A few weeks ago I was island hopping in Rota, Tinian and Saipan working with our Homeland Security partners on several NWS related programs. While in Saipan, I met the folks at KKMP Radio and discussed the NWS Weather-Ready Nation program and talked about the importance of weather awareness, education and awareness. That morning, I had the privilege of speaking with several high school interns at the radio station for this outreach program.
At the National Weather Service, our top priority is to protect life and property. We do this by timely and accurate forecasts, or as close as possible. However, if someone in the audience doesn’t understand our text bulletins, weather forecasts, or warnings, are we really doing our job as well as we should?
I posed some sample questions to the students: What does a tropical storm watch mean? How about a typhoon warning? What is the difference? Do you know the difference between these?
Understanding these terms and what they mean can provide some clarity to anyone faced with a situation such as a watch or warning. I have had interviews with local media over the years who have not fully understood the warning process. Even some of our forecasters new to Guam haven’t fully understood the process, especially if they come from a non-tropical location.
As we head into our annual peak period for tropical cyclone activity, I will focus on tropical cyclone watches and warnings. First, you will commonly see the term “tropical cyclone”. It’s an all-encompassing term that we use to include tropical depressions, tropical storms, typhoons, and super typhoons. We issue watches and warnings for tropical storms, typhoons and super typhoons.
In recent years, tropical depressions have formed near or near overhead, forcing us to make a complicated decision about whether to issue a tropical storm watch or warning with little or no no delay due to uncertainty of initial escalation. In these situations, pre-event communication is critically important to ensure the public is well-informed and prepared.
Watches and warnings are issued to strengthen tropical depressions, tropical storms and typhoons based on the expected occurrence of damaging winds. Damaging winds are sustained winds of 39 mph or greater, also known as tropical storm-force winds (tropical storms have maximum sustained winds of 39 to 73 mph).
In the case of a tropical storm or typhoon watch, this means that damaging winds (tropical storm force/39 mph) are possible within 48 hours. This accounts for the uncertainty of such conditions occurring for a specific location due to the possibility that the storm may slow down or speed up, or move to the left or right of the predicted track.
With respect to a typhoon watch, this still means damaging winds are possible within 48 hours, but with the added potential that winds could intensify to typhoon force (74 mph or more) . This can be issued for a typhoon or for a tropical storm that is expected to turn into a typhoon.
A tropical storm or typhoon warning means damaging winds are expected within 24 hours. In the case of a typhoon, a typhoon warning means that these damaging tropical storm force winds are expected within 24 hours and will change to typhoon force winds.
Why do we set watches and warnings for damaging winds? For your safety. All tropical cyclone preparedness actions must be completed before these damaging winds begin, with people off the roads and in safe shelter. We also want to ensure that our first responders, homeland security officers and other government partners are ready and ready to engage with mother nature.
Keep in mind that we may be in a warning for sustained winds of 40-45 mph (tropical storm), winds of 80-85 mph (typhoon) or winds of 160-180 mph (super typhoon). Make sure you know and understand our conditions and bulletins so you are prepared for the weather. I can’t say it enough, if you ever have any doubts about our text bulletins, our communications or our terminology, give us a call or send us an email. We are here at your service.