Do all of the recent Heat Advisories, Excessive Heat Watches, and Excessive Heat Warnings have you confused and wondering why we can’t just say “IT’S HOT“?? I’ll get to that in a minute.
First a few stats about the Memphis summer of 2011:
- Since May 28, there have only been 5 days that the temperature has NOT reached at least 90. In July, we reached 90 every day except the 7th (it was 86).
- So far, there have been 7 days in which the low has not dropped below 80.
- The average temperature for June-July 2011 is 84.9 degrees, which ties 1980 for the warmest June-July period on record. Yes, THAT 1980!
So, the main threshold to watch for is the 110-degree heat index. An Excessive Heat Watch may be issued 3 days in advance of a forecast heat index of 110. Then, the day before the event, if the heat index is expected to only reach 105-109, a Heat Advisory will replace the Watch. If the heat index is still expected to hit 110, the Warning will be issued instead. An Advisory is basically a “toned-down” Warning. A Watch is issued for longer lead times (similar to a Tornado Watch, which means conditions are favorable, versus a Warning, which means the event is imminent).
Hopefully this helps sort out the plethora of headlines the NWS has used during this heat wave. By the way, the Memphis office has put together a well-done summary of all of their watch and warning products. You can find it here: Headlines Issued by NWS-Memphis.
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