California and National Drought Summary for May 5, 2015
Hawaii, Alaska and Puerto Rico
April was a relatively good month for drought recovery in Hawaii, with improvement of D0 and D1 noted across Oahu and the Big Island. There was some expansion, however, across Maui due to USDA reports of vegetation and pasture stress. The Big Island reflects a mixed bag with some reduction of D1 in the lower North Kona and South Kona districts coupled with degradation from D0 to D1 over the Pohakuloa, Waikoloa, Kawaihae and leeward North Kohala regions. The rest of the islands remain unchanged from last week.After a very dry April, Puerto Rico just can’t seem to shake this dry spell in early May, which is usually the time of year that they should be coming out of the dry season. (May and October are normally Puerto Rico’s wettest months of the year.) As such, streamflows on the island are suffering and fires are becoming more of a concern as the much-needed wet season approaches. This has led to the expansion of D0 across all of eastern Puerto Rico and the Isla de Vieques as well. In addition, an introduction of D1 is depicted this week in the southeastern reaches of the island east of Ponce and situated around the Guayama region.
No changes were made to the Alaska depiction this week.
The Midwest
All but portions of Iowa, Illinois and northwestern Missouri saw a dry week and all but Indiana and portions of southern Missouri and Illinois recorded above-normal temperatures. As a result, D0 receded in eastern Iowa and expanded in northwestern Iowa. Expansion of D0 spilled out into central Missouri as well this week, where year-to-date rainfall is sitting at only 50-70 percent of normal.Minnesota continues to bear the brunt of the early-year dryness. D1-D2 expanded this week to cover all of the northern counties and pushed eastward to cover more of the central part of the state, where deficits are running anywhere from 4 to7 inches, dating back to October 1, 2014. As the dry spring persists, concerns continue with regards to the lack of soil moisture recharge, along with already-low streamflow and lower lake levels being reported virtually statewide.
The Northeast
Last week brought continued dryness coupled with warmer temperatures (4-6 degrees above normal). Precipitation deficits are beginning to accumulate to the tune of 3-6 inches (less than 50% of normal) over the past 60 days. This has resulted in an expansion of D0 across southeastern Pennsylvania, northern New Jersey, eastern New York, Massachusetts and Connecticut. Water supply and soil moisture conditions are generally in good shape given the short-term nature of the dryness.The Plains
The best of this week’s rains fell outside most of the primary drought areas in the, but some beneficial rains helped to continue the recovery process across parts of Kansas, western Oklahoma and western Texas. The lack of rainfall in South Dakota means D2 has advanced westward toward the Black Hills. While this has provided favorable planting conditions, it has also led to an early stress on range and pasture conditions across much of the northern Plains.Other changes worth noting this week are shown in western Oklahoma and north and northwestern Texas, including the Panhandle. This has led to a reduction of D1-D3 this week based on the favorable short-term pattern and prospects for future rains looking quite promising over the next week as well. These recent rains and the resultant short-term benefits (soil moisture, streamflows, rangeland conditions) means that the short-long term impact line (SL) has been pushed northward into the Texas and Oklahoma Panhandles and a bit eastward into western Oklahoma as well. Long-term drought hangover impacts are still noted in those areas falling under the long-term (L) impact line designation, reflecting longer-term lack of deep soil moisture, tree stress, and below-normal groundwater and reservoir levels, which will need to continue to see recovery before this 5-year drought is truly broken.
The Southeast
A drier and cooler pattern settled in across the Southeast last week with the only heavy rains (3-4 inches) falling in the D0-D1 area in southern Florida. This led to some slight adjustments for the better to the D0-D1 there, but lingering seasonal dryness means the D0-D1 hasn’t been totally eradicated. Expansion of D0 is noted this week in southern and southwestern Alabama, with D0 edging over into extreme eastern Mississippi and into a portion of the northwestern Florida Panhandle.The West
On the heels of last week’s favorable rains in eastern New Mexico, more modest rains, but rain nonetheless, fell again across eastern New Mexico, helping to continue pushing back the D0-D2 conditions found in the northeastern corner of the state. This relief hasn’t stopped at the border, as southeastern Colorado shares in the improvement this week, with a chipping away of D0-D2. Streamflow levels continue to respond favorably, but surface water storage has a ways to go, with Elephant Butte remaining at only 19.9 percent full (based on conservation storage and conservation capacity) as compared to 18.5 percent this time last year. However, it is up from just six months ago when the reservoir was below 10 percent full.To the west of New Mexico, Arizona’s relatively favorable short-term precipitation led to the removal of the small D3 area found in the southeastern corner of the state. Long-term impacts and overall recovery are still lacking, heading into an important monsoon season, as D1-D2 conditions still cover over 80 percent of the state.
The situation continues to deteriorate across northern California and Oregon as well. This is reflected by a slight expansion of D1-D2 to the west in extreme northwest California and extreme southwest Oregon. The northwest corner of Oregon also sees a bump downward this week with an expansion of D2 there.
Idaho has also taken a turn for the worse as the wet season winds down, with expansions of D0 across the Panhandle and central regions and of D1 in the west-central region of the state. Water supply forecasts continue to decline along with the early melt-out of an already below-normal snow pack. The D0 also expanded to the east into Montana along the Bitterroot Range. Speaking of Montana, this week’s map reflects an expansion of D1 in the southwest corner along with a push eastward of the D0 into the southeastern corner of the state.
Looking Ahead
For the upcoming 5-day period, May 7-May 11, a large, slow moving system will churn out into the country’s mid-section, bringing with it potentially heavy rains on the order of 2 to 4 inches. These widespread rains are forecasted along the Rocky Mountains Front Ranges of Colorado and Wyoming along with most of the Great Plains and into the Midwest. Temperatures are expected to be well above-normal in the Pacific Northwest (3 to 9 degrees F) and east of the Mississippi (3 to 9 degrees F). Well below-normal temperatures are likely (6 to 15 degrees F) in southern California, the Great Basin, the Rocky Mountain range and Front Range, the northern Plains and up into Minnesota and western Wisconsin.For the 6-10 day period, May 12-16, above-normal temperatures are expected across all of Alaska, the Pacific Northwest (including Montana) and the Atlantic Seaboard. Below-normal readings are expected for most of California, the Four-Corner region, the central and southern Plains and the Midwest. As for precipitation, below-normal rainfall is more likely in the northern and central Plains, the Midwest and Ohio Valley. The prospects for above-normal precipitation are located across the Great Basin, Desert Southwest, Texas and the Gulf Coast region.
Author(s):
Mark Svoboda, National Drought Mitigation Center
Dryness Categories
D0 ... Abnormally Dry ... used for areas showing dryness but not yet in drought, or for areas recovering from drought.Drought Intensity Categories
D1 ... Moderate DroughtD2 ... Severe Drought
D3 ... Extreme Drought
D4 ... Exceptional Drought
Drought or Dryness Types
S ... Short-Term, typically <6 months (e.g. agricultural, grasslands)L ... Long-Term, typically >6 months (e.g. hydrology, ecology)
