Drought - September 2017


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

Issued 16 October 2017
Contents Of This Report:
Map showing Palmer Z Index
Percent Area of U.S. in Moderate to Extreme Drought, Jan 1996 to present
Louisiana statewide precipitation, September, 1895-2017

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 October 3, 2017
The U.S. Drought Monitor drought map valid October 3, 2017.

During September 2017, the upper-level circulation flipped from a ridge-West/trough-East pattern during the first half of the month to a trough-West/ridge-East pattern during the second half of the month. Much of the West was warmer and drier than normal during the first half of the month, which kept numerous wildfires going (wildfire maps for September 1, 11, 15, 25, 27, 30) and expanded and intensified drought, especially in the Northwest and northern High Plains of Montana. In the East, a northwesterly flow at the upper levels of the atmosphere generally kept Gulf of Mexico moisture out of the CONUS, with much of the Plains and Midwest having below-normal precipitation. Remnants of tropical cyclones brought above-normal precipitation to parts of the Southwest (Tropical Storm Lidia) and Southeast to Midwest (Hurricanes Harvey and Irma). During the second half of the month, Pacific fronts and lows, and cooler Canadian air masses were funneled into the West beneath a long-wave upper-level trough, bringing widespread above-normal precipitation to the West and Great Plains which contracted drought areas. But drier-than-normal weather continued to the east. For the month as a whole, drought and abnormally dry areas contracted across parts of the Northwest, northern Rockies, and central to northern Plains, especially in the Dakotas and Montana which had been suffering from significant drought. Above-normal precipitation also helped eliminate abnormally dry areas in Alaska and Puerto Rico. But the dry weather from eastern Texas to the Great Lakes and across much of the Mid-Atlantic to Northeast states was, in some areas, a continuation of dryness that has lasted for the last two to three months. Drought and abnormal dryness expanded or intensified in the Arklatex, Midwest, and parts of the Mid-Atlantic to Northeast. Continued dryness in Hawaii (last 1, 2, and 3 months) expanded and intensified drought in the Aloha State. Expansion outweighed contraction, so the USDM-based national moderate-to-exceptional drought footprint across the CONUS expanded from 11.8 percent of the CONUS at the end of August to 14.4 percent of the CONUS at the end of September (from 10.0 percent to 12.1 percent for all of the U.S.). According to the Palmer Drought Index, which goes back to the beginning of the 20th century, about 8.6 percent of the CONUS was in moderate to extreme drought at the end of September, a decrease from last month's 9.8 percent.

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 October 3rd, 2017 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 in 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 occurred across a wide band from eastern Texas and southern Louisiana to the Great Lakes, decreasing previous long-term wetness and, over parts of Iowa and Michigan, adding to long-term drought conditions. Short-term dry conditions from the Mid-Atlantic states to New England intensified long-term drought conditions over southern New England and became manifested as long-term drought in coastal Maine. Short-term dry conditions in Washington state became manifested as long-term drought conditions in western Washington. Short-term wet conditions across much of the interior West to Great Plains contracted long-term drought conditions in the Great Basin, northern Rockies, and northern Plains.



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 is evident at all time scales. Eastern Texas, Louisiana, and Arkansas were extremely dry this month (on the 1-month map) but extreme wetness from Hurricane Harvey in August and from earlier months shows this region to be very wet at the other time scales. Dryness from the Mid-Mississippi Valley and Great Lakes to the Mid-Atlantic and Northeast is widespread at the 1- and 2-month time scales, and patchy at 3 months. Parts of Iowa and Illinois have dryness at all time scales except 24 months, and parts of southern New England have dryness at all time scales except 6 months. Extreme south Texas shows up as dry at all time scales except 24 months. Parts of the Southeast are dry on the 2-, 3-, and 12-month maps. The Northwest is especially dry at 2 to 3 months, and parts are dry at the 1- and 6-month time scales, but the Northwest is wet at the longer time scales. Parts of the northern Rockies show up as dry on the 2- to 6-month SPI maps. The northern Plains are dry at the 2- to 12-month time scales, with the dryness in western regions at 2 to 3 months, more widespread at 6 to 9 months, focused more in eastern Montana and the western Dakotas at 12 months, and even evident in parts of the western Dakotas at 24 months. On the other hand, there are large areas of wetness at all time scales.


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



Regional Discussion




Lihue, Hawaii, precipitation, July-September, 1950-2017
Lihue, Hawaii, precipitation, July-September, 1950-2017.

Hawaii: September 2017 was drier than normal across most of the Hawaiian Islands. The precipitation anomaly pattern was mixed for the last 2 to 3 months, although dry conditions seemed to dominate. Lihue had the fourth driest September, sixth driest August-September, fourth driest July-September, and fifth driest June-September in the 1950-2017 record. Wet conditions dominated Hawaii at the 6-month time scale, except over the Big Island. Dry conditions dominated once again at longer time scales (last 9, 12, 24, and 36 months). Streamflow was mostly below normal. On the USDM map, abnormally dry conditions, moderate drought, and extreme drought expanded this month, with moderate to extreme drought continuing to cover about two-thirds of the state on the October 3rd, 2017 USDM map.



Alaska precipitation percentiles map, January-September 2017
Alaska precipitation percentiles map, January-September 2017.

Alaska: September 2017 had a mixed precipitation anomaly pattern across Alaska. It was wetter than normal from the southwest to northeast, and drier than normal across the Aleutian island chain, on the climate division, gridded, and low elevation station maps. Some stations were drier than normal in the southwest to interior southeast regions on the low elevation station maps, while the high elevation (SNOTEL) stations were drier than normal in the central to north central region, with some dry stations in the south central coastal region. The last two months were mostly wetter than normal, except drier than normal in the interior southeast and coastal south central areas. July-September 2017 was mostly wetter than normal, except drier than normal along the Aleutian chain, in the northwest, and interior southeast. Dryness is evident along the Aleutian chain and in the interior south central to southeast for the last six months. For the year to date, the drier-than-normal conditions are more widespread in the southern regions (climate division and low elevation station maps) and also evident in the northwest. Drier-than-normal conditions dominate the state, except for the central to northeast regions, for the last 12 months (climate division, low elevation station, SNOTEL station and basin maps). Drier-than-normal conditions are evident in the south central to southeast even at the 24- to 36-month time scales. September was warmer than normal across most of the state (low elevation station, gridded, divisional maps). Warmer-than-normal conditions dominated during August-September, the last three months (low elevation station, gridded, divisional maps), the last six months, and year to date (gridded, divisional maps). For the last 12 months, colder-than-normal temperatures were evident in the southeast with warmer-than-normal temperatures to the west and north (low elevation station, divisional maps). Mountain snow water content was below normal, but this is early in the snow season. Streamflow was above normal. Abnormal dryness disappeared this month on the October 3rd USDM map.



Puerto Rico precipitation amount, September 2017
Puerto Rico precipitation amount, September 2017.

Puerto Rico: Puerto Rico was inundated with precipitation from Hurricanes Irma and Maria this month. Precipitation anomaly maps were not available this month, but over 50 inches of rain was estimated to have fallen over parts of the island over the last two to three months. Streamflow was much above normal across the island. As seen on the October 3rd, 2017 USDM map, Puerto Rico was free of drought and abnormal dryness.



CONUS State Precipitation Ranks:

Map showing September 2017 state precipitation ranks Louisiana statewide precipitation, September, 1895-2017

September 2017 was drier than normal in a wide swath from eastern Texas and Louisiana, in the south, to the Great Lakes in the north; it was also drier than normal across much of the Ohio Valley and Mid-Atlantic to Northeast and across parts of the Southwest and Northwest. On a statewide basis, 20 states ranked in the driest third of the 123-year historical record with five states in the top ten driest category. Of these, Louisiana tied the driest September on record; Illinois, Michigan, and Missouri had the fifth driest September, and Arkansas had the eighth driest.

Map showing July-September 2017 state precipitation ranks Washington statewide precipitation, July-September, 1895-2017

July-September 2017 was drier than normal across much of the Pacific Northwest to Montana High Plains and parts of the central Plains to Mid-Mississippi Valley, Great Lakes, Mid-Atlantic, and New England. On a statewide basis, 13 states ranked in the driest third of the historical record, but the dry areas were mixed in with wetter-than-normal areas so only Washington ranked in the top ten driest category at third driest.

Map showing April-September 2017 state precipitation ranks Map showing January-September 2017 state precipitation ranks

April-September 2017 was drier than normal in large parts of the West and northern Plains and smaller parts of the Midwest, southern Great Lakes, and New England. But wetter-than-normal areas were mixed in next to the dry areas in many of these states, so only three states ranked in the driest third of the historical record. These included Montana (12th driest April-September), North Dakota (14th driest), and Iowa (39th driest).

For the year to date, near- to wetter-than-normal conditions dominated the CONUS with only the northern Plains having widespread dryness. Patchy below-normal precipitation could be seen in parts of the Southwest, Midwest, and southern New England. Again, only three states ranked in the driest third of the historical record and included North Dakota (13th driest January-September), Montana (24th driest), and Massachusetts (34th driest).

The last 12 months had a similar spatial pattern of precipitation anomalies, with wet conditions dominating. Again, only three states ranked in the driest third of the historical record, this time including North Dakota (27th driest October-September), Illinois (38th driest), and Massachusetts (34th driest).


Agricultural Belts


Primary Corn and Soybean Belt precipitation, September, 1895-2017
Primary Corn and Soybean Belt precipitation, September, 1895-2017.
Primary Corn and Soybean Belt precipitation, March-September, 1895-2017
Primary Corn and Soybean Belt precipitation, March-September, 1895-2017.

September 2017 was drier and warmer than normal across much of the Primary Corn and Soybean agricultural belt. The month ranked as the 19th driest and 26th warmest September, regionwide, in the 1895-2017 record. March marks the beginning of the growing season for the Primary Corn and Soybean agricultural belt. March-September 2017 was generally warmer and wetter than normal across most of the region, although some parts (Iowa to Illinois) were drier than normal. Regionwide, March-September 2017 ranked as the 27th wettest and 26th warmest March-September on record.

On a national scale, as of October 3rd, 2017, only 11 percent of corn production, 11 percent of soybean production, 17 percent of hay acreage, 13 percent of cattle inventory, and 20 percent of winter wheat production were within an area experiencing drought, but 51 percent of spring wheat production was. According to October 1st reports by the U.S. Department of Agriculture (USDA), only 12 percent of the nation's corn crop, 12 percent of soybeans, and 26 percent of the nation's pasture and rangeland were in poor to very poor condition, but 41 percent of the nation's topsoil moisture and 43 percent of subsoil moisture were short to very short of moisture.


NOAA Regional Climate Centers:


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


As described by the High Plains Regional Climate Center, the fall season began quite warm across a large portion of the High Plains, with the southern and eastern parts of the region experiencing above-normal temperatures in September. The majority of the High Plains experienced heavy rainfall during September. Two primary areas where above-normal precipitation occurred included an area from western Wyoming stretching northeastward through western North Dakota, as well as a swath from eastern Colorado northeastward through eastern North Dakota. In drought-stricken areas of western North Dakota and eastern Montana, September precipitation ranged from 150-300 percent of normal.

The wetness that was present throughout much of the region in September was both beneficial and problematic. For instance, heavy rain fell across many drought-stricken areas of the region, which provided welcomed relief from drought conditions. Pasture conditions improved and water supplies were replenished, but the rainfall came too late in the season to vastly improve row crop conditions. Although the damage has already been done to many crops, the rainfall helped green up pastures, replenish streams and reservoirs, and provide much-needed moisture in winter wheat growing areas. Soil moisture conditions also improved from the end of August to late September. The percent of topsoil moisture rated short to very short decreased from 54% to 32% in North Dakota, 45% to 37% in South Dakota, 36% to 23% in Nebraska, and 65% to 39% in Wyoming. However, there were drawbacks to the heavy precipitation. Dry weather is generally favored by producers this time of year, but periodic rainfall slowed down harvest. Additionally, white mold in soybeans was reported in parts of South Dakota and Nebraska.

The beneficial rainfall in September improved streamflows throughout the Dakotas and eastern Montana where drought has been present. Steady, soaking rains allowed streams to return to normal for this time of year. Much-above-normal streamflows could be found in areas where the heaviest precipitation occurred throughout the Missouri Basin in September, which included the Wind River region of Wyoming, central Colorado, eastern South Dakota, and central Nebraska. Meanwhile, drought persisted in the Missouri Basin headwaters in western Montana, so streamflows continued to be below normal. Streamflows declined rapidly in central and eastern Kansas in September, as this region has experienced several consecutive months of below-normal precipitation. The driest areas have only received 50 percent of normal precipitation, at best, since July.

Drought conditions continued to improve across the Northern Plains region in September, thanks to heavy rainfall across drought-stricken areas. The largest departures occurred across western North Dakota where much of the region received 150-200 percent of normal precipitation. Therefore, this region saw the greatest improvements in drought conditions, with some areas receiving a 2-class improvement on the USDM over the course of the month. For instance, a large portion of extreme drought (D3) was removed from North Dakota, and severe drought (D2) conditions improved across the area as well. While not in the region, it is worth noting that eastern Montana experienced above-normal precipitation in September as well, leading to slight improvements in drought conditions. Although the rainfall was untimely for row crops such as corn and soybeans, September rainfall improved pasture conditions across the Northern Plains. The rain was welcomed by winter wheat producers who have already planted some of the crop, but it slowed down harvest of row crops. Elsewhere in the High Plains, drought conditions in Nebraska and Kansas improved, as a swath of heavy rain occurred across western and central portions of the two states. However, prolonged dryness in western Colorado prompted the expansion of abnormally dry conditions (D0) and the introduction of a small area of moderate drought (D1) to western Colorado, extending west into eastern Utah. This area should be monitored for drought expansion if ample precipitation does not occur in October.

As explained by the Southern Regional Climate Center, September temperatures and precipitation varied throughout the region. The central part of the region received below normal precipitation whereas parts of the western and eastern part of the region received above normal precipitation. Central Louisiana, western Arkansas, southern Mississippi, eastern Oklahoma, and northeastern and southeastern Texas received below 25 percent of normal precipitation. Most of Louisiana and Arkansas received 25-50 percent below normal precipitation. Parts of eastern Tennessee, central Mississippi, eastern Texas, and eastern Oklahoma received 50-70 percent below normal precipitation. In contrast, western Tennessee, northern Mississippi, east central Arkansas, western Oklahoma, and southwestern and northern Texas received 150-300 percent above normal precipitation. Overall, Tennessee, Oklahoma, Texas, and Mississippi had a large spatial gradient of precipitation.

Over the month of September 2017, drought conditions worsened to moderate classification in parts of southern and central Texas. Abnormally dry conditions expanded throughout parts of the region and now include: eastern Tennessee, western and central Arkansas, eastern Mississippi, northern and eastern Oklahoma, and northeastern, central, and southern Texas. The Texas, Mississippi, and Louisiana state climatologists discussed drier conditions throughout their states. They state it is possible for abnormally dry to moderate drought conditions to expand throughout their states if the dry conditions persist and no tropical weather impacts the area during the month of October.

As summarized by the Midwest Regional Climate Center, September precipitation in the Midwest varied from more than 200 percent of normal to less than 10 percent of normal. The wettest areas were in northwestern Minnesota and Kentucky with much of the area between being well below normal for September. A wide swath from Missouri to Lower Michigan had precipitation totals below 50 percent of normal with many areas below 25 percent and some locations with less than 10 percent of normal. Heavy rainfall in Kentucky was largely due to the remnants of Hurricane Harvey passing over the state in the first couple days of the month. September temperatures were below normal across the Midwest for the first several days of the month. After a few days with warmth in the northwest and continued cooler weather in the southeast, very warm conditions dominated for two weeks until seasonal temperatures returned for the last couple days of September.

Drought expanded from just under 7.5 percent of the Midwest on August 29th to just under 12 percent of the region on October 3rd according to the US Drought Monitor. The portion of the region noted as abnormally dry or worse increased from about 19 percent to 38 percent in the same time. The small area of extreme drought in southern Iowa shrank slightly during the month. Corn and soybean harvest began across much of the Midwest in September. As has been the case for most of the growing season, impacts were localized making it hard to generalize across the region. Corn harvest was running behind in Iowa and Illinois in particular. Soybean harvest was well behind average in Minnesota while running ahead in Illinois and Michigan. The soybean harvest in Indiana and Ohio was hampered, despite good field access, by the dryness that led to combine fires and concerns about splitting or shattering of the beans.

As noted by the Southeast Regional Climate Center, precipitation was highly variable across the Southeast region during September, with several wet extremes recorded, and temperatures were near average across much of the region. However, well-above-average temperatures (driven primarily by extremely warm minimum temperatures) continued across portions of central and southern Florida, as well as Puerto Rico. Unusual dryness was found in portions of Virginia, central and coastal North Carolina, west-central and southwestern Alabama, and the western tip of the Florida Panhandle, where monthly precipitation totals were 50 to less than 25 percent of normal. Several locations in these areas recorded at least 14 consecutive days with no measurable rainfall. In contrast, the wettest locations were found primarily across broad portions of the Florida Peninsula, southeastern Georgia, central and southern South Carolina, Puerto Rico, and the U.S. Virgin Islands. Monthly precipitation totals ranged from 150 to more than 300 percent of normal in these areas.

With the removal of moderate (D1) drought in southwestern Puerto Rico at the beginning of September, drought conditions (D1 and greater) were not observed across the Southeast region during the remainder of the month. On the 11th and 12th, heavy rainfall from Tropical Storm Irma eliminated abnormally dry (D0) conditions in Georgia and South Carolina. However, well-below-average precipitation during the month caused abnormally dry conditions to persist and expand across broad portions of North Carolina and Virginia, with additional development occurring in localized areas of western Alabama. Indeed, the unusual dryness stunted the growth of pastures and hay fields in areas of northern and western Virginia, with a few livestock producers having to haul water to their herds. During the second half of the month, a persistence of dry weather across much of the region was generally favorable for crop and hay harvesting. Numerous agricultural and livestock impacts were reported across the southern portion of the region following Hurricane's Irma and Maria.

As explained by the Northeast Regional Climate Center, September was a dry month for the Northeast. The region received 2.40 inches (60.96 mm) of precipitation, 61 percent of normal, making it the 19th driest September since recordkeeping began. Despite a cool start to the month, temperatures rebounded and September wrapped up on the warm side of normal. The USDM released on September 7 showed parts of northern and eastern Maine, totaling 5 percent of the Northeast, was in a moderate drought. Abnormal dryness covered 8 percent of the region, including parts of Maine, southeastern New Hampshire, southeastern Massachusetts, southern Rhode Island, southern Connecticut, and New York's Long Island. While moderate drought and abnormal dryness eased somewhat in Maine, dry conditions lingered in the other areas. In addition, abnormal dryness expanded in southern New England and was introduced in parts of Vermont, New York, Pennsylvania, and West Virginia. The USDM released on September 28 showed 4 percent of the Northeast was in a moderate drought and 18 percent of the region was abnormally dry.

As summarized by the Western Regional Climate Center, September saw major shifts in weather patterns, typical for the autumn season. Well-above normal precipitation was observed in much of the Inland Northwest and Great Basin as well as portions of southern California and New Mexico. Areas west of the Sierra Nevada and Cascades observed above normal temperatures this month, while temperatures were generally within 2 F (1 C) of normal elsewhere. The month opened with a strong ridge of high pressure situated over the West Coast; thunderstorms associated with the remnants of TS Lidia brought scattered precipitation to typically dry southern California in the first few days on the month, and the following week a persistent cutoff low developed off the California coast, favoring thunderstorm development in southern California and the Great Basin. Later in the month, a series of low-pressure system brought cooler temperatures and abundant precipitation to some Northwest and Great Basin locations.

Above-normal precipitation across southern Montana provided some improvement to ongoing drought conditions, though 86% of the state remains in drought. Drier-than-normal conditions were observed in many areas of Washington this month. Much of Washington and northeastern Oregon are now experiencing moderate drought according to the USDM following a very dry summer and start to September. Not uncommon for September, Arizona and much of central and northern California received very little precipitation.

Wildfires burned throughout the month in the West. Fires continued to burn in western Montana, creating poor air quality and straining firefighting resources. In early September, many areas of Pacific Northwest experienced poor air quality associated with wildfire smoke, which reached hazardous levels at times. Falling ash was observed in metropolitan areas such as Portland and Seattle.

Drought conditions persisted across Hawaii this month due to below-normal precipitation across much of the state. Lihue, Kauai recorded 0.54 in (14) mm, 25% of normal, the 4th driest September since records began in 1950. Hilo, on Big Island, reported 3.91 in (99 mm) 39% of normal. Moving north, temperatures were above normal for much of Alaska with some of the greatest departures from normal at interior locations. Bettles reported an average temperature of 44.8 F (7.1 C), tie for 6th warmest September since records began in 1951. Precipitation was variable across Alaska, with some areas of above-normal precipitation in the northern part of the state and interior, such as Fairbanks, which recorded 1.42 in (36 mm), 130% of normal. Some stations in the eastern part of the Southcentral region recorded drier-than-normal conditions like Northway, which observed 0.37 in (9 mm), 35% of normal. Precipitation was near normal elsewhere.

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), September 2017 was drier than normal at Saipan, Yap, Lukonor, Kapingamarangi, and Pago Pago and wetter than normal at Koror, Guam, Chuuk, Pohnpei, Kosrae, Kwajalein, and Majuro.

Rainfall amounts were below the minimum thresholds (4 or 8 inches) required to meet most monthly water needs at Ulithi, Woleai, and Fananu (in the FSM); Jaluit and Utirik (in the RMI); and Pago Pago (in American Samoa). September rainfall was above the monthly minimum thresholds at the rest of the regular reporting stations in Micronesia. The 4- and 8-inch thresholds are important because, if monthly precipitation falls below the threshold, then water shortages or drought become a concern.

Significant dryness developed in the northern Marshall Islands in December 2016, with six of the last ten months having less than 2 inches each at Utirik (eight had less than 8 inches), and five of the last ten months having less than 2 inches each at Wotje (eight had less than 8 inches). Eight inches is the monthly minimum in the RMI. The last two months at Utirik were the driest August-September out of 11 years of data, the last three were the driest July-September out of 10 years of data, the last four the driest June-September out of 8 years of data, and the last five and six the driest May-September and April-September out of 6 years of data. The last five months were the driest May-September in 34 years of record at Jaluit; it was also the second driest June-September, April-September, and March-September out of 34 years. The National Weather Service office on Guam issued a revised Drought Information Statement on September 28 which noted that drought continues to be a serious concern for the northern Marshall Islands, especially Utirik and likely Enewetak, Ailuk, and other islands north of 10 degrees North latitude, following an April 24th declaration of a state of emergency by the President of the RMI for the northern atolls and islands affected by the dry conditions.

Parts of the FSM were on the dry side of normal, although drought was not a concern there at this time. Lukonor had the second driest August-September in 21 years of data and third driest April-September in 21 years of data. Kapingamarangi had the sixth driest August-September in 23 years of data and sixth driest June-September in 19 years of data. Chuuk had the sixth driest April-September in 66 years of data.

As measured by percent of normal precipitation, Lukonor and Saipan have been drier than normal in the short term (September and the last 3 months [July-September]) as well as the long term (year to date [January-September] and last 12 months [October 2016-September 2017]). Pago Pago has been near to below normal for all four of these time periods. Yap has been drier than normal in the near term and wetter than normal in the long term. Kapingamarangi was wetter than normal for the year to date and drier than normal for the other three time periods, while Chuuk was wetter than normal for September but drier than normal for the other three time periods. Guam was drier than normal for the last three months and year to date, but wetter than normal for the other two time periods. Pohnpei was drier than normal for the last three months, but wetter than normal for the other three time periods. Koror, Kosrae, Kwajalein, and Majuro were near to wetter than normal at all four time periods.


X
  • Percent of Normal Precip
  • Precipitation
  • Normals
Pacific Island Percent of 1981-2010 Normal Median Precipitation
Station Name Oct
2016
Nov
2016
Dec
2016
Jan
2017
Feb
2017
Mar
2017
Apr
2017
May
2017
Jun
2017
Jul
2017
Aug
2017
Sep
2017
Oct 2016-
Sep 2017
Chuuk58%98%176%113%114%189%60%83%73%99%91%110%98%
Guam NAS115%137%170%155%167%256%340%56%136%97%66%118%103%
Kapingamarangi26%71%114%159%207%126%159%114%81%102%41%92%97%
Koror153%144%64%131%175%245%76%107%89%130%104%161%117%
Kosrae90%56%168%103%213%150%112%115%80%104%93%155%101%
Kwajalein168%126%156%285%212%46%65%77%156%70%64%205%126%
Lukonor74%198%128%138%66%160%85%80%60%103%63%84%88%
Majuro120%129%103%228%138%199%110%49%118%112%111%187%127%
Pago Pago55%127%111%72%153%52%87%240%93%84%145%96%96%
Pohnpei120%115%142%182%71%115%96%92%141%113%55%122%111%
Saipan48%79%95%182%199%108%115%66%128%72%65%84%82%
Yap164%156%101%198%370%205%110%69%68%121%55%93%118%
Pacific Island Precipitation (Inches)
Station Name Oct
2016
Nov
2016
Dec
2016
Jan
2017
Feb
2017
Mar
2017
Apr
2017
May
2017
Jun
2017
Jul
2017
Aug
2017
Sep
2017
Oct 2016-
Sep 2017
Chuuk6.7310.3919.8311.378.2715.747.519.408.5011.8611.6512.92134.17
Guam NAS13.1410.138.686.225.065.308.601.898.409.869.7314.92101.93
Kapingamarangi2.146.5811.2214.5419.1814.4421.7013.7511.1514.473.359.13141.65
Koror18.0616.387.1313.3014.9918.265.5412.6115.5324.1413.9818.90178.82
Kosrae9.877.7626.9917.2127.5124.1619.6220.3411.7315.5713.2322.02216.01
Kwajalein18.7314.1610.369.005.601.073.445.2010.806.916.2822.06113.61
Lukonor8.4118.0214.4211.585.9014.839.619.416.9716.478.888.51133.01
Majuro15.2817.3611.7717.659.5013.0710.364.9313.0312.5213.0020.93159.4
Pago Pago5.1212.8614.249.5718.325.608.1423.234.944.667.786.26120.72
Pohnpei18.3917.0022.8324.006.7615.1617.6818.4520.8517.457.8215.27201.66
Saipan5.074.423.674.615.152.043.021.584.636.458.598.4757.7
Yap20.0013.788.5912.6719.199.356.195.408.1618.278.2012.59142.39
Pacific Island 1981-2010 Normal Median Precipitation (Inches)
Station Name Oct
2016
Nov
2016
Dec
2016
Jan
2017
Feb
2017
Mar
2017
Apr
2017
May
2017
Jun
2017
Jul
2017
Aug
2017
Sep
2017
Oct 2016-
Sep 2017
Chuuk11.5110.6111.2510.107.258.3212.4711.3011.6611.9812.8611.71136.77
Guam NAS11.447.385.114.013.032.072.533.406.1810.1414.7412.6699.09
Kapingamarangi8.199.279.849.159.2711.4313.6412.0813.7814.158.139.93145.85
Koror11.8411.3911.1610.188.567.447.3211.8317.4818.5313.5011.77152.90
Kosrae10.9413.8316.1116.6712.9316.0617.5117.7514.6414.9114.2214.22213.87
Kwajalein11.1811.286.663.162.642.355.266.726.939.879.7410.7490.41
Lukonor11.329.0811.278.418.939.2611.3111.6911.6515.9314.0410.15151.36
Majuro12.7313.4411.397.746.886.589.4210.1111.0111.1711.6911.17125.25
Pago Pago9.2610.1412.8413.3412.0010.689.399.665.335.555.386.53125.57
Pohnpei15.2714.8316.0813.189.5513.1718.4119.9614.8115.4314.2612.55182.36
Saipan10.625.613.852.532.591.892.632.383.628.9113.1310.0970.25
Yap12.188.838.516.395.194.565.637.8512.0415.0814.8213.50120.31

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 September 2017, April-September 2017 (last 6 months), and October 2016-September 2017 (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 September 2017, April-September 2017, and October 2016-September 2017.
Rank of 1 = driest.
Station Sep 2017
Rank
Sep
No. of Years
Apr- Sep 2017
Rank
Apr- Sep
No. of Years
Oct 2016- Sep 2017
Rank
Oct- Sep
No. of Years
Period of Record
Jaluit 7 34 2 34 15 32 1981-2017
Koror 61 67 49 66 61 66 1951-2017
Woleai 8 36 7 28 9 24 1968-2017
Yap 31 67 12 66 57 66 1951-2017
Majuro 62 64 42 63 58 63 1954-2017
Ulithi 2 36 3 35 MSG 32 1981-2017
Ailinglapalap 27 34 5 33 25 31 1981-2017
Kosrae 43 46 23 38 19 29 1954-2017
Lukonor 9 34 3 21 8 20 1981-2017
Saipan 8 37 4 37 3 28 1981-2017
Pohnpei 40 67 28 66 45 66 1951-2017
Kwajalein 66 66 31 65 50 65 1952-2017
Kapingamarangi 14 26 10 18 9 16 1962-2017
Chuuk 34 67 6 66 22 66 1951-2017
Guam 34 61 25 61 34 60 1957-2017
Nukuoro 32 35 27 33 29 32 1981-2017
Pago Pago 27 52 35 52 23 51 1966-2017
Wotje 33 34 24 34 23 31 1981-2017
Utirik 3 14 1 6 MSG 1 1985-2017

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 September 2017, published online October 2017, retrieved on October 22, 2017 from https://www.ncdc.noaa.gov/sotc/drought/201709.

Metadata