Tuesday, March 27, 2012

Dramatic Precipitation changes in 2011

Dr. Jeff Masters' WunderBlog

Wettest year on record in Philadelphia; 2011 sets record for wet/dry extremes in U.S.
Posted by: JeffMasters, 3:00 PM GMT on December 12, 2011 +19
This year is now the wettest year in nearly 200 years of record keeping in Philadelphia, Pennsylvania. A large, wet low pressure system soaked the Northeast U.S. on Wednesday and early Thursday, bringing 2.31 inches of rain to the City of Brotherly Love, bringing this year's precipitation total in Philly to 62.26 inches. This breaks the old yearly precipitation record of 61.20 inches, set in 1867. In a normal year, Philadelphia receives about 40 inches. According to wunderground's weather historian Christopher C. Burt, this is one of the most difficult U.S. city records to break, since rainfall records in Philadelphia go back to 1820. The only other sites with a longer continuous precipitation record in the U.S. are Charleston, SC (1738 -) and New Bedford, MA (1816 -).

Figure 1. Departure of precipitation from average for 2011, as of December 6, 2011. Image credit: NOAA/HPC.

20+ inches above average precipitation in Ohio Valley, Northeast
Philadelphia is not alone in setting a wettest year in recorded history mark in 2011. Over a dozen major cities in the Ohio Valley and Northeast have set a new wettest year record, or are close to doing so. Thanks to rains associated with this year's tremendous tornado outbreaks in April in May, plus exceptionally heavy summer thunderstorm rains, combined with rains from Tropical Storm Lee and Hurricane Irene, portions of at least twelve states have seen rains more than twenty inches above average during 2011.

The fraction of the country covered by extremely wet conditions (top 10% historically) was 32% during the period January through November, ranking as the 2nd highest such coverage in the past 100 years. And if you weren't washing away in a flood, you were baking in a drought in 2011--portions of sixteen states had precipitation more than twenty inches below average (Figure 1.) The fraction of the country covered by extremely dry conditions (top 10% historically) was 22% during the period January through November, ranking as the 8th highest in the past 100 years. The combined fraction of the country experiencing either severe drought or extremely wet conditions was 56% averaged over the January - November period--the highest in a century of record keeping. Climate change science predicts that if the Earth continues to warm as expected, wet areas will tend to get wetter, and dry areas will tend to get drier--so this year's side-by-side extremes of very wet and very dry conditions should grow increasingly common in the coming decades.

Figure 2. Percentage of the contiguous U.S. either in severe or greater drought (top 10% dryness) or extremely wet (top 10% wetness) during the period January - November, as computed using NOAA's Climate Extremes Index. Remarkably, more than half of the country (56%) experienced either a top-ten driest or top-ten wettest year, a new record. Image credit: NOAA/NCDC.

Unofficial state yearly precipitation record set in Ohio
The Wilmington, Ohio NWS office announced last week that three stations in Southwest Ohio had unofficially broken the 140-year old state yearly precipitation record. Cheviot, Miamitown, and Fernbank have recorded 73.81", 71.89", and 70.85", respectively so far in 2011, beating the old record of 70.82" set at Little Mountain in 1870. According to wunderground's weather historian Christopher C. Burt, the old record should be 72.08” at Mt. Healthy, Ohio in 1880.

Wunderground's weather historian Christopher C. Burt summarizes the global weather extremes in November in his latest post.

Jeff Masters

() end quote from: http://www.wunderground.com/blog/JeffMasters/comment.html?entrynum=2001

So, if you look at the drought which tends to be the most damaging you can see the worst of the drought was in Texas and in the Southwest and South east which was the worst over the largest amounts of areas. Though too much rain might bring flash floods or floods in the end droughts tend to damage areas sometimes for years (5, 10, or more).

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