Drought - March 2018


Issued 11 April 2018
Contents Of This Report:
Map showing Palmer Z Index
Percent Area of U.S. in Moderate to Extreme Drought, Jan 1996 to present
Oklahoma panhandle (climate division 1) precipitation, November-March, 1895-2018
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 April 3, 2018
The U.S. Drought Monitor drought map valid April 3, 2018.

The atmospheric circulation during March 2018 consisted of several upper-level short-wave troughs and lows, and their associated Pacific weather systems, moving through a vigorous upper-level westerly flow. Long-wave patterns would become established for a few days, then quickly shift. The result was above-normal precipitation along the storm tracks across much of the West, northern Plains, and eastern Texas to the eastern Great Lakes. But for much of the Southwest, Southeast, Mid-Atlantic, and western Great Lakes, which were missed by the main storm tracks, the month was drier than normal. The dry conditions during March were a continuation of persistent dryness since October in the southern High Plains to central Plains and coastal Southeast to Mid-Atlantic region, and for much of the last 12 months in the Four Corners States (Standardized Precipitation Index maps for the last 1, 2, 3, 6, 9, 12 months). Drought and abnormal dryness contracted, where the heavy March precipitation fell on drought areas, but expanded or intensified where the dryness continued. Contraction outweighed expansion again this month, so the USDM-based national moderate-to-exceptional drought footprint across the CONUS shrank from 31.3 percent of the CONUS at the end of February to 29.4 percent of the CONUS at the end of March (from 26.2 percent to 25.0 percent for all of the U.S.). According to the Palmer Drought Index, which goes back to the beginning of the 20th century, about 26.6 percent of the CONUS was in moderate to extreme drought at the end of March, increasing about 2.2 percent from the 24.4 percent at the end of February.

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 April 3rd, 2018 USDM map, included the following core drought and abnormally dry areas:

Hawaii and Puerto Rico continued free of drought and abnormal dryness.



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 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 across the Southwest to southern and central Plains, expanding and intensifying previous long-term drought. Short-term dry conditions occurred in the western Great Lakes and parts of the Lower Mississippi Valley, reducing previous long-term wet conditions. Short-term dry to near-normal conditions occurred in the Southeast to Mid-Atlantic region, maintaining long-term drought conditions. Short-term wet conditions occurred in the northern Plains, shrinking previous long-term drought.



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 across the southern and central High Plains to the Southwest is evident on the 1- to 3-month maps, from the southern and central Plains to the West Coast on the 6- to 12-month maps, and in parts of the Southwest (Four Corners States) at 24 months. Dryness is evident in parts of the Pacific Northwest at the 1- to 12-month time scales. Parts of the northern Plains are dry at the 6- to 24-month time scales, but especially at 12 months. Large parts of the Southeast are dry at all time scales except 12 months. Dryness can be seen across the western Great Lakes at 1 to 3 months. Parts of the Mid-Atlantic States are dry at the 1-, 6-, and 9-month time scales. Parts of southern New England show long-term dryness at 24 months.


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



Regional Discussion




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

Hawaii:

March 2018 had a mixed precipitation anomaly pattern across the Hawaiian Islands. February-March was mostly wetter than normal. A few areas of dryness were evident amidst the wetness at longer time scales (last 3, 6, 9, 12, 24, and 36 months). Streamflow was mostly near to above normal. Abnormal dryness and drought were absent from the state, as seen on the April 3rd, 2018 USDM map.



Alaska gridded precipitation rank map, January-March 2018
Alaska gridded precipitation rank map, January-March 2018.

Alaska:

March 2018 continued the drier-than-normal conditions of previous months across south central Alaska and in the Alaskan panhandle, and wetter-than-normal across most of the rest of the state (climate division, gridded percentile, gridded percent of average, low elevation station, high elevation [SNOTEL] station, Leaky Bucket model precipitation percentile maps). The pattern of dryness in the south and in some interior locations continued for the last 2 to 3 (climate division, gridded percentile, gridded percent of average, low elevation station maps) months, but was concentrated more along the southern coastal locations at 6 (climate division, gridded percent of average, low elevation station, SNOTEL station, SNOTEL basin maps), 9, 12 (climate division, low elevation station maps), and 24 months. At 36 months, the precipitation anomaly pattern was mixed. Similar to February, temperatures were warmer than normal across most of the state, but near normal in the southeast, during March (low elevation station, gridded temperature percentile, gridded departure from average, divisional, Leaky Bucket model temperature percentile maps). The southeast was cooler than normal, with the rest of the state warmer than normal, at the 2-month time scale, but the pattern reverted more to a near-normal southeast/warmer-than-normal rest of state pattern for the last 3 (low elevation station, gridded temperature percentile, gridded departure from average, divisional maps), 6 (low elevation station, gridded departure from average, divisional maps), and 12 (low elevation station, divisional maps) months, with record warmth in the north and west at the longer time scales. Snow pack and snow water content were below normal at the stations and in the basins in the panhandle and southern coastal regions, but above normal to the north. Streamflow in the south was mostly above normal. The Leaky Bucket model suggested a drying trend for the soils in the south. There were reports of some water supply concerns in the southern parts of the panhandle and drought causing hydroelectric power reductions. Abnormally dry (D0) conditions were reduced in the southwest but persisted in the panhandle and south central regions, and an area of moderate drought (D1) was introduced into the panhandle, on the April 3rd USDM map.



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

Puerto Rico: Puerto Rico was drier than normal in the south central to southeastern sections, and wetter than normal in the north and west, during March. This pattern was evident for the last 2, 3, and 6 months, although the southeast became near to wetter than normal as the time scales got longer. Soils were a little dry in the south central region, but streamflow was mostly above normal. As seen on the April 3rd USDM map, Puerto Rico was free of drought and abnormal dryness.



CONUS State Precipitation Ranks:

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

March 2018 was drier than normal across much of the Southwest, western Great Lakes, and Southeast, and parts of the coastal Northwest and Mid-Atlantic to New England. But there were enough areas of near- to above-normal precipitation mixed in with the below-normal areas that, on a statewide basis, only 16 states ranked in the driest third of the 124-year historical record and none ranked in the top ten driest category. Michigan and Wisconsin had the driest ranks at 14th and 16th driest, respectively, out of 124 years.

Likewise, January-March 2018 was drier than normal across much of the Southwest to central Plains, western Great Lakes, and Southeast, and parts of the coastal West. There were even some record dry areas centered around the Texas and Oklahoma panhandles. But, like March, there were enough areas of near- to above-normal precipitation mixed in with the below-normal areas that, on a statewide basis, only eleven states ranked in the driest third of the 124-year historical record and none ranked in the top ten driest category.

Map showing October 2017-March 2018 state precipitation ranks Utah statewide precipitation, October-March, 1895-2018

October 2017-March 2018 was dry from California to the southern and central Plains, and across parts of the northern Plains and Southeast to Mid-Atlantic coast. Fifteen states ranked in the driest third of the historical record, with three states (Utah at second driest, Arizona at third driest, and Colorado at fourth driest) in the top ten driest category.

Southwest Kansas (division 7) precipitation, November-March, 1895-2018 Oklahoma panhandle (division 1) precipitation, November-March, 1895-2018

Parts of the southern High Plains have been extremely dry since mid-October 2017. The first week of October 2017 was extremely wet in the southern High Plains, resulting in parts of eastern New Mexico to the Texas panhandle being very wet on a monthly basis for October. But the precipitation in this region essentially shut down starting in mid-October, resulting in record to near-record dry conditions since then. The wet start to October makes the October-March precipitation ranks not as dry as they otherwise would be. Using monthly data, November 2017-March 2018 ranks as the driest November-March in the 1895-2018 record for southwest Kansas, the Oklahoma panhandle, and the northeastern Plains of New Mexico, and second driest for the Texas panhandle/High Plains. For this region, which was the epicenter for the 1950's drought episode, 2017-2018 has been as dry or drier than the comparable period in the 1950's drought.

Map showing April 2017-March 2018 state precipitation ranks North Dakota statewide precipitation, April-March, 1895-2018



Northeast Montana (division 6) precipitation, April-March, 1895-2018

The last 12 months (April 2017-March 2018) were notably dry across much of the West and northern Plains, with dryness in parts of the central to southern Plains, Mid-Mississippi Valley, and coastal Southeast. Six states ranked in the driest third of the historical record, with North Dakota in the top ten driest category at tenth driest. Arizona and Utah ranked eleventh driest. Even with the above-normal precipitation of recent months, northeast Montana still had the third driest April-March on record, bested only by two years in the 1930s.


Agricultural Belts


Primary Hard Red Winter Wheat Belt precipitation, October-March, 1895-2018
Primary Hard Red Winter Wheat Belt precipitation, October-March, 1895-2018.
Primary Hard Red Winter Wheat Belt temperature, October-March, 1895-2018
Primary Hard Red Winter Wheat Belt temperature, October-March, 1895-2018.

March 2018 was drier and warmer than normal in the Primary Hard Red Winter Wheat agricultural belt. The month ranked as the 31st driest and 28th warmest March, regionwide, in the 1895-2018 record. October marks the beginning of the growing season for the Primary Hard Red Winter Wheat belt. October 2017-March 2018 was drier and warmer than normal across most of the agricultural belt, ranking as the 15th driest and 22nd warmest October-March, regionwide. Precipitation in early October masked the extreme dryness that occurred since then, as seen by November 2017-March 2018 ranking fourth driest in the historical record. Also of interest is the noticeable overall warming trend (as shown by the red filtered curve on the temperature graph) during the last 30 years. Primary Hard Red Winter Wheat Belt precipitation, November-March, 1895-2018
Primary Hard Red Winter Wheat Belt precipitation, November-March, 1895-2018.

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

March also marks the beginning of the growing season for the Primary Corn and Soybean agricultural belt. March 2018 was near to wetter than normal across most of the region with some dryness in the north, and near to cooler than normal. The month ranked as the 52nd wettest and 59th warmest March, regionwide, in the 1895-2018 record.

The prolonged below-normal precipitation has dried soils and inhibited crop growth in many states in the Plains. According to statistics from the U.S. Department of Agriculture (USDA), 24 percent of the topsoil and 28 percent of the subsoil was rated short or very short of moisture (dry or very dry) nationwide, and 30 percent of the winter wheat was rated in poor to very poor condition. Conditions were much worse on a state by state basis, especially in the Southwest, southern to central Plains, and Southeast:


Percentage of winter wheat and pasture and rangeland in poor to very poor condition, and percentage of topsoil and subsoil moisture short to very short (dry to very dry), based on April 2, 2018 USDA reports.
State Topsoil Moisture Subsoil Moisture Winter Wheat Pasture/Rangeland
Colorado 62% 45% 40%
Florida 58% 53% 40%
Georgia 27% 25% 3% 9%
Kansas 68% 72% 48%
Montana 13% 35% 3% 62%
New Mexico 93% 79% 67% 28%
North Dakota 43% 50% 14%
Oklahoma 60% 64% 46% 34%
Oregon 28% 33% 1%
South Dakota 28% 45% 16%
Texas 54% 52% 59% 27%
Utah 35% 40% 19%

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, March yielded contrasting climate conditions across the High Plains region. Temperatures were cooler in the Northern Plains and warmer in the Central Plains during March, while the month was wet for the Northern Plains and dry conditions prevailed throughout the Central Plains.

More specifically, in the Northern Plains it was cold and snowy, as frequent cold air outbreaks and ample moisture produced several rounds of snow across the Dakotas. Several locations ended up in the top 10 of wettest and/or snowiest Marches on record, particularly in North Dakota. While cold temperatures were not record-breaking for the month, the continuation of below-normal temperatures throughout the winter and early spring combined with the lack of available feed due to last year's drought led to increased instances of cattle and calf deaths across the Dakotas and Montana. Farther south, precipitation deficits continued to accumulate in March, and drought expanded and intensified across portions of Colorado and Kansas. While the Colorado Rockies received some beneficial snowfall in March, mountain snowpack was still well below normal for the season, and with the normal peak of the mountain snowpack season approaching, it is unlikely that the deficit will be made up. Although the drought developed over winter, it has already impacted agriculture. For instance, the lack of precipitation and snow cover may have damaged alfalfa in the San Luis Valley in south-central Colorado, according to an extension agent in the region. In Kansas, the worsening drought situation prompted the governor to make an official drought declaration for the entire state. Shortly after the drought declaration, Kansas lawmakers requested emergency haying and grazing of Conservation Reserve Program (CRP) lands. Another immediate concern was wildfires, as conditions in March were ripe for wildfires to develop and spread. Although winter conditions allowed for the improvement of drought across the Northern Plains, this region is still dealing with impacts, such as the lack of available feed contributing to cattle deaths as mentioned above. According to NOAA, the 2017 Northern Plains drought had an economic impact of $2.5 billion on the Dakotas and Montana. Producers are concerned that this region will endure a second year of drought, hampering recovery from last year's drought.

Drought conditions improved across the north while worsening throughout the southern portion of the High Plains during March. According to the USDM, the overall area experiencing drought or abnormal dryness (D0-D4) decreased from 69 percent to 63 percent, but areas experiencing severe (D2), extreme (D3), and exceptional (D4) drought increased. As for improvements, a wet pattern prevailed throughout March in the Dakotas, bringing drought relief to the region. Heavy snows fell across this region during the early part of the month, removing drought across the eastern Dakotas and improving conditions in the west. However, the drought situation continued to worsen throughout Colorado and Kansas. This region missed out on much-needed precipitation, with the majority of the two states receiving less than 50 percent of normal precipitation for the month. As a result, D2 and D3 conditions expanded across southern, central, and eastern portions of Colorado and Kansas, and D4 conditions expanded across southwestern Kansas. As for impacts, topsoil moisture and winter wheat conditions were suffering from the lack of precipitation. According to the March 27th USDA Weekly Weather and Crop Bulletin, topsoil moisture was rated 69 percent and 63 percent short to very short in Kansas and Colorado, respectively. Winter wheat conditions were rated 49 percent poor to very poor in Kansas and 21 percent poor to very poor in Colorado. Spring precipitation is badly needed for winter wheat growth and for other crops to be planted.

As explained by the Southern Regional Climate Center, precipitation values for the month of March varied spatially throughout the Southern region, and temperatures temperatures had a defined gradient. Parts of western and eastern Texas and west central Louisiana received 200-300 percent of normal precipitation. Southwestern Tennessee, northwestern and central Mississippi, southern Arkansas, western Louisiana and parts of central Texas received 150-200 percent of normal precipitation. In contrast, western Oklahoma and northern and western Texas received 5 percent or less of normal precipitation. Areas of extreme southern Louisiana and southern, west central, and northern Texas received 50 percent or less of normal precipitation. In western Oklahoma, central and northern Louisiana, and most of Texas temperatures were 4 to 6 degrees F (2.22 to 3.33 degrees C) above normal. Parts of central and southern Texas experienced 6 to 8 degrees F (3.33 to 4.44 degrees C) above normal. In contrast, parts of central Mississippi and eastern Tennessee were 2 to 4 degrees F (1.11 to 2.22 degrees C) below normal.

In March, the exceptional drought classification appeared in northwestern Oklahoma and northern Texas. The severe drought classification was expanded through parts of central Texas and drought conditions worsened to moderate in southern Texas. The moderate drought classification was expanded throughout parts of western Texas. Drought conditions improved from moderate to no official drought designation in central Oklahoma and north central Arkansas. Conditions also improved from abnormally dry to normal or wetter than normal conditions in central Mississippi, southeastern Tennessee and northwestern Arkansas.

As summarized by the Midwest Regional Climate Center, precipitation totals in March varied from less than 0.50 inches (13 mm) to more than 6.00 inches (152 mm). Totals, viewed as a percentage of normal, ranged from less than 25 percent of normal in northeastern Minnesota to nearly twice normal in southern Illinois and western Minnesota. Below-normal totals stretched from eastern Minnesota, across Wisconsin and nearly all of Michigan, northeastern Iowa, northern Illinois, and northwestern Indiana. Western Missouri was also below normal. March temperatures were near or below normal across the Midwest. Drought eased slightly in March, falling from over 4 percent of the region to about 2.5 percent during the month.

As noted by the Southeast Regional Climate Center, precipitation was near normal to well below normal across much of the Southeast region during March, and temperatures ranged from near average to well below average across the region. The driest locations were found across much of Florida, as well as portions of southern Alabama, southeastern Georgia, and coastal South Carolina. Monthly precipitation totals were 50 to less than 10 percent of normal in these areas. The coldest weather of the month across the Southeast occurred on the 9th and 15th, as continental high pressure systems ushered in unseasonably cold, dry air from the northwest, while the warmest weather of the month occurred from the 28th through the 29th, as the circulation around the Bermuda High, situated off the Atlantic coast, transported warm, humid air over the Southeast. From the 4th through the 7th, the powerful cyclone situated over the Northwest Atlantic Ocean generated exceptionally large swells with waves of 25 to 30 feet in height along the coastline of Puerto Rico and the U.S. Virgin Islands, which are located about 1,500 miles away. Coastal flooding caused significant beach erosion and damaged numerous homes, roads, docks, and other structures along the northern and western coast of Puerto Rico.

Drought intensified and expanded in coverage across the southern half of the region during March, with about 22 percent of the Southeast classified in moderate-to-severe (D1-D2) drought at the end of the month. The greatest drought coverage was found in Georgia and South Carolina, where more than 50 and 30 percent of each state, respectively, were covered in moderate-to-severe drought in late March. Additional development of moderate drought occurred in northwestern Alabama and portions of the Florida Peninsula, while drought conditions were nearly eliminated in northeastern Virginia and the Florida Panhandle. By the end of March, North Carolina was the only drought-free (i.e., less than D1) state in the Southeast. Cooler-than-normal weather during March delayed the preparation and planting of crop fields and slowed the growth of small grains, livestock pastures, and hayfields across much of the region. Pastures and hayfields in southern Florida were stressed by a persistent lack of rainfall during the month, while several frosts damaged and slowed the green-up of pastures in northern Florida. Due to the poor grazing conditions across much of Florida, livestock producers continued to provide water and supplemental feed to their cattle. Below-average precipitation required many fruit and vegetable producers in Florida, including the citrus industry, to use their irrigation systems extensively during the month. Periods of sub-freezing temperatures during March damaged the early-season peach crop in several states. About 10 to 50 percent of the flowering blossoms on peach trees in northern and central Georgia were lost to excessively cold temperatures. Moderate damage to the blueberry crop in southern Georgia was also reported, particularly in farms lacking frost protection. While these crops were able to acquire sufficient chill hours from December through January, extreme warmth during February caused the fruit trees to bud or bloom prematurely, which increases their vulnerability to spring freezes.

As explained by the Northeast Regional Climate Center, March wrapped up on the dry side of normal for the Northeast, with the region receiving 3.12 inches (79.25 mm) of precipitation, 89 percent of normal. March was only slightly warmer than February in the Northeast. The region's average temperature for March was 32.4 degrees F (0.2 degrees C), 2.1 degrees F (1.2 degrees C) colder than normal, compared to February's average temperature of 32.1 degrees F (0.1 degrees C), 5.9 degrees F (3.3 degrees C) warmer than normal.

Dry conditions within a small region of the Northeast have persisted throughout most of March, mainly in parts of Maryland. At the beginning of March, about two percent of the entire Northeast was abnormally dry. By the end of the month, one percent of the Northeast was experiencing abnormal dryness. Drought conditions improved over the course of the month within Maryland. At the start of the month, 47 percent of Maryland was abnormally dry, and three percent of the state was experiencing moderate drought. By the end of March, 23 percent of Maryland was abnormally dry, and two percent of the state was experiencing moderate drought.

As summarized by the Western Regional Climate Center, an active storm track featuring several atmospheric rivers delivered above normal precipitation to a wide swath of the West stretching from central California northeastward to western Montana. Temperatures were below normal in the northern and western parts of the region, while temperatures in the southeastern part of the West were slightly warmer than normal.

Above normal March precipitation was extremely beneficial to areas such as the Sierra Nevada, southern Cascades, Great Basin, and central Rockies, which observed below normal winter season precipitation and snowpack. Many basins in these areas were at 30-50% of median snowpack at the beginning of March, but ended the month at more than 60-70% of median.

In the USDM valid 27 March, 43% of the West was experiencing drought conditions. Improvements were observed in California, northern Oregon, and eastern Montana in association with this month's above normal precipitation. Severe to extreme drought conditions were present in 27% of the region, all within the Four Corners states and southern California. With the exception of southwestern California, these areas generally observed below-normal March precipitation. Phoenix, Arizona, reported 0.04 in (1 mm), 4% of normal. Albuquerque, New Mexico logged 0.18 in (5 mm), 32% of normal. These regions most affected by drought depend on spring and summer snowmelt from the Colorado River Basin; the Upper Basin reported 71% and the Lower Basin 31% of median snowpack at month's end.

Warmer than normal temperatures were observed in the northern and western parts of Alaska. Utqiagvik (Barrow) recorded its warmest March since records began in 1920 at -0.7 F (-18.2 C), 12 F (6.7 C) above normal. Kotzebue had its 2nd warmest March in a more than 60-year record at 12.8 F (-10.7 C), 11.7 F (6.5 C) above normal. Arctic sea ice extent reached its second lowest annual maximum extent in a 39-year record this month, contributing to above normal temperatures. Precipitation was above normal across much of the state, except for the south-central and southeastern regions where precipitation was generally less than 75% of normal. Nome reported 2.46 in (62 mm) of precipitation, the highest March total since 1935. Further south, precipitation was variable across Hawaii. The southern to southeastern portions of the islands observed above normal precipitation while other areas reported near or slightly below normal precipitation. Lihue received 9.03 in (229 mm), 196% of normal and the 9th wettest March since records began in 1950. A storm on the 14th-15th caused flooding and road closures on Maui and Kauai; some areas of Kauai received over 6 in (152 mm) of rainfall in 24 hours.

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), March 2018 was drier than normal at Guam, Koror, Lukonor, Pago Pago, and Saipan, and wetter than normal at Chuuk, Kapingamarangi, Kosrae, Kwajalein, Majuro, Pohnpei, and Yap.

Rainfall amounts were below the minimum thresholds (4 or 8 inches) required to meet most monthly water needs at Guam, Mangilao, Rota, Saipan, and Tinian (in the Marianas); Fananu, Lukonor, Nukuoro, Ulithi, and Woleai (in the FSM); and Pago Pago (in American Samoa). March 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.

Beneficial rain fell across the Marshall Islands this month. Significant dryness developed in the northern Marshall Islands in December 2016, with 8 of the last 16 months each having less than 2 inches at Utirik, 12 had less than 8 inches, and 2 months were missing; that equates to just 2 months having more than 8 inches (November 2017 and this month). At Wotje, 5 of the last 16 months had less than 2 inches each, and 12 had less than 8 inches, with only 3 (June, September, and November 2017 as well as this month) having more than 8 inches. Eight inches is the monthly minimum in the RMI. Jaluit recorded 10.46 inches of rain in November 2017, 9.30 inches in December, 7.80 inches in January 2018, 8.15 inches in February 2018, and 11.02 inches in March 2018, but still had the third driest April-March and May-March out of 33 years of data. Ailinglapalap had the seventh driest May-March out of 32 years of data.

Dryness has developed in the last 5 months in the Marianas Islands. Guam had the driest January in their 1957-2018 record and seventh driest March. Even though 2.72 inches of rain was recorded in February, which ranked 20th driest, Guam still had the driest November-March on record. Rota and Saipan have each had less than 4 inches (the monthly minimum in the Marianas) of rain for November and December 2017 and January, February, and March 2018; March, April, and May 2017 were also each dry at Saipan. October 2017-March 2018 was the driest October-March in 29 years of data at Saipan, and each of the time periods from April-March through September-March, as well as November-March, ranked as the second driest (out of 29years of data). In the FSM, Nukuoro had the fourth driest March out of 35 years of data. The National Weather Service office on Guam issued a revised Drought Information Statement on March 21, then updated it on April 5, warning of developing impacts from drought in the Marianas and northern Marshall Islands, as well as dry conditions in the Republic of Palau. Moderate drought impacts have developed on the Marianas, including browning vegetation and some grass fires, low streamflows on Guam, and some springs drying up on Saipan.

As measured by percent of normal precipitation, Guam, Saipan, and Lukonor have been drier than normal in the short term (March and the last 3 months [January-March 2018]) as well as the long term (last 12 months [April 2017-March 2018]). Koror was drier than normal in the short term and near normal in the long term. Pago Pago was drier than normal for March but wetter than normal for the other 2 time periods. Chuuk, Kapingamarangi, Kosrae, Kwajalein, Majuro, Pohnpei, and Yap were near to wetter than normal for all 3 time periods.


X
  • Percent of Normal Precip
  • Precipitation
  • Normals
Pacific Island Percent of 1981-2010 Normal Median Precipitation
Station Name Apr
2017
May
2017
Jun
2017
Jul
2017
Aug
2017
Sep
2017
Oct
2017
Nov
2017
Dec
2017
Jan
2018
Feb
2018
Mar
2018
Apr 2017-
Mar 2018
Chuuk60%83%73%99%91%110%127%105%120%99%175%131%99%
Guam NAS340%56%136%97%66%118%161%57%88%23%90%68%86%
Kapingamarangi159%114%81%102%41%92%72%64%420%95%222%171%120%
Koror76%107%89%130%104%161%118%84%160%82%105%37%100%
Kosrae112%115%80%104%93%155%143%168%123%100%147%181%106%
Kwajalein65%77%156%70%64%205%88%83%71%458%159%662%125%
Lukonor85%80%60%103%63%84%116%136%70%129%106%84%80%
Majuro110%49%118%112%111%187%143%76%172%204%120%343%135%
Pago Pago87%240%93%84%145%96%217%127%94%115%271%60%123%
Pohnpei96%92%141%113%55%122%81%95%130%167%219%440%135%
Saipan115%66%128%72%65%84%66%62%60%117%87%49%74%
Yap110%69%68%121%55%93%156%106%132%182%163%270%109%
Pacific Island Precipitation (Inches)
Station Name Apr
2017
May
2017
Jun
2017
Jul
2017
Aug
2017
Sep
2017
Oct
2017
Nov
2017
Dec
2017
Jan
2018
Feb
2018
Mar
2018
Apr 2017-
Mar 2018
Chuuk7.519.408.5011.8611.6512.9214.6411.1513.5210.0112.7010.86134.72
Guam NAS8.601.898.409.869.7314.9218.474.234.490.942.721.4085.65
Kapingamarangi21.7013.7511.1514.473.359.135.935.9541.308.7120.5919.60175.63
Koror5.5412.6115.5324.1413.9818.9014.039.5517.898.389.032.75152.33
Kosrae19.6220.3411.7315.5713.2322.0215.6523.2119.8516.6219.0329.00225.87
Kwajalein3.445.2010.806.916.2822.069.839.404.7214.464.2015.55112.85
Lukonor9.619.416.9716.478.888.5113.1012.387.9010.839.507.76121.32
Majuro10.364.9313.0312.5213.0020.9318.2110.2719.5915.768.2922.54169.43
Pago Pago8.1423.234.944.667.786.2620.1112.8912.0615.3732.476.36154.27
Pohnpei17.6818.4520.8517.457.8215.2712.3114.1320.8622.0320.9457.92245.71
Saipan3.021.584.636.458.598.477.013.482.312.972.250.9351.69
Yap6.195.408.1618.278.2012.5918.999.4011.2711.648.4412.29130.84
Pacific Island 1981-2010 Normal Median Precipitation (Inches)
Station Name Apr
2017
May
2017
Jun
2017
Jul
2017
Aug
2017
Sep
2017
Oct
2017
Nov
2017
Dec
2017
Jan
2018
Feb
2018
Mar
2018
Apr 2017-
Mar 2018
Chuuk12.4711.3011.6611.9812.8611.7111.5110.6111.2510.107.258.32136.77
Guam NAS2.533.406.1810.1414.7412.6611.447.385.114.013.032.0799.09
Kapingamarangi13.6412.0813.7814.158.139.938.199.279.849.159.2711.43145.85
Koror7.3211.8317.4818.5313.5011.7711.8411.3911.1610.188.567.44152.90
Kosrae17.5117.7514.6414.9114.2214.2210.9413.8316.1116.6712.9316.06213.87
Kwajalein5.266.726.939.879.7410.7411.1811.286.663.162.642.3590.41
Lukonor11.3111.6911.6515.9314.0410.1511.329.0811.278.418.939.26151.36
Majuro9.4210.1111.0111.1711.6911.1712.7313.4411.397.746.886.58125.25
Pago Pago9.399.665.335.555.386.539.2610.1412.8413.3412.0010.68125.57
Pohnpei18.4119.9614.8115.4314.2612.5515.2714.8316.0813.189.5513.17182.36
Saipan2.632.383.628.9113.1310.0910.625.613.852.532.591.8970.25
Yap5.637.8512.0415.0814.8213.5012.188.838.516.395.194.56120.31

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 March 2018, October 2017-March 2018 (last 6 months), and April 2017-March 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 March 2018, October 2017-March 2018, and April 2017-March 2018.
Rank of 1 = driest.
Station Mar 2018
Rank
Mar
No. of Years
Oct 2017- Mar 2018
Rank
Oct- Mar
No. of Years
Apr 2017- Mar 2018
Rank
Apr- Mar
No. of Years
Period of Record
Jaluit 21 35 17 33 3 33 1981-2018
Koror 5 67 29 67 39 66 1951-2018
Woleai 17 36 15 30 9 22 1968-2018
Yap 65 67 61 67 43 66 1951-2018
Majuro 63 64 63 64 62 63 1954-2018
Mili 32 35 31 32 MSG 31 1981-2018
Ulithi 23 36 33 34 22 34 1981-2018
Ailinglapalap 28 35 19 33 8 32 1981-2018
Kosrae 44 48 30 35 23 30 1954-2018
Lukonor 11 34 14 32 3 21 1981-2018
Saipan 4 37 1 29 2 29 1981-2018
Pohnpei 67 67 67 67 66 66 1951-2018
Kwajalein 63 66 60 66 55 65 1952-2018
Kapingamarangi 24 28 20 20 12 13 1962-2018
Chuuk 45 67 52 67 24 66 1951-2018
Guam 7 62 11 61 14 61 1957-2018
Nukuoro 4 35 29 33 30 32 1981-2018
Pago Pago 10 52 50 52 46 52 1966-2018
Wotje 33 35 29 32 27 32 1981-2018
Utirik 14 15 6 7 1 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 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 March 2018, published online April 2018, retrieved on November 17, 2018 from https://www.ncdc.noaa.gov/sotc/drought/201803.

Metadata