Overview
It has come to my attention that the meanings behind National Weather Service alerts aren't always fully understood. During severe weather season, it is extremely important that everyone properly understand the meaning behind the different alerts and the actions required when such alerts are issued. I am going to try my best to explain and simplify the most common alerts we will see this spring, summer and fall.
Severe Thunderstorms
Definition of a Severe Thunderstorm--The National Weather Service has specific criteria for determining whether or not a storm is severe. Winds in excess of 58mph or greater and hail to 1 inch in diameter or larger classify a storm as severe. As long as one of these criteria are met, the storm will be considered severe.
Watch
A SEVERE THUNDERSTORM WATCH will be issued by the Storm Prediction Center in Norman, Oklahoma when the atmospheric conditions are favorable for the development of severe weather in and close to the watch area. These are usually issued several hours in advance of storms and often go into effect before any storms have even developed. They are designed to alert the public about a significantly elevated risk of severe thunderstorms, and that they should pay close attention to the weather as conditions could change rapidly.
Summary--> Severe T-Storm Watches simply mean conditions are favorable for severe thunderstorms.
Actions Required--> When a watch is issued, you should monitor the weather very closely and be prepared for rapidly changing weather conditions.
Warning
A SEVERE THUNDERSTORM WARNING is issued by your local National Weather Service office.
Here are a few Ohio cities and their NWS offices
Columbus, Cincinnati and Dayton = NWS in Wilmington
Cleveland, Toledo and Akron = NWS in Cleveland
Coshocton, New Philadelphia and Zanesville = NWS in Pittsburgh
Lima and Defiance = NWS in Northern Indiana
Athens and New Lexington = NWS in Charleston
Each local office monitors their forecast area and will issue a severe thunderstorm warning if a storm enters their area that is producing severe wind or hail. These warnings are based off of radar data and/or storm reports from local law enforcement, storm spotters or the public. A warning means that the threat is occurring or highly likely. They are usually issued 20 minutes to about an hour before the storm hits, but the lead times can vary dramatically for each individual situation. The warnings are only issued for those who are in, or very close to, the track of the severe storm. If you visit the National Weather Service's website, which you should, you can see exactly who is in the alert during the severe weather. You should be seeking shelter as soon as a severe thunderstorm warning is issued and securing loose objects if time allows. You should move indoors and away from windows, or get into a vehicle and wait until the storm has passed. If you must wait it out in a vehicle, be sure it is not parked under a tree or power lines, as they could fall on the vehicle. If you are planning to do outdoor activities, you need to wait until there has been 30min since the last clap of thunder. Severe thunderstorms are capable of downing trees and power lines, damaging structures and producing large damaging hail. They can produce life-threatening situations if the proper precautions are not taken.
Summary--> A Severe Thunderstorm Warning means damaging wind and/or large hail (>1" in diameter) is occurring or is highly likely, often within the hour.
Actions Required--> You MUST heed the warning and seek shelter inside a sturdy building or vehicle. Stay away from windows and secure loose objects IF time allows.
Tornadoes
Watch
A TORNADO WATCH is issued by the Storm Prediction Center in Norman, Oklahoma. They, like the severe thunderstorm watch, are issued hours in advance and signify that conditions are favorable for the development of severe weather including tornadoes. Tornado watches include all the hazards possible in a severe thunderstorm watch, but add a heightened risk for tornado development. You should monitor the weather very closely when a tornado watch is issued because weather conditions can change quickly in those situations.
Summary--> Tornado Watches mean conditions are favorable for the development of severe weather including tornadoes in and close to the watch area.
Actions Required-->When a watch is issued, you should monitor the weather very closely and be prepared for rapidly changing weather conditions.
Warning
A TORNADO WARNING is issued by your local National Weather Service office, just like the severe thunderstorm warnings. These warnings rarely get issued more than 30 minutes in advance of the threat. When a tornado warning is issued, the tornado sirens will sound in the warning area. These warnings are based off of radar data and/or reports from local law enforcement, storm spotters and the public. It is NOT a guarantee, when a tornado warning is issued, that a tornado is on the ground. The warning is an indication, at the very least, that there is a significant threat for a tornado to develop. You must read and understand each individual tornado warning, as they will tell you if the threat is radar indicated or if there is a confirmed tornado on the ground. However, it is ALWAYS a good idea to take tornado warnings very seriously and move to an interior room on the lowest floor of a sturdy building. If you are caught outside, immediately move to the nearest substantial structure. If a building is not in the area, you have two last resort options. You can either stay in your car with your seat belt on and your head below the windows if possible, or get in a ditch and cover your head to protect yourself from flying debris. In most situations, it is becoming safer to remain in your car instead of getting in a ditch, because of the airbags, seat belt restraints and added protections from flying debris. I can not stress enough how important it is to always seek shelter during a tornado warning and to not become complacent. I know that tornado warnings are sometimes issued and a tornado never forms or misses the area that was warned. This can lead people to believe that the threat isn't as serious as it really is. Predicting when and where a tornado will form is an extremely difficult task and is being researched constantly, but until forecasts can be better improved, you must listen to the warnings issued by the National Weather Service to protect your own life! Hopefully we won't have to deal with a devastating tornado any time soon, but if we do, many more people will survive if the warning is taken seriously. They are not issued very often, so just take the time to protect yourself and your family the next time one is issued and be thankful that we were spared this time.
Summary-->Tornado warnings are issued when a tornado is on the ground or could form at any time. When issued, there is a serious threat to life and property and it must be taken seriously at all times.
Actions Required--> Move indoors to an interior room on the lowest level of a sturdy building. Stay away from windows and put as many walls between yourself and the outside. These actions must be taken immediately as the warning time may be extremely limited.
Flash Floods
Warning
A FLASH FLOOD WARNING is issued by your local National Weather Service office. They indicate that very heavy rainfall has lead to the threat of flooding and rapid rises on creeks and streams. High water can appear very quickly during a flash flood and it is important to know if you are in a flood prone area. These warnings are particularly important if you are traveling because flooded roadways are extremely dangerous. The number one cause of weather related deaths in the United States is from flooding. You should never attempt to drive through water of an unknown depth, as only 1 foot of water can float a small car. It is also dangerous because you cannot be sure that the road has not been washed out by the flood waters. Driving through flood waters puts you, and those who have to rescue you, in danger. Avoid this all together by listening to the tip from the National Weather Service that states "turn around, don't drown".
Summary--> Flash flood warnings are issued when there is an occurring or imminent threat of flooding.
Actions Required--> If you live in a flood prone area, you would need to move to higher ground immediately to protect your life. If driving, remember turn around, don't drown!
Hopefully this information is helpful to better understand the alerts issued by the National Weather Service and the Storm Prediction Center. Please take these alerts seriously as they are designed to protect you. The NWS meteorologists do their best to prevent issuing warnings and watches when they aren't warranted, but in this inexact science sometimes the forecasts are wrong. It is better to issue a warning and not have a tornado or severe weather than the other way around. Just respect the power of the weather and heed the warnings and we will all make it through severe weather season.
Thanks for reading, and stay safe!