June - August 2014

Outlook Graphic: PNG   PDF 

Latest Seasonal Assessment - As of May 13, 2014, drought covered approximately 38 percent of the contiguous 48 states, according to the U. S. Drought Monitor. This number has not changed much since late January. However, the area affected by extreme or exceptional drought (D3 or D4) has expanded from about 10 percent of the contiguous states in mid-April to 14 percent in mid-May. Most of the deterioration occurred in the southern half of the Plains before mid-May rains halted deterioration in the southeastern half of Texas and adjacent parts of Oklahoma and Louisiana. Most of the Texas and Oklahoma Panhandles, northeastern New Mexico, and southwestern Kansas received only a few tenths of an inch of rain from mid-April to mid-May, when precipitation is usually on the increase in this region. To the north and west of the central Plains, only a few scattered areas experienced worsening drought, but improved conditions were limited to parts of the northern and eastern tiers of the broad drought area in the central and western states. Alaska, Hawaii, Puerto Rico, and areas east of the Mississippi River remained almost entirely drought free, except for small areas in the upper Southeast and on central Molokai Island in Hawaii.

The drought outlook valid from May 15 to August 31, 2014 is based primarily on initial conditions, medium- and long-range forecasts, and climatology. Persistence is highly probable along the West Coast and in the Intermountain West, where summer is a relatively dry time of year and both surface and subsoil moisture almost always decline. Persistence is also forecast, though with less confidence, from southern Kansas southward through the High Plains of New Mexico and all but westernmost Texas, including the broad area of exceptional drought over and near the Texas and Oklahoma Panhandles. Drought is forecast to expand into the remainder of far southern Texas, much of southeastern Texas, and the southwestern quarter of Louisiana by the end of summer. At least mild dryness exists across these regions as of mid-May, and there are significantly enhanced chances for a drier than normal summer in the Seasonal Outlook. In contrast, drought improvement or removal is forecast from central Kansas northward into the northern Plains, where forecasts from late May onward generally favor above-normal precipitation. Also, improvement or removal is expected in the southern Rockies, but likely not until seasonal monsoon rains begin in late July or August. Summer is a relatively wet time of year in the southern Rockies, throughout the High Plains, and in the central and northern Great Plains, so there is the potential for substantial drought improvement in these areas if above-normal rainfall is recorded. Typically, between 40 and 50 percent of each year’s rainfall occurs during June – August from the southern Rockies and the Big Bend of Texas northeastward through the Dakotas and Minnesota.

Tools used in the U.S. Seasonal Drought Outlook (SDO) included the official Climate Prediction Center (CPC) temperature and precipitation outlooks for June 2014 and June – August 2014, various short- and medium-range forecasts and models such as the 5-day and 7-day precipitation totals from the Weather Prediction Center, the 6-10 day and 8-14 day CPC forecasts, the NAEFS precipitation outlooks, the soil moisture tools based on the Constructed Analog on Soil Moisture (CAS), dynamical models (CFSv2, NMME, and IMME), the 384-hour total precipitation forecasts from several runs of the GFS, the four-month Palmer drought termination and amelioration probabilities, climatology, and initial conditions. The chances of El Niño increase during the 2014 summer, with the May 8, 2014 ENSO Advisory (from CPC and the International Research Institute for Climate and Society (IRI)) indicating a 65% chance of El Niño conditions developing by the end of August.

For the week following the release of this Outlook (May 15 - 22, 2014), little precipitation is expected to fall on most of the nation’s areas of drought. Amounts of 0.5 to 1.0 inch, with isolated higher totals, are anticipated from Nebraska, Iowa, and northeast Colorado northward to the Canadian border. The eastern side of the small drought area in the interior Southeast (near where Tennessee, Mississippi, and Alabama meet) may also get 0.5 inch of rain or more. Otherwise, only a few tenths of an inch are expected at most. The chances for notable rainfall in at least some drought areas increase from the last week of May onward, thus the Seasonal Drought Outlook is based primarily on forecasts for the 8- to 14-day period and beyond.

Summer is a dry time of year along the West Coast, especially in California. Typically, less than 10 percent of a given year’s precipitation falls during June – August on areas west of the Cascades and Sierra Nevada, with very little precipitation falling on most of the Golden State. In the Great Basin and Intermountain West, summer is drier than other times of the year, though not so markedly. However, surface and subsoil moisture content declines much more frequently than it increases in these regions during the summer, making drought recovery highly unlikely despite forecasts for above-normal rainfall in some areas.
Forecast confidence for The Far West and the Intermountain West is high.

Climatologically, summer starts out dry across the southern Rockies, but rainfall picks up starting in July or August as monsoonal moisture pours into the region, triggering shower and thunderstorm activity. The odds favor dry weather through May across most of Arizona and New Mexico. Over the summer, there are enhanced chances for above-normal rainfall across most of the southern Rockies, and in areas where wetter-than-normal weather is not particularly favored, the monsoon climatologically recharges the moisture budget more often than not. This is a markedly wet time of the year from central Arizona eastward to the border separating New Mexico and Texas, and in the Big Bend region (40 to 50 percent the total annual precipitation falls during this 3-month period). No compelling reason exists to expect monsoon rains to fail this year, so because of climatology and the June – August forecast, drought improvement (removal in areas of moderate drought) is forecast.
Forecast confidence for the southern Rockies is moderate.

For the drought areas in the southern half of the Plains -- roughly from central Kansas and eastern Colorado southward to the Mexican border and the Gulf Coast -- drought is expected to persist, with some expansion into deep south Texas, much of southeastern Texas, and the southwestern quarter of Louisiana. The persistence forecast includes most of the large area of extreme to exceptional drought extending from west-central Texas northward to the central Plains. Some much-needed moisture is expected across most of this region during the last week of May. Thereafter, the June forecast calls for a slight tilt of the odds toward wetter than normal conditions in southern Kansas and adjacent locales, but there is no discernable signal elsewhere. The summer forecast, in contrast, does not highlight above-normal precipitation anywhere in this region, and below-normal precipitation is favored across Louisiana and roughly the southeastern half of Texas. Summer is a relatively wet time of year from the Texas Panhandle and central Oklahoma northward, but soil moisture does not reliably increase climatologically, and in fact a decrease in total soil moisture is more common outside the Oklahoma and Texas Panhandles and the western tier of Kansas. Considering climatology and the 3-month forecast, drought persistence seems the most probable scenario, and since the odds favor a relatively dry summer in deep south Texas and the southeastern Plains, conservative expansion is forecast in areas where the highest odds for subnormal summer precipitation coincide with mild to moderate antecedent dryness.
Forecast confidence for the southern half of the Plains is moderate.

In the drought areas across the Plains and Midwest from central Kansas northward, drought improvement is expected (removal in areas of only moderate drought). Enhanced chances for above-normal rainfall are indicated by the 8- to 14-day, June monthly, and June – August seasonal outlooks. Also, this is a wet time of the year climatologically, and moisture budget increases are not uncommon, occurring in about half of all summers historically. Improvement/removal is the only logical forecast, although the uncertain nature of summer precipitation tempers confidence a bit.
Forecast confidence for the northern half of the Plains and the Midwest is moderate.

The drought area in the interior Southeast near where Mississippi, Tennessee, and Alabama meet is small, and the June forecast indicates slightly enhanced chances for above-normal precipitation there. However, wetness is not favored during the last week of May, nor for the summer as a whole, and moisture recharge is uncommon in this area during summer. Thus, persistence is forecast, though not with much confidence given the lack of non-climatological indicators.
Forecast confidence for the upper Southeast is low.

The only remaining drought area in Hawaii is on central Molokai, associated with low water levels on the Kualapuu reservoir. The June – August forecast favors neither dryness nor wetness in this region, but precipitation should be on the increase toward the end of the summer climatologically, and outlooks for the July – September and August – October periods both slightly favor above-normal rainfall. Drought removal is forecast for this area of moderate drought for these reasons, though with low confidence.
Forecast confidence for Hawaii is low.