August 2019 Drought Report

Overview

A high pressure ridge dominated the upper-level circulation during August 2019, keeping temperatures warmer than normal and precipitation drier than normal across most of the West into the southern Plains. The lack of precipitation and excessive heat increased moisture stress which resulted in an abnormally high Evaporative Demand Drought Index (EDDI). This was especially true over the Southwest. The upper-level ridge extended into southern Alaska, where record warm and dry conditions occurred. Upper-level lows and short-wave troughs migrated through the storm track along the U.S.-Canadian border. They frequently intensified and deepened across the southern Canadian Prairies to Great Lakes, sending cold fronts into the CONUS east of the Rockies. These gave the month a colder-than-normal character from the northern Plains to Ohio Valley. The fronts also triggered above-normal precipitation from the northern Plains to Lower Mississippi Valley. The fronts were dry as they crossed the Upper Mississippi Valley to Great Lakes, leaving this region with below-normal precipitation for the month. Precipitation was spotty from the Southeast to Northeast and across Puerto Rico, while parts of Hawaii were wetter than normal and other parts drier than normal. A monsoon trough and tropical circulations brought abundant rainfall to Micronesia. As a result of these conditions, drought and abnormal dryness expanded or intensified across much of the Southwest, southern Plains, and Upper Midwest in the CONUS; across much of southern coastal Alaska; and in spotty areas along the East Coast and in Hawaii and Puerto Rico. Drought and abnormal dryness contracted or became less intense in east-central Alaska and parts of the Plains, Pacific Northwest, Southeast, Ohio Valley, Puerto Rico, U.S. Virgin Islands, Hawaii, and Micronesia. Drought expansion was more than contraction this month, with the USDM-based national moderate-to-exceptional drought footprint across the CONUS rising from 3.5 percent of the CONUS at the end of July to 10.0 percent of the CONUS at the end of August (from 6.9 percent to 11.3 percent for the 50 States and Puerto Rico). According to the Palmer Drought Index, which goes back to the beginning of the 20^th century, about 8.2 percent of the CONUS was in moderate to extreme drought at the end of August, increasing about 1.6 percent from the 6.6 percent at the end of July.

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

Drought conditions at the end of August, as depicted on the September 3^rd, 2019 USDM map, included the following core drought and abnormally dry areas:

• Areas of abnormal dryness (D0) to moderate drought (D1), with embedded areas of severe drought (D2), continued in the Southwest, Pacific Northwest, and far northern Rockies.
  • According to the USDM, 11.2 percent of the West was experiencing moderate to severe drought at the end of July. This is nearly double the area at the end of July. Some contraction occurred in the Northwest where precipitation was above normal this month, but this was offset by expansion in the Southwest. Below-normal precipitation and warmer-than-normal temperatures, which increased evapotranspiration, dried soils, stressed vegetation, and lowered stream levels in the Southwest. Several large wildfires burned across the West throughout the month (wildfire maps for August 1, 5, 12, 16, 19, 29, 31). Much of the West has been in drought for most of the last 20 years.
  • The percent area of the West (from the Rockies to the West Coast) in moderate to extreme drought (based on the Palmer Drought Index) increased compared to last month to about 14.6 percent. The area of the West experiencing moist conditions fell some more to 24.4 percent at the end of August.
• Abnormal dryness to severe drought expanded, and extreme drought (D3) developed, in the southern Plains. Drought coverage grew from 2.9 percent of the region at the end of July to 23.9 percent by the end of August.
• Abnormal dryness to severe drought shrank from the eastern and central parts of Alaska, but moderate drought expanded and severe to extreme drought developed in the southern portions while severe to extreme drought continued in the Alaskan panhandle.
• In Hawaii, there was contraction of drought and abnormal dryness on The Big Island but expansion of moderate to extreme drought on the central islands.
• There was some contraction, but abnormal dryness and moderate drought continued in the northern Plains, while in the Southeast, abnormal dryness to severe drought contracted in some areas and expanded in others.
• Abnormal dryness to severe drought continued in Puerto Rico, while moderate to severe drought was eliminated in the U.S. Virgin Islands.
• Abnormal dryness expanded and moderate drought developed in the Midwest.
• Abnormal dryness and drought shrank in the U.S.-Affiliated Pacific Islands (USAPI), with moderate to severe drought remaining in parts of the Republic of the Marshall Islands.

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 (as well as wet spell conditions) in some parts of the country than the PHDI map because the meteorological conditions that produce drought and wet spell conditions are not as long-lasting as the hydrological impacts.

Used together, the Palmer Z Index and PHDI maps show that short-term drought occurred across the Southwest to southern Plains, shrinking or making less intense the previous long-term wet conditions and expanding or intensifying the previous long-term drought. Short-term drought occurred in parts of the Southeast, adding a spot of long-term drought conditions in South Carolina and keeping the previous areas of long-term drought (PHDI maps for August vs. July). Short-term drought in parts of the Great Lakes lessened or contracted previous long-term wetness. Short-term wet conditions in the northern to central Plains intensified or expanded previous long-term wetness.

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.

The SPI maps illustrate how moisture conditions have varied considerably through time and space over the last two years. Most of the Southwest to southern Plains are dry for the last 1 to 3 months, with smaller parts (mainly Arizona, New Mexico, and southern Texas) dry at the 6- to 9-month and 24-month time scales. Most of the West is dry at the 3-month time scale, with parts of the Pacific Northwest dry at 6 to 24 months. Parts of the Mid-Mississippi Valley and Great Lakes are dry for the last 1 to 3 months. Parts of New England are dry at the 2-month time scale. Large parts of the Southeast are dry at the 2- and 6-month time scales. The dryness extends into the southern to central Appalachians for the last 1 to 2 months. Wet conditions dominate much of the Plains for the last 1 to 6 months, and most of the country east of the Rockies at the 9- to 24-month time scales.

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.

Temperatures during August 2019 were warmer than normal across the West to southern Plains, especially in the Southwest. Precipitation was below normal from the Southwest to southern Plains. The combination of drier- and warmer-than-normal conditions resulted in the increased evapotranspiration making drought conditions worse in the Southwest to southern Plains as seen by the more extreme SPEI there than the SPI. In contrast, the cooler-than-normal conditions reduced evapotranspiration, resulting in a more severe SPI than SPEI in the northern part of Lower Michigan where it was drier than normal. Temperatures in the Southwest were unusually warm for the last two months. The last three months were still warmer than normal here, but the warmth was not as widespread or severe, and the last four months were near to cooler than normal across much of this region. Extremely dry conditions persisted in the Southwest for the last two to three months. This combination resulted in a more extreme 2-month SPEI than 2-month SPI, but the three-month SPEI and SPI had more similar patterns.

The dryness for the last one to three months was especially focused in Arizona. The state had the driest and twelfth warmest June-August on record in 2019, and the sixth driest and second warmest August. This combination resulted in the most severe statewide SPEI on record for August, July-August, and June-August. The statewide SPI for August was not the most severe on record (although it ranked in the top ten); the July-August SPI was second most severe; while the June-August SPI was the most severe on record (but just barely). In all three cases, however, the Arizona statewide SPEI still had a more severe value than the statewide SPI.

Much of the West, especially from California to the central Rockies, experienced drier- and warmer-than-normal conditions for much of the last six years. The persistent and excessive heat increased evapotranspiration and made the drought conditions worse, as seen in a more extreme SPEI compared to SPI during this period (SPEI maps for last 24, 36, 48, 60, 72 months) (SPI maps for last 24, 36, 48, 60, 72 months).

Regional Discussion

Hawaii:

August 2019 was wetter than normal across portions of the southern islands, but drier than normal across the central to northern main Hawaiian Islands. This pattern was also evident for the last 2 months. A mixed pattern of precipitation anomalies could be seen on the maps for the last 3, 4, and 5 months. Drier-than-normal conditions dominated at the 6-, 8-, 9-, and 11-month time scales, with Honolulu having the sixth driest December-August and third driest November-August in the 1941-2019 record. The precipitation anomaly pattern shifted to a mixed pattern at longer time scales (last 12, 24, 36, 48, 60 months). Streamflow was below normal at many gauges from Oahu to Maui. At mid-August, reports were received of ranchers near Paauilo and Ookala in the Hamakua District hauling water for their livestock. The August rains contracted drought and abnormal dryness on the Big Island, but it expanded on the central islands. The Big Island is the largest of the main Hawaiian Islands, so the statewide drought area contracted from 28.7 percent at the end of July to 21.7 percent of Hawaii at the end of August. Moderate to extreme drought remained on the September 3^rd USDM map.

Alaska:

August 2019 was a month of contrasts across Alaska. The northeastern portions of the state were much wetter than average, while the south coastal area was record dry. This pattern was evident for much of the year, with the wet areas covering the northern, western, and interior eastern regions and the dry areas along the south central to panhandle regions. Anchorage had the driest August, July-August, and June-August, and second driest May-August and March-August in the city's 1952-2019 record. The epicenter of dryness shifted more to the panhandle at longer time scales, although some stations in the south central region were still drier than normal even at the 5-year time scale (low elevation station precipitation anomaly maps for the last 1, 2, 3, 4, 5, 6, 8, 9, 11, 12, 24, 36, 48, 60 months) (high elevation SNOTEL station precipitation maps for last 1 and 11 months, and SNOTEL basin map for last 11 months) (gridded precipitation percentile maps for the last 1, 3, 8 months) (climate division precipitation rank maps for the last 1, 3, 6, 8, 12 months) (Leaky Bucket model precipitation percentile map) (low elevation station Standardized Precipitation Index maps for the last 1, 2, 3, 4, 6, 9, 12, 24 months). Temperatures during August were warmer than normal in the southern and western portions of the state, with record warmth occurring along the southern coast; the northeastern interior regions were cooler than normal. But warmer-than-normal conditions dominated across the state at longer time scales, with record warmth in the south for the last three months, nearly statewide for the last six months, and in the north and west for the year to date to last 12 months (low elevation station temperature maps for the last 1, 2, 3, 4, 8, 11, 12 months) (gridded temperature percentile maps for the last 1, 3, 8 months) (climate division temperature rank maps for the last 1, 3, 6, 8, 12 months). (Leaky Bucket model temperature percentile map). Modeled soil moisture and satellite-based soil moisture estimates showed drier-than-normal conditions in eastern interior to southwestern areas, and south-central coastal to panhandle areas, and streamflow was below normal, especially at streams in the south central to panhandle areas. Several dozen large wildfires burned across the state from the eastern interior to southwestern regions at the beginning of the month. Precipitation at mid-month quenched many of these fires. The wildfire focus shifted to the south central areas near the end of the month (wildfire maps for August 1, 5, 8, 12, 16, 19, 29, 31). According to the National Interagency Fire Center's (NIFC) National Interagency Coordination Center, as of early September, 2.59 million acres have been burned in Alaska so far this year. In southern Alaska, widespread areas of deciduous trees and bushes are turning brown and dropping leaves now, which is unprecedented; Kodiak implemented voluntary water restrictions; the community of Chignik reported severe water issues and a water emergency; there were impacts to the community water supply in Nanwalek; the communities of Seldovia, Chignik Lagoon, Chignik Lake, and Tatilek reported water shortages and boil water advisories; and the salmon spawning habitat of Jaklof Creek near Seldovia was threatened as streamflow dried up. Abnormally dry to drought conditions contracted in the eastern to central interior regions, but expanded or intensified in the southern coast to Aleutian chain. Extreme drought increased from 0.9 percent to 1.5 percent of the state, but moderate to extreme drought contracted statewide, shrinking from 24.5 percent at the end of July to 17.8 percent on the September 3^rd USDM map, with abnormally dry to drought conditions shrinking from 69.6 percent to 30.9 percent.

Puerto Rico and U.S. Virgin Islands:

Hurricane Dorian moved across the U.S. Virgin Islands (USVI) near the end of August, dropping several inches of rain on the northern islands of St. John and St. Thomas. Some of Dorian's rain fell on eastern Puerto Rico, but much of Puerto Rico was drier than normal for August. Much of southern and parts of eastern Puerto Rico were drier than normal during the summer, while other parts, as well as the USVI, were wetter than normal. This pattern persisted across Puerto Rico, with a mixed precipitation anomaly pattern over the USVI, for the rest of the year. Dry conditions dominated at the 12-month time scale, with wet conditions prevailing at longer time scales (radar-based precipitation anomaly estimates for the last 1, 2, 3, 6, 8, 11 months) (low elevation station precipitation maps for the last 1, 2, 3, 4, 5, 6, 8, 9, 11, 12, 24, 36, 48, 60 months). Soils continued dry across much of Puerto Rico in the south and central regions, and August streamflow was below normal in these dry areas. As seen on the September 3^rd USDM map, abnormal dryness and drought contracted, but severe drought expanded slightly, across parts of Puerto Rico, with the total drought area shrinking from 23.7 percent at the end of July to 19.2 percent at the end of August. In the USVI, drought and abnormal dryness ended on the northern islands of St. Thomas and St. John, while moderate drought improved to abnormal dryness on St. Croix.

CONUS State Precipitation Ranks:

August 2019 was drier than normal across much of the West (especially the Southwest) to southern Plains and parts of the Midwest. Nine states had a rank in the driest third of the 125-year historical record for August, including Arizona and Utah which ranked sixth driest.

The summer (June-August 2019) was drier than normal across the West (again, especially the Southwest) to southern Plains, parts of the Midwest, and scattered areas in the Southeast to Northeast. Ten states had a rank in the driest third of the historical record, including Arizona (driest summer on record), Utah (sixth driest), California (ninth driest), and New Mexico (tenth driest).

The precipitation anomaly maps for the last six and eight months were similar — drier than normal in parts of the Northwest, Southwest, and Southeast, as well as extreme northern Plains. Five states (in the Northwest, Southwest, and Southeast) ranked in the driest third of the historical record for March-August, and four states in the same regions so ranked for January-August. Arizona and Washington had the tenth driest March-August, and Washington had the eighth driest January-August. Otherwise, a wet circulation pattern dominated much of the country for these two periods. The wet circulation pattern persisted across much of the CONUS for the last 12 months. Only Washington ranked in the driest third of the 1895-2019 record for September 2018-August 2019, while at the other end of the spectrum, eleven states (all east of the Rockies) were record wet.

Agricultural Belts

During August 2019, the Primary Corn and Soybean agricultural belt was cooler than normal, while the western and southern ends were mostly wetter than normal and the northern and eastern ends were mostly near to drier than normal. The month ranked as the 29^th wettest and 51^st coolest August, regionwide, in the 1895-2019 record.

March marks the beginning of the growing season for the Primary Corn and Soybean agricultural belt. March-August 2019 was mostly wetter and near to cooler than normal. The 6-month period ranked as the second wettest and 45^th coldest March-August, regionwide, in the 1895-2019 record.

With the persistently wet pattern across much of the CONUS in recent months, especially over agricultural lands, there is little drought in the major agricultural regions, but dryness this month increased the percentages just a few points. As of September 3^rd, drought was affecting seven percent of the nation's corn production; five percent of soybean production; six percent of hay acreage; eight percent of cattle inventory and winter wheat production; and zero percent of spring wheat production. According to September 3^rd U.S. Department of Agriculture (USDA) reports, 13 percent of the nation's corn crop, 13 percent of soybeans, 15 percent of cotton, eight percent of spring wheat, and 18 percent of pasture and range were in poor to very poor condition, while 31 percent of the nation's topsoil and 29 percent of subsoil were short to very short of moisture (dry to very dry). But these national conditions reflect an average of very wet and very dry areas. The states having the driest soils were scattered around the country — in the West, southern Plains, Southeast to Mid-Atlantic, Midwest, and Northeast. They included (percent area with short to very short topsoil / subsoil): California (85% / 70%), Oregon (73% / 71%), Washington (50% / 39%), Idaho (55% / 51%), Montana (31% / 35%), Wyoming (53% / 52%), Nevada (60% / 45%), Utah (45% / 45%), New Mexico (68% / 73%), Texas (84% / 77%), Michigan (45% / 47%), Iowa (30% / 29%), Indiana (36% / 37%), Kentucky (42% / 42%), Arkansas (40% / 41%), Louisiana (38% / 26%), Mississippi (37% / 34%), Alabama (31% / 36%), Georgia (42% / 43%), South Carolina (53% / 52%), North Carolina (41% / 32%), Virginia (61% / 51%), West Virginia (30% / 34%), Maryland (63% / 55%), Delaware (78% / 68%), New Jersey (39% / 36%), Massachusetts (72% / 36%), and New Hampshire (30% / 21%).

NOAA Regional Climate Centers:

More information, provided by the NOAA Regional Climate Centers and others, can be found below.

As summarized by the High Plains Regional Climate Center, for much of the High Plains region, the ongoing wet pattern continued into August. In August, the High Plains region was split down a line running from north-central Wyoming through south-central Kansas. Generally, east of the line, cool, wet conditions dominated, while west of the line, warm, dry conditions prevailed. Although wet conditions prevailed across much of the region, drier conditions were present throughout a large part of Colorado, Wyoming, and far southwest Kansas. In some of these areas, precipitation was less than 50 percent of normal for the month. For instance, Grand Junction, Colorado had its 3rd driest August on record, with only 0.04 inch (1 mm) of precipitation (period of record 1983-present).

Heavy rains staved off the development of drought conditions for the majority of the High Plains region this month. Drought conditions (D1-D4) developed or expanded in small areas of Colorado, Kansas, and North Dakota, however. According to the USDM, the area experiencing drought or abnormally dry conditions (D0-D4) increased slightly over the past month, from approximately 9 percent to 12 percent. Shower and thunderstorm activity was abundant over much of the High Plains region, with a swath of above-normal precipitation stretching from eastern Montana to the southeast through central Oklahoma and Arkansas. Many locations within this area had their wettest August on record. Despite this precipitation, some areas missed out, and abnormally dry conditions (D0) persisted over parts of southwestern Kansas. A small area of moderate drought (D1) developed in that area as well. To the west, D0 developed and expanded in parts of Colorado and Wyoming. D1 also spread into the southwest corner of Colorado, with drought now encompassing a larger area of the Four Corners region. The combination of ongoing below-normal precipitation and recent above-normal temperatures was a contributing factor to these changes in the USDM map in the western part of the High Plains region.

As explained by the Southern Regional Climate Center, temperatures and precipitation for the month of August varied spatially across the Southern region, with above-average temperatures in the west and below-normal temperatures in the north. The dry areas included parts of northern, western, southern, central, and eastern Texas; central and northern Louisiana, and southern Arkansas, which received 50 percent or less of normal precipitation. Parts of northern, western, and southern Texas as well as southern Arkansas received 25 percent or less of normal precipitation, while parts of southern and western Texas received 5 percent or less of normal precipitation.

At the end of August, drought conditions deteriorated across the Southern region. Extreme drought conditions developed across parts of southern and northern Texas as well as southwestern Oklahoma. Severe drought classifications were still present in far southern Texas, while new areas formed in northern Texas and southwestern Oklahoma. Moderate drought classifications expanded across northern and southern Texas as well as southwestern Oklahoma, with new areas developing in central, western, and eastern Texas, western Oklahoma, southwestern Arkansas, and northwestern Louisiana. There were no drought conditions in Tennessee or Mississippi. There was an increase in the overall area experiencing abnormally dry conditions as abnormally dry conditions developed or expanded across parts of southern, central, western, eastern, and northern Texas; southwestern, southeastern, and western Oklahoma; southwestern Arkansas, northern Louisiana, and southeastern Tennessee.

As described by the Midwest Regional Climate Center, a mix of wet and dry areas across the Midwest averaged out to slightly above-normal precipitation in August. Significantly drier conditions were common across Michigan with a statewide total 1.00 inch (25 mm) below normal. Parts of northern lower Michigan received less than half the normal amount for the month. June through August precipitation was wetter than normal for the Midwest. The average temperature for the region in August was 70.3 degrees F (21.3 C) which was 0.6 degrees F (0.3 C) below normal.

Drought was noted in the Midwest for the first time in 2019 in the August 13 USDM. This broke a stretch of 32 consecutive weeks without drought in the region, by far the longest in the history of the USDM (2000-2019). Drier conditions in July and August in eastern Iowa and northwestern Illinois contributed to the development of drought. Drought also formed in Kentucky and northern Michigan during the month. Rainfall late in August eliminated drought in Kentucky shortly after it emerged. Impacts on crops were felt, especially in areas where a wet spring led to soil compaction and poorer root structures.

As noted by the Southeast Regional Climate Center, temperatures were near average (i.e. within 3 degrees F (1.5 degrees C)) across the Southeast and Puerto Rico for the month of August, and precipitation was highly variable, as is common during the summer. The driest locations were found across the western parts of Virginia and North Carolina, as well as the much of South Carolina, western Georgia, and parts of the panhandle and southern Florida. Monthly precipitation totals were 70 to less than 25 percent of normal in these areas. Hurricane Dorian brought over 4 inches (102 mm) of rain to St. Thomas, USVI (1953-2019) on August 28th, while San Juan, PR (1898-2019), just to the west, reported only 0.2 inch (5 mm). Consequently, monthly precipitation totals across the U.S. Virgin Islands were up to 2.5 inches (64 mm) above normal.

Drought conditions changed little throughout the month of August. At the end of the month, severe drought (D2) still covered small areas in Alabama and South Carolina that did not experience localized thunderstorms that are common during the summer. Moderate drought (D1), ringed by an area of dry conditions (D0), covered parts of southeastern North Carolina, central South Carolina, central Georgia, northern Florida, and central and southern Alabama. Dry conditions (D0) also developed in parts of Virginia. Little change was observed in Puerto Rico as well, with severe drought (D2) covering the southern area, ringed by moderate drought (D1) and dry conditions (D0). Recently planted crops, such as soybeans, benefited from rain that fell in parts of North Carolina; however, it came too late for the early-summer corn crop, especially in drought-affected parts of Onslow, Pender, and Columbus counties. Both oranges and grapefruits were producing good yields in the citrus counties of Florida, especially Polk County. The complete citrus region remained drought free for the month of August.

As explained by the Northeast Regional Climate Center, August precipitation for the Northeast was 3.87 inches (98.30 mm), which is normal for the month. Summer precipitation averaged out to be 13.28 inches (337.31 mm), 108 percent of normal. The Northeast's average temperature for August was 68.6 degrees F (20.3 degrees C), 0.5 degrees F (0.3 degrees C) above normal. Summer was also warmer than normal for the region.

August started off with the Northeast being free of abnormally dry and drought conditions; however, abnormal dryness was introduced in northeastern New York, southern Maine, southwestern Massachusetts, northwestern Connecticut, and parts of West Virginia (totaling 3 percent of the Northeast) in the USDM released on August 8. Over the next two weeks, abnormal dryness was introduced in southern Vermont, western New Hampshire, and southern Maryland and lingered or expanded elsewhere. More abnormal dryness was introduced at the end of the month in parts of western New York, northern Vermont, northern New Hampshire, and western Maine, with the USDM released on August 29 showing 14 percent of the Northeast as abnormally dry.

As summarized by the Western Regional Climate Center, precipitation was below-normal across most of the southern half of the western U.S. while much of the northern half experienced near-normal to slightly above-normal precipitation accumulations for the month. Across most of the West, average temperatures were above-normal with the largest departures observed across the Four Corners states. In Alaska, anomalously warm temperatures and dryness persisted across parts of state with well below-normal precipitation observed in South-central, Southeast, and Southwest Alaska.

In the Southwest, the end of August marked one of the driest monsoon seasons on record for parts of the region. The combination of above-normal temperatures and dryness led to the introduction of areas of moderate drought in northern Arizona, according to the August 27 USDM map. Across this area, precipitation was well below normal with record dryness for the month of August reported at several observing stations. In the Pacific Northwest, drought conditions persisted across portions of northern and western Washington, northwestern Oregon, northern Idaho, and northwestern Montana despite some isolated shower activity during the month. According to the USGS, 28-day average streamflow levels in western Washington were well below-normal with numerous creeks and rivers having flows in the less than 10th percentile range. Average temperatures across much of the region were above normal.

In Alaska, the record-breaking warm temperatures continued across much of the state in August. Anchorage experienced its warmest (+5.9 F [3.3 C] departure) and driest (0.04 in [1 mm], 1% of normal) August on record as well as its warmest and driest summer on record. According to NOAA NCEI, Alaska (statewide) experienced its 2nd warmest summer on record. On a climate division level, the Cook Inlet, Northeast Gulf, and Northwest Gulf all experienced their driest August on record. For the summer, wildfires burned about 2.59 million acres across the state, which represents the 6th highest summer total in the past 50 years.

In the Hawaiian Islands, average temperatures were above-normal across the island chain for the month. On the Big Island, beneficial rainfall led to improvement in drought conditions in the Ka'u District on the leeward side.

U.S.-Affiliated 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 [FSM], Northern Mariana Islands, Marshall Islands [RMI], Republic of Palau, American Samoa, basinwide), August 2019 was drier-than-normal at Lukonor and Yap, and wetter than normal at the rest of the primary stations.

Convergence associated with a monsoon trough, along with several tropical disturbances, gave Micronesia the wet conditions during August. The tropical disturbances included Krosa, which was a tropical storm as it crossed the Marianas. Tropical Storms Francisco and Lekima, which developed north or northwest of the USAPI, enhanced the convergence, and upper-level troughs along the northern fringe of the USAPI also enhanced rainfall over the region. Monthly precipitation amounts were above the monthly minimum needed to meet most water needs (4 inches in the Marianas and 8 inches elsewhere) across the USAPI, except for Jaluit in the southern RMI. The 4- and 8-inch thresholds are important because, if monthly precipitation falls below the threshold, then water shortages or drought become a concern.

The tropical Pacific climatology can experience extremes in precipitation, from very low precipitation during the dry season to very high precipitation during the wet season. This can result in monthly normal precipitation values that are well above the monthly minimum needed to meet most water needs. This was the case during August 2019. The monthly precipitation was enough to end or stay out of drought, but still below normal because the normals were so high, at Yap (August 2019 precipitation 11.58 inches, August monthly normal mean 15.46 inches) and Lukonor (Lukunoch) (13.47 inches, normal 14.18 inches).

As measured by percent of normal precipitation, Yap was drier than normal in the short term (August and the last 3 months [June-August 2019]) and long term (year to date [January-August] and last 12 months [September 2018-August 2019]). Guam, Koror, Kwajalein, and Majuro were wetter than normal for August but drier than normal for the other three time periods. Lukonor was wetter than normal for the 3-month time period but drier than normal for the other three time periods. Kosrae and Pohnpei were drier than normal for two of the time periods but wetter than normal for the other two time periods. Saipan was slightly drier than normal for the year to date but wetter than normal for the other three time periods. Chuuk, Kapingamarangi, and Pago Pago were wetter than normal for all four time periods. As noted earlier, the monthly normal precipitation amount can vary significantly from month to month due to the strong seasonality of equatorial Pacific precipitation.

In the Marianas Islands, precipitation was wetter than normal regionwide for August. A mixed precipitation anomaly pattern exists at 2- to 5-month time scales, mostly drier-than-normal conditions at the 6- to 12-month and 48-month time scales, and mostly wetter-than-normal conditions at the 24- to 36-month and 60-month time scales (percent of normal precipitation maps for the last 1, 2, 3, 4, 5, 6, 8, 9, 11, 12, 24, 36, 48, 60 months). In the Marshall Islands, precipitation was mostly wetter than normal in August. Drier than normal conditions dominate for most of the last 2 to 12 months and at the 48-month time scale, with mixed anomalies at the 24- to 36-month time scales (percent of normal precipitation maps for the last 1, 2, 3, 4, 5, 6, 8, 9, 11, 12, 24, 36, 48 months).

According to the August 31^st USDM produced for the USAPI, drought persisted only in parts of the RMI. Conditions had improved from extreme drought (D3) to moderate drought (D1) at Utirik and from severe drought (D2) to moderate drought at Wotje, and drought or abnormal dryness ended at Ailinglapalap, Kwajalein, and Majuro. Severe drought continued at Jaluit. Storage in the Majuro reservoirs improved during the month, rising from 26.7 million gallons at the beginning of the month to 29.4 million gallons at the end of the month, or about 82 percent of maximum, which is above the 80 percent threshold for concern. The National Weather Service office in Guam issued two Drought Information Statements in August (August 8, August 22) discussing the improving conditions in the USAPI.

The abundant rainfall in August resulted in moderate to wet 1-month precipitation ranks for most of the USAPI stations. But the dryness during previous months still kept ranks low for longer time scales. Kosrae had the 21^st wettest (out of 51 years of data) August but 11^th driest (out of 49 years) July-August and seventh driest (31 years) September-August. Lukonor ranked tenth wettest (23 years) for August 2019, but ninth driest (23 years) for March-August and February-August and eighth driest back to September-August. Woleai had the 18^th driest August (38 years) and fifth driest July-August (35 years), with May-August back to September-August each ranking fifth to seventh driest. Guam ranked 18^th wettest (63 years) for August but ninth driest (62 years) for October-August. Koror had the ninth wettest August (68 years) but twelfth driest (67 years) December-August. Ailinglapalap ranked ninth wettest (35 years) for August but sixth driest for April-August. Wotje had the second wettest August (36 years) but tenth driest September-August (32 years). Kwajalein had the 34^th wettest (68 years) August but fifth driest June-August and ninth driest September-August. Majuro ranked 23^rd wettest for August (66 years) but 15^th driest for July-August and eleventh driest for October-August. Jaluit had the third driest August (36 years) and driest to third driest rank for all other time scales, but there may be an undercatch issue with Jaluit's rain gauge.

The following 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, helps put the current data into historical perspective by computing ranks based on the period of record. The table below lists the precipitation ranks for August 2019, March-August 2019 (last 6 months), and September 2018-August 2019 (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.

Station	Aug 2019 Rank	Aug No. of Years	Mar- Aug 2019 Rank	Mar- Aug No. of Years	Sep 2018- Aug 2019 Rank	Sep- Aug No. of Years	Period of Record
Pago Pago	41	54	48	53	52	53	1966-2019
Saipan	35	39	27	38	22	30	1981-2019
Kapingamarangi	22	29	22	22	17	17	1962-2019
Kosrae	31	51	29	41	7	31	1954-2019
Lukonor	14	23	9	23	8	22	1981-2019
Nukuoro	28	36	16	35	13	34	1981-2019
Pingelap	19	35	17	34	MSG	32	1981-2019
Woleai	18	38	6	30	6	25	1968-2019
Yap	17	69	15	68	19	68	1951-2019
Pohnpei	32	69	26	68	22	68	1951-2019
Chuuk	53	69	25	68	42	68	1951-2019
Guam	46	63	14	63	21	62	1957-2019
Koror	56	68	21	67	19	67	1951-2019
Ailinglapalap	27	35	7	35	9	33	1981-2019
Jaluit	3	36	2	35	1	33	1981-2019
Mili	34	35	24	34	20	32	1981-2019
Utirik	13	16	1	7	1	4	1985-2019
Wotje	35	36	15	35	10	32	1981-2019
Kwajalein	35	68	10	67	9	67	1952-2019
Majuro	44	66	23	65	13	65	1954-2019

For additional, or more localized, drought information, please visit:

• The U.S. Drought Portal
• National, Regional, and State Drought Resources