This week’s extreme weather spotlights nation’s feast and famine water situation

The freak weather system that spawned a swarm of tornadoes in the South and unleashed torrents of rain from Pensacola to New York City has cast light on a remarkable precipitation disparity between the eastern and western U.S.

Percent of normal precipitation last 30 days (National Weather Service)

Percent of normal precipitation last 30 days (National Weather Service)

First, consider these historic rainfall totals from the Gulf Coast to around New York City:

* Pensacola, Florida had its wettest day in 134 years of records Tuesday, logging an astonishing 15.55 inches. Its two-day rainfall total of 20.47 inches was “a 1 in 100 to 1 in 200 year event” according to the National Weather Service.

Doppler estimated rainfall totals Monday night to Wednesday morning around Pensacola, Florida (National Weather Service)

Doppler estimated rainfall totals Monday night to Wednesday morning around Pensacola, Florida (National Weather Service)

* Washington Dulles Airport received 3.99 inches of rain Wednesday, its wettest day on record between the months of November and May.

* Baltimore received 3.06 inches of rain Wednesday, a record for the date, pushing its monthly rainfall total to 8.6 inches, just 0.1 inches away from its wettest April on record from 1889.

* Philadelphia picked up 4.42 inches of rain Wednesday, its wettest day on record between the months of November and May. (hat tip: Capital_Climate on Twitter)

* New York City logged 4.97 inches of rain Wednesday, more than 5 times its previous record for April 30 of 0.89 inches from 1963. (hat tip: Capital_Climate on Twitter)

Estimated rainfall over the last four days from Washington, D.C. to New York City (National Weather Service)

Estimated rainfall over the last four days from Washington, D.C. to New York City (National Weather Service)

Now, contrast that with the state of affairs described in the latest U.S. Drought Monitor:

U.S. Drought Monitor effective April 30, 2014.

U.S. Drought Monitor effective April 30, 2014.

* Over 60 percent of the western U.S. is in drought.

* 100 percent of California is in drought, and 77 percent of the state is in extreme to exceptional drought.

* “April 27 U.S. Department of Agriculture (USDA) reports indicated that 78% of Texas and 72% of Oklahoma topsoil was short or very short of moisture”

Precipitable water on April 30 (Image obtained using Climate Reanalyzer, Climate Change Institute, University of Maine, USA, via Paul Douglas blog)

Precipitable water simulation on April 30 shows giant moisture plume surging up East Coast. The western U.S. is bone dry.  (Image obtained from Climate Reanalyzer, Climate Change Institute, University of Maine, USA, via Paul Douglas blog)

To put this contrast into some perspective consider:

* Washington, D.C., Baltimore, Philadelphia, and New York City all received approximately 5 inches of rain since Monday.  That’s the same amount of rain that has fallen in Los Angeles this entire year (5.11″) so far.

* The 20.47 inches that fell in Pensacola, Florida (Monday to Wednesday) is more rain than Los Angeles has received in 2012, 2013, and 2014 combined (16.86 inches)

What’s causing the striking precipitation contrast?

The high altitude atmospheric flow pattern (i.e. jet stream) on April 29. (earth.nullschool.net)

The high altitude atmospheric flow pattern or jet stream) on April 30. (earth.nullschool.net)

This tale of precipitation haves and haves not ties back to the overall jet stream pattern. The “ridiculously resilient ridge” or bump in the jet stream retains warm, dry weather in the West while a big jet stream trough or dip in the central and eastern U.S. brings cool weather to the north central U.S. and stormy weather on its southern and eastern flank.  The pattern has held for months and has yet to show signs of caving.

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