Drought - August 2016


NCEI 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 13 September 2016
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

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Detailed Drought Discussion


Overview


The U.S. Drought Monitor drought map valid August 30, 2016
The U.S. Drought Monitor drought map valid August 30, 2016.

During August 2016, the weather over the eastern CONUS was dominated by the North Atlantic (Bermuda) High pressure system and in the Far West by the North Pacific High, while the interior West to Great Plains region fell under the influence of upper-level troughs moving in the jet stream flow. The troughs dragged cold fronts along the surface which brought cooler Canadian air masses behind them. The troughs and fronts also provided a lifting mechanism for precipitation. This circulation pattern gave the Far West and areas east of the Mississippi a warmer-than-normal month, while August was cooler than normal in the interior West and Great Plains. Much of the West was drier than normal due to the North Pacific High and a northwesterly jet stream flow, while the Bermuda High kept the Southeast to Mid-Atlantic Coast drier than normal. Rain from slow-moving cold fronts and tropical systems gave the Southern Plains to Great Lakes a wetter-than-normal month, and the summer monsoon dropped above-normal precipitation over the Southwest. Upper-level ridging, in association with the North Pacific High, produced a southerly flow which funneled moist and warmer-than-normal air into Alaska, giving the state the third warmest and 22nd wettest August in its 1925-2016 record. Hurricane Madeline brushed Hawaii by the end of the month, helping give the state a wetter-than-normal August. Western and northern parts of Puerto Rico were wetter than normal, but the southeast drought area had below-normal precipitation. When precipitation is integrated across the CONUS, August 2016 ranked as the second wettest August in the 1895-2016 record.

With precipitation reduced by the subtropical highs, and above-normal temperatures enhancing evapotranspiration, especially in the East, drought and abnormal dryness expanded in parts of the Northern Rockies and Pacific Northwest and intensified in the Northeast, but contracted in Hawaii. There were areas of drought expansion and nearby contraction in the Central and Southern Plains, Southeast, and Northeast. Overall, drought contraction outweighed drought expansion, so the USDM-based national moderate-to-exceptional drought footprint decreased across the CONUS from 21.1 percent at the end of July to 19.5 percent at the end of August (from 17.7 percent to 16.3 percent for all of the U.S.). According to the Palmer Drought Index, which goes back to the beginning of the 20th century, about 22.1 percent of the CONUS was in moderate to extreme drought at the end of August, a slight increase compared to last 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 in parts of the West 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 across much of the West, Southeast, coastal Mid-Atlantic and Northeast, and parts of the Northern High Plains. This short-term dryness expanded or intensified long-term dry conditions in August compared to July in most of these areas. Short-term wet conditions expanded or intensified long-term wet conditions in the Southern and Central Plains to Ohio Valley and western Great Lakes, and contracted long-term drought conditions in the Southwest.



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 dominates much of the West for the last 1 to 3 months and parts of the Rocky Mountains at the 6- to 24-month time scales. Dry conditions are seen along parts of the East Coast at the 1-month time scale, dominate the Southeast at the 2- to 6-month time scales, and are evident in parts or much of the Northeast at the 2- to 24-month time scales. Parts of the Central Plains are dry at the 1- and 3-month time scales. Wet conditions dominate parts of the Southwest at 1 month and 24 months, much of the Great Plains at all time scales except the 2- and 3-month time scales, parts of the Mid-Atlantic to Southeast at the 9- to 24-month time scales, and the Mississippi and Ohio Valleys and western Great Lakes at all time scales.


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.

1-month SPEI for current month
1-month SPEI for current month.
1-month SPI for current month
1-month SPI for current month.

Temperatures were much warmer than normal across the States east of the Mississippi River, and along the West Coast, during August. The combination of these unusually warm temperatures and the lack of precipitation resulted in the 1-month SPEI map showing more severe drought conditions than the 1-month SPI map, especially in the West. When the heat and dryness of the last two months is examined, the 2-month (July-August) SPEI map shows even more severe drought conditions than the SPI map in parts of the West. Warmer temperature anomalies for the last six months across the country contributed to more severe drought on the 6-month SPEI map compared to the SPI map, especially in the West where precipitation was below normal. Widespread warm temperature anomalies for the last 12 months resulted in more severe drought in the areas with below-normal precipitation on the September 2015-August 2016 SPEI map compared to the SPI map, and also resulted in less extreme wetness where above-normal precipitation fell.

August-July temperatures for western U.S., 1895-2016

Significant differences between the SPEI and SPI maps begin to appear in the West at the 24-month time frame (SPEI vs. SPI) and become increasingly significant at the 36-month (SPEI vs. SPI), 48-month (SPEI vs. SPI), 60-month (SPEI vs. SPI), and even 72-month (SPEI vs. SPI) time scales. This is due to persistent above-normal temperatures in the West for the last several years which have increased evapotranspiration and exacerbated drought conditions. Twelve of the last 17 years (September-August periods) rank in the top 20 warmest category, with last year (September 2014-August 2015) being the warmest. Even with widespread cooler-than-normal temperatures across the West in August 2016, the September 2015-August 2016 12-month temperature still ranked as the fourth warmest on record.


36-month SPEI map 48-month SPEI map 60-month SPEI map

This is especially the case in California, where the last four September-August 12-month periods ranked in the top six warmest such periods for the state in the 1895-2016 record. The last four years cap a period of persistent unusual warmth which has lasted over three decades. The precipitation for the last 12 months gave California a statewide precipitation rank of 51st wettest (71st driest) for September 2015-August 2016. But the persistent dryness since 2000 still gave the state the driest SPI for the last 60 months and fourth driest for the last 48 months. When the temperature is factored in, California has had the most severe SPEI on record for the last 60 and 72 months, second most severe SPEI for the last 48 months, and third most severe SPEI for the last 36 months.

California statewide temperature, September-August, 1895-2016
California statewide temperature, September-August, 1895-2016.
California statewide 60-month SPEI for August, 1895-2016
California statewide 60-month SPEI for August, 1895-2016.



Regional Discussion


USDA topsoil and subsoil short and very short of moisture
USDA topsoil and subsoil short and very short of moisture.
West Statewide reservoir status
West Statewide reservoirs status.



CONUS Agricultural & Hydrological Impacts:

The dry and hot weather of August increased short-term drought conditions and, for some areas, exacerbated long-term drought. This is reflected in numerous agricultural, hydrological, and other meteorological indicators, both observed and modeled. The dry weather, with increased evapotranspiration, dried soils and stressed vegetation. Where the dry conditions have been continuing for several months, hydrological conditions such as streamflow and groundwater supplies were reduced. This is especially true in the West and along the East Coast. But precipitation was above normal in the nation's heartland. On a national scale, as of August 30th, 15 percent of the nation's cattle inventory, 14 percent of the nation's hay, 11 percent of winter wheat production, and 3 percent of corn and soybean production were in drought. These percentages are all less than the values for the end of July. According to August 28th U.S. Department of Agriculture (USDA) reports, only 7 percent of the nation's corn crop and 7 percent of soybeans were rated in poor to very poor condition, but 16 percent of the pasture and rangeland were so rated, which are about the same as at the end of July. And 25 percent of the nation's topsoil moisture and 26 percent of the subsoil moisture were rated short to very short (dry to very dry), both improvements over last month. On a regional basis, conditions varied and were more extreme.

Drought conditions at the end of the month, as depicted on the August 30th USDM map, included the following CONUS core drought and abnormally dry areas:



Hawaii: Rains from Hurricane Madeline at the end of the month helped to give Hawaii a wetter-than-normal August. The last 2, 3, 5, and 6 months have generally been wetter than normal. A mixed to drier-than-normal pattern is evident at the longer time scales (last 8, 11, 12, 24, and 36 months). Moderate to severe drought contracted to cover about 6 percent of the state according to the August 30th USDM map.

Alaska gridded percent of normal precipitation for the current month
Alaska gridded percent of normal precipitation for the current month.

Alaska: August 2016 had a mixed precipitation anomaly pattern across Alaska, although the high elevation (SNOTEL) stations were mostly wetter than normal. Based on the climate division (last 2 and 3 months) and low elevation station (last 2 and 3 months) maps, the last two to three months were wetter than normal across most of the state, except in the panhandle where it was drier than normal. This was reflected by below-normal monthly streamflow levels in the panhandle. A wetter-than-normal pattern dominates for much of the last 12 months (climate division maps for last 6, 8, 11, and 12 months) (gridded maps for last 6 and 8 months) (low elevation station maps for last 5, 6, 8, 11, and 12 months) (high elevation station and basin maps for the last 12 months). A mixed to wetter-than-normal pattern was evident on the 24- and 36-month maps. Temperatures were warmer than normal at all time scales for the last 12 months (station maps for the last 1, 2, 3, 8, 11, 12 months) (climate division maps for last 1, 2, 3, 6, 8, 11, and 12 months) (gridded maps for last 1, 3, 6, 8 months). In fact, the divisional maps show that it was record-warm virtually across the state for the last 8, 11, and 12 months. Statewide, Alaska had the third warmest and 22 nd wettest August in the 1925-2016 record. The state was free of abnormal dryness and drought on the August 30th USDM map.

Puerto Rico: Puerto Rico was drier-than-normal in the southeast drought area and wetter than normal across the rest of the island during August. This pattern is fairly consistent for the last 2, 3, 6, 8, and 11 months, although the dryness is most widespread at the 1-month time scale. Soils were still dry across parts of the southern coastal area. As shown by the August 30th USDM map, abnormal dryness and drought shrank to about 12 percent of Puerto Rico, with moderate drought at about 6 percent of the island.



CONUS State Precipitation Ranks:

Map showing August 2016 state precipitation ranks Map showing June-August 2016 state precipitation ranks

South Carolina statewide precipitation, June-August, 1895-2016
South Carolina statewide precipitation, June-August, 1895-2016.

August 2016 was drier than normal across much of the West and parts of the Plains and East Coast. The dryness showed up on the statewide level, with nine states in the CONUS ranking in their driest third of the 1895-2016 record. Two states had a top ten driest August, including Idaho and New Jersey, both eighth driest.

The dryness was persistent in the West and evident in the Northeast and Southeast at the 3-month period. Nineteen states in the CONUS ranked in their driest third of the historical record. Three ranked in the top ten driest category, including Massachusetts (seventh driest June-August), Wyoming (seventh driest), and South Carolina (eighth driest).

Map showing March-August 2016 state precipitation ranks Connecticut precipitation, March-August, 1895-2016

Massachusetts statewide precipitation, March-August, 1895-2016
Massachusetts statewide precipitation, March-August, 1895-2016.

There were areas of dryness across the West during the last six months, but areas of wetness masked the statewide ranks. The dry March-August is evident in the Northeast and Southeast on both the precipitation anomaly and state rank maps. Twelve states ranked in the driest third of the historical record, with Connecticut and Massachusetts having the eighth driest March-August, and Georgia ranking eleventh driest.

For the year to date (January-August), dry areas occurred in the West, Southeast, and Northeast, but localized wet areas moderated the state ranks in most areas. Twelve states ranked in the driest third of the historical record, with Connecticut ranking seventh driest and Massachusetts tenth driest.

Connecticut precipitation, January-August, 1895-2016 Massachusetts precipitation, January-August, 1895-2016


Map showing September 2016-August 2016 state precipitation ranks Connecticut statewide precipitation, September-August, 1895-2016

There were areas of dryness for the last 12 months in the West, Southeast, and Northeast, but areas of wetter-than-normal precipitation dominated, masking the statewide ranks in most areas except southern New England. Five states had a September 2015-August 2016 precipitation rank in the driest third of the historical record, with Connecticut ranking eighth driest. The last three such 12-month periods have been much drier than average in Connecticut, reflecting the prolonged nature of the dryness in this region.


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 earlier, August was much drier than normal across much of the West, except in the Southwest. The water year-to-date (October 1, 2015-August 31, 2016), overall, has been near to wetter than normal for much of the West. But portions of the Rockies and adjacent High Plains, especially in Montana and Wyoming, have been persistently dry, with water year-to-date precipitation percentiles in the driest 5 percent. Even though precipitation during this water year has been above normal in many areas, one wet season cannot make up for several years of moisture deficits. This is especially true in California, where ten of the last 16 (since 2000) September-August periods have been much drier than average. So drought continued in both the USDM and Palmer analyses. The dryness of the last three months resulted in expansion of drought on both maps. According to the USDM, 34.8 percent of the West was experiencing moderate to exceptional drought at the end of August, about 2.6 percent more than the previous month. The Palmer Drought Index percent area statistic for the West increased to 43.2 percent.

Agricultural Belts


Primary Corn and Soybean Belt precipitation, August, 1895-2016
Primary Corn and Soybean Belt precipitation, August, 1895-2016.
Primary Corn and Soybean Belt precipitation, March-August, 1895-2016
Primary Corn and Soybean Belt precipitation, March-August, 1895-2016.

August was wetter and generally warmer than normal in the Primary Corn and Soybean agricultural belt. Regionwide, August 2016 ranked as the wettest and 20th warmest August in the 1895-2016 record. March serves as the beginning of the growing season. Regionwide, March-August 2016 was warmer and generally wetter than normal. Regionwide, this six-month period ranked as the fourth wettest and tenth warmest March-August in the 1895-2016 record.


NOAA Regional Climate Centers:


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


As described by the High Plains Regional Climate Center, precipitation continued to be variable across the region in August, with extreme wetness and dryness present throughout the area. One dry area stretched from western Wyoming down through eastern Colorado, then northeast through central Nebraska. Another area of dryness occurred across western North Dakota. These areas generally received only 25-50 percent of normal precipitation during August. A disparity in precipitation across the Missouri River Basin resulted in lower streamflows in the Upper Basin and higher streamflows in the Lower Basin, causing the U.S. Army Corps of Engineers to refrain from making releases to meet downstream targets, which is uncommon. The summer ended with near-normal temperatures in August across the High Plains, but it was cooler compared to the above-normal temperatures experienced in most of the region in June and July. As for drought conditions, beneficial rainfall improved conditions in western South Dakota/northeastern Wyoming, but the compounding precipitation departures across northwestern Wyoming caused expansion and intensification of drought in that area. Regionwide, the area in drought in the High Plains improved slightly in August, thanks to cooler temperatures and beneficial rainfall occurring in drought-stricken locations. Since late July, the area in drought or abnormal dryness (D0-D4) shrank from about 35 percent to 32 percent. However, there were both improvements and degradations in drought conditions throughout the region in August.

The Black Hills region of South Dakota extending west into Wyoming fared worst over the summer, but beneficial rainfall over the past month brought significant improvements in drought conditions to the area, especially across South Dakota. The areal coverage of drought in the state improved from 48 percent to about 35 percent over the month. The heaviest rain fell in early August, but several systems brought rain to the area the rest of the month, allowing conditions to continue to improve. Moderate drought (D1) was removed from the Nebraska panhandle. The area of D1 that had been present in northeastern South Dakota/southeastern North Dakota was also removed. As for degradations, drought that has been present in the Bighorn Mountains region of northern Wyoming expanded into the northwestern part of the state. It was very dry in this area in August, as it received no more than about 50 percent of normal precipitation. Other areas that missed out on precipitation in August included north-central Colorado, where a small area of D1 was introduced, and south-central Nebraska, where D1 was upgraded to severe drought (D2).

During this time of year, climate conditions can impact crops as they near maturity, as well as the beginning of harvest season. Corn and soybeans were faring well across the region, although their conditions were not as good in South Dakota where drought has been present. The drought-stricken areas of South Dakota continued to experience issues with forage and hay. In Wyoming, dryness was causing pasture and range conditions to suffer. Thanks to ample rainfall, topsoil moisture improved in South Dakota and Kansas during August, but topsoil was drying out across Nebraska and Colorado.

As explained by the Southern Regional Climate Center, August proved to be a wet month for the entire Southern region. August temperatures varied spatially, with stations in the western counties of Oklahoma and Texas experiencing a slightly cooler than normal month and temperatures in Mississippi and Tennessee well above average. Due to heavy rain through the month, drought conditions have improved dramatically across the Southern region. The state of Texas is now nearly drought-free, while drought conditions in south and central Mississippi have been eliminated. Moderate to severe drought conditions are still listed in parts of southern Oklahoma, northern Mississippi, and south eastern Tennessee.

As summarized by the Midwest Regional Climate Center, August temperatures were above normal for the Midwest and August precipitation was above normal for nearly the entire region with very wet conditions (more than twice normal) scattered across all nine Midwest states. Abundant rainfall in August has reduced drought in the Midwest to less than 2 percent of the region, mostly in northern Ohio. Soil moisture is well above average for August and stream flows are also well above average for most locations. Flooding and flash flooding was a problem especially late in the month. Conditions of corn and soybeans were good or excellent in more than 70 percent of seven states according to the NASS Crop Progress report. Michigan was lower with only 58 percent of the corn and 64 percent of the soybeans rated such. Ohio had only 45 percent of corn and 54 percent of soybeans rated good or better. The poorer crop conditions in Ohio and Michigan were due to dryness earlier in the summer.

As noted by the Southeast Regional Climate Center, precipitation was highly variable across the Southeast region during August, with numerous extremes recorded, and temperatures were well above average across the region, also with numerous record-breaking extremes observed. The driest locations were found across northeastern Florida, east-central Georgia, central and coastal South Carolina, eastern North Carolina, and southeastern Virginia. Monthly precipitation totals were between 5 and 50 percent of normal in these areas. Temperatures were above average in Puerto Rico and the U.S. Virgin Islands during the month. Precipitation was generally above normal across western Puerto Rico and the U.S. Virgin Islands and below normal in eastern Puerto Rico. Coloso, PR (1905-2016) observed its driest August on record with only 1.28 inches (32.5 mm) of precipitation.

Some improvement in drought conditions occurred across much of the Southeast region during August, especially in Alabama and the Carolinas. The percentage of the region under drought-free conditions (less than D1) increased from 79 percent on August 2nd to 82 percent on August 30th. The coverage of moderate-to-extreme (D1-D3) drought across Alabama, South Carolina, and North Carolina decreased by 14, 7, and 6 percent during the month, respectively. While extreme drought was reduced substantially in parts of northern Georgia, moderate-to-severe drought conditions expanded in coverage across portions of central Georgia. In addition, an area of moderate drought developed along a portion of the Georgia and South Carolina coastline. A small area of southeastern Puerto Rico remained in moderate drought during the month. Across much of the region, dryland crops remained stressed from excessive heat and dryness, but some improvement occurred in scattered locations that received higher amounts of rainfall. By the end of the month, nearly 40 percent of the corn crop in Alabama was reported to be in poor or very poor condition. However, coastal areas of South Carolina expected several bumper crops (i.e., a crop with an unusually high yield at harvest) this year, and exceptionally high yields of corn and sweet potatoes were anticipated in parts of North Carolina. Despite some improvement during the month, pasture conditions remained very poor across Alabama, Georgia, and South Carolina due to a lack of rainfall and a widespread infestation of fall armyworms.

As explained by the Northeast Regional Climate Center, the Northeast had its warmest August on record with an average temperature of 71.9 degrees F (22.2 degrees C), 3.7 degrees F (2.1 degrees C) above normal. August precipitation was 101 percent of normal. Eight states were drier than normal, with amounts ranging from 48 percent of normal in New Jersey, its eighth driest, to 99 percent of normal in New Hampshire. For the wetter-than-normal states, totals ranged from 103 percent of normal in Vermont to 112 percent of normal in Maine.

The USDM released on August 4 indicated 27 percent of the Northeast was in a moderate or severe drought, with another 32 percent being abnormally dry. Below-normal precipitation led to intensifying drought conditions mid-month, with extreme drought introduced in parts of New York and New England. It was the first time several counties had experienced extreme drought since at least 2000, which is when USDM data began. Some rain later in the month led to slight improvements in a few spots and generally kept conditions from worsening elsewhere. The August 30 USDM (released September 1) showed 27 percent of the region was experiencing moderate, severe, or extreme drought, with another 31 percent being abnormally dry. In early August, Pennsylvania issued a Drought Warning for Potter County and a Drought Watch for 34 other counties, while New York upgraded 22 counties to a Drought Warning. Later in the month, Rhode Island declared a statewide Drought Advisory, while Massachusetts upgraded each of their regions by one level (i.e. watch to warning, etc.). Streamflow and groundwater levels were at record or near record low levels and reservoir levels remained below normal. There continued to be reports of wells going dry in the drought region. As of August 29, Scituate, MA's reservoir was at 21.5 percent of capacity. Water bans and restrictions were in place for more than 165 Massachusetts and more than 115 New Hampshire water systems at the end of August. Warm temperatures, a lack of rain, and low water levels led a few fish-kills (in Connecticut) and heat-stressed fish. As a result, state officials in Pennsylvania and Connecticut closed parts of several waterways to protect the fish. According to the USDA Farm Service Agency (FSA), crop losses in Massachusetts are estimated to exceed $13 million as of late August for the 2016 growing season for those producers participating in FSA programs. The largest losses, of over 50 percent, were hay crops. Farmers in 24 New York counties, eight New Hampshire counties, four Pennsylvania counties, and three Massachusetts counties are eligible for federal assistance. Grape growers in the drought region indicated berries were ripening faster and were expected to be smaller-sized, but higher quality. Due to the elevated fire risk in Massachusetts, state firefighters were not sent to help fight fires in the western U.S. as they normally would. According to the Massachusetts chief fire warden, the drought made fighting fires in the state more labor intensive.

As summarized by the Western Regional Climate Center, temperatures were within a few degrees of normal across the West, with slightly warmer than normal temperatures observed in the coastal states and slightly cooler than normal temperatures for the inland states. After a break for much of July, the Southwest Monsoon was active in August, bringing above normal precipitation to many areas of the Southwest. Many locations in the Southwest and Rocky Mountain states observed above normal precipitation, while dry conditions dominated throughout California, the Great Basin, and the Pacific Northwest, which for many locations was not abnormal. Several large fires impacted the West this month, most notably in California.

Los Angeles received no precipitation, consistent with August in over 100 other years in the station's 140-year record. Los Angeles' August normal is 0.04 in (1 mm). Medford, Oregon, also received no precipitation, as in 35 other years in the station's 106-year record. Normal August precipitation for Medford is 0.4 in (10 mm). Further north, the lack of precipitation was more anomalous. Seattle, Washington received only 0.17 in (4 mm), 19% of normal and the 10th driest August since records began in 1945. Dillon, Montana recorded 0.12 in (3 mm) for August, 11% of normal and the 5th driest August in a 77-year record. In northeastern Idaho, Dubois reported 0.12 in (3 mm) 7% of normal and the 8th driest August since records began in 1925. Drier than normal conditions in western Montana, eastern Idaho, and northwestern Wyoming prompted the introduction of abnormally dry conditions or increased severity of drought conditions in the USDM this month. Drought conditions also worsened in a large area of northeastern Oregon, and abnormally dry conditions were noted along the Utah-Wyoming-Colorado border area.

August was a uniformly warm month across Alaska, with most stations reporting one of their top-three warmest Augusts on record. Annette Island (63.6 F/17.6 C), Cold Bay (56.5 F/13.6 C), King Salmon (59.5 F/15.3 C), Kodiak (58.9 F/14.9 C), and Yakutat (57.7 F/14.3 C) all saw their warmest average August temperatures on record. Precipitation was generally near normal across mainland Alaska; however, Anchorage observed several days of locally heavy rain and precipitation totaled 5.45 in (138 mm), 168% of normal and the 4th wettest August since records began in 1952. Further south, an upper level disturbance passing over the Hawaiian Islands on the 22-24th brought abundant precipitation to windward locations; Hilo, on Big Island, reported 7.15 in (182 mm) on the 23rd. Tropical Storm Madeline brushed the southern part of the state over the last few days of the month, bringing heavy rainfall to the southeast side of Big Island and light rain to other parts of the state. August rainfall totaled 24.68 in (627 mm) in Hilo, 250% of normal and the 4th wettest since records began in 1949. Honolulu, Oahu, also observed above normal precipitation at 1.58 in (40 mm), 282% of normal and the 8th wettest August since records began in 1940.

Pacific Islands: The NOAA National Weather Service (NWS) offices, the Pacific ENSO Applications Climate Center (PEAC), and partners provided reports on conditions across the Pacific Islands.

In the U.S. Affiliated Pacific Islands (USAPI) (maps — Federated States of Micronesia, Northern Mariana Islands, Marshall Islands, Republic of Palau, American Samoa, basinwide), August 2016 was wetter than normal at Guam, Pohnpei, and Saipan, and drier than normal at the rest of the primary stations.

Rainfall amounts were below the minimum thresholds (4 or 8 inches) required to meet most monthly water needs at stations in the Federated States of Micronesia (FSM) (Nukuoro, Pingelap, and Woleai), the Marshall Islands (Jaluit), and American Samoa (Pago Pago). August rainfall was above the monthly minimum thresholds at the rest of the regular reporting stations in Micronesia. The 4- and 8-inch thresholds are important because, if monthly precipitation falls below the threshold, then drought becomes a concern.

As measured by percent of normal precipitation, Chuuk, Kapingamarangi, Koror, Kosrae, Lukonor, Majuro, and Yap have been drier than normal in the short term (August and the last 3 months [June-August 2016]) as well as the long term (year to date [January-August 2016] and last 12 months [September 2015-August 2016]). Pohnpei was wetter than normal in the short term but drier than normal in the long term. Pago Pago was near normal in the long term but drier than normal in the short term. Kwajalein was near normal at the 3-month time scale but drier than normal at the other three time scales. Guam was drier than normal at the 12-month time scale but near to wetter than normal at the other three time scales. Saipan was wetter than normal for all four time periods.


X
  • Percent of Normal Precip
  • Precipitation
  • Normals
Pacific Island Percent of 1981-2010 Normal Median Precipitation
Station Name Sep
2015
Oct
2015
Nov
2015
Dec
2015
Jan
2016
Feb
2016
Mar
2016
Apr
2016
May
2016
Jun
2016
Jul
2016
Aug
2016
Sep 2015-
Aug 2016
Chuuk188%53%70%82%63%29%85%86%107%91%94%74%84%
Guam NAS108%125%81%74%65%120%79%52%53%125%67%141%85%
Kapingamarangi112%63%89%134%103%65%88%94%34%24%66%91%69%
Koror143%53%69%41%26%30%36%135%115%93%45%61%65%
Kosrae115%63%33%95%60%113%32%23%72%130%88%88%63%
Kwajalein95%105%88%59%64%17%45%21%57%142%101%83%80%
Lukonor149%40%123%56%123%61%51%113%102%73%43%73%71%
Majuro96%83%40%61%14%46%20%22%110%66%90%75%63%
Pago Pago18%88%210%183%34%54%101%329%102%73%81%83%103%
Pohnpei124%78%67%71%102%49%44%60%80%143%79%112%82%
Saipan92%198%64%154%54%105%106%68%87%57%42%186%114%
Yap68%43%37%58%35%34%15%62%113%54%67%88%58%
Pacific Island Precipitation (Inches)
Station Name Sep
2015
Oct
2015
Nov
2015
Dec
2015
Jan
2016
Feb
2016
Mar
2016
Apr
2016
May
2016
Jun
2016
Jul
2016
Aug
2016
Sep 2015-
Aug 2016
Chuuk22.076.097.469.256.402.097.0810.7312.1110.6111.279.50114.66
Guam NAS13.7114.265.963.772.623.631.631.311.807.736.7720.8584.04
Kapingamarangi11.085.138.2813.209.406.0410.0212.784.073.309.337.38100.01
Koror16.886.247.864.592.642.532.689.9013.5516.258.288.2099.6
Kosrae16.366.904.5515.379.9514.565.153.9912.7018.9913.0712.48134.07
Kwajalein10.2411.719.983.902.020.461.051.133.809.819.968.1272.18
Lukonor15.154.5311.186.3510.375.444.7512.8311.928.496.8410.31108.16
Majuro10.7210.525.336.931.113.171.332.0511.127.2710.098.7878.42
Pago Pago1.208.1521.3323.534.496.4910.7630.879.893.884.484.49129.56
Pohnpei15.5911.869.9511.4113.494.645.7611.0116.0621.1812.1215.91148.98
Saipan9.2621.003.615.941.362.722.001.782.072.053.7624.4079.95
Yap9.215.293.314.932.231.770.703.478.906.4610.0313.1069.4
Pacific Island 1981-2010 Normal Median Precipitation (Inches)
Station Name Sep
2015
Oct
2015
Nov
2015
Dec
2015
Jan
2016
Feb
2016
Mar
2016
Apr
2016
May
2016
Jun
2016
Jul
2016
Aug
2016
Sep 2015-
Aug 2016
Chuuk11.7111.5110.6111.2510.107.258.3212.4711.3011.6611.9812.86136.77
Guam NAS12.6611.447.385.114.013.032.072.533.406.1810.1414.7499.09
Kapingamarangi9.938.199.279.849.159.2711.4313.6412.0813.7814.158.13145.85
Koror11.7711.8411.3911.1610.188.567.447.3211.8317.4818.5313.50152.90
Kosrae14.2210.9413.8316.1116.6712.9316.0617.5117.7514.6414.9114.22213.87
Kwajalein10.7411.1811.286.663.162.642.355.266.726.939.879.7490.41
Lukonor10.1511.329.0811.278.418.939.2611.3111.6911.6515.9314.04151.36
Majuro11.1712.7313.4411.397.746.886.589.4210.1111.0111.1711.69125.25
Pago Pago6.539.2610.1412.8413.3412.0010.689.399.665.335.555.38125.57
Pohnpei12.5515.2714.8316.0813.189.5513.1718.4119.9614.8115.4314.26182.36
Saipan10.0910.625.613.852.532.591.892.632.383.628.9113.1370.25
Yap13.5012.188.838.516.395.194.565.637.8512.0415.0814.82120.31

The end of the El Niño and development of ENSO-neutral conditions in the tropical Pacific has resulted in the return of much-needed rainfall to most of the USAPI region. The rains have ended the drought, although long-term drought impacts linger on some islands due to the extreme dryness of this recent El Niño episode as seen in the table below.

An analysis of historical data for the USAPI stations in the Global Historical Climatology Network-Daily (GHCN-D) dataset, augmented with fill-in data from the 1981-2010 Normals, indicated that several stations had record or near-record dryness during 2016 and 2015-2016. The following table lists the precipitation ranks for August 2016, January-August 2016 (year to date), and September 2015-August 2016 (the last 12 months). Some stations have a long period of record and their dataset is fairly complete, while other stations have a shorter period of record and the dataset has some missing data. The year to date was the second driest January-August on record for Kapingamarangi (based on a record from 1962-2016), Majuro (1954-2016), and Yap (1951-2016), and the driest on record for Utirik (based on data from 1985-2016 but only 5 years of non-missing values). The last twelve months (September 2015-August 2016) was the driest such September-August period on record at Ailinglapalap (1981-2016), Majuro, Woleai (1968-2016), and Yap, and second driest at Koror (1951-2016), Kosrae (1954-2016), Lukonor (1981-2016), and Ulithi (1981-2016).

Rank, Number of Years with data, and Period of Record for USAPI stations for August 2016, January-August 2016, and September 2015-August 2016.
Rank of 1 = driest.
Station Aug 2016
Rank
Aug
No. of Years
Jan- Aug 2016
Rank
Jan- Aug
No. of Years
Sep 2015- Aug 2016
Rank
Sep- Aug
No. of Years
Period of Record
Koror 5 66 4 65 2 65 1951-2016
Woleai 7 35 3 25 1 22 1968-2016
Yap 27 66 2 65 1 65 1951-2016
Majuro 14 63 2 62 1 62 1954-2016
Ulithi 27 35 3 33 2 32 1981-2016
Ailinglapalap 20 32 3 32 1 30 1981-2016
Kosrae 17 48 4 35 2 28 1954-2016
Lukonor 5 20 3 20 2 19 1981-2016
Saipan 35 36 23 35 9 27 1981-2016
Pohnpei 33 66 8 65 4 65 1951-2016
Kwajalein 27 65 9 64 7 64 1952-2016
Kapingamarangi 11 26 2 18 3 14 1962-2016
Chuuk 8 66 7 65 9 65 1951-2016
Guam 46 60 19 59 17 59 1957-2016
Nukuoro 3 33 9 32 12 31 1981-2016
Pago Pago 21 51 18 50 30 50 1966-2016
Wotje 32 33 26 33 N/A 30 1981-2016
Utirik 13 13 1 5 N/A 2 1985-2016

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

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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

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

Citing This Report

NOAA National Centers for Environmental Information, State of the Climate: Drought for August 2016, published online September 2016, retrieved on September 27, 2016 from http://www.ncdc.noaa.gov/sotc/drought/201608.