Drought in Arkansas John Lewis National Weather Service Little Rock, Arkansas firstname.lastname@example.org Emilie Nipper National Weather Service Little Rock, Arkansas email@example.com
Recent TrendsSince 2010, La Niña conditions (coolerthan normal water in the equatorialPacific Ocean) were dominant.The Arctic Oscillation (AO) played asignificant role in temperature trendsand precipitation amounts.There have been a lot of extremes,with either feast (i.e. very activeweather) or famine (i.e. littlerain/heat/drought) and not much in-
A Closer Look at AO 1995: 6 th Driest Late 2005: A Summer at Little Early 2005: Wet Period Rock (4.84”) Very Dry (Rita)Late 2001/Early 2002: Early 2008:Widespread Flooding Tornadoes, Flooding & Heavy Snow
Forecasting With AOImpacts associated with AO mostlyoccur from the fall into the spring(October through May).Long range forecasting, at leastbeyond a few weeks, is difficult toimpossible with the AO.Any impacts (due to fluctuationbetween positive and negative) areusually short-lived.
La Niña Setup Warm Surface Water Cool Water/UpwellingWest East
A Closer Look at ENSO Typical Winter ForecastCold Warm Wet Dry
Forecasting with ENSOThere is at least some confidence in along term forecast when keying on LaNiña/El Niño conditions.While there may be strengthening orweakening over several months, thestate (La Niña/El Niño) is fairlysteady.The forecast can be altered(sometimes significantly) by the short-term effects of AO.
Combine La Niña/AO Temperature (Jan - Mar) 2012 2011
Combine La Niña/AO Precipitation (Jan – Mar) 2012 2011
AO in 2011 Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec2011 -1.68 +1.58 +1.42 +2.28 -0.04 -0.86 -0.47 -1.06 +0.67 +0.80 +1.46 +2.22 The AO Index was mostly negative, with a strong positive surge in the spring of 2011 and again late in the year.
Big Time Rain April, 2011 Percent of normal rainfall.
Drought Status October 25, 2011 An extreme to exceptional drought was noted in much of southwest Arkansas.
Wet PatternNovember/Early December, 2011 Fronts (boundaries) moved into Arkansas from the northwest and stalled. Heavy rain focused along and north of the fronts.
A Lot of of Rain Nov 12 – Dec 11, 2011Rainfall (3.5” to 5.5” is normal)
Drought Status December 27, 2011 A severe to extreme drought remained in the far southwest, but was over elsewhere.
Good/Bad TimingThe deluge to end 2011 plus a wet startin 2012 helped charge the soil withwater at a time when vegetation wasdormant.The rain stopped coming in April, withwell below normal amounts measured.
Arctic Oscillation (AO) AO+ in March Flat AO in A largely April positive AO from January through March went flat in April.
Precipitation Trends January through July, 2012 J F M A M J J 10 5 Harrison Fort Smith 0 Jonesboro Little Rock -5 El Dorado Texarkana-10 Pine Bluff-15Departure From Normal
A Lack of Rain April through July, 2012Statewide Average: 9.03” (Driest onRecord)
Drought ImpactsA University of Arkansas Division ofAgriculture report revealed that 85%of pastures were in poor or very poorcondition, with the smallest hayyields since 1954.According to the Arkansas ForestryCommission, there were 855 fires thatburned almost 16,000 acres in Julyand August.Record low levels on area tributaries.
Widespread Drought Late August, 2012Coverage: 1,800 Counties in 38
Playing the OddsResearch showed that odds for a Top25 warm summer were somewhat low(42% chance locally) following arecord warm first five months of 2012.After June/July, we had a Top 5 warmsummer going at several locations,including Little Rock.If the research was correct, changeswere coming in August (and possiblybeyond), especially given a developingEl Niño.
Tropical ReliefRemnants of Hurricane Isaac broughtheavy rain to eastern Arkansas onAugust 30-31, 2012.
And Even More Rain…The first half of September featuredwell below normal temperatures attimes and areas of heavy rain.From July 31st to September 17th,precipitation departures from normalwent from -7.75 inches to -1.19 inchesat Little Rock (Pulaski County) andfrom -10.92 inches to +0.74 inches atPine Bluff (Jefferson County).
Precipitation Trends January through September, 2012 J F M A M J J A S 10 Note: September is 5 Harrison through the 17th. Fort Smith 0 Jonesboro Little Rock -5 El Dorado Texarkana-10 Pine Bluff-15Departure From Normal
Precipitation Forecast Late Winter/Early Spring El NiñoAO+ AO-
The ForecastA continued “correction” toward cooland wet (at/above normal rain andat/below normal temperatures) isexpected through the end of the year(El Niño driven).There may be a return to dryconditions in the late winter/earlyspring (favored in eastern Arkansas).However, a positive AO could reversethis.Drought conditions will likely improve
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