Issued 12 August 2019
Contents Of This Report:
Map showing Palmer Z Index
Percent Area of U.S. in Moderate to Extreme Drought, Jan 1996 to present
Washington Statewide Precipitation, January-July, 1895-2019

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 July 30, 2019
The U.S. Drought Monitor drought map valid July 30, 2019.

Hurricane Barry dropped heavy rain across the Lower Mississippi Valley at mid-July, resulting in above-normal precipitation and below-normal temperatures in this region for the month. Otherwise, a high pressure ridge dominated the upper-level circulation across the southern and western CONUS during July 2019, keeping precipitation below normal. Parts of the Southeast, Northeast, and Mid-Mississippi Valley were also drier than normal. Pacific weather systems moved over the top of the ridge, bringing below-normal temperatures to the Northwest and cooler- and wetter-than-normal conditions to the northern Plains. The upper-level ridge spread above-normal heights and warmer-than-normal temperatures over the Great Lakes and Northeast. Another upper-level ridge gave Alaska a mostly drier- and warmer-than-normal July. Moist tropical waves were interspersed with drier Saharan dust-laden air masses over Puerto Rico and the U.S. Virgin Islands. The development of a monsoon trough and tropical circulations brought abundant rainfall to Micronesia. Parts of Hawaii were wetter than normal and other parts drier than normal. Consequently, drought and abnormal dryness contracted in the northern Plains and Southeast, much of Micronesia, and in parts of Hawaii and Puerto Rico. Drought and abnormal dryness expanded in other parts of the Southeast, Hawaii, and Puerto Rico; in parts of the Northwest, southern Plains, and Midwest; and across much of Alaska. Drought expansion was a bit more than contraction this month, with the USDM-based national moderate-to-exceptional drought footprint across the CONUS rising from 3.2 percent of the CONUS at the end of June to 3.5 percent of the CONUS at the end of July (from 3.3 percent to 6.9 percent for the 50 States and Puerto Rico). According to the Palmer Drought Index, which goes back to the beginning of the 20th century, about 7.5 percent of the CONUS was in moderate to extreme drought at the end of July, increasing about 4.8 percent from the 2.7 percent at the end of June.

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.





Drought conditions at the end of July, as depicted on the July 30th, 2019 USDM map, included the following core drought and abnormally dry areas:



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.

Palmer Z Index map Palmer Hydrological Drought Index map

Used together, the Palmer Z Index and PHDI maps show that short-term drought occurred across much of the Southeast, bringing back the building long-term drought that had begun to appear as long-term drought on the May map and which had disappeared on the June map (PHDI maps for May and June). Short-term drought occurred in the Southwest, expanding previous long-term drought conditions in New Mexico and shrinking long-term wet conditions in Arizona (PHDI maps for July vs. June). In the Pacific Northwest, there were a few areas of short-term dry conditions but more near-normal conditions which shrank the long-term dry conditions. Short-term dry conditions in the Mid-Mississippi Valley and northern New England shrank or lowered the intensity of long-term wet conditions in those regions.



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. Parts of the Pacific Northwest were dry at every time scale, but the most widespread dryness occurred over the last 2 months and the most severe dryness occurred over western Washington at 6 months. Much of the Southwest was dry at the 1- and 2-month time scales, and parts of the Southwest were dry at the 3-, 6-, 9-, and 24-month time scales. The Mid-Mississippi Valley, and much of the southern Plains, were dry for the past month, and parts were dry for the past 2 months. Much of the Southeast was dry at 1 and 6 months, and parts were dry at 2 and 3 months. Otherwise, wet conditions dominated much of the country at the 2- to 12-month time scales, and east of the Rockies at the 1- and 24-month 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 during July 2019 were warmer than normal across the Southwest and East Coast to Great Lakes. In these areas, only the Southwest had widespread significant below-normal precipitation. The combination of drier- and warmer-than-normal conditions resulted in the increased evapotranspiration making drought conditions worse in the Southwest 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 Kansas and Oklahoma where it was drier than normal. This was also true in the Pacific Northwest for the last two months (June-July SPEI vs. SPI) where temperatures were cooler than normal.

72-month SPEI for current month
72-month SPEI for current month.
72-month SPI for current month
72-month SPI for current month.

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 percent of normal precipitation map, November 2018-July 2019
Hawaii percent of normal precipitation map, November 2018-July 2019.

Hawaii:

July 2019 was wetter than normal across western portions of the Big Island and over Lanai, but wetter than normal across the rest of the main Hawaiian Islands. Wetter-than-normal conditions were more widespread at the 2- to 6-month time scales, while drier-than-normal conditions were more widespread at the 7- to 10-month time scales. Wetter-than-normal conditions dominated at longer time scales (precipitation anomaly maps for the last 1, 2, 3, 4, 6, 7, 9, 10, 12, 24, 36, 48, 60 months). Streamflow was below normal at many gauges from Oahu to western portions of the Big Island. Significant agricultural drought impacts were reported on Maui, across the lower leeward slopes of Haleakala. Earlier in the month, reports were received of poor pastureland and dried-out vegetation and crops across northern sections of the Big Island. The July rains contracted drought on the lee side of the islands, reducing the drought area from 43.3 percent of Hawaii at the end of June to 28.7 percent at the end of July. But severe to extreme drought expanded slightly, and abnormally dry to drought conditions remained roughly the same, on the July 30th USDM map.



Alaska gridded precipitation rank map, May-July 2019
Alaska gridded precipitation rank map, May-July 2019.

Alaska:

July was drier than normal across much of Alaska except for parts of the western and northern coasts. This precipitation anomaly pattern persisted for the last 2 to 3 months, and even the last 6 to 7 months although it was not as pronounced in the eastern interior regions at these longer time scales. Dryness was evident in the panhandle and eastern interior regions at the 9- to 10-month time scales, too. But at 12-month and longer time scales, the drier-than-normal conditions were limited mostly to just the panhandle (low elevation station precipitation anomaly maps for the last 1, 2, 3, 4, 6, 7, 9, 10, 12, 24, 36, 48, 60 months) (high elevation SNOTEL station precipitation maps for last 1 and 10 months, and SNOTEL basin map for last 10 months) (gridded precipitation percentile maps for the last 1, 3, 7 months) (climate division precipitation rank maps for the last 1, 3, 6, 7, 12 months) (Leaky Bucket model precipitation percentile map) (low elevation station Standardized Precipitation Index maps for the last 1, 2, 3, 4, 6, 9, 10, 12, 24, 60 months). Temperatures during July were much warmer than normal to record warm across the state, with warmer than normal to record warm temperatures statewide at all time scales examined (low elevation station temperature maps for the last 1, 2, 3, 4, 7, 10, 12 months) (gridded temperature percentile maps for the last 1, 3, 7 months) (climate division temperature rank maps for the last 1, 3, 6, 7, 12 months) (Leaky Bucket model temperature percentile map). Modeled soil moisture and satellite-based soil moisture estimates showed drier-than-normal conditions in the panhandle and parts of the south coast and eastern interior areas, and streamflow was below normal at streams in these areas. Several dozen large wildfires burned across the state throughout the month (wildfire maps for July 1, 12, 26, 31). According to the National Interagency Fire Center's (NIFC) National Interagency Coordination Center, as of early August, 2.27 million acres have been burned in Alaska so far this year. In southeastern Alaska, impacts ranging from reduced hydroelectric power generation and municipal water restrictions to low streamflow for fish migration, and fish mortality, have been reported. Abnormally dry conditions expanded to cover most of the state during July, with moderate drought developing in the south and moderate to severe drought developing in the northeastern interior region. Moderate to extreme drought conditions continued in the panhandle. Moderate to extreme drought grew from 2.8 percent of Alaska at the beginning of July to 24.5 percent on the July 30th USDM map, with abnormally dry to drought conditions growing from 12.4 percent to 69.6 percent.



Puerto Rico and U.S. Virgin Islands percent of normal precipitation map, August 2018-July 2019
Puerto Rico and U.S. Virgin Islands percent of normal precipitation map, August 2018-July 2019.

Puerto Rico and U.S. Virgin Islands:

The weather during July 2019 over Puerto Rico and the U.S. Virgin Islands (USVI) consisted of a series of tropical waves alternating with drier and more stable air masses interspersed with Saharan dust. The tropical waves brought rain while the intervening air masses were dry and hazy. July 2019 ended up wetter than normal across St. Croix and St. Thomas in the USVI, and northern portions of Puerto Rico, but it was drier than normal in St. John and southern portion of Puerto Rico. The last 2 to 12 months were drier than normal across southern and eastern parts of Puerto Rico, with the last 2 to 4 months especially dry. In the USVI, drier-than-normal conditions dominated over the last 6 to 12 months, with the 9- to 12-month time scales especially dry. Puerto Rico was mostly wetter than normal at 24-month and longer time scales (radar-based precipitation anomaly estimates for the last 1, 2, 3, 6, 7, 10, 12 months) (low elevation station precipitation maps for the last 1, 2, 3, 4, 6, 7, 9, 10, 12, 24, 36, 48, 60 months) (climate engine model percent of normal precipitation map). Soils continued dry across much of Puerto Rico in the south and central regions, and July streamflow across Puerto Rico was mostly near to higher than normal, with a few stream gauges below normal. As seen on the July 30th USDM map, abnormal dryness and drought contracted, but severe drought expanded, across parts of Puerto Rico, with the total drought area shrinking from 31.8 percent at the beginning of July to 23.7 percent at the end of July. In the U.S. Virgin Islands, moderate drought continued on St. Croix and developed on St. John, with moderate drought worsening to severe drought on St. Thomas, by the end of July. (It should be noted that the USDM analysis was made for July 30th. On July 31st, 4.88 inches of rain was recorded at the Cyril E. King Airport weather station on St. Thomas, which is a record for the date and which pushed the monthly total for July to 7.75 inches, which is also a record for July. This rainfall is not reflected on the weekly end-of-July USDM; it will be reflected on the August 6th USDM.)



CONUS State Precipitation Ranks:

Map showing July 2019 state precipitation ranks Arizona state precipitation, July, 1895-2019

July 2019 was drier than normal across much of the West to southern Plains and parts of the Mid-Mississippi Valley, Southeast, and New England. Fifteen states had a rank in the driest third of the 125-year historical record for July, including Arizona which ranked eleventh driest. Wet conditions dominated much of the country for May-July, with six states (in the Northwest, Southwest, and Southeast) ranking in the driest third of the historical record.

Map showing February-July 2019 state precipitation ranks Washington state precipitation, February-July, 1895-2019

A similar precipitation anomaly pattern was seen for the last six and seven months — drier than normal in parts of the Northwest, Southwest, and Southeast, as well as extreme northern Plains. Four states (in the Northwest and Southeast) ranked in the driest third of the historical record for February-July, and three states so ranked for January-July. Washington had the eleventh driest February-July and January-July. 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 August-July, while at the other end of the spectrum, 16 states (all east of the Rockies) were record wet.


Agricultural Belts


Primary Corn and Soybean Belt precipitation, July, 1895-2019
Primary Corn and Soybean Belt precipitation, July, 1895-2019.
Primary Corn and Soybean Belt precipitation, March-July, 1895-2019
Primary Corn and Soybean Belt precipitation, March-July, 1895-2019.

During July 2019, the northern and southern ends of the Primary Corn and Soybean agricultural belt were cooler and wetter than normal, while the middle to northeastern part was drier and warmer than normal. The month ranked as the 36th wettest and 37th warmest July, regionwide, in the 1895-2019 record.

March marks the beginning of the growing season for the Primary Corn and Soybean agricultural belt. March-July 2019 was mostly wetter and near to cooler than normal. The 5-month period ranked as the third wettest and 47th coldest March-July, 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 very little drought in the major agricultural regions. As of July 30th, drought was affecting zero percent of the nation's corn production; one percent of soybean production; two percent of hay acreage and cattle inventory; three percent of winter wheat production; and two percent of spring wheat production. According to July 29th U.S. Department of Agriculture (USDA) reports, 12 percent of the nation's corn crop, 13 percent of soybeans, 11 percent of cotton, six percent of spring wheat, and ten percent of pasture and range were in poor to very poor condition, while 31 percent of the nation's topsoil and 23 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, Midwest, and Northeast. They included (percent area with short to very short topsoil / subsoil): California (85% / 70%), Oregon (68% / 58%), Washington (54% / 41%), Idaho (40% / 37%), Wyoming (45% / 50%), New Mexico (63% / 68%), Texas (60% / 43%), Oklahoma (55% / 25%), Kansas (40% / 23%), Michigan (51% / 33%), Illinois (40% / 25%), Georgia (44% / 40%), South Carolina (46% / 51%), Delaware (96% / 93%), Connecticut (100% / 100%), and Vermont (49% / 49%). About 30 percent or more of the pasture and rangeland was in poor to very poor condition in Arizona (35%), California (40%), and New Mexico (39%).


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, the High Plains experienced both ends of the precipitation spectrum during July, as areas of South Dakota and Nebraska continued to get pounded with heavy rainfall while other parts of the region remained dry. A positive outcome of the heavy precipitation was the relief from drought conditions in northern North Dakota, although the rains may have come too late to lessen agricultural impacts in the region. On the other hand, abnormal dryness developed across several areas of the High Plains in July due to short-term precipitation deficits, and some minor impacts to crops were being reported. As for temperatures, they were nothing out of the ordinary for July, averaging near normal, although a mid-month heat wave caused roads to buckle in eastern portions of the region.

The dryness was present throughout a large part of the High Plains in July, including the majority of Kansas, Colorado, Wyoming, and eastern Nebraska where precipitation was less than 50 percent of normal. Alamosa, Colorado had its 3rd driest July on record. To some extent, the dryness was welcome in areas that have been excessively wet during the spring and early part of summer. However, dryness issues can develop quickly this time of year due to high crop water use and evaporative demand. The decline in topsoil moisture during July was evident throughout much of the High Plains. According to the USDA Weekly Weather and Crop Bulletin, topsoil moisture was in very good shape at the beginning of the month, but by the end of July, conditions had deteriorated rapidly. For instance, from July 7th to August 4th, the percent of topsoil moisture rated short to very short increased from four percent to 26 percent in Nebraska and from six percent to 40 percent in Kansas. With a month of summer left, this is something to watch closely moving forward.

Crop progress continued to be behind the five-year average throughout the High Plains, especially in the Dakotas, but generally crops were in good condition. One issue that has been prevalent is many crops developed poor root systems this year, which was due to being planted into wet and compacted soils. A crop with a poorly-developed root system cannot easily tap into the deeper soil moisture profile when needed. This has become a concern in some parts of the region because of the short-term dryness that has developed, which has rapidly depleted topsoil moisture. As crops continue to mature, they will use more water, but if their root systems are not well developed and there is little topsoil moisture available, they will quickly become stressed. Additionally, freeze risk is still a concern across the region because a large majority of crops were planted late and may not reach maturity in time, but it is still too early to determine with any certainty when the first fall freeze will occur.

Drought conditions eased in northern North Dakota, while abnormal dryness developed in several areas of the High Plains during July. According to the USDM, the area experiencing drought or abnormal dryness (D0-D4) increased from approximately six percent to nine percent over the course of the month, while the area in drought (D1-D4) decreased from about two percent to only a quarter of a percent. Heavy showers and thunderstorms that occurred around the middle of the month provided relief to northern North Dakota, where drought developed and intensified during June. Severe drought (D2) was removed, while the areas experiencing moderate drought (D1) or abnormal dryness (D0) were reduced. Despite the welcomed rainfall, impacts still remained. For instance, hay production was low and a hay hotline was established, as the rains came too late to vastly improve the situation. Furthermore, this area is experiencing cumulative effects from drought that occurred during the past two summers. Elsewhere in the High Plains, short-term precipitation deficits caused D0 to develop during the latter half of July in southwestern and northwestern Colorado, southwestern Wyoming, central Kansas, and eastern Nebraska. These areas were quite dry during July, receiving less than 50 percent of normal precipitation. Only South Dakota was free of dryness, as above-normal precipitation occurred throughout much of the state.

As explained by the Southern Regional Climate Center, precipitation values for the month of July exhibited a west-to-east pattern across the Southern region, with below-normal precipitation in the west and above-normal precipitation in the east, and temperatures varied spatially across the region. Parts of northern, central, and southern Oklahoma; northwestern Louisiana; and central, eastern, southern, and western Texas received 50 percent or less of normal precipitation. Parts of northern and central Oklahoma, northwestern Louisiana, and central, western, southern, and eastern Texas received 25 percent or less of normal precipitation, while parts of southern and central Texas received 5 percent or less of normal precipitation.

At the end of July, drought conditions deteriorated across the Southern region. Severe drought classifications were still present in far southern Texas, while moderate drought classifications expanded in far southern Texas and developed in northern Texas as well as southwestern Oklahoma. There were no drought conditions in Tennessee, Louisiana, Mississippi, and Arkansas. There was an increase in the overall area experiencing abnormally dry conditions, despite improvement or removal in southern Louisiana, western and southeastern Tennessee, and northeastern Mississippi, as abnormally dry conditions developed or expanded across parts of southern, central, western, and northern Texas as well as southwestern and western Oklahoma.

As described by the Midwest Regional Climate Center, widespread heat and an intense heat wave led to above normal temperatures for almost all the Midwest in July despite cooler temperatures to end the month. Temperatures were 74.4 degrees F (23.6 C) regionwide which was 1.7 degrees F (0.9 C) above normal. Precipitation followed two main storm tracks across Minnesota and Wisconsin and across the southern Midwest during July. Regionwide precipitation was 4.07 inches (103.4 mm) which was near the normal of 4.06 inches (103.1 mm).

As of the July 30th USDM, the Midwest reached its 31st consecutive week without drought. The streak of drought-free conditions began on January 1st, 2019. This more than doubled the previous record streak of 14 weeks from January 5-April 5th, 2016 (USDM records go back to January 2000). However, a dry month of July aided in the development of abnormally dry conditions across southeastern Iowa, northwestern Illinois and several other areas in the Midwest. The effects of the dryness on agriculture compounded the previous impacts of a wet spring. Soil compaction led to poorer root systems for corn and soybeans and increased their susceptibility to dryness and drought.

As noted by the Southeast Regional Climate Center, precipitation was variable across the Southeast during the month of July, which is common during the summer. Precipitation across Puerto Rico, on the other hand, was near normal, with San Juan (1898-2019) receiving 6.72 inches (170 mm) and Juncos (1931-2019) receiving 5.79 inches (147 mm). Temperatures were near average (i.e. within 3 degrees F (1.5 degrees C)) across the Southeast and Puerto Rico for the month of July. Monthly precipitation totals ranged from 50 to less than 5 percent of normal across much of Alabama, Georgia, and South Carolina. Oneonta, AL (1894-2019) observed its driest July on record, with only 0.68 inch (17 mm) of precipitation.

Drought conditions changed little throughout the month of July. At the end of the month, severe drought (D2) still covered pockets in Alabama that did not experience localized thunderstorms that are common during the summer. Moderate drought (D1), ringed by an area of abnormally dry conditions (D0), covered parts of southeastern North Carolina, northeastern South Carolina, central Georgia, northern Florida, and central and southern Alabama. Puerto Rico ended the month with D2 conditions covering the southern areas at 13 percent, D1 conditions at 23 percent and D0 conditions at 48 percent. This season continues to produce a great peach crop in Georgia due to the relative absence of extreme weather. Crops are beginning to show signs of stress in areas that have not seen as much rain in the Piedmont and Coastal North Carolina, as well as parts of Alabama and Georgia. However, areas that have seen some rain are reporting normal crop conditions. The citrus region in Florida continues to remain drought-free, and groves are progressing well. However, Dixie and Lafayette counties in Florida are seeing peanut losses due to standing water in the fields from the July thunderstorms.

As explained by the Northeast Regional Climate Center, in July, the Northeast received 4.28 inches (108.71 mm) of precipitation, which was 101 percent of normal, and had its ninth warmest July on record with an average temperature of 72.3 degrees F (22.4 degrees C), 2.7 degrees F (1.5 degrees C) above normal. Seven states were drier than normal, while five states were wetter than normal. Precipitation for all states ranged from 69 percent of normal in Vermont to 135 percent of normal in New Jersey.

The Northeast started off July free of abnormal dryness and drought. However, in mid-July, short-term precipitation deficits led to declining streamflow and soil moisture and the introduction of abnormal dryness in a small area in northwestern Connecticut, southwestern Massachusetts, and eastern New York. The USDM released on July 18 showed 1 percent of the Northeast as abnormally dry. The following week, these areas received between 2 and 3 inches of rain, easing abnormal dryness. The USDM released on July 25 showed the Northeast was free of drought and abnormal dryness once again.

As summarized by the Western Regional Climate Center, precipitation was generally below normal across much of the Western U.S. with the exception of some spotty monsoon rainfall events, which impacted isolated areas in Colorado, Nevada, New Mexico, and Utah. Overall, the monsoon season has had a slow start across much of Desert Southwest as well as in the higher elevations of the Intermountain West. In the Pacific Northwest, precipitation for the month was near normal to slightly above normal across much of the drought-stricken areas of western Washington and northwestern Oregon. Average temperatures were generally near normal to cooler than normal across much of the West with the exception of the Desert Southwest, Colorado Plateau, and Southern Rocky Mountains where temperatures were above normal.

In the Pacific Northwest, drought conditions have persisted into the summer months in portions of northern and western Washington, northwestern Oregon, northern Idaho, and northwestern Montana. Since the beginning of the Calendar Year (Jan 1), cumulative precipitation deficits across western Washington have ranged from 4 to 20+ inches with areas in the Cascade Range and Olympic Peninsula experiencing the largest deficits. However, some beneficial rainfall (2 to 3.5 inch accumulations) was observed in July in these areas providing some limited improvement in drought-related conditions.

In Alaska, temperatures were well above normal in association with a large dome of high pressure that settled in over the region from July 4-8 leading to numerous high temperature records being broken around the state. The excessive heat and below-normal precipitation exacerbated wildland fire conditions across parts of the state where a reported 1.93 million acres burned in July.

In the Hawaiian Islands, average temperatures were mainly above normal across the island chain for the month.


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), July 2019 was drier than normal in the northwest over the Marianas to eastern Micronesia over the Marshalls, and wetter than normal in the southwest to southern locations near the equator. Drier-than-normal stations included Koror, Yap, Guam, Saipan, Chuuk, Kosrae, Kwajalein, and Majuro, and wetter-than-normal stations included Lukonor, Pohnpei, Kapingamarangi, and Pago Pago.

Convergence associated with a monsoon trough gave western Micronesia rain late in this month, while tropical disturbances and trade wind convergence contributed to rainfall in the east and south. Monthly precipitation amounts were above the monthly minimum needed to meet most water needs (4 inches in the Marianas and 8 inches elsewhere) in western and southern portions of Micronesia, including Koror (Palau); Guam, Rota, Saipan (Marianas); Yap, Chuuk, Lukonor, Nukuoro, Kapingamarangi, Pohnpei, Pingelap, Kosrae (FSM); and Pago Pago (American Samoa). The month was dry (by this criteria) in Fananu, Mwoakilloa, Woleai (FSM); and Ailinglapalap, Jaluit, Kwajalein, Majuro, Mili, Utirik, and Wotje (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 to meet most water needs. This was the case during July 2019. The monthly precipitation was enough to end drought, but still below normal because the normals were so high, at Guam (July 2019 precipitation 4.63 inches, July monthly normal mean 12.14 inches), Rota (10.59 inches, normal 10.71 inches), Saipan (6.73 inches, normal 8.27 inches), Koror (15.04 inches, normal 18.12 inches), and Yap (12.25 inches, normal 15.04 inches).

Pacific Island Percent of 1981-2010 Normal Median Precipitation
Station Name Aug
2018
Sep
2018
Oct
2018
Nov
2018
Dec
2018
Jan
2019
Feb
2019
Mar
2019
Apr
2019
May
2019
Jun
2019
Jul
2019
Aug-
Jul
Chuuk96%158%93%142%76%183%122%175%48%42%125%97%105%
Guam NAS149%183%78%61%152%106%228%39%45%77%46%46%90%
Kapingamarangi67%128%158%223%93%195%44%197%127%169%172%110%125%
KororN/A63%119%140%111%96%40%84%94%57%93%81%N/A
Kosrae159%65%34%58%49%93%98%143%137%152%103%62%83%
Kwajalein193%81%63%107%99%49%183%52%22%159%69%48%91%
Lukonor83%96%89%78%70%148%71%103%126%32%127%104%82%
Majuro102%94%67%69%112%93%74%102%35%160%103%64%88%
Pago Pago181%132%128%117%176%83%200%107%108%154%117%316%128%
Pohnpei166%93%100%74%100%134%79%143%66%45%159%101%100%
Saipan146%172%90%83%137%70%59%28%35%243%58%76%107%
Yap100%109%46%136%125%249%30%107%52%91%109%81%96%
Pacific Island Precipitation (Inches)
Station Name Aug
2018
Sep
2018
Oct
2018
Nov
2018
Dec
2018
Jan
2019
Feb
2019
Mar
2019
Apr
2019
May
2019
Jun
2019
Jul
2019
Aug-
Jul
Chuuk12.33"18.55"10.66"15.02"8.53"18.49"8.87"14.56"6.00"4.74"14.62"11.65"144.02"
Guam NAS21.89"23.17"8.87"4.51"7.75"4.24"6.90"0.81"1.15"2.61"2.85"4.63"89.38"
Kapingamarangi5.47"12.67"12.98"20.71"9.13"17.87"4.06"22.56"17.33"20.46"23.68"15.52"182.44"
KororN/A7.37"14.12"15.92"12.37"9.79"3.45"6.24"6.89"6.78"16.30"15.04"N/A
Kosrae22.60"9.19"3.70"8.09"7.92"15.58"12.62"23.02"23.96"26.91"15.08"9.19"177.86"
Kwajalein18.81"8.65"7.05"12.12"6.58"1.54"4.82"1.22"1.14"10.71"4.76"4.77"82.17"
Lukonor11.70"9.79"10.06"7.12"7.89"12.41"6.33"9.58"14.30"3.75"14.80"16.63"124.36"
Majuro11.96"10.46"8.53"9.29"12.71"7.23"5.09"6.74"3.34"16.14"11.31"7.12"109.92"
Pago Pago9.76"8.60"11.83"11.90"22.59"11.10"24.04"11.47"10.17"14.91"6.24"17.54"160.15"
Pohnpei23.61"11.70"15.31"10.97"16.13"17.68"7.57"18.84"12.23"8.94"23.56"15.64"182.18"
Saipan19.12"17.39"9.59"4.64"5.28"1.76"1.54"0.53"0.93"5.78"2.11"6.73"75.4"
Yap14.82"14.65"5.56"12.03"10.68"15.90"1.57"4.88"2.92"7.15"13.14"12.25"115.55"
Pacific Island 1981-2010 Normal Median Precipitation (Inches)
Station Name Aug
2018
Sep
2018
Oct
2018
Nov
2018
Dec
2018
Jan
2019
Feb
2019
Mar
2019
Apr
2019
May
2019
Jun
2019
Jul
2019
Aug-
Jul
Chuuk12.86"11.71"11.51"10.61"11.25"10.10"7.25"8.32"12.47"11.30"11.66"11.98"136.77"
Guam NAS14.74"12.66"11.44"7.38"5.11"4.01"3.03"2.07"2.53"3.40"6.18"10.14"99.09"
Kapingamarangi8.13"9.93"8.19"9.27"9.84"9.15"9.27"11.43"13.64"12.08"13.78"14.15"145.85"
Koror13.50"11.77"11.84"11.39"11.16"10.18"8.56"7.44"7.32"11.83"17.48"18.53"152.90"
Kosrae14.22"14.22"10.94"13.83"16.11"16.67"12.93"16.06"17.51"17.75"14.64"14.91"213.87"
Kwajalein9.74"10.74"11.18"11.28"6.66"3.16"2.64"2.35"5.26"6.72"6.93"9.87"90.41"
Lukonor14.04"10.15"11.32"9.08"11.27"8.41"8.93"9.26"11.31"11.69"11.65"15.93"151.36"
Majuro11.69"11.17"12.73"13.44"11.39"7.74"6.88"6.58"9.42"10.11"11.01"11.17"125.25"
Pago Pago5.38"6.53"9.26"10.14"12.84"13.34"12.00"10.68"9.39"9.66"5.33"5.55"125.57"
Pohnpei14.26"12.55"15.27"14.83"16.08"13.18"9.55"13.17"18.41"19.96"14.81"15.43"182.36"
Saipan13.13"10.09"10.62"5.61"3.85"2.53"2.59"1.89"2.63"2.38"3.62"8.91"70.25"
Yap14.82"13.50"12.18"8.83"8.51"6.39"5.19"4.56"5.63"7.85"12.04"15.08"120.31"

As measured by percent of normal precipitation, Guam, Koror, Kwajalein, and Yap were drier than normal in the short term (July and the last 3 months [May-July 2019]) and long term (year to date [January-July] and last 12 months [August 2018-July 2019]) (the 12-month time period was missing for Koror). Lukonor and Majuro were drier than normal for 3 of the time periods (including the long-term) and wetter than normal for one (one of the short-term time periods). Chuuk, Kosrae, Pohnpei, and Saipan were near to drier than normal for 2 time periods and near to wetter than normal for 2 others. Kapingamarangi and Pago Pago were wetter than normal for all 4 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.

Percent of normal precipitation for current month for the Marianas Islands
Percent of normal precipitation for current month for the Marianas Islands.
Percent of normal precipitation for current month for the Marshall Islands
Percent of normal precipitation for current month for the Marshall Islands.

In the Marianas Islands, precipitation mostly has been drier than normal regionwide for the last one to ten months. A mixed precipitation anomaly pattern exists at longer time scales (percent of normal precipitation maps for the last 1, 2, 3, 4, 6, 7, 9, 10, 12, 24, 36, 48, 60 months). In the Marshall Islands, precipitation mostly has been drier than normal regionwide for the last one to nine months. The spatial pattern of precipitation transitioned to generally drier-than-normal conditions in the north and west and near- to wetter-than-normal conditions in the southeast for the last ten months and longer (percent of normal precipitation maps for the last 1, 2, 3, 4, 6, 7, 9, 10, 12, 24, 36, 48 months).



The USAPI U.S. Drought Monitor drought map valid for the end of July 2019
The USAPI U.S. Drought Monitor drought map valid for the end of July 2019.

According to the end-of-July USDM produced for the USAPI, drought had ended in the Marianas, Palau, and western FSM. Conditions improved from moderate drought (D1) to abnormally dry (D0) at Fananu, and from exceptional drought (D4) to extreme drought (D3) at Utirik and severe drought (D2) at Wotje. Conditions deteriorated from moderate drought to severe drought at Jaluit and Kwajalein, from abnormally dry to moderate drought at Majuro, and from no drought or abnormal dryness to abnormally dry at Ailinglapalap. Storage in the Majuro reservoirs slowly declined throughout the month, falling from 28.9 million gallons at the beginning of the month to a low of 23.9 million gallons on the 23rd, or about 66 percent of maximum, which is below the 80 percent threshold for concern. Reservoir levels began to rise at the end of the month, reaching 27.1 million gallons by the 31st, which is still 75 percent of maximum. According to reports relayed by the Guam NWS office (July 11, July 25), water restrictions was a concern for the Marshalls, and draw-down of fresh water resources was a concern in the Marianas.

The dryness in parts of the RMI during July was significant. Only 2.60 inches of rain fell at Jaluit, which makes July 2019 the driest July in 36 years of data. Kwajalein had only 4.77 inches, making July 2019 the second driest July in a 68-year record. The 3.58 inches that fell at Utirik marked the fourth driest July in 16 years of data. It was the third driest July at Ailinglapalap (out of 35 years) with 6.75 inches, and fourth driest at Mili (34 years, 5.92 inches) and Majuro (66 years, 7.12 inches). All of these stations had less than the monthly minimum (8 inches) needed to meet most water needs, and all (except Wotje) were below normal. The prolonged dryness since last fall gave Jaluit the driest August-July in 33 years of data, Wotje (32 years) and Kwajalein (67 years) the fifth driest September-July, and Ailinglapalap the sixth driest August-July (32 years).

On the other hand, Guam had 4.63 inches of rain, which was enough to bring the island out of drought, but normals are so high and climatology is normally so wet this time of year that this amount gave July 2019 a rank of driest July in the 63-year record. Kosrae received 9.19 inches but still had the third driest July in 51 years of data.

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 July 2019, January-July 2019 (the year to date), and August 2018-July 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.

Rank, Number of Years with data, and Period of Record for USAPI stations for July 2019, January-July 2019, and August 2018-July 2019.
Rank of 1 = driest.
Station Jul 2019
Rank
Jul
No. of Years
Jan- Jul 2019
Rank
Jan- Jul
No. of Years
Aug 2018- Jul 2019
Rank
Aug- Jul
No. of Years
Period of Record
Pago Pago 53 54 52 53 52 53 1966-2019
Saipan 14 39 7 38 22 30 1981-2019
Kapingamarangi 23 30 22 22 16 16 1962-2019
Kosrae 3 51 22 39 12 32 1954-2019
Lukonor 23 35 13 35 8 22 1981-2019
Nukuoro 15 36 14 35 8 34 1981-2019
Pingelap 24 35 MSG 33 MSG 32 1981-2019
Woleai 2 38 6 29 7 25 1968-2019
Yap 19 69 24 68 22 68 1951-2019
Pohnpei 35 69 28 68 31 68 1951-2019
Chuuk 27 69 34 68 35 68 1951-2019
Guam 1 63 6 62 15 62 1957-2019
Koror 29 69 11 68 MSG 67 1951-2019
Ailinglapalap 3 35 10 35 6 32 1981-2019
Jaluit 1 36 3 35 1 33 1981-2019
Mili 4 34 18 34 18 32 1981-2019
Utirik 4 16 2 8 1 4 1985-2019
Wotje 17 35 7 35 8 32 1981-2019
Kwajalein 2 68 11 67 12 67 1952-2019
Majuro 4 66 15 65 13 65 1954-2019

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, Monthly Drought Report for July 2019, published online August 2019, retrieved on March 28, 2024 from https://www.ncei.noaa.gov/access/monitoring/monthly-report/drought/201907.