2011-05-20 03:23:35Floods, Droughts Are 'New Normal' Of Extreme U.S. Weather Fueled By Climate Change, Scientists Say
Dana Nuccitelli

Good Reuters article linking extreme weather to climate change.

2011-05-20 03:33:21Definitions?
John Hartz
John Hartz

Are there commonly accpeted defitions of what constitutes an extreme weather event? If so, where are they published?

2011-05-20 03:33:40
Paul D


Was listening to Farming Today this morning on BBC Radio 4, they had a farmer on who said he had about 10% of the 'normal' rainfall this April/May. Reckons he might only get 50% of the normal crop. It's pretty dry here. Could see hose pipe bans.

2011-05-20 03:54:15
Julian Brimelow

Good question Badger.  Defining what is considered an extreme varies and is difficult to quantify for some variables.  I bet there is something in the IPCC.

Most groups use the standardized precipitation index or the the Palmer drought index or derivatives thereof to identify unusual or extreme precipitation events (including drought)-- Google those terms.  The baseline used is a factor though, so the "new normal" data could really mess things up if they are included.

For severe thunderstorms, most groups identify a severe day as one with hail of 2 cm diameter or more, or a tornado or straight-line winds greater than 90 km/hr.  Some also use rainfall amounts too, but the thresholds and time windows vary.

2011-05-20 05:06:40Albatross
John Hartz
John Hartz

I have done a cursory serch of the WMO website but couldn't find anything resembling a set of definitions of "severe weather events." I'll continue to nose around in other webistes as I have the time to do so.