MESONET TICKER ... MESONET TICKER ... MESONET TICKER ... MESONET TICKER ... July 12, 2012 July 12, 2012 July 12, 2012 July 12, 2012
Drought encompasses entire state for first time since last November
Fueled by the Oklahoma's sixth driest April 1-July 12th period since 1921, and despite recent localized heavy downpours, drought now encompasses virtually the entire state for the first time since Nov. 15, 2011.
http://ticker.mesonet.org/archive/20120712/ok_dm.png
Nearly 39% of the state is now labeled in severe-extreme drought, although the extreme portion is only 11%. The severe-extreme percentage is up 20% from last week's map. No part of the state has made it back to exceptional drought, the U.S. Drought Monitor's worst designation. Exceptional drought is beginning to build in central Arkansas, however, and similar conditions are creeping towards eastern Oklahoma.
http://ticker.mesonet.org/archive/20120712/south_dm.png
At this time last year, 33% of Oklahoma was suffering from exceptional drought.
Further intensification occurred in southeastern Oklahoma, where severe drought is now labeled extreme. Moderate drought worsened to severe drought from northwestern through west central Oklahoma. Several indicators led to the intensification, from steadily dwindling lake levels detailed a couple of days ago to a rapid decline in soil moisture and rangeland/pasture conditions. The main factor is rainfall, of course. And that is something that has been in short supply right through Oklahoma's primary rainy season of April through mid-June, bleeding right into the heart of summer. According to data from the Oklahoma Mesonet, the statewide average rainfall total since April 1 is 8.83", a deficit of 4.93" or 64% of normal. Southeastern and east central Oklahoma are sporting deficits of 8.34" and 8.13" and rankings of second driest and third driest on record, respectively.
April 1-July 12 Mesonet rainfall maps http://ticker.mesonet.org/archive/20120712/apr1-july12-totals.png http://ticker.mesonet.org/archive/20120712/apr1-july12-pct.png http://ticker.mesonet.org/archive/20120712/apr1-july12-departures.png
-****- April 1-July 12 Mesonet climate division rainfall statistics Climate Division Total Depart. Pct. Norm. Rank Since 1921 OK-1: Panhandle 6.11" -2.99" 67% 15th driest OK-2: N. Central 9.23" -3.63" 72% 17th driest OK-3: Northeast 11.30" -4.06" 74% 11th driest OK-4: W. Central 7.08" -5.00" 59% 6th driest OK-5: Central 9.66" -4.79" 67% 10th driest OK-6: E. Central 7.90" -8.13" 49% 3rd driest OK-7: Southwest 9.59" -2.86" 77% 25th driest OK-8: S. Central 9.10" -5.41" 63% 8th driest OK-9: Southeast 8.60" -8.34" 51% 2nd driest Oklahoma Statewide 8.83" -4.93" 64% 6th driest -***-
There are a few broad areas in those maps that show above normal rainfall, such as northern Oklahoma where heavy rains fell in April. The problem is that is really the last of the widespread rains in the midst of suddenly hot moisture-sapping summer heat. Here are those same rainfall maps since May 1. The statewide average since May 1 is 5.01", 5.42" below normal and the third driest such period since 1921.
http://ticker.mesonet.org/archive/20120712/may1-july12-totals.png http://ticker.mesonet.org/archive/20120712/may1-july12-pct.png http://ticker.mesonet.org/archive/20120712/may1-july12-departures.png
So what we're dealing with is a battle and/or combination of short- and long- term dryness. In places that had nice rains in April, like north central Oklahoma, the intervening period since has been exceedingly dry. And for those places that received recent rains, long-term concerns overwhelm those benefits. Add to that the cutoff point of Tuesday morning for any precipitation to be considered by the Drought Monitor and you get the most recent map. The localized areas that received nice rains have seen relief, but those small areas are difficult to portray on the Drought Monitor map, which is not meant to display down to a sub-county scale. Spotty showers are in the forecast for the next few days, but those are expected to bring only localized benefits. The latest 5-day rainfall forecast by the HPC is pretty bleak.
http://ticker.mesonet.org/archive/20120712/5-day-rainforecast.gif
Past that, the CPC is calling for increased chances for normal rainfall amounts and temperatures, but that is again part of the problem. Normal rainfall amounts during the summer are not enough to overcome the consumptive demands of humans and plants, and also evaporation due to heat, intense sunshine and wind.
The heat is reflected in the latest map of days at or above 100 degrees from the Oklahoma Mesonet.
http://ticker.mesonet.org/archive/20120712/tmax.ge100.png
That map is still a far cry from last year at this time, with nearly 50 days above 100 degrees in southwestern Oklahoma, and from 20-30 across much of western Oklahoma.
http://ticker.mesonet.org/archive/20120712/july12_2011-100s.png
The 100s started much earlier last year with a more mature drought already in place entering June. This year is well on its way to being the warmest on record based for the state, but that is largely due to a lack of any type of frigid air through winter into spring. The first six months of the year and also the spring period were the warmest statewide since records began in 1895. That accelerated vegetative growth and also evaporative demands much earlier this year.
You can read about those other drought indicators from the past couple of Tickers.
Pastures/Rangeland and Soils http://ticker.mesonet.org/select.php?mo=07&da=12&yr=2012
Lake Levels http://ticker.mesonet.org/select.php?mo=07&da=06&yr=2012
Again, the key is rainfall. More summer rains will bring a milder summer while further drought will beget more heat. Summertime rains are very difficult to predict, although most residents know what you "normally" get during an Oklahoma summer, and widespread relief from the skies usually isn't on the list.
But this is Oklahoma, land of normally not-normal weather. Forrest Gump's Mom was a pretty smart lady.
Gary McManus Associate State Climatologist Oklahoma Climatological Survey (405) 325-2253 gmcmanus@mesonet.org
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