January 2012 Drought Report

January 2012 was another warmer- and drier-than-average month (4^th warmest and 28^th driest, based on data back to 1895) when weather conditions are averaged across the country. This reflected persistent weekly regional patterns of temperature anomalies (weeks 1, 2, 3, 4, 5) and fairly persistent weekly precipitation anomalies (weeks 1, 2, 3, 4, 5). These weekly patterns are reflected in the monthly patterns of temperature and precipitation. As a result, compared to the end of December, drought areas at the end of January contracted in the Southern Plains where beneficial precipitation fell. But persistent dryness resulted in expansion of moderate drought and abnormally dry areas in the West, Central to Northern Plains, Upper Midwest, and Coastal Southeast. Below-normal rainfall over most of Hawaii expanded the moderate to extreme drought area from 47 percent last month to 51 percent this month. Nationally, the moderate-to-exceptional drought footprint increased to about 32 percent of the country while the percentage in the worst category (D4, exceptional drought) remained the same at about 3 percent.

The U.S. Drought Monitor drought map valid January 31, 2012.

By the end of the month, the core drought areas in the U.S. included:

• a large area of moderate (D1) to exceptional (D4) drought across the Southwest to Southern and Central Plains;
• moderate to exceptional drought in the Southeast;
• areas of expanding moderate to severe (D2) drought in the Upper Midwest to Northern Plains;
• expanding moderate drought across much of the West; and
• parts of Hawaii, where moderate to extreme drought persisted.

Palmer Drought Index

The Palmer drought indices measure the balance between moisture demand (evapotranspiration driven by temperature) and moisture supply (precipitation). The Palmer Z Index depicts moisture conditions for the current month, while the Palmer Hydrological Drought Index (PHDI) and Palmer Drought Severity Index (PDSI) depict the current month's cumulative moisture conditions integrated over the last several months.

As seen on the January 2012 Palmer Z Index map, low precipitation led to short-term drought across parts of the West, Upper Mississippi Valley, and Southeast this month. Wet conditions are evident on the Z Index map across parts of Texas and Oklahoma in the Southern Plains drought area, and in the Ohio Valley to eastern Great Lakes. Compared with the December 2011 PHDI map, the January 2012 PHDI map indicates that drought conditions improved in parts of the Southern Plains but intensified in parts of the Southeast and Pacific Northwest, and wet conditions decreased in the interior West and Central to Northern Plains. The January 2012 PHDI map also reflects the long-term nature of the drought conditions. The Z Index and PHDI maps in combination show that precipitation brought relief to parts of the Southern Plains drought area, and moisture conditions further declined across the interior West; but for the Southwest, Northwest, Upper Mississippi Valley, Southeast Coast, and Ohio Valley to eastern Great Lakes — precipitation fell where it was already wet and it was drier than normal over the existing drought areas.

Standardized Precipitation Index

The Standardized Precipitation Index (SPI) measures moisture supply. The SPI maps here show the spatial extent of anomalously wet and dry areas at time scales ranging from 1 month to 24 months.

Dryness is evident across much of the West at the 2 to 6 month time scales, and parts of the West at 1, 9, and even 12 months; Northern Plains dryness is evident at 2 to 6 months, with the adjoining Midwest dry at 2 to 9 months; dryness can be seen in the Upper Mississippi Valley and adjoining western Great Lakes at 1 to 12 months, with a hint of abnormally dry conditions even as far back as 24 months; northern New England is dry at the 3 month time scale; and the Southeast Coast and Central Gulf Coast dryness shows up at every time period from 1 to 24 months. For the Southwest and Southern to Central Plains, beneficial December and January precipitation is reflected in wet to neutral conditions on the January (1 month) map back as far as 6 months, but the prolonged deficits make themselves most evident as dryness at 9 to 24 months. Wet conditions caused by several frontal and low pressure systems can be seen along bands from the Southern Plains to Northeast at 1 to 3 months. Wet conditions caused by weather systems from 2011 are evident in the Ohio Valley to Northeast at 3 to 24 months and in the Northern Plains at 9 to 24 months. This illustrates the persistence of the dry and wet areas.

Agricultural and Hydrological Indices and Impacts

Leaky Bucket soil moisture percentiles

USGS monthly streamflow percentiles

Drought conditions were reflected in numerous agricultural, hydrological, and other meteorological indicators, both observed and modeled:

hydrological:

USGS groundwater map.

• USGS (U.S. Geological Service) observed streamflow;
• NOAA Climate Prediction Center (CPC) modeled runoff anomalies and percentiles;
• VIC (University of Washington Variable Infiltration Capacity macroscale hydrologic model) 1-, 2-, 3-, and 6-month runoff percentiles;
• NLDAS (North American Land Data Assimilation System) modeled streamflow anomalies and percentiles;
• NLDAS model runoff anomalies and percentiles;
• USGS groundwater observations (real-time network, climate response network, total active network);

agricultural:

Map showing VIC modeled soil moisture percentiles.

• CPC modeled soil moisture anomalies and percentiles for end of January, soil moisture anomaly change;
• CPC's Leaky Bucket model soil moisture percentiles;
• NLDAS modeled soil moisture percentiles for the top soil layer and total soil layer;
• VIC modeled soil moisture percentiles, soil moisture percentile change;
• Vegetation Drought Response Index (VegDRI);
• the NESDIS satellite-based Vegetation Health Index (VHI);

meteorological:

Map of maximum consecutive dry days.

• total precipitation (plotted by the USGS, NOAA National Weather Service [NWS], and NOAA High Plains Regional Climate Center [HPRCC]);
• percent of normal precipitation and precipitation percentiles (NWS, HPRCC station observations, Leaky Bucket model, CPC);
• USGS number of days with precipitation and maximum number of consecutive dry days;
• temperature departures from normal (HPRCC, CPC) and percentiles (CPC, Leaky Bucket);
• number of record warm daily low temperatures, record daily high temperatures, record daily low temperatures, and record cool daily high temperatures set in January 2012 (from NCDC's daily records analysis).

Regional Discussion

January 2012 was drier than normal for most stations in the Hawaiian Islands, resulting in expansion of moderate to extreme drought to 51 percent of the islands. Longer-term conditions continued drier than normal (last 2, 3, 6, 12, 24, 36 months), especially for the southern islands; January SPI values were very dry to extremely dry, especially in Maui County; and streamflow was below to much below normal.

The precipitation pattern over Alaska during January was mixed. In spite of a wet December, precipitation deficits are evident at longer time scales, especially at interior stations (2, 3, 6, 12, 24, 36 months, water year to date). However, snowpack and snow water content (for most stations and basinwide) were generally near to above normal, and there was no drought or abnormal dryness indicated on the January 31^st USDM. Modeled soil moisture was still drier than normal in south central coastal to interior locations.

The southeastern third of Puerto Rico was drier than normal during January. Dryness in the southeastern and northwestern thirds of the island is evident at 2, 3, and 4 months, especially in the southeast, but disappears at 6 months. With streamflow near average, the January 31^st USDM map had no drought or abnormally dry areas on the island.

On a statewide basis, January 2012 ranked in the top ten driest Januaries for two states in the Central Plains (Kansas [third driest] and Nebraska [eighth driest]) and one state in the Southeast (Florida [also eighth driest]). Several other states from the Plains to the West and in the Southeast to Mid-Atlantic coast ranked in the driest third of the historical record. The dryness in the West and Northern Plains to Upper Mississippi Valley extends back six months. Six states (California, Nevada, Idaho, Montana, North Dakota, and Minnesota) had the tenth driest, or drier, November-January in the 1895-2011 record, and five states (California, Oregon, Idaho, Montana, and Minnesota) ranked in the top ten driest category for August-January. In addition to having the second driest August-January, Minnesota also had the third warmest August-January. Beneficial precipitation during the last three months gave the Southern Plains states ranks in the wettest third of the historical record.

The pattern was reversed at longer time periods, with the Northern Plains states having wet ranks and the Southern Plains dry ranks. Three states in the Southern Plains (Texas, New Mexico, and Louisiana) and two in the Southeast (Georgia and South Carolina) had the tenth driest, or drier, February-January. The beneficial precipitation of December and January was enough to raise the 12-month (February 2011-January 2012) rank for Texas statewide, and the Texas Gulf Coast river basin, to third driest. The Rio Grande river basin had the second driest February-January.

During January, moderate to exceptional drought contracted to cover 61 percent of the South region but expanded to affect 56 percent of the Southeast region, 51 percent of Hawaii, 41 percent of the West, 23 percent of the High Plains region, 22 percent of the Midwest region, and 32 percent nationally. The two worst USDM drought categories (D3-D4, extreme to exceptional drought) shrank to 60 percent of Texas, held steady at 27 percent of Oklahoma, and expanded slightly to 25 percent of New Mexico and 67 percent of Georgia, while dropping slightly to 8 percent nationally.

Percent area of the Western U.S. in moderate to extreme drought, based on the Palmer Drought Index.

While January 2012 was wetter than normal across parts of the West, the month was drier than normal for other parts. The net result was a continuation of below-normal precipitation for the water year to date (October 2011-January 2012). This is reflected in both the low elevation and high elevation (SNOTEL) station precipitation data, the PHDI, and SPI maps which show that the January moisture was not enough to alleviate the deficits which have built up over the last 2, 3, and 6 months. Fortunately, last year's wet season provided sufficient precipitation to replenish the reservoirs in most states. However, the mountain snowpack — a crucial water supply during the following melt season — lagged well behind normal, as reflected in snow course snow pack data and station and basin snow water content. For most of the previous water year (October 2010-September 2011), drought in the West was confined to the Southwest. But now drought has expanded to cover much of the West. According to the USDM, 41 percent of the West was experiencing moderate to exceptional drought at the end of January, a 13-point increase compared to December, while the Palmer Drought Index statistic was about 36 percent, nearly double last month's value.

A more detailed drought discussion, provided by the NOAA Regional Climate Centers and others, can be found below.

As noted by the Southeast Regional Climate Center, precipitation in January was below average for much of the Southeast region, including Puerto Rico and U.S. Virgin Islands. The driest locations were found across eastern and southern Florida, where monthly precipitation totals were less than 10 percent of normal. The lack of precipitation contributed to an expansion and intensification of drought conditions. Most notably, an area of exceptional drought (D4) re-emerged across southern Georgia and extreme southeastern Alabama. Along the Florida Peninsula, which was largely drought-free at the end of December, moderate drought (D1) conditions emerged by the end of January, while the areas of severe (D2) and extreme (D3) drought expanded into the Florida Panhandle. Drought conditions also intensified across eastern sections of the Carolinas, while abnormally dry (D0) conditions returned to the Tidewater region of eastern Virginia. Mean temperatures in January were above normal across the contiguous Southeast U.S., but generally below average across Puerto Rico and the U.S. Virgin Islands. Cold weather at the beginning of the month caused damage to fruit and vegetable crops across Florida and hindered the shipping of earlier harvests, while the ensuing warmth caused some plants and trees to begin blooming, making them susceptible to a late winter/early spring freeze.

As explained by the Southern Regional Climate Center, the month of January proved to be a warm month for the entire Southern region, while precipitation varied spatially with parts of the region having a wetter than normal month, while for other areas, it was much drier than normal. Conditions were quite dry in southern Texas and western Oklahoma with most stations receiving only between 5 and 50 percent of normal precipitation and several stations reporting zero precipitation for the month. Drought conditions in the Southern region improved slightly from the previous month, with drought being removed in north central Texas and in eastern Oklahoma. Much of eastern Texas also saw a one-category improvement in drought conditions. As of January 31^st, 61.19 percent of the Southern region remained in drought, which was approximately an 8 percent improvement from the end of last month. Drought conditions in Louisiana, Arkansas, and Mississippi did not change much over the course of the month, and Tennessee remained the only state in the region to be completely drought-free.

As summarized by the Midwest Regional Climate Center January temperatures were above normal across the Midwest, while precipitation was generally below normal in the western half of the Midwest and above normal in the eastern half.

As noted by the Northeast Regional Climate Center, the string of warmer-than-normal months continued in January. January's weather pattern left much of the eastern half of the region on the dry side, while western New York, Pennsylvania and northern West Virginia saw above normal precipitation. Overall, the Northeast's precipitation total of 3.17 inches (80.5 mm) was 103 percent of normal.

As explained by the High Plains Regional Climate Center, January 2012 was warm and dry across the High Plains region. Liquid equivalent precipitation was less than 25 percent of normal in many areas of Kansas, Nebraska, eastern Colorado, and North Dakota. Many locations in Colorado, Kansas, and Nebraska received no measurable precipitation this month. Many locations ranked in the top 10 driest Januaries on record. Although January liquid equivalent precipitation is usually light, the ongoing lack of rain and snow caused drought conditions to develop or worsen in these dry areas. The USDM had many changes this month. Abnormally dry (D0) conditions spread to western areas of the Dakotas and also through north and central Nebraska. Moderate drought conditions (D1) in eastern North Dakota spread to include all areas near the Minnesota border. Western Colorado and southwestern Wyoming also had degradations this month as D0 developed and spread during the middle of the month. By the end of the month, D1 had developed in central and northwestern Colorado and south-central Wyoming. Low water-year-to-date (the water year starts October 1) precipitation led to this degradation. Except for a small expansion of D0 in western Kansas, drought conditions there remained largely the same.

As summarized by the Western Regional Climate Center, January 2012 was a month of extremes in the West. Alaska experienced bitter cold and heavy coastal snows, while record-breaking highs and extended warm periods dominated the Southwest and Inland Northwest. Heavy rain and snowfall throughout the second half of the month helped much of the Northwest recover some of their moisture deficit, while the Southwest remained nearly dry. Strong and persistent ridging took hold over the West for most of January 2012, resulting in positive temperature departures from normal for most of the region. In mid-January, a procession of moisture-laden systems tracked through the Pacific Northwest, bringing rainfall totals to over 100 percent of a normal January in much of Washington, Oregon, Idaho, and portions of Montana. Another strong precipitation event associated with a deep subtropical moisture tap occurred in the Northwest on January 24^th and 25^th and produced additional precipitation records, though in this case slightly further south, targeting southern Washington, Oregon, far northern Nevada, and Southern Idaho. While the Northwest was being inundated, moderate drought developed or maintained through the month in Central and Southern California, the Great Basin, Arizona, New Mexico, and Hawaii. Phoenix, Arizona tied its driest January on record receiving only trace precipitation; normal at that location is 0.91 in (23 mm). Elsewhere in the Southwest, San Diego, California airport recorded 0.4 in (3.9 cm), tying for the 21^st driest year in a record that began in 1914. In the Great Basin, Reno, Nevada completed its 56^th consecutive day with no measurable precipitation on January 15^th. The previous record stretch (in winter; the summer record is 129) had been 54 days from December 2, 1960 through January 24, 1961. Reno received late month precipitation to finish with a total of 1.54 in (39 mm), 0.48 in (12 mm) above the 1971-2000 normal, the first month since June 2011 with above-normal precipitation. Reno ended a 7-month stretch (mid-June to mid-January) with a total of only 0.33 in (8.4 mm).

Upper Colorado River Basin: As reported by the Colorado Climate Center, the January 31^st NIDIS (National Integrated Drought Information System) assessment for the Upper Colorado River Basin (UCRB) indicated that, after a dry December through most of the UCRB, drier than average conditions were again observed across much of the UCRB for the month of January. Spotty areas of near normal precipitation for the month occurred in some of the higher elevations in the central Colorado mountains and in the Wasatch mountains in Utah. Near to above normal precipitation was seen in the Upper Green River basin in Wyoming. Much of the lower elevations of the UCRB have received less than 75 percent of average precipitation for the month. Southeast Colorado also was drier than average. Water-year-to-date SNOTEL precipitation percentiles were low for much of the Yampa and Colorado headwaters basins, and along the Wasatch range in Utah. Percentiles in those areas ranged from the single digits to around the 20^th percentile, with the higher values mainly on north facing slopes or east of the Continental Divide. Snotel percentiles in the Upper Green basin in Wyoming were generally above the 50^th percentile, and most in the San Juan basin in southern Colorado were near the 50^th percentile. Snowpack conditions around the UCRB were all below normal with most of the sub-basins recording 75 percent of average or less for snowpack. As of January 29^th, 87 percent of the USGS streamgages in the UCRB recorded normal (25^th - 75^th percentile) or above normal 7-day average streamflows. All of the major reservoirs above Lake Powell were above their January averages. Most reservoirs have seen storage decreases in January, which is normal for this time of year.

Pacific Islands: According to reports from National Weather Service offices, the Pacific ENSO Applications Climate Center (PEAC), and partners, conditions varied across the Pacific Islands.

As noted by the National Weather Service office in Honolulu, following very wet conditions over the windward slopes during December, the new year has started out dry in most areas except for the island of Kauai. Leeward drought worsened on the Big Island with existing extreme drought, or D3 category conditions on the USDM map, expanding northward into ranch lands near Waimea. Severe drought, or D2 category conditions, continued within a belt extending from Puako toward the south-southeast to Pahala and South Point. Moderate drought, or D1 conditions, persisted over portions of the south Kona district. On the island of Maui, extreme drought spread from the Kihei area into the Maalaea and Lahaina areas of leeward west Maui. Drought conditions also worsened on Molokai where existing severe drought downgraded to extreme drought over the western third of the island. Similarly, drought on Lanai degraded to a severe classification in the ongoing dry conditions.

Some drought impacts in Hawaii include the following:

• On Kauai, there were no drought impacts to report as Kauai has been the only island to receive significant rainfall over the past month.
• On Oahu, the water supply in the Waimanalo reservoir has changed little so the 10 percent mandatory water use restriction remained in place.
• On Molokai, a recent assessment by agriculture officials indicated that pastures and general vegetation conditions were in very poor condition over the western third of the island. The State of Hawaii Department of Agriculture has continued the mandatory 30 percent cutback in irrigation water consumption for the Kualapuu reservoir system.
• On Lanai, pastures and general vegetation conditions have worsened over the past month.
• On Maui, pastures and vegetation remained dry over the leeward areas of Maui and especially from Ulupalakua to Lahaina. After improving rapidly following ample December windward rainfall, water supply levels for upcountry Maui have declined just as quickly during January. The Maui County Department of Water Supply has maintained their call for a 5 percent reduction in water use. The request for a 10 percent reduction in water use by central and south Maui residents also remained in effect.
• On the Big Island, pastures and general vegetation over most of the south Kohala district were in very poor condition and brush fires have been a significant ongoing concern. Ranchers in these areas have already destocked cattle and water hauling operations have been ongoing for several months. Some Kona coffee growers have had to irrigate more than normal to sustain their orchards.

SPI values for seven time periods for Hawaiian Island stations, computed by the Honolulu NWS office.

On other Pacific Islands, January was drier than normal for about two-thirds of the stations and near to above normal for the rest. Total rainfall for the last 12 months (February 2011-January 2012) was near to above normal for all stations except Pago Pago.

SPI values for seven time periods for Pacific Islands, computed by the Honolulu NWS office.

• Palmer Drought Indices
• Standardized Precipitation Index
• long-term (36 to 60 month) percent of normal precipitation maps
• airport station percent of normal precipitation maps
• statewide precipitation rank maps
• Cooperative station percent of normal precipitation maps
• percent of average maps for the SNOTEL stations in the western mountains provided by the Western Regional Climate Center
  • hydrologic year precipitation
  • snow water equivalent of snowpack
• satellite-based observations of vegetative health
• National Weather Service model calculations of soil moisture, runoff, and evaporation
• National Weather Service model calculations of soil moisture using the Leaky Bucket Model
• Midwest Regional Climate Center model calculations of soil moisture
• topsoil moisture conditions observed by the USDA and mapped by the Climate Prediction Center
• pasture and range land conditions observed by the USDA and mapped by the Climate Prediction Center
• streamflow maps maintained by the USGS

• The U.S. Drought Portal