Monday, October 23, 2017

National Drought Mitigation Center

Drought and Climate for February 2017: Storms bring significant precipitation to western United States

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

Drought

February brought substantial improvements to drought conditions in parts of the western United States as a series of storms brought significant precipitation to California, Oregon, and Washington.  In other parts of the country, abundant rainfall helped alleviate drought conditions in southern Oklahoma and central Georgia, and heavy snowfall brought improvements to parts of the Northeast.  Drought and abnormally dry conditions expanded across parts of the Midwest, South, and Southeast. Changes in the overall drought area for the contiguous United States were relatively minor, with moderate drought (D1) decreasing slightly from 14.55 to 14.08 percent, severe drought decreasing from 3.83 to 3.68 percent, and extreme drought increasing from 0.41 to 0.49 percent.  Exceptional drought (D4) was not present during the month.  February ended with approximately 87.5 million people in drought compared to approximately 89 million at the beginning of the month.

Drought Outlook

The monthly drought outlook for March 2017 shows continued improvement and removal of drought in California’s central coast region, while the remaining drought areas are expected to persist in southern California and Arizona.  Drought is likely to persist or develop across the central and southern Plains and much of the eastern United States. Outside of the contiguous United States, drought removal is expected in Hawaii while Alaska and Puerto Rico are forecast to remain drought-free.

Temperatures

Temperatures across much of the country were above normal in February, with many locations in the eastern half of the country setting records for the warmest February.  Departures in excess of 8 degrees above normal were observed in parts of the Plains, Midwest, and South.  The only areas with seasonably cool temperatures were in the Northwest, where temperatures departures were 4 to 8 degrees below normal.

Precipitation

A series of Pacific storms brought above-normal precipitation to the western United States. Precipitation totals generally ranged from 0 to 4 inches above normal, although excesses of 8 inches were recorded in northern California and coastal Oregon.  The Midwest, South, and Southeast generally saw below-normal precipitation, with departures generally ranging from 0 to 4 inches below normal.

 

Regional Overviews

Northeast

Warmer than normal temperatures dominated the Northeast in February, with locations across the region recording monthly averages that fell within the top 10 warmest on record.  Temperature departures ranged from 2 degrees above normal in northern Maine to 10 degrees above normal in parts of Pennsylvania and West Virginia. Precipitation in the region ranged from less than 25 percent of normal to more than 200 percent of normal. The driest areas in southern Maryland and Connecticut saw departures of more than 2 inches below normal while the wettest locations in New York and Maine saw departures of more than 2 inches above normal.  Drought continued to persist in the region where long-term precipitation deficits and hydrologic indicators are driving the drought depiction. February began with 34.82 percent of the region in drought and ended with 27.08 percent in drought.  Severe drought improved from 7.88 to 6.96 percent and extreme drought from 1.10 to 0.70 percent.

Southeast

The entire region experienced above-normal temperatures during February, with departures ranging from 1 degree above normal in the Florida Peninsula to 10 degrees above normal in South Carolina. Locations across the region reported their warmest February on record.  The warm temperatures were accompanied by drier than normal conditions across the majority of the region.  Precipitation varied from more than 6 inches above normal in southeastern Alabama to more than 6 inches below normal in northern Alabama. The warm temperatures and dry weather have caused an increase in abnormally dry conditions and drought in Virginia, North Carolina, the Florida Peninsula, and the northern parts of Alabama, Georgia, and South Carolina. Overall, drought increased from 20.71 to 30.13 percent of the region.  Severe drought increased from 9.25 to 14.72 percent and extreme drought from 1.15 to 3.98 percent.  The region was not experiencing exceptional drought.

Movers & Shakers for February 2017
State

Percent area Jan. 31, 2017

Percent area Feb. 28, 2017 Status Percentage point change
Biggest increases in drought
Alabama 48.58 53.63 Moderate 5.05
23.88
31.96
Severe
8.08
Arkansas  30.46 34.06
Moderate 3.60
 12.50  18.29 Severe 5.79
Delaware
10.58
100.00
Moderate 89.42
Florida  0 25.47
Moderate 25.47
Georgia  3.57 8.69
Extreme 5.12
Hawaii 1.55
7.36
Moderate  5.81
Kansas 26.02
37.34
Moderate 11.32
Louisiana
0
 5.39 Moderate
5.39
Maryland
31.02
70.10
Moderate
 39.08
0
8.21
Severe
8.21
Mississippi 10.78
23.25
Moderate
12.47
0.46
7.27
Severe
6.81
Missouri
8.51
64.42 Moderate
55.91
New Jersey 42.39
52.12 Moderate
9.73
North Carolina
12.43
26.52 Moderate
14.09
2.91
15.77 Severe
12.86
0.01 4.74 Extreme
4.73
South Carolina
21.88
26.85 Moderate
4.97
4.12 17.61 Severe
13.49
0 4.16 Extreme
4.16
Tennessee 5.32 9.13 Severe
3.81
Virginia
0.49 17.12 Moderate
16.63
Biggest improvements in drought

California

50.80
8.73 Moderate 42.07
20.30 4.08 Severe 16.22
Connecticut 38.58 28.39 Extreme 10.19
Georgia 36.22 27.56 Moderate 8.66
Maine
38.02 2.84 Moderate
35.18
Massachusetts 3.75 0.01 Extreme 3.74
Nevada 5.93
0.00 Moderate 5.93
New Hampshire
75.35 67.00 Moderate 8.35
New Jersey
9.47
6.15 Severe
3.32
New York 25.09
14.89 Moderate 10.20
7.67
2.96 Severe
4.71
Oklahoma 79.46 73.14 Moderate 6.32
3.90
0.18 Extreme 3.72
South Dakota
26.01 17.85 Moderate
8.16
Vermont 65.19 14.32 Moderate 50.87

Midwest

All of the Midwest experienced warmer than normal temperatures.  Departures ranged from 5 degrees above normal in northern Wisconsin to 13 degrees above normal in southwest Minnesota. All states in the region had stations reporting average temperatures that landed them in the top 3 warmest Februarys on record.  Precipitation was split across the region, with the north generally receiving above-normal precipitation and the south below-normal precipitation.  The wettest areas in Minnesota, Iowa, Michigan, and Wisconsin received 1 to 3 inches above (more than 150 percent) normal precipitation for the month while the driest areas of Missouri, southern Illinois, and southern Indiana received 2 to 3 inches below (less than 5 percent) normal.  Drought expanded over much of Missouri and into western Illinois so that 9.33 percent of the Midwest is now in drought, compared to 1.37 at the beginning of February.

High Plains

As with much of the rest of the country, the High Plains experienced warmer than normal temperatures during February. Temperature departures generally ranged from 2 to 6 degrees above normal across the western parts of Nebraska and the Dakotas and northern Wyoming while departures of more than 8 degrees above normal were recorded elsewhere.  Sites across Kansas, southern Nebraska, and the eastern Dakotas reported temperatures that were among their top 5 warmest on record. Precipitation was variable across the region, with departures generally ranging from 1.5 inches above normal across eastern Wyoming, northern Nebraska, and parts of the Dakotas to more than 3 inches below normal in southeast Kansas. The High Plains saw minor increases in drought area with 19.34 percent of the region in drought at the end of February, compared to 18.61 percent at the beginning of the month.  Severe drought also increased, expanding from 1.23 to 1.41 percent of the region.

South

Above-normal temperatures once again dominated the South, with most areas seeing departures of 6 to 12 degrees above normal. Much of the eastern half of the region was dry, with precipitation departures of more than 3 inches below normal observed in east Texas, central Louisiana, and southern Mississippi.  Parts of Oklahoma and Texas saw above-normal rainfall, with the wettest areas receiving 1 to 3 inches above normal. Drought expanded to 19.35 percent of the region by the end of February, compared to 17.70 percent at the beginning of the month.  Severe drought also expanded to cover 7.59 percent of the region, compared to 6.40 percent at the beginning of the month.  Meanwhile, the area affected by extreme drought decreased slightly, from 0.73 to 0.35 percent.

West

Outside of the Northwest, the West generally saw above-normal temperatures during February, with portions of Colorado and New Mexico seeing temperature departures of 8 degrees above normal, landing them in the top warmest February on record. Meanwhile, parts of Washington, Oregon, and Montana experienced seasonably cooler temperatures with departures of up to 8 degrees below normal.  Much of the West continued to be wet during February, with departures of 1 to 4 inches above normal common.  Portions of northern California and coastal Oregon recorded values of more than 8 inches above normal, earning the title of the wettest February on record. February ended with 6.98 percent of the area in drought compared to 13.38 percent at the beginning of the month.  Severe drought improved from 2.83 from 0.75 percent and the last area of extreme drought was eradicated.

 

 

 

 

February 2017 impact summary: California goes from drought to flood; CoCoRaHS observers note signs of drought

The two charts above summarize information from the Drought Impact Reporter.
 
Daily Statewide Hydrologic Update and snow water content graphs are from the California Department of Water Resources.

By Denise Gutzmer, NDMC Drought Impact Specialist

February 2017 was a month of tremendous rainfall and snowfall that catapulted much of central and southern California out of drought after five plus years.  One of the state’s wettest wet seasons on record alleviated drought in northern and central portions of the state since October 2016, but the immense rainfall in February led to flooding, more infrastructure damage, and the threat of Oroville dam failing, sending 180,000 people to higher ground. 

Sierra Nevada snowpack deepening

Electronic readings from 98 stations in the Sierra Nevada indicated that the snow water equivalent had reached 45.5 inches, or 185 percent of average for the date, on March 1.  The figure was an increase from 6.5 inches, or 64 percent of average, in early January, to 30.5 inches, or 174 percent of average, in early February.

Snowpack’s Water Content Remains Far above Average, by Doug Carlson, Ted Thomas, and Chris Orrock, California Department of Water Resources, Sacramento, Calif., Mar. 1, 2017

State, federal water allocations increase

Since snow melt from the Sierra Nevada supplies about 30 percent of California’s water needs, having such a bounty was a tremendous relief, allowing state and federal water projects to deliver more water than in previous years.  The U.S. Bureau of Reclamation announced on February 28 that initial water allocations for the Central Valley Project will be 100 percent for many of its customers, but will wait until the end of March to reveal other water allocations.  Central Valley Project contractors to receive full allocations include those near the American River, Millerton Lake, and New Melones Reservoir, and settlement contractors.

The State Water Project increased its allocation to 60 percent in mid-January and has not yet offered an update.  Water customers last received a full allocation in 2006, which is difficult to achieve, owing to Delta pumping restrictions to protect threatened and endangered fish species. 

State Water Project Allocation Increased, by Ted Thomas and Doug Carlson, California Department of Water Resources, Sacramento, Calif., Jan. 18, 2017

California farms given good news as reservoirs fill and snowpack builds, by Kurtis Alexander, SFGate.com (San Francisco), Feb. 28, 2017

California storms fill reservoirs

Storms moving across California dropped heavy rainfall, which filled reservoirs more quickly than anticipated, forcing dam operators to release water to relieve pressure on dams.  Such was the case at Lake Oroville in northern California, where 55,000 cubic gallons of water per second rushed down the dam’s spillway and caused erosion, forcing the closure of the main spillway in favor of using the emergency spillway, which also showed signs of potentially failing.  After sufficient water was released, lowering the water level, people were allowed to return to their homes. 

Spillway crumbles as California reservoirs max out capacity, by Kurtis Alexander, San Francisco Chronicle, Feb. 7, 2017

In Shadow of California Dam, Water Turns From Wish to Woe, by Mike McPhate and Jess Bidgood, The New York Times, Feb. 13, 2017

Subsidence continues in California's San Joaquin Valley

In past years, farmers turned to pumping more groundwater to water their crops as poor snowfall in the Sierra Nevada meant less water available for distribution via the state and federal water systems.  More groundwater withdrawals led to more land subsidence, which is a problem in certain areas, apart from drought.  Researchers from NASA’s Jet Propulsion Laboratory assessed subsidence between 2015 and 2016 and found that two major bowls of subsidence near Chowchilla, south of Merced, and Corcoran, north of Bakersfield, continued to sink as much as 2 feet per year.  Other parts of the San Joaquin Valley continued to sink, as well.  Some subsidence occurred in the Sacramento Valley near Davis and Arbuckle. A new patch of subsidence was discovered in Sierra Valley, north of Lake Tahoe.

NASA Data Show California’s San Joaquin Valley Still Sinking, by NASA Jet Propulsion Lab, YubaNet.com (Nevada City, Calif.), Feb. 28, 2017

CoCoRaHS network shares drought observations

Of the 128 drought impacts entered into the Drought Impact Reporter for February, 79 were from CoCoRaHS observers.  CoCoRaHS is the acronym for the Community Collaborative Rain, Hail and Snow Network, which is a grassroots volunteer network of backyard weather observers working together to measure and map precipitation (rain, hail, and snow) in their local communities.  These observers uncover some of the earliest signs of dryness, making their input a very valuable stream of information for the DIR.

CoCoRaHS observers sometimes note emerging dryness before it becomes newsworthy to the media, as in the case of parts of North Carolina.  All twenty-one of the state’s impacts stem from CoCoRaHS reports, documenting low pond levels, poor cover crop growth, concern about fire danger, wildlife boldly seeking food and water, dead shrubs, and so forth.  Nine of Florida’s thirteen impacts came from CoCoRaHS folks, as did seven of Texas’ eleven impacts, seven of Colorado’s nine impacts, four of Oklahoma’s eight impacts, and six of Missouri’s seven impacts. 

For more drought information, see the Drought Impact Reporter.

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