of Guam tonight through Thursday morning heading in a general west direction. 

As of this news release, the disturbance is now the subject of a Tropical Cyclone Formation Alert by the Joint Typhoon Warning Center which means 99W could be upgraded to a tropical depression within the next 24 hours.

Guam can expect winds to strengthen and rain showers to increase through Thursday as the monsoon strengthens in response to 99W.

We do not expect damaging winds for Guam, Rota, Tinian or Saipan.  Seas and surf could become hazardous across the Marianas on Thursday.

Heavy Rains and what to expect:
  • Be aware of flash flood alerts.  If there is a possibility of a flash flood occurring, move immediately to higher ground.  Do not wait for instructions to move.
  • Listen to radio, television or your local news outlets for local alerts and information.
  • Be aware of streams, drainage channels and areas know to flood suddenly.

Visit the following links for the latest advisory information: The Offices of Guam Homeland Security and Civil Defense (GHS/OCD) remind the community to practice caution if traveling in the rainy conditions.

For more information, contact GHS/OCD Acting Public Information Officer, Dee Cruz at (671) 478-0291 or via email at


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June 2018 is Typhoon Preparedness Month