Drought - April 2015


NCDC added Alaska climate divisions to its nClimDiv dataset on Friday, March 6, 2015, coincident with the release of the February 2015 monthly monitoring report. For more information on this data, please visit the Alaska Climate Divisions FAQ.

Issued 12 May 2015
Contents Of This Report:
Map showing Palmer Z Index
Percent Area of U.S. in Moderate to Extreme Drought, Jan 1996 to present

Please note that the values presented in this report are based on preliminary data. They will change when the final data are processed, but will not be replaced on these pages.


National Drought Overview

[top]


Detailed Drought Discussion


Overview


The weather and upper-level circulation during April 2015 was influenced by an El Niño in the eastern CONUS and by a long-wave ridge over the West. Short-wave troughs and low pressure centers migrated through the upper-level flow, bringing cooler temperatures and weakening the ridge, but the ridge was still strong enough to inhibit precipitation across the West. A southerly storm track brought above-normal precipitation to the Southern Plains, Southeast, and Ohio Valley, but kept moisture out of the Northern Plains and parts of the Upper Midwest and Northeast. As a result, drought and abnormally dry conditions intensified and expanded in the drier-than-normal West, Northern Plains, and Upper Midwest. Drought and abnormally dry conditions contracted in the Southern Plains to Southeast where above-normal precipitation fell. April was drier than normal across most of Puerto Rico, interior Alaska, and part of the Hawaiian Islands. Abnormal dryness expanded in Puerto Rico, but drought and abnormal dryness contracted where beneficial precipitation fell in Hawaii and Alaska. When integrated across the CONUS, April 2015 ranked as the 37th wettest April in the 1895-2015 record. On balance, the national drought footprint expanded when compared to last month, increasing from 30.8 percent of the U.S. as a whole to about 31.3 percent of the U.S. in moderate to exceptional drought, according to USDM statistics. According to the Palmer Drought Index, which goes back to the beginning of the 20th century, about 25.3 percent of the CONUS was in moderate to extreme drought at the end of April, an increase of about 3.3 percent compared to last month.

The U.S. Drought Monitor drought map valid April 28, 2015
The U.S. Drought Monitor drought map valid April 28, 2015.

By the end of the month:

Percent area of the CONUS in moderate to exceptional drought, January 4, 2000 to present, based on the U.S. Drought Monitor
Percent area of the CONUS in moderate to exceptional drought, January 4, 2000 to present, based on the U.S. Drought Monitor.


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. While both the PDSI and PHDI indices show long-term moisture conditions, the PDSI depicts meteorological drought while the PHDI depicts hydrological drought. The PDSI map shows less severe and extensive drought and wet spell conditions in parts of the Northern Plains than the PHDI map because the meteorological conditions that produce drought and wet spell conditions are not as long-lasting as the hydrological impacts.

Palmer Z Index map Palmer Hydrological Drought Index map

Used together, the Palmer Z Index and PHDI maps show that short-term dry conditions occurred over much of the West, Northern Plains, and Upper Midwest, and parts of the Northeast. Long-term drought continued in the West and intensified in parts of the Northwest and Upper Midwest, which had areas in long-term drought during March. In the Northern Plains, the continued short-term dryness caused areas of long-term drought to develop and shrank the area of long-term wet conditions that were evident in March. Short-term wet conditions were sufficient to cause long-term drought from March to disappear in April along the Gulf of Mexico coast.



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.

1-month Standardized Precipitation Index 2-month Standardized Precipitation Index 3-month Standardized Precipitation Index

6-month Standardized Precipitation Index

The SPI maps illustrate how moisture conditions have varied considerably through time and space over the last two years. Dryness across the Pacific Northwest is evident for the last 1 to 3 months and across the Northern Rockies at the 2- to 3-month time scales. Much of the West is dry at the 2- to 6-month, and 24-month, time scales, but parts of the West are dry at the 1- and 9- to 12-month time scales as well. The Northern Plains to Upper Midwest, and parts of the Northeast, have been dry at the 1- to 9-month time scales, while the Great Lakes to Central Plains have dryness at the 2- to 6-month time scales. Parts of the Southeast (primarily southern Alabama) have dryness at the 9- to 12-month time scales. Widespread precipitation from the summer of last year reduced the areas of dryness at the 12-month time scale.


9-month Standardized Precipitation Index 12-month Standardized Precipitation Index 24-month Standardized Precipitation Index



Standardized Precipitation Evapotranspiration Index


The SPI measures water supply (precipitation), while the SPEI (Standardized Precipitation Evapotranspiration Index) measures the combination of water supply (precipitation) and water demand (evapotranspiration as computed from temperature). Warmer temperatures tend to increase evapotranspiration, which generally makes droughts more intense.

3-month SPEI for current month
3-month SPEI for current month.
3-month SPI for current month
3-month SPI for current month.

Temperatures were near to slightly below normal across the West, and near to slightly above normal in the Great Plains, during April 2015. With the lack of warm temperature anomalies, the dry conditions in these regions were depicted about the same on the 1-month SPEI and SPI maps. It isn't until the 3-month time scale that the unusual warmth in the West shows up as more intense drought on the SPEI compared to the SPI. When the entire year is considered, the record warm temperatures in the West significantly intensified drought conditions when the 12-month SPEI is compared to the SPI. The unusual western warmth of the last several years contributed to more intense drought on the SPEI maps compared to the SPI maps at longer time scales as well.

36-month SPEI for current month
36-month SPEI for current month.
36-month SPI for current month
36-month SPI for current month.


Agricultural, Hydrological, and Meteorological Indices and Impacts

USDA topsoil moisture short to very short
USDA topsoil moisture short to very short
USGS monthly streamflow percentiles
USGS monthly streamflow percentiles

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

The dryness of April 2015 was reflected in below-normal precipitation totals, few days with precipitation, and long runs of dry days, especially across parts of the West to Northern Plains. April marked a continuation of abnormally dry conditions which started in the middle of last autumn across parts of the Northern Plains and Upper Midwest. As temperatures rose and the ground thawed this spring, the dry soils became more evident, both in modeled data (CPC, NLDAS, SMOS, VIC) and observations by the U.S. Department of Agriculture (USDA). As of May 3rd USDA reports, nearly three-fourths (74%) of the topsoil in South Dakota was rated short or very short of moisture (dry or very dry), with over a third so rated in Minnesota (45%), Montana (42%), Wyoming (42%), South Dakota (39%), Kansas (38%), and Nebraska (36%). This was more than the 5- and 10-year averages. The lack of precipitation is allowing farmers to make progress planting crops in fields, but the dry weather is detrimental to crops and vegetation already planted. According to May 4th USDA reports, 39 percent of the pastures and rangeland in South Dakota, and 33 percent of the winter wheat crop in South Dakota, Nebraska, and Kansas, were rated in poor to very poor condition. Above-normal temperatures increased evaporative stress in the Northern Plains, as seen in the Evaporative Stress Index (ESI) and Evaporative Demand Drought Index (EDDI). The dry conditions laid the groundwork for the development of numerous large wildfires, especially during the first half of the month. The persistent lack of precipitation reduced stream levels.

Satellite observations of vegetative health (VHI, VegDRI), modeled and observed soil moisture, and crop condition also revealed stress in New England. Over half of the topsoil in Connecticut (55%) was rated short or very short of moisture, over a third was so rated in Massachusetts (39%), and a third (34%) of the pastures and rangeland in New England was rated in poor or very poor condition.

Conditions were especially dire in the West. Only the highest elevation mountain ranges still had a snow pack at the end of the month. With the well below-normal snow pack mostly melted out, the spring and summer source of meltwater for streams and irrigation is simply gone, resulting in much below normal to record low streamflow across the West. Statewide, reservoirs were below average in Arizona, Nevada, New Mexico, Oregon, and Utah. In California, reservoir levels continue to drop. When the reservoir level is expressed as percentiles, the reservoirs in southern California are worse off than those in the north. May 4th USDA reports revealed half of the pasture and rangeland rated in poor to very poor condition in California (50%) and a fourth so rated in Colorado (29%) and Oregon (25%). About a third of the stock water was short or very short in Utah (40%) and New Mexico (30%). Trees across large portions of forests in southern California are dying due to the drought.

Above-normal precipitation over the last two to six months has improved soil moisture conditions in Texas, where only 8 percent of the pasture and rangeland and 15 percent of the winter wheat crop are in poor to very poor condition. But the hydrological conditions have been slower to improve, with Texas reservoirs still stuck at the lowest levels in 30 years, statewide, and some stream levels still much below normal.

Some groundwater well stations in the West, Plains, and Northeast have reached the lowest levels observed in the last 20 to 50 years. According to April 28th USDM statistics, the percent acreage of several crops in drought rose during April. Corn producing areas in drought rose from 22 percent at the end of March to 26 percent at the end of April, soybean acreage in drought rose from 18 to 22 percent, and winter wheat acreage from 42 to 44 percent. Hay acreage remained steady at 28 percent in drought and cattle production remained steady at 36 percent. Nationally, 20 percent of the winter wheat crop was in poor to very poor condition.



Regional Discussion


Hawaii: Hawaii had a mixed precipitation pattern for April 2015 and the last 2 to 3 months. A drier-than-normal pattern was dominant at the 4-, 6-, and 7-month time scales. A wetter-than-normal pattern became dominant at the 10-, 12-, and 24-month time scales, while it was mostly drier than normal at 36 months. On the USDM map, moderate drought covered about a fourth (23.3 percent) of the state, reflecting the short-term wet conditions in some areas and the continued low reservoir situation in central Molokai and the Upcountry Maui area.

Alaska: April had a mixed precipitation pattern across Alaska. Stations in the interior locations were generally drier than normal, while coastal stations were generally wetter than normal, both at the lower elevation stations and at the higher elevation (SNOTEL) stations. This pattern was generally consistent for the last 2 to 3 months. The drier-than-normal pattern spread southward at longer time scales (last 4, 6, 7, 10, and 12 months). The precipitation anomaly pattern became more mixed at 24 to 36 months. The persistent upper-level circulation pattern (ridge), which reduced the precipitation at interior locations, also brought widespread above-normal temperatures for much of the last year (last 1, 3, 4, 7, and 12 months). The above-normal temperatures helped reduce the winter snowpack and increase streamflow. Soil moisture models indicated drying soils in the south central and southwest portions of the state. Abnormal dryness covered about a fourth (23.9 percent) of the state on the April 28th USDM map.

Puerto Rico: April was drier than normal for much of Puerto Rico, especially in the east. The pattern of drier-than-normal conditions in the east and wetter-than-normal conditions in the west persisted throughout the winter (last 2, 3, 4, 6, 7 months). The dryness was reflected in low streamflow in the streams on the eastern half of the island. On the April 28th USDM map, abnormal dryness expanded to over a third (39.1 percent) of Puerto Rico.

CONUS State Ranks:

Current month state precipitation ranks South Dakota statewide precipitation, April, 1895-2015

The April precipitation anomaly pattern of dryness in the West, Northern Plains to Upper Midwest, and Northeast was reflected in the state ranks, with 14 states ranking in the driest third of the historical record. South Dakota had the lowest rank at eleventh driest. Parts of other states in the West and Midwest were very dry, but well-above-normal precipitation in other parts gave the states ranks in the mid (near average) range.

3-month state precipitation ranks Connecticut statewide precipitation, February-April, 1895-2015

The April pattern of dryness reflected a pattern that has persisted for much of the last three to four months. For February-April 2015, 23 states ranked in the driest third of the historical record, ten of which had the tenth driest, or drier, February-April. These included one in the West, four in the Great Plains to Great Lakes, and five in the Northeast. South Dakota had the second driest February-April in the 1895-2015 record; Vermont ranked fourth driest; Connecticut fifth driest; Minnesota, Maine, and New Hampshire seventh driest; Michigan eighth driest; North Dakota ninth driest; and Idaho tenth driest.

year-to-date state precipitation ranks South Dakota statewide precipitation, January-April, 1895-2015

California statewide precipitation, January-April, 1895-2015

The year-to-date pattern of dryness was similar to that for February-April, except more widespread and intense in the West and Plains. For January-April 2015, 26 states ranked in the driest third of the historical record, 11 of which had the tenth driest, or drier, January-April. These included four in the West, three in the Northeast, and four in the Great Plains to Great Lakes. South Dakota had the driest January-April in the 1895-2015 record, with this year marking the second consecutive drier-than-average such four-month period. California ranked third driest, with 2015 marking the third consecutive much drier-than-average January-April. Eight of the last nine, and 12 of the last 15, years have had a drier-than-average January-April for the state. New York ranked fifth driest, with five of the last seven January-April periods much drier than average.

The drier-than-average conditions have been accompanied by much warmer-than-average temperatures in the West. All of the states from the Rockies westward had a top eleven warmest January-April, with two of them (California and Arizona) ranking warmest on record. When the dryness and heat are integrated together in the SPEI, January-April 2015 ranks as the worst drought on record for California, and second worst on record for Nevada and South Dakota, for this time of year.

6-month state precipitation ranks Minnesota statewide precipitation, November-April, 1895-2015

The precipitation pattern for November 2014-April 2015 is similar to those of the last three to four months, except for areas of wetness which tempered some of the precipitation ranks. Twenty-one states ranked in the driest third of the historical record, four of which had the tenth driest, or drier, November-April. These included one in the Northeast and three in the Northern Plains to Upper Midwest. South Dakota and Minnesota had the fifth driest November-April, North Dakota sixth driest, and New York eighth driest.


California statewide precipitation, May-April, 1895-2015

The wet summer 2014 resulted in precipitation being more widespread over the last 12 months, with only six states ranking in the driest third of the historical record for May 2014-April 2015. These included California, Nevada, Oregon and Idaho in the West, and Connecticut and Rhode Island in the Northeast. At 19th driest, May 2014-April 2015 marked the fourth consecutive much-drier-than-average such 12-month period for California, with seven of the last nine May-Aprils much drier than average and eleven of the last 16 being drier than average. Temperatures were record warm across much of the West for the last six to 12 months. The combination of dryness and record heat gave California the second worst SPEI for May 2014-April 2015, with last year (May 2013-April 2014) being the worst.

Western U.S.


Percent Area of the Western U.S. in Moderate to Extreme Drought, January 1996-present, based on the Palmer Drought Index Percent Area of the Western U.S. in Moderate to Exceptional Drought, January 4, 2000-present, based on the U.S. Drought Monitor

Percent area of the Western U.S. in moderate to extreme drought, January 1900 to present, based on the Palmer Drought Index
Percent area of the Western U.S. in moderate to extreme drought, January 1900 to present, based on the Palmer Drought Index.

As noted above, dry weather has dominated the West for much of the last three to four years, resulting in significant hydrological (low lake, reservoir, and stream levels) and agricultural impacts. According to the USDM, 62.1 percent of the West was experiencing moderate to exceptional drought at the end of April, which is an increase of about 2.3 percent compared to the previous month. The Palmer Drought Index percent area statistic for the West was 66.3 percent, an increase of about eight percent compared to the previous month.

Agricultural Belts


Primary Hard Red Winter Wheat Belt precipitation, April, 1895-2015
Primary Hard Red Winter Wheat Belt precipitation, April, 1895-2015.
Primary Hard Red Winter Wheat Belt precipitation, October-April, 1895-2015
Primary Hard Red Winter Wheat Belt precipitation, October-April, 1895-2015.

October marks the start of the growing season for the Primary Hard Red Winter Wheat agricultural belt. Most of the region was wetter than normal this month, with April 2015 ranking as the 22nd wettest and 30th warmest April in the 1895-2015 record, regionwide. The growing season to date ranked as the 57th driest and 23rd warmest October-April in the 120-year record. The last three growing season-to-date periods have averaged drier than average, regionwide.

Primary Corn and Soybean Belt precipitation, April, 1895-2015
Primary Corn and Soybean Belt precipitation, April, 1895-2015.
Primary Corn and Soybean Belt precipitation, March-April, 1895-2015
Primary Corn and Soybean Belt precipitation, March-April, 1895-2015.

March serves as the beginning of the growing season for the Primary Corn and Soybean agricultural belt. The region had a mixed pattern of precipitation anomalies this month, with April 2015 ranking as the 46th wettest and 24th warmest April on record, regionwide. The growing season to date ranked as the 59th driest and 31st warmest March-April on record, regionwide.

NOAA Regional Climate Centers:


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

SoutheastSouthMidwestNortheastHigh Plains
West


As described by the High Plains Regional Climate Center, April 2015 was mild with a wide range in precipitation across the High Plains region. Generally, average temperatures ranged from near normal up to 4.0 degrees F (2.2 degrees C) above normal. Precipitation varied widely, however, with areas like southeastern Wyoming receiving over 200 percent of normal precipitation, while areas such as central South Dakota failed to reach 25 percent of normal. Deficits of at least 1.50 inches (38 mm) were common across central and eastern South Dakota. The dry weather had both positive and negative impacts this month. Early in the season, dry weather can have a positive impact on agriculture. For instance, dry areas in the Dakotas have been good for farming activities as drier soils have allowed for field work to commence with some early planting of small grains, like oats and spring wheat. The dry weather also had some negative impacts, such as an increased risk of wildfires. Wildfires are not uncommon in the spring and this month was no exception, especially across the Dakotas. Multiple reasons for the increased risk include an abundance of fuel built up from the past few years, low snowpack this winter, and overall low precipitation totals. North Dakota had many wildfire issues this month.

Areas of the Dakotas largely missed out on precipitation and this was reflected in the latest release of the USDM. Much of South Dakota received less than 50 percent of normal precipitation. These low amounts caused most locations across the state to be ranked in the top 20 driest Aprils on record. This dryness is not a recent development, however, as precipitation has been lacking since last fall. For instance, Water Year to Date (October 1-April 30) precipitation totals rank in the top 10 driest for locations all across the state. Examples include Rapid City in the west (4th), Pierre in the central part of the state (7th), and Aberdeen in the east (3rd). The past couple of months have been particularly dry for Rapid City which has only received 0.76 inch (19 mm) of liquid equivalent precipitation and 1.2 inches (3 cm) of snow over these two months. This marks the 2nd driest and 3rd least snowiest March and April on record for Rapid City (period of record 1942-2015). Although there were small improvements, drought conditions have generally expanded across the High Plains region according to the latest release of the USDM. The total area in drought (D1-D4) increased from about 35 percent to nearly 45 percent. South Dakota fared the worst this month. The total area in drought (D1-D4) increased from about 43 percent to 77 percent and a rather large new area of severe drought (D2) has emerged in the central and eastern parts of the state. In these areas, winter wheat winterkill has been an issue. Winterkill can be the result of many factors, including a lack of snow cover in the winter and early spring, and a recent lack of rainfall. Additionally, the USDA's National Agricultural Statistics Service (NASS) indicated that topsoil moisture across South Dakota was rated at 69 percent Short or Very Short at the end of the month. Other degradations around the region included an expansion of moderate drought (D1) in eastern North Dakota, northeastern Nebraska, and southwestern Wyoming. Meanwhile, in south-central Kansas, D2 expanded slightly and a new area of extreme drought (D3) emerged as well. Improvements were made in only a few areas, such as western Colorado where a small area of D2 was improved to D1. Additionally, abnormally dry conditions (D0) were removed from northeastern Colorado, portions of central Nebraska, an area of west-central North Dakota, and a very small area of eastern Kansas.

As explained by the Southern Regional Climate Center, April was a wetter and warmer than normal month for all six states within the Southern region. Precipitation totals varied spatially with each state showing some dryness in select counties/parishes. Drought conditions in the Southern region improved significantly for the second consecutive month. Anomalously high precipitation, from lows and frontal systems that passed through the region, has led to a large reduction in the areal coverage of extreme and exceptional drought. As of April 28, 2015, only 6.05 percent of the Southern region was classified as extreme drought or worse, compared to 12.60 percent on March 31, 2015. Along the central Gulf coast, heavy rains have alleviated all drought conditions in southern Louisiana and southern Mississippi.

The heavy rains this month in Texas proved valuable for wheat growers, but more problematic for other crops. Onions are growing great, along with peaches due to the cool winter. The warmer and wetter spring, however, is causing concern over invasive weed growth in the coming months. Muddy and soggy grounds in the wettest portions of the state are causing issues for farmers that are wanting to plant crops for the spring growing period as soil moisture is still running too high. Ecologically, cattle are still doing well and have plentiful water in their stock tanks from the rain. As for the drought conditions, as of the end of the month only sixteen percent of the state is under severe drought or worse. This is the lowest percentage since November of 2010. Statewide, reservoirs now stand at 73.9 percent full, which is nearly a four percent jump since the end of March, which included a nine percent increase in storage in North Central Texas, easing sprinkler use restrictions for the first time since 2013. West Central Texas and the Highland Lakes have not improved as much, however, with Austin area reservoirs still sitting at forty percent and mandatory Stage 1 water restrictions being considered by the Brazos Valley River Authority (Information provided by the Texas Office of State Climatology).

As summarized by the Midwest Regional Climate Center, overall, April 2015 temperatures were above normal across much of the region, but only by 1 to 3 degrees F (0.6 to 1.7 degrees C). April 2015 precipitation was 150 to 300 percent of normal across the Ohio River Valley after numerous rounds of showers and thunderstorms occurred during the month, while the remainder of the Midwest experienced near to below normal April precipitation. Precipitation totals ranged from only 0.10 inch (3 mm) in northwest Minnesota to 10 to 12 inches (254 to 305 mm) in central Kentucky. Five states in the Midwest were drier than normal for April. The greatest departures were in Minnesota, which had a statewide value of only 1.39 inches (35 mm), which is 0.85 inch (22 mm) below normal. Drought conditions worsened as a result of the dry conditions in Minnesota. In northwest Minnesota, moderate drought intensified to severe drought by the end of the month. The USDM showed worsened drought conditions across Minnesota by the end of April with much of the state classified as moderate to severe drought. However, combined with the observed seasonally warmer temperatures, the dry conditions have provided suitable field work days and planting in the state ahead of normal. Farmers report being optimistic for a good crop provided spring rains finally arrive. Much of Wisconsin, central Michigan, and northern Indiana were classified as abnormally dry by the end of April. Due to the wetter than normal conditions across the Ohio River Valley during April, planting was slightly behind in Indiana, Illinois, Ohio, and Kentucky at the end of the month compared to 5-year averages available via state crop progress reports.

As noted by the Southeast Regional Climate Center, monthly mean temperatures in April were above average across much of the Southeast region, including Puerto Rico and the U.S. Virgin Islands. Guayama, PR (1914-2015) observed its second warmest mean temperature for April on record. Precipitation was above normal across much of the region. Portions of north-central Florida and the North Carolina coastal region observed unusually dry conditions during the month, where monthly precipitation totals were 75 to as little as 25 percent of normal. Precipitation was also below normal for much of Puerto Rico and the U.S. Virgin Islands during April. Juncos, PR (1931-2015) observed its third driest April on record with only 0.58 inch (14.7 mm) of precipitation.

An improvement in drought conditions was observed across the region during April. The percentage of the region under drought-free conditions (less than D1) increased from approximately 96 percent on March 31st to 99 percent on April 28th. Moderate (D1) drought conditions were completely eliminated in southern Alabama and the western half of the Florida Panhandle, and the localized coverage of severe (D2) drought conditions in Miami-Dade County was also ameliorated. Only a small portion of far southern Florida remained in moderate drought at the end of the month. While the unusually warm temperatures during April promoted rapid growth in the corn fields of Georgia, excessive amounts of precipitation leached fertilizers below the root zone of the corn plants, causing a deficiency in the uptake of these essential nutrients. The wet conditions during April also contributed to the development of a fungal disease, known as fusarium head blight, within some Georgia wheat fields.

As explained by the Northeast Regional Climate Center, since the start of 2015, the region has been colder than normal and averaged below-normal precipitation each month. For April, the Northeast received 3.48 inches (88.39 mm) of precipitation, or 95 percent of normal. State departures ranged from 52 percent of normal in Rhode Island to 164 percent of normal in West Virginia, making it the state's 4th wettest April on record. April temperature departures ranged from 2.1 degrees F (1.2 degrees C) below normal in Maine and Vermont to 1.1 degrees F (0.6 degrees C) above normal in West Virginia. According to the USDM released on April 2, 45 percent of the Northeast was abnormally dry. Dryness eased slightly in parts of Pennsylvania and New York so that by month's end 40 percent of the region was abnormally dry. The growing season was running up to a month behind schedule for parts of the region due to cold temperatures and lingering snow cover.

As summarized by the Western Regional Climate Center, April brought near to slightly below normal temperatures to the West, breaking a four-month stretch of widespread above normal temperatures. This month showed a typical springtime transitional pattern, with two cold storm systems passing across much of the West interspersed with strong high pressure and above normal temperatures. Precipitation was variable across the West, though generally below normal. Scattered areas of the Southwest observed above normal precipitation.

Along the northern tier of the West, conditions were generally drier than normal for April. In south-central Washington, Yakima had its 5th April since 1946 with no measurable precipitation. Further east in south-central Idaho, Jerome recorded only 0.12 in (3 mm), 11% of normal and the 4th driest April since records began in 1915. In northwestern Montana, Cut Bank reported 0.15 in (4 mm), 19% of normal and the 13th driest April in a 113-year record. Snowpack across the West continued to decline this month. At month's end, the Sierra Nevada snowpack stood at only 3% of normal and the Cascades were generally at 10% of normal or less. Snowpack in the Rocky Mountains was in the 40-60% of normal range. Drought conditions expanded in northeastern California, eastern Washington, northern Oregon, and southern Idaho, but improved somewhat in southeastern New Mexico, eastern Colorado, and along the Utah-Colorado border consistent with the above normal precipitation observed in these areas.

Precipitation in parts of California and Nevada was far from sufficient to alleviate multi-year drought conditions. The region's precipitation season is coming to an end and this winter's meager snowpack promises little runoff for the spring and summer months, suggesting the drought may intensify. California's governor declared a mandatory 25% reduction in urban water use and the replacement of 50 million square feet of lawn with artificial turf or drought tolerant landscapes, among other actions.

Near to well above normal temperatures were observed across Alaska this month. Anchorage recorded its warmest April on record at an average 40.7 F (4.8 C), 3.9 F (2.2 C) above normal; records there began in 1952. Precipitation was significantly above normal across southern Alaska. King Salmon reported 2.18 in (55 mm) precipitation, 223% of normal, the 6th wettest April in a 99-year record. Further south, several locations in Hawaii saw wetter than normal conditions and lessening of drought on all major islands. Kahului, Maui, recorded 2.81 in (71 mm) rainfall, 181% of normal. Temperatures were also above normal in many locations throughout the state. On the windward side of Oahu, Kaneohe recorded an average 77.3 F (25.2 C) for the month, 3.2 F (1.8 C) above normal and the warmest April since records began in 1942.

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.

In the U.S. Affiliated Pacific Islands (maps — Micronesia, Marshall Islands, basinwide), April 2015 was drier than normal at the southern and western primary stations and wetter than normal at the northern and eastern stations (including Pago Pago). April is in the dry season for the northern and western stations (Koror, Yap, Lukonor, Guam, Kwajalein, Majuro, and Saipan).

Above-normal April rainfall was reported by stations in the Republic of the Marshall Islands, Mariana Islands, northern stations in Micronesia, and American Samoa, including Guam, Saipan, Yap, Chuuk, Pohnpei, Kwajalein, Majuro, and Pago Pago. Rainfall was below normal at Koror, Lukonor, Kapingamarangi, and Kosrae. April is in the wet season for the southern stations Kapingamarangi and Kosrae, so normals are high.

The rainfall amounts were below the minimum thresholds (4 or 8 inches) required to meet most monthly water needs at stations in the Republic of Palau and adjacent western Micronesia. These included Koror, Yap, Ulithi, and Woleai. Wotje (in the Marshall Islands) was also below the 8-inch threshold. The 4- and 8-inch thresholds are important because, if monthly precipitation falls below the threshold, then drought becomes a concern. Koror and Yap were below the 8-inch threshold for the fourth consecutive month. Five of the last six months have been drier than 8 inches at Yap, and six of the last seven months have been drier than 8 inches at Koror.

As measured by percent of normal precipitation, Koror and Kosrae were drier than normal in both the short term (April, the last 3 months [February-April 2015], and year to date [January-April 2015]) and long term (12-month time scale, May 2014-April 2015). Kapingamarangi and Lukonor were wetter than normal for the year-to-date, but otherwise drier than normal. Pago Pago was drier than normal for the last 3 months but mostly wetter than normal. Yap was wetter than normal in April, but otherwise drier than normal. Chuuk, Guam, Kwajalein, Majuro, Pohnpei, and Saipan were wetter than normal at both the short- and long-term time scales.


X
  • Percent of Normal Precip
  • Precipitation
  • Normals
Pacific Island Percent of 1981-2010 Normal Median Precipitation
Station Name May
2014
Jun
2014
Jul
2014
Aug
2014
Sep
2014
Oct
2014
Nov
2014
Dec
2014
Jan
2015
Feb
2015
Mar
2015
Apr
2015
May 2014-
Apr 2015
Chuuk116%76%125%121%166%120%66%57%142%134%209%104%112%
Guam NAS99%98%290%62%108%164%75%76%213%6%198%263%110%
Kapingamarangi83%56%86%96%109%130%140%116%229%131%62%87%93%
Koror63%57%121%77%137%63%54%118%64%83%69%74%77%
Kosrae93%117%175%59%77%114%68%86%116%114%91%92%84%
Kwajalein80%104%120%58%88%154%96%68%74%149%994%322%131%
Lukonor116%110%78%77%146%138%70%86%228%97%99%83%94%
Majuro75%90%201%82%134%88%66%67%106%63%329%162%113%
Pago Pago81%154%333%60%40%29%136%141%201%102%64%153%108%
Pohnpei87%121%108%74%128%100%108%104%78%100%138%119%102%
Saipan205%92%113%71%191%105%265%47%184%14%315%203%130%
Yap39%83%110%65%125%77%84%197%92%89%93%139%93%
Pacific Island Precipitation (Inches)
Station Name May
2014
Jun
2014
Jul
2014
Aug
2014
Sep
2014
Oct
2014
Nov
2014
Dec
2014
Jan
2015
Feb
2015
Mar
2015
Apr
2015
May 2014-
Apr 2015
Chuuk13.068.9114.9215.5519.4413.786.996.4614.329.6817.3713.03153.51
Guam NAS3.366.0829.399.0813.6618.775.513.878.560.184.096.65109.2
Kapingamarangi9.977.7712.167.8410.8610.6413.0211.3720.9112.197.0511.82135.6
Koror7.459.9122.4510.4016.107.456.1213.146.487.075.115.42117.1
Kosrae16.5917.0826.068.3211.0012.519.3813.8019.2814.7314.5716.12179.44
Kwajalein5.367.2211.885.619.4917.1710.804.542.333.9423.3716.94118.65
Lukonor13.5812.8512.5010.8014.7915.576.379.6519.168.709.169.36142.49
Majuro7.589.8622.499.6414.9311.148.857.688.244.3221.6515.23141.61
Pago Pago7.848.2218.483.222.602.6813.7618.1326.8712.226.8814.35135.25
Pohnpei17.3317.9516.7410.5216.0615.3215.9716.6710.249.5818.1421.94186.46
Saipan4.873.3210.049.3319.3111.1514.871.804.660.355.955.3490.99
Yap3.079.9516.629.5816.899.347.4016.775.864.604.227.80112.1
Pacific Island 1981-2010 Normal Median Precipitation (Inches)
Station Name May
2014
Jun
2014
Jul
2014
Aug
2014
Sep
2014
Oct
2014
Nov
2014
Dec
2014
Jan
2015
Feb
2015
Mar
2015
Apr
2015
May 2014-
Apr 2015
Chuuk11.3011.6611.9812.8611.7111.5110.6111.2510.107.258.3212.47136.77
Guam NAS3.406.1810.1414.7412.6611.447.385.114.013.032.072.5399.09
Kapingamarangi12.0813.7814.158.139.938.199.279.849.159.2711.4313.64145.85
Koror11.8317.4818.5313.5011.7711.8411.3911.1610.188.567.447.32152.90
Kosrae17.7514.6414.9114.2214.2210.9413.8316.1116.6712.9316.0617.51213.87
Kwajalein6.726.939.879.7410.7411.1811.286.663.162.642.355.2690.41
Lukonor11.6911.6515.9314.0410.1511.329.0811.278.418.939.2611.31151.36
Majuro10.1111.0111.1711.6911.1712.7313.4411.397.746.886.589.42125.25
Pago Pago9.665.335.555.386.539.2610.1412.8413.3412.0010.689.39125.57
Pohnpei19.9614.8115.4314.2612.5515.2714.8316.0813.189.5513.1718.41182.36
Saipan2.383.628.9113.1310.0910.625.613.852.532.591.892.6370.25
Yap7.8512.0415.0814.8213.5012.188.838.516.395.194.565.63120.31

Precipitation amount for current month for U.S. Affiliated Pacific Island stations

Percent of normal precipitation for current month for U.S. Affiliated Pacific Island stations

Percent of normal precipitation for last 3 months for U.S. Affiliated Pacific Island stations

Percent of normal precipitation for the year to date for U.S. Affiliated Pacific Island stations

Percent of normal precipitation for last 12 months for U.S. Affiliated Pacific Island stations

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

[top]


State/Regional/National Moisture Status
A detailed review of drought and moisture conditions is available for all contiguous U.S. states, the nine standard regions, and the nation (contiguous U.S.):

States
alabama arizona arkansas california colorado connecticut
delaware florida georgia idaho illinois indiana
iowa kansas kentucky louisiana maine maryland
massachusetts michigan minnesota mississippi missouri montana
nebraska nevada new hampshire new jersey new mexico new york
north carolina north dakota ohio oklahoma oregon pennsylvania
rhode island south carolina south dakota tennessee texas utah
vermont virginia washington west virginia wisconsin wyoming

Regional
northeast u. s. east north central u. s. central u. s.
southeast u. s. west north central u. s. south u. s.
southwest u. s. northwest u. s. west u. s.

National
Contiguous United States

[top]


Contacts & Questions
For additional, or more localized, drought information, please visit:

Citing This Report

NOAA National Climatic Data Center, State of the Climate: Drought for April 2015, published online May 2015, retrieved on May 29, 2015 from http://www.ncdc.noaa.gov/sotc/drought/201504.