Time for a review. It doesn’t matter what time of year it is, we hear these words used with the threat of impending bad weather. Severe Thunderstorm Warning, Tornado Watch, Lake Effect Snow Warning, Wind Advisory, Freezing Rain Advisory… we’ve heard all of these before and will hear them again. But, which of these should have us taking life saving measures and which should we all but ignore? Well, a lot of the time it comes down to whether it is an Advisory, a Watch or a Warning.
No matter what the actual weather you are dealing is, here is the basic rule of thumb.
WATCH essentially means a “chance” this condition will happen and usually covers a large geographical area for a lengthy time period.
WARNING means the said weather is already occurring or is likely to occur and to take proper protective measures. Warnings are usually issued for much smaller geographical areas and usually for shorter more definite time periods.
ADVISORIES are sort of in between a WATCH and WARNING. The expected weather condition has a pretty good chance of occurring, even a likely chance of occurring, but typically an advisory is used for “less” severe type of weather conditions. A Wind Advisory might be issued or a Freezing Rain Advisory issued instead of a High Wind Warning or an ice Storm Warning.
Yes, it can get confusing, even to us as meteorologists. There are a multitude of advisories, watches and warnings, all of which were developed by the good folks at the National Weather Service. Below I am listing mainly “summer” terms courtesy of the National Weather Service. It is likely you won’t remember what each means. If so, simply try to keep in mind what we already talked about. The difference between Advisory, Watch and Warning, and be sure to stay tuned to our CNYcentral TV stations, WSTM, WTVH CW-6 and , WSTQ CW6, and to keep checking in on our WEB site www.CNYcentral.com daily and more often when bad weather hits. And remember, when we do have any type of precipitation, be sure to track it right down to street level with our one of a kind Interactive Doppler Radar on www.CNYcentral.com.
Before we get to the “terms”, here are a few links you may find of interest.
Storm Prediction Center: http://www.spc.noaa.gov/
National Weather Service Home page: http://www.nws.noaa.gov/
Precision Weather Service: My company: http://www.precisionweather.com
NOTE: If you’re really into weather and FACEBOOK, then be sure to become a fan of Precision Weather Service on FACEBOOK, and suggest to friends. All weather, all the time!
Now those weather terms I promised:
Tornado Watch - Conditions are favorable for the development of severe thunderstorms and tornadoes in and close to the watch area. These watches are issued for large areas by the Storm Prediction Center in Norman, Oklahoma, and are usually valid for five to eight hours.[1]
Particularly dangerous situation Tornado Watch - Conditions are favorable for the development of severe thunderstorms and destructive tornadoes in and close to the watch area. These watches are occasionally issued, and usually mean that a major tornado outbreak is possible. These watches are usually issued for a larger area by the Storm Prediction Center in Norman, Oklahoma than a regular Tornado Watch, and are usually valid for a longer period of time than a regular Tornado Watch. This type of watch is usually only reserved for forecast "high-end" severe weather events.[2]
Tornado Warning - Strong rotation in a thunderstorm is indicated by Doppler weather radar or a tornado is sighted by Skywarn spotters.
Tornado Emergency - Sent as a "severe weather statement", this is an unofficial, high end tornado warning issued when a violent tornado is expected to impact a heavily populated area. Such warnings have been issued for the 1999 F5 Moore, Oklahoma tornado, and the 2007 EF5 Greensburg, Kansas tornado.
Severe Thunderstorm Watch - Conditions are favorable for the development of severe thunderstorms in and close to the watch area. A severe thunderstorm contains large damaging hail of 1 inch (27 mm) diameter or larger, and/or damaging winds greater than 58 mph (95 km/h or 50 knots) or greater. Isolated tornadoes are also possible but not expected to be the dominant severe weather event. These watches are issued for large areas by the Storm Prediction Center in Norman, Oklahoma, and are usually valid for five to eight hours.[4]
Particularly dangerous situation Severe Thunderstorm Watch - Conditions are favorable for the development of severe thunderstorms in and close to the watch area. Isolated tornadoes are possible but not expected to be the dominant severe weather event, hence these watches are very rarely issued. An expected severe wind event (derecho) is the mostly likely reason for a PDS Severe Thunderstorm Watch to be issued, with widespread winds greater than 90 mph (150 km/h or 80 knots) possible. These watches are usually issued for a larger area by the Storm Prediction Center in Norman, Oklahoma than a regular Severe Thunderstorm Watch, and are usually valid for a longer period of time than a regular Severe Thunderstorm Watch. This type of watch is usually only reserved for forecast "high-end" severe weather events.[5]
Severe Thunderstorm Warning - A severe thunderstorm is indicated by Doppler weather radar or sighted by Skywarn spotters. A severe thunderstorm contains large damaging hail of 1 inch in diameter or larger, and/or damaging winds greater than 58 mph (95 km/h or 50 knots) or greater. These warnings are currently issued on a polygonal basis.[6]
Flash Flood Watch - Conditions are favorable for (flash) flooding in and close to the watch area. These watches are issued by the Weather Forecast Office and are usually issued six to twenty-four hours in advance of expected flood potential. In Canada, a Heavy Rainfall Warning has a similar meaning.
Flash Flood Warning - Flash flooding is occurring, imminent, or highly likely. A flash flood is a flood that occurs within 6 hours of excessive rainfall and that poses a threat to life and/or property. Ice jams and dam failures can also cause flash floods. These warnings are issued on a county by county basis by the local Weather Forecast Office and are generally in effect for up to 6 hours.[7]
Flood Warning - General or areal flooding of streets, low-lying areas, urban storm drains, creeks, and small streams is occurring, imminent, or highly likely. Flood warnings are issued for flooding that occurs more than 6 hours after the excessive rainfall. These warnings are issued on a county by county basis by the local Weather Forecast Office and are generally in effect for 6 to 12 hours.[8]
Special Marine Warning - A warning to mariners of hazardous thunderstorms or squalls with wind gusts of 34 knots (39 mph or 63 km/h) or more, hail 3/4 inch (2 cm) diameter or larger, or waterspouts.[9]