Thursday, March 22, 2018

National Drought Mitigation Center


Drought and Climate for December 2016: Conditions improve in Southeast, West, Northeast

Access the latest monthly drought outlook from NOAA's Climate Prediction Center.
The two maps above are from the High Plains Regional Climate Center.
Find these and other products related to the U.S. Drought Monitor on the USDM website.

By Deborah Bathke, NDMC Climatologist


December brought with it an improvement or elimination of drought conditions in many locations across the contiguous United States.  Most notably, the Southeast saw an elimination of exceptional (D4) drought, with additional categorical decreases throughout much of the region.  Long-term drought conditions in the West and Northeast also saw improvements.  On January 3, 2017, drought was affecting 22.53 percent of the contiguous United States, compared to 31.46 percent on November 30, 2016. Improvements were seen in all drought categories.  Severe drought decreased from 16.60 to 8.63 percent, extreme drought decreased from 8.66 to 3.15 percent, and exceptional drought decreased from 2.68 to 0.96 percent. Drought area also decreased in Hawaii, from 8.34 to 2.47 percent. There was no drought in Alaska and Puerto Rico. Drought is now impacting 119.3 million people in the United States, compared to 148.6 at the end of November.

Drought Outlook

The Climate Prediction Center’s Monthly Drought Outlook projects that much of New England will see drought improvement or removal during the month of January, while the mid-Atlantic states will generally see a persistence of drought conditions.  Continued improvement is expected in the majority of the drought-afflicted areas of the Southeast with the exception of Florida, where drought is expected to persist and expand throughout the Peninsula.  Drought is also expected to persist throughout the central United States as little precipitation typically occurs this time of year.  Some areas, such as south-central Kansas, southeastern Colorado, and parts of Texas, are expected to see an expansion of drought.  In the West, drought improvement or removal is forecast for western Nevada, the Sierra Nevada, and adjacent eastern California. Other drought-affected areas of California, Nevada, and Arizona are expected to see a persistence of drought conditions.


This year’s weak La Niña generally brought warmer than average temperatures to the southern tier of the United States during December with temperatures up to 8 degrees above average, and cooler than average temperatures to  the northern tier with temperatures as low as 10 degrees below average.


Typically, La Niña means drier than average conditions to the southern United States and wetter than average conditions across the northern tier.  However, this year’s La Niña is weak compared to previous events and its effects weren’t as strong. Areas that typically see above-average precipitation during a La Niña (such as the coastal Pacific Northwest and northern California) and across Missouri, Illinois, and Indiana all saw deficits of more than 2 inches of precipitation.  Parts of the southern United States that typically see below-average precipitation during a La Niña winter, such as southern California, the southern edge of the Texas-Louisiana border, and the tristate region of Georgia, Alabama, and northern Florida, all saw surpluses of more than 6 inches of precipitation. 


Regional Overviews


December average temperatures ranged from 3°F below normal to more than 3°F above normal in the Northeast. The coolest spots were in Maine, while the warmest spots were generally in northern New York and portions of West Virginia.  Precipitation for most of the region ranged from 50 percent of normal to 200 percent of normal.  The driest area was in southeastern Massachusetts, which had a shortage of 2.3 inches for the month.  Wetter than normal areas were scattered throughout the region.  Drought decreased throughout the region, with the exception of Delaware and New Jersey.  As of January 3, drought covered 43.67 percent of the region, compared to 54.36 percent on November 29. Severe drought (D2) also decreased from 19.69 to 11.68 percent and extreme drought (D3) from 3.4 to 1.39 percent.  The region was not experiencing exceptional drought.


Average temperatures in December ranged from normal to more than 8 degrees above normal. The warmest locations were recorded in Alabama, Georgia, and Florida.  Heavy rainfall across the region during the month brought more than 10 inches of rain to western Florida, southeastern Alabama, and southwestern Georgia.  Despite the widespread rainfall, monthly deficits of more than 3 inches are still present in the interior locations of the Southeast.  Florida’s peninsula also remains dry. The rain helped to improve drought conditions so that 38.51 percent of the region is in drought compared to 54.89 percent on November 29.  Decreases occurred across all categories, with severe drought (D2) decreasing from 43.33 to 21.05 percent and extreme drought (D3) from 36.15 to 8.85 percent. Exceptional drought, previously at 14.06 percent, was removed from the region.

Movers & Shakers for December 2016

Percent area Nov. 29, 2016

Percent area Jan. 3, 2017 Status Percentage point change
Biggest increases in drought
Illinois 1.32 6.50 Moderate 5.18
Kansas 10.50 13.58 Severe 3.08
 9.19 26.62
New Jersey
Oklahoma 56.94
South Dakota
Biggest improvements in drought
Alabama 100.00 68.12 Moderate 31.88
Severe  51.42
 23.32 Extreme
Exceptional 32.75
Arkansas 86.49 39.03
Moderate 47.46
46.92 7.99 Severe 38.93
Arizona 44.76 24.76 Moderate 20.00


73.04 67.61 Moderate 5.43
60.27 54.02 Severe 6.25
Connecticut 44.28 40.97 Extreme 3.31
Florida 24.37 6.07 Moderate 18.30
Severe 17.37
Georgia 88.87 73.48 Moderate 15.39
 33.22 0
Hawaii 8.34 2.47 Moderate 5.87
Kentucky 98.49 0 Moderate 98.49
89.71 0 Severe 89.71
24.76 0 Extreme 24.76
99.61 15.85 Moderate 83.76
Extreme 20.79
Maine 72.36
 0.57 Severe  38.51
42.70 32.68 Moderate 10.02
Massachusetts 41.35
Extreme 32.76
Mississippi 100.00
Moderate 44.64
0 Extreme
New Hampshire
75.35 Moderate
 57.42 44.93 Severe
 4.67 0 Extreme
New York
64.82 40.21 Moderate
9.70 Severe
North Carolina
32.61 26.90 Moderate
12.41 Severe
12.75 1.57 Extreme
 4.46 0 Exceptional 4.46
Ohio  3.14 0.00 Moderate 3.14
Oregon 23.22
5.29 Moderate
Pennsylvania 34.34
27.60 Moderate
South Carolina
 40.49 30.28 Moderate
19.83 Severe
4.12 Extreme
0 Exceptional
South Dakota
31.81 26.01 Moderate
37.78 Moderate
 99.08 13.03 Severe
1.83 Extreme
0 Exceptional
14.18 6.29 Moderate
28.39 15.39 Moderate
0 Severe
 79.99 64.92 Moderate 15.07
12.40 2.58 Severe 9.83
West Virginia
4.06 0 Moderate 4.06


In the Midwest, mean temperatures ranged from 4 degrees below to 4 degrees above normal. The coolest areas were located around the southern edge of Lake Michigan and the warmest areas were along the northern edge. Precipitation was above normal in December in the Upper Midwest and in Kentucky and southern Ohio.  Heavy snowfall in the Upper Midwest had multiple stations recording surpluses of 0.7 to 2.3 inches for the month, landing them in the top 10 wettest Decembers.  An area of dryness extended from southwestern Missouri to the northeast into Indiana, with stations receiving less than 50 percent of normal precipitation. Surplus rainfall eliminated drought from Indiana, Ohio, and Kentucky, while moderate drought (D2) increased in Illinois and Missouri.  As a whole, drought decreased in the region, from 10.67 to 4.45 percent of the region between November 29 and January 3.  Severe (D2) and extreme drought (D3), previously at 7.89 and 2 percent of the region, respectively, were eliminated.

High Plains

Below-normal temperatures were common across the High Plains during December as a result of an Arctic air outbreak mid-month.  Stations from North Dakota to Kansas set daily record lows on December 17-18, contributing to average monthly temperatures of 1-8 degrees below normal. Snow storms in the Dakotas left the majority of this area with monthly precipitation totals of 0.4 to 1.6 inches above normal. Meanwhile, deficits of up to 1 inch were recorded at stations in Kansas. The abundant snowfall eliminated the small areas of moderate drought in North Dakota and eastern South Dakota.  However, drought expanded in southwestern South Dakota, eastern Colorado, and southwest Kansas.  By January 3, drought was affecting 21.54 percent of the region, compared to 21.97 percent on November 29.  Severe drought (D2) expanded slightly, from 2.7 percent to 3.85 percent.  The region was not experiencing extreme (D3) or exceptional (D4) drought.


The South was not immune to the cold air outbreaks.  Multiple stations in Oklahoma and north and central Texas also set daily record lows on December 17-18. Meanwhile, temperatures along the coasts of Texas and Louisiana were warmer than normal, with stations recording monthly averages that fell within the top 10 warmest Decembers.  At month’s end, average temperatures in the region ranged from 1 degree below to 6 degrees above normal. Precipitation was mixed throughout the region; locations in eastern Oklahoma, the north central plains of Texas, and northwest Arkansas had precipitation deficits of more than 2 inches for the month while other locations, such as south Texas and southeastern Louisiana, received surpluses of more than 4 inches.  With the exception of Oklahoma, states within the region generally saw a reduction of drought area. For the region as a whole, drought now covers 27.69 percent of the region, down from 49.52 percent on November 29.  Severe drought (D2) also decreased, falling from 32.07 to 11.09 percent. Extreme drought (D3) fell from 13.67 to 1.11 percent and exceptional drought (D4) decreased from 1.11 to 0 percent.


Cooler than average temperatures dominated the northern part of the region, where monthly averaged temperatures ranged from 2 to 10 degrees below normal. Many stations in Montana, Idaho, Washington, and Oregon ranked among their top 10 coldest Decembers on record.  Meanwhile, the southern part of the region experienced warmer than normal temperatures, with monthly averaged temperatures of up to 4 degrees above normal. Stations in eastern Arizona and western New Mexico ranked in the top 10 warmest on record. Precipitation in the West ranged from monthly deficits of 4.2 inches in the coastal Pacific Northwest to surpluses of 3.9 inches in northeast California. Cold storms in the latter half of the month improved western snowpack—particularly across the Great Basin, the Intermountain West, and the Pacific Northwest—and have helped improve conditions in drought-affected areas. As a whole, drought in the West decreased from 25.58 to 21.51 percent of the region.  Severe drought decreased from 9.90 to 8.53 percent. Extreme drought decreased from 5.73 to 5.11 and exceptional drought from 2.81 to 2.44 percent.





December 2016 impact summary: Winter storms bring relief to Southeast, other drought-stricken parts of U.S.

The two charts above summarize information from the Drought Impact Reporter.
The two charts above summarize information from the California Department of Water Resources Water Conditions page.

By Denise Gutzmer, NDMC Drought Impact Specialist

Abundant rainfall changed the drought status of parts of the United States in December, with the Southeast feeling drought relief wash over them and seeing the fire danger decrease.  Heavy rain early in the month allowed local and state authorities in parts of the Southeast to lift restrictions on outdoor burning, but the need for caution remained.  Meanwhile, in California, the water year had gotten off to a very promising start in December, particularly in the north, but by early January, heavy rainfall from a series of storms had inundated parts of the state.  Despite the rain, California had the most drought impacts in December with 15, while Georgia, Alabama, Connecticut, and North Carolina followed with 7, 6, 5, and 5, respectively. 

California's snowpack still shallow

At the end of December, the snowpack in the Sierra Nevada was still on the shallow side, with electronic monitors revealing a water content of 72 percent.  The first manual snow survey at Phillips Station on January 3 indicated a water content of just 53 percent of normal, but higher elevations had more snow.  By both measures, the state needed more snow to avoid a sixth year of drought.                            

California Snowpack Measures Low, But Big Storms Coming, by Rich Pedroncelli and Scott Smith, The Associated Press, Jan. 3, 2017

Water bill to benefit California

In mid-December, President Obama signed a bill authorizing water projects across the nation, including $558 million for drought relief projects in California. The funds were to "help assure that California is more resilient in the face of growing water demands and drought-based uncertainty." Some felt that the bill would send too much water to the state’s farms and businesses and would undermine protections for endangered species, while others viewed the bill as a boon to California water policy.

Obama signs bill for Flint water, Calif. Drought, by Matthew Daly, The Associated Press, Dec. 16, 2016

Drought-affected tree falls on wedding party in Whittier, California

A tall eucalyptus tree fell on a wedding party taking photographs in Whittier’s Penn Park, killing one woman and injuring seven other people. Authorities suspected that the five-year drought played a role in the tree’s collapse, as other trees have fallen in the same way.

“We’ve seen this happen throughout Southern California with both the drought conditions — trees are stressed — and we did have a large amount of rain,” said Deputy Chief John Tripp of the Los Angeles County Fire Department.

A similar incident occurred in Pasadena in July 2015 when an 85-foot tall pine tree suddenly fell on dozens of young children outside a museum in Pasadena’s Brookside Park. An arborist concluded that the prolonged drought, the absence of strong roots, and a spate of rainy days preceding the event were the main reasons the tree fell.

Whittier park closed after tree toppled over, killing 1 and injuring 7, by Matt Hamilton, Los Angeles Times (Calif.), Dec. 18, 2016

Tree cutters in demand to remove dead trees from California's southern Sierra Nevada

The southern Sierra Nevada was host to millions of dead trees, needing to be felled and removed for public safety and to reduce the amount of combustible material in the landscape, but the task of removing so many trees was daunting and costly. The Forest Service estimated that there were more than 24 million dead trees in the Fresno and Tulare portion of the Sierra Nevada alone.

Tree cutters, however, see prosperity in the dead trees. The owner of a tree service charged $1,700 daily for his services. His outfit was one of more than two dozen cutting dead trees along California Highway 168 east of Fresno to Huntington Lake.

The 102 million dead trees in California's forests are turning tree cutters into millionaires, by Thomas Curwen, Los Angeles Times, Dec. 14, 2016

Drought killing California's giant sequoia trees

Drought has killed millions of trees in California’s forests since 2011, but scientists have recently realized that the state’s giant sequoia trees were also succumbing to the drought. Dozens of dead sequoias have been observed lately, although seeing dead sequoias still standing used to be a rare event among trees that live thousands of years.

Drought is damaging California’s giant sequoias, by Vicky Hallett, The Washington Post (D.C.), Dec. 9, 2016

Lull in tick-borne diseases in Maine, but a rebound during fall

Despite a lull in tick-borne diseases in Maine earlier in 2016, the number of Lyme disease cases shot up in the fall and could hit record levels before the end of the year. Through December 5, the number of Lyme disease cases was up 12 percent, compared to all of 2015, according to data from the Maine Center for Disease Control and Prevention. In July, Lyme disease cases were below the five-year average. It seemed that 2016 would be a mild year for the malady.

Oftentimes, 70 percent of Lyme cases occur through August, with a few more cases trickling in during the fall, but 2016 did not follow the typical pattern. Another tick-borne disease, anaplasmosis, also struck in record numbers, with 358 cases in 2016, in comparison with 186 cases through December 5, 2015.

Despite drought, Lyme disease cases come roaring back this fall, by Joe Lawlor, Portland Press Herald (Maine), Dec. 12, 2016



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