Drought - August 2018


Issued 12 September 2018
Contents Of This Report:
Map showing Palmer Z Index
Percent Area of U.S. in Moderate to Extreme Drought, Jan 1996 to present
Percent Area of Western 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 28, 2018
The U.S. Drought Monitor drought map valid August 28, 2018.

Like the last several months, the upper-level circulation pattern was quite active during August 2018 with ridge and trough patterns migrating through the jet stream flow over the CONUS. This activity occurred within a broadscale/long-wave ridge. But this month, troughs favored the central CONUS, which split the ridge on the monthly circulation map. Cold fronts and surface lows moved into the trough bringing near- to below-normal temperatures to a region stretching from the northern Plains to Southeast, and this parted the "sea of heat" to the Southwest and Northeast. The frontal systems also brought above-normal precipitation to parts of the central and southern Plains, eastward to the Mid-Atlantic and Northeast coast. Monsoon showers peppered parts of the Southwest, but the dominance of upper-level ridging kept most of the West drier than normal. As a result, drought and abnormal dryness expanded, intensified, or developed in the Pacific Northwest to central Rockies and parts of the northern and southern Plains, Mid-Mississippi Valley, Great Lakes, Hawaii, and Puerto Rico, but contracted in parts of the Southwest, southern to central Plains, and Northeast, and other parts of the Great Lakes, Mid-Mississippi Valley, and Hawaii. The dry conditions during August were a continuation of persistent dryness for much of the West that has lasted 12 months, and for parts of the Southwest for the last 24 months (Standardized Precipitation Index maps for the last 1, 2, 3, 6, 9, 12, 24 months). Drought expansion outweighed contraction this month, but just barely, so the USDM-based national moderate-to-exceptional drought footprint across the CONUS expanded from 34.1 percent of the CONUS at the end of July to 34.4 percent of the CONUS at the end of August (from 29.0 percent to 29.2 percent for all of the U.S.). According to the Palmer Drought Index, which goes back to the beginning of the 20th century, about 40.8 percent of the CONUS was in moderate to extreme drought at the end of August, increasing about 4.9 percent from the 35.9 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

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 the month, as depicted on the August 28th, 2018 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 dry conditions continued in August across much of the West, and a few places in the Plains and Southeast, over areas that were in drought at the end of July, expanding and intensifying long-term drought. Short-term dry conditions occurred in northern parts of the Northeast over areas that were not in drought or wet spell conditions according to the PHDI. Short-term wet conditions occurred over parts of the southern Plains to Mid-Mississippi Valley, reducing the intensity of previous long-term dry conditions. Short-term wet conditions occurred in parts of the central to northern Plains, Midwest, and Mid-Atlantic to Northeast, expanding and intensifying previous long-term wet conditions.



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 in parts of the Southwest can be seen at all time scales. Much of the West is dry at all time scales except 6 and 24 months. Parts of the extreme northern Plains and Upper Mississippi Valley are dry at all time scales except 3 months. Dryness in the central Plains to Mid-Mississippi Valley is evident at 6 to 24 months. The southern Plains to Lower Mississippi Valley are dry at 3 to 12 months. A small part of the Carolinas is persistently dry at all time scales except 6 months. Northern New York and part of the Great Lakes have dryness at the 1- to 6-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 August 2018 were above normal across most of the West, especially the Southwest, with record warmth occurring in some areas. For areas that were drier than normal during August, this resulted in a more extreme SPEI compared to SPI.



Regional Discussion


Map of percent of normal precipitation for Hawaii, August 2018
Map of percent of normal precipitation for Hawaii, August 2018.

Hawaii:

August 2018 was wetter than normal across the Hawaiian islands, due to heavy rains from Hurricane Lane later in the month. The wetness of August tipped the multi-month precipitation totals into the wet category for most stations for the last 2, 3, 4, 5, 6, 8, 11, 12 months, except for some leeward stations on the Big Island, Oahu, and Molokai. Dryness in these leeward areas was more pronounced and widespread at the longer time periods (last 24 and 36 months). Lane left well-above-normal streamflow across the island chain. Moderate to severe drought covered about a third (35.8 percent) of the state at the end of the month, mostly in the leeward areas, reflecting the longer-term dryness and lingering agricultural drought impacts.



Alaska climate division precipitation rank map, September 2017-August 2018
Alaska climate division precipitation rank map, September 2017-August 2018.

Alaska:

August 2018 was wetter than normal across most of Alaska, with some drier-than-normal conditions in the southern panhandle in across northwest Alaska. At longer time scales, dryness lingers in some parts of the northwest while the panhandle dryness is greater and more widespread, and the wetter-than-normal conditions continue for the areas in between these two dry regions. The southern portions of the panhandle are record dry for the last 12 months, and dryness is more widespread across the southern portions of the state at 24 to 36 months. (Low elevation station precipitation anomaly maps for the last 1, 2, 3, 4, 5, 6, 8, 11, 12, 24, 36 months.) (Divisional precipitation rank maps for the last 1, 3, 6, 8, 12 months.) (Gridded precipitation percentile maps for the last 1, 3, 8 months.) Temperatures during August were cooler than average in the northern portions of the state and near to warmer than average from the western to southern regions. This pattern held for the last 2 to 4 months, with the warm anomalies in the west to south becoming more pronounced and widespread. Warmer-than-normal temperatures began to dominate across the state at the 6-month time scale, with record warmth in the north at the 12-month time scale. (Low elevation station temperature anomaly maps for the last 1, 2, 3, 4, 8, 11, 12 months.) (Divisional temperature rank maps for the last 1, 3, 6, 8, 12 months.) (Gridded temperature percentile maps for the last 1, 3, 8 months.) Streamflow was mostly near to above normal with some below-normal stream levels in the panhandle and northwest. The Leaky Bucket model suggested some lingering dryness in the soils in the panhandle, south central, and a few other sections. Numerous wildfires (not related to drought) were burning throughout the month in the central and eastern parts of the state (wildfire maps for August 1, 8, 18, 30). Moderate drought continued in the southern portions of the panhandle, with abnormally dry to moderate drought conditions covering about 4.4 percent of the state on the August 28th USDM map.



Puerto Rico percent of normal precipitation map, August 2018
Puerto Rico percent of normal precipitation map, August 2018.

Puerto Rico: Southern and eastern portions of Puerto Rico were drier than normal during August, with wetter-than-normal conditions in the northwest and north central regions. This anomaly pattern persisted at the 2- and 3-month time scales. Drier-than-normal conditions dominated the south-central to southwestern areas, with wetter-than-normal conditions to the north and east, at longer time scales (last 6, 8, 11 months). Soils were dry in the south central region to southwest coast, but streamflow was mostly near normal except for some low streams in the southwest. As seen on the August 28th USDM map, abnormal dryness extended across the southwest and south central areas to the northern coast and expanded to about a half (51.6 percent) of the island.



CONUS State Precipitation Ranks:

Map showing August 2018 state precipitation ranks Map showing June-August 2018 state precipitation ranks

August 2018 was drier than normal across much of the West and parts of the Plains. But localized wet areas in the West affected the state ranks, so that only five states ranked in the driest third of the 124-year historical record. California had the tenth driest August on record.

The summer (June-August 2018) was drier than normal across much of the West and southern Great Plains, and parts of the northern Plains, Mid-Mississippi Valley, Great Lakes, Northeast, and the Carolinas. Record dry conditions occurred in a few local areas in the West. On a statewide basis, ten states ranked in the driest third of the 124-year historical record, with Washington ranking eleventh driest.

Map showing March-August 2018 state precipitation ranks Map showing January-August 2018 state precipitation ranks

The last six months (March-August) and year to date (January-August) had similar precipitation anomaly patterns, except California's March wetness gave it a wet rank for March-August and mid-range for January-August. In both cases, it was drier than normal across much of the West, southern Plains, central Plains to Mid-Mississippi Valley, and parts of the northern Plains to Upper Mississippi Valley, Northeast, and Carolinas. On a statewide basis, eight states ranked in the driest third of the 124-year historical record for March-August and six states ranked in the driest third of the historical record for January-August. Colorado had the twelfth driest March-August and January-August, and New Mexico ranked ninth driest for March-August and tenth driest for January-August.

Map showing September 2017-August 2018 state precipitation ranks Southwest region precipitation, September-August, 1895-2018

A similar pattern of dryness was seen for the last 12 months (September 2017-August 2018) as existed for the last 6 and 8 months. The dry conditions were especially pronounced across the Southwest, northeast Kansas to northwest Missouri, and parts of Texas. On a statewide basis, eleven states ranked in the driest third of the 124-year historical record. Three states in the Southwest ranked in the top ten driest category, including Utah (ninth driest) and Arizona and Colorado (both seventh driest). New Mexico had the 17th driest September-August. These four states, taken collectively, gave the Southwest the fifth driest September-August on record.


Agricultural Belts


Primary Corn and Soybean Belt precipitation, August, 1895-2018
Primary Corn and Soybean Belt precipitation, August, 1895-2018.
Primary Corn and Soybean Belt precipitation, March-August, 1895-2018
Primary Corn and Soybean Belt precipitation, March-August, 1895-2018.

For the Primary Corn and Soybean agricultural belt during August 2018, temperatures ranged from warmer than normal in the northeast to cooler than normal in the west and south, while precipitation was mostly wetter than normal. The month ranked as the seventh wettest and 43rd warmest August, regionwide, in the 1895-2018 record.

March is the beginning of the growing season for the Primary Corn and Soybean agricultural belt. For March-August 2018, temperatures were mostly near to warmer than normal and precipitation had a spatially variable pattern of anomalies. This 6-month period ranked as the 33rd wettest and 39th warmest March-August, regionwide, in the 1895-2018 record.

The prolonged below-normal precipitation has dried soils and inhibited rangeland, pasture land, and crop growth in many states in the Plains and West. According to September 2nd statistics from the U.S. Department of Agriculture, 33 percent of the topsoil and 37 percent of the subsoil was rated short or very short of moisture (dry or very dry) nationwide, 28 percent of the pasture and rangeland was rated in poor to very poor condition, and (only) 12 percent of the corn crop and 11 percent of the soybean crop was rated in poor to very poor condition, but 33 percent of the cotton crop was rated poor to very poor. As of August 28th, drought was affecting nine percent of corn production, 12 percent of soybean production, 29 percent of hay acreage, 27 percent of cattle inventory, 22 percent of winter wheat production, and 30 percent of spring wheat production.


NOAA Regional Climate Centers:


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


As summarized by the High Plains Regional Climate Center, precipitation in August varied throughout the High Plains region and, similar to July, August was rather cool across much of the region. Portions of Nebraska and Kansas saw record-breaking rainfall and flooding, while much of the rest of the region was dry. As for summer precipitation, it also varied across the High Plains. An area of excessively wet conditions extended from the Black Hills region southward and eastward into Nebraska and central Kansas. Although streamflows ran high and flooding occurred in some locations, drought conditions significantly improved in parched areas. Meanwhile, much of Colorado and eastern Kansas experienced a very dry summer, and as a result, drought expanded and intensified and streamflows were especially low.

The dryness was prevalent throughout a large portion of the Dakotas, Colorado, western Nebraska, and southern Wyoming. Akron, Colorado only received 0.29 inch (7 mm) of precipitation and had its 7th driest August on record. Topsoil moisture both improved and degraded across the region in August. Heavy rains replenished soil moisture in Nebraska and Kansas. However, dryness caused soil moisture depletion in North Dakota, South Dakota, and Wyoming. Statewide, Colorado experienced little change in soil moisture conditions in August. Streamflows improved across portions of Kansas in August, thanks to welcomed precipitation. However, streamflows remained below normal in the northeastern part of the state. Low streamflows continued in western and central Colorado where there has been little drought relief.

Despite some areas receiving relief, overall the area in drought or abnormal dryness (D0-D4) increased across the High Plains in August, according to the USDM. The greatest improvements occurred in eastern Colorado as well as portions of Kansas. A continuation of above-normal precipitation, much of which was due to the monsoon, brought additional relief to eastern Colorado in August, where exceptional drought (D4) and extreme drought (D3) were pulled back. August was a particularly wet month for parts of Kansas, as heavy rainfall events led to improvements in drought conditions in the southwestern, central, and southeastern portions of the state. Meanwhile, conditions continued to worsen in portions of the Dakotas, northwestern Colorado, southern and western Wyoming, and northeastern Kansas. While some of these areas experienced slightly above-normal precipitation in August, it was not enough to improve or maintain conditions, as July was very dry across these areas. Several impacts have been reported as a result of the drought. For instance, in eastern Kansas, an additional 22 counties were placed into a drought emergency, which brought the total number of counties in a drought emergency to 72. Several communities issued water-use restrictions, and corn was being cut for silage. In the Red River Valley of North Dakota, damage to soybean crops was reported. It is worth noting that drought conditions were present in North Dakota last summer, and lingering impacts may exacerbate issues caused by the current drought.

As explained by the Southern Regional Climate Center, temperatures and precipitation for the month of August varied spatially throughout the Southern region. Parts of western and southern Texas received 5 percent or less of normal precipitation. Northern, northeastern, eastern, southeastern, southern, western, and central Texas; areas in southwestern and eastern Oklahoma, northern, central, and part of eastern Louisiana; southwestern Arkansas, southwestern Tennessee, and areas in northeastern and southwestern Mississippi received 50 percent or less of normal precipitation. At the end of August, exceptional drought conditions were present in southwestern Texas. Extreme drought classifications were present in southwestern and southern Oklahoma, southwestern, northern, central, and eastern Texas; and northwestern Louisiana. Severe drought classifications were present throughout parts of northern, central, southwestern, and northeastern Texas; southwestern and northeastern Oklahoma, southwestern Arkansas, and northwestern Louisiana. Moderate drought classification was present throughout extreme western, northern, central, southern, and eastern Texas; extreme western, southwestern, southeastern, and northeastern Oklahoma; southwestern and northwestern Arkansas, eastern, northwestern, and part of southwestern Louisiana; and parts of southwestern and northeastern Mississippi. There were no drought conditions in Tennessee.

As described by the Midwest Regional Climate Center, August temperatures were near normal in the western and southern portions of the region and slightly above normal in the northeastern sections, while precipitation was a mix of above and below normal rainfall. All nine Midwest states had areas with both above and below normal totals. The driest areas in August were in north central Minnesota where less than half the normal rain fell. Other areas with less than 75 percent of normal were in Minnesota, eastern Upper Michigan, and near the confluence of the Ohio and Wabash rivers at the southwestern tip of Indiana. Scattered pockets of rainfall more than two times normal were scattered across every Midwest state except Minnesota. Regionwide, rainfall was 133 percent of normal. Summer precipitation was also a mix of above and below normal values.

Drought in August was mainly focused on two regions. The first was Missouri and southeastern Iowa where extreme and exceptional drought were reported throughout August. The other region was in Lower Michigan where widespread moderate drought and even some severe drought were reported. Drought peaked in mid-August at just under 20 percent of the Midwest and over 80 percent of Missouri. In Missouri, extreme drought covered more than 25 percent of the state and exceptional drought covered more than 5 percent of the state. Rains late in August brought those numbers down slightly as the month came to a close.

As noted by the Southeast Regional Climate Center, temperatures during August were near average across most of the Southeast region, including Puerto Rico and the U.S. Virgin Islands, and precipitation was highly variable across the region, as is common during the summer. The driest areas included most of the Florida peninsula and South Carolina, and eastern Georgia. Dry conditions were also noted in far eastern Virginia and North Carolina, where the hottest conditions occurred. Drought conditions (D1 and greater) were not observed across the Southeast region for the third consecutive month, though small pockets of abnormal dryness (D0) persisted across Alabama and grew slightly in the interior Carolinas. No abnormally dry conditions were identified in Georgia, Florida and Virginia this month except in part of Escambia County in the far western Panhandle of Florida. In Puerto Rico, abnormally dry conditions expanded from the south-central part of the island to cover more than half of Puerto Rico by the end of the month. Grape growers in Georgia harvested some varieties early to reduce yield loss from rot caused by the humid conditions but were pleased by drier harvest conditions at the end of the month. Irrigation was in use in some of the drier regions of the Piedmont to help improve crop yields as their growing seasons drew to a close.

As explained by the Northeast Regional Climate Center, the Northeast experienced its second warmest August on record with an average temperature of 71.5 degrees F (21.9 degrees C), which was 3.3 degrees F (1.8 degrees C) above normal, and received 5.27 inches (133.9 mm) of precipitation on average this month, which was 135 percent of normal, ranking this as the 11th wettest August on record for the region. On average, Maine and Vermont were slightly drier than normal, but the other states in the region recorded a wetter-than-normal August. Dry conditions improved across the Northeast as the month progressed. At the beginning of August, dry conditions were largely present in northern New York and New England. Abnormal dryness was impacting 18 percent of the Northeast, and 10 percent of the region was in moderate drought. Abnormal dryness eased in much of New Hampshire and southern Maine throughout the course of the month. By the end of August, 13 percent of the Northeast was abnormally dry and seven percent of the region was experiencing moderate drought.

As summarized by the Western Regional Climate Center, temperatures were near normal across much of the western US this month, though a few locations in the Southwest reported well above normal temperatures. Monsoon activity brought above normal precipitation to some areas of the Southwest; above normal precipitation was also observed along the Montana-Wyoming border. The coastal states as well as Nevada and Idaho generally received little to no precipitation, typical for August. However, some isolated areas in these regions that commonly see summertime thunderstorm development experienced above normal precipitation. A cold low-pressure system moved across the northern Rockies during the last week of August, bringing a few inches of wet snow to higher elevation locations. Drought conditions improved in small areas of southern Arizona, southern Utah, and eastern New Mexico in association with August precipitation in these areas. Drought conditions expanded in southern and eastern Oregon and portions of western Washington, and abnormally dry conditions were introduced in eastern Idaho. Hurricane Lane brought impressive precipitation across the State of Hawaii. Temperatures across Alaska were generally near normal, though a few North Slope locations were much cooler than normal; precipitation was near to above normal across the state, except in the far Southeast.

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 2018 was drier than normal at Chuuk, Kapingamarangi, and Lukonor; near normal at Majuro and Yap; and wetter than normal at Guam, Kosrae, Kwajalein, Pago Pago, Pohnpei, and Saipan. Data for Koror were not available this month.

It was a dry month in terms of drought at the southern stations in the Federated States of Micronesia (FSM) and at some stations in the Republic of the Marshall Islands (RMI), with rainfall amounts below the minimum thresholds (4 or 8 inches) required to meet most monthly water needs at Kapingamarangi and Lukonor (in the FSM), and at Ailinglapalap, Jaluit, and Utirik (in the RMI). It was a wet month (above the minimum thresholds) at the rest of the regular reporting stations in the USAPI. The 4- and 8-inch thresholds are important because, if monthly precipitation falls below the threshold, then water shortages or drought become a concern.

Jaluit had the driest August in a data record spanning 35 years, Nukuoro had the third driest August in 35 years of data, Utirik was sixth driest in 15 years, Kapingamarangi had the seventh driest August in 28 years of data, and Ailinglapalap ranked eighth driest in 34 years. Lukonor was in the middle of the historical rankings, with tenth driest in 22 years of data for August. For the year to date, it was the fifth driest January-August in 22 years of record at Lukonor and eighth driest at Nukuoro. On the other hand, long-term wet conditions resulted in the wettest year to date for Pohnpei (out of 67 years of data), Kwajalein (66 years), and Majuro (64 years), while Kapingamarangi had the wettest September-August 12-month period in 16 years of data (as did Pohnpei, Kwajalein, and Majuro).

As measured by percent of normal precipitation, Lukonor has been drier than normal in the short term (August and the last 3 months [June-August 2018]) as well as the long term (year to date [January-August] and last 12 months [September 2017-August 2018]). Kapingamarangi was drier than normal in the short term and wetter than normal in the long term. Chuuk was drier than normal for August but wetter than normal for the other three time scales. Yap was drier than normal for the last 3 months, near normal for August, and wetter than normal in the long term. Guam, Kosrae, Kwajalein, Majuro, Pago Pago, Pohnpei, and Saipan were wetter than normal in both the short term and long term time scales.


X
  • Percent of Normal Precip
  • Precipitation
  • Normals
Pacific Island Percent of 1981-2010 Normal Median Precipitation
Station Name Sep
2017
Oct
2017
Nov
2017
Dec
2017
Jan
2018
Feb
2018
Mar
2018
Apr
2018
May
2018
Jun
2018
Jul
2018
Aug
2018
Sep 2017-
Aug 2018
Chuuk110%127%105%120%99%175%131%45%124%143%107%96%108%
Guam NAS118%161%57%88%23%90%68%316%240%88%146%149%106%
Kapingamarangi92%72%64%420%95%222%171%127%92%67%142%67%120%
Koror161%118%84%160%82%105%37%113%92%66%87%N/AN/A
Kosrae155%143%168%123%100%147%181%105%136%74%106%159%111%
Kwajalein205%88%83%71%458%159%662%229%332%227%90%193%175%
Lukonor84%116%136%70%129%106%84%56%61%67%123%83%81%
Majuro187%143%76%172%204%120%343%189%216%151%142%102%159%
Pago Pago96%217%127%94%115%271%60%189%96%61%192%181%124%
Pohnpei122%81%95%130%167%219%440%102%85%92%130%166%141%
Saipan84%66%62%60%117%87%49%332%384%161%88%146%111%
Yap93%156%106%132%182%163%270%67%94%97%105%100%115%
Pacific Island Precipitation (Inches)
Station Name Sep
2017
Oct
2017
Nov
2017
Dec
2017
Jan
2018
Feb
2018
Mar
2018
Apr
2018
May
2018
Jun
2018
Jul
2018
Aug
2018
Sep 2017-
Aug 2018
Chuuk12.9214.6411.1513.5210.0112.7010.865.6014.0116.6712.7712.33147.18
Guam NAS14.9218.474.234.490.942.721.407.998.155.4214.8421.89105.46
Kapingamarangi9.135.935.9541.308.7120.5919.6017.3911.089.1720.155.47174.47
Koror18.9014.039.5517.898.389.032.758.2510.9111.6016.19N/AN/A
Kosrae22.0215.6523.2119.8516.6219.0329.0018.4524.1610.7715.8322.60237.19
Kwajalein22.069.839.404.7214.464.2015.5512.0522.3315.758.8818.81158.04
Lukonor8.5113.1012.387.9010.839.507.766.287.147.8319.6611.70122.59
Majuro20.9318.2110.2719.5915.768.2922.5417.7921.8116.6215.8811.96199.65
Pago Pago6.2620.1112.8912.0615.3732.476.3617.769.263.2410.689.76156.22
Pohnpei15.2712.3114.1320.8622.0320.9457.9218.8016.9113.5820.1123.61256.47
Saipan8.477.013.482.312.972.250.938.729.145.837.8819.1278.11
Yap12.5918.999.4011.2711.648.4412.293.807.4111.6715.8114.82138.13
Pacific Island 1981-2010 Normal Median Precipitation (Inches)
Station Name Sep
2017
Oct
2017
Nov
2017
Dec
2017
Jan
2018
Feb
2018
Mar
2018
Apr
2018
May
2018
Jun
2018
Jul
2018
Aug
2018
Sep 2017-
Aug 2018
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 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 2018, January-August 2018 (year to date), and September 2017-August 2018 (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 August 2018, January-August 2018, and September 2017-August 2018.
Rank of 1 = driest.
Station Aug 2018
Rank
Aug
No. of Years
Jan- Aug 2018
Rank
Jan- Aug
No. of Years
Sep 2017- Aug 2018
Rank
Sep- Aug
No. of Years
Period of Record
Jaluit 1 35 MSG 34 MSG 32 1981-2018
Koror MSG 67 MSG 66 MSG 67 1951-2018
Woleai 15 37 20 27 17 24 1968-2018
Yap 37 68 45 67 50 67 1951-2018
Majuro 39 65 64 64 64 64 1954-2018
Mili 30 34 MSG 33 MSG 31 1981-2018
Ulithi 12 37 16 34 26 33 1981-2018
Ailinglapalap 8 34 16 34 14 32 1981-2018
Kosrae 43 50 26 37 23 30 1954-2018
Lukonor 10 22 5 22 7 21 1981-2018
Saipan 35 38 36 37 25 29 1981-2018
Pohnpei 65 68 67 67 67 67 1951-2018
Kwajalein 65 67 66 66 66 66 1952-2018
Kapingamarangi 7 28 16 20 16 16 1962-2018
Chuuk 25 68 35 67 41 67 1951-2018
Guam 50 62 40 61 39 61 1957-2018
Nukuoro 3 35 8 34 22 33 1981-2018
Pago Pago 43 53 51 52 51 52 1966-2018
Wotje 34 35 MSG 34 MSG 31 1981-2018
Utirik 6 15 6 6 3 3 1985-2018

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 2018, published online September 2018, retrieved on September 22, 2018 from https://www.ncdc.noaa.gov/sotc/drought/201808.

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