January 2019 Drought Report

Overview

The upper-level circulation during January consisted of a number of Pacific weather systems moving in the jet stream flow across the southern parts of the CONUS, with some taking a track across the Midwest and up along the East Coast. They spread above-normal precipitation across parts of the West and Plains, and across much of the eastern CONUS along and east of the Mississippi River. The long-wave pattern shifted to a ridge over the western CONSU and trough over the east during the last half of the month, which funneled cold and dry Canadian air masses across the country east of the Rockies. In the end, the parts of the country that missed out on the precipitation included parts of the Pacific Northwest, Plains, and a strip along the Gulf of Mexico and Southeast coast, as well as most of Hawaii and parts of Alaska, Puerto Rico, and the U.S.-Affiliated Islands in the western Pacific. The precipitation this month fell on many areas that were in drought, so drought contraction far outweighed expansion. Drought and abnormal dryness contracted across much of the West and parts of the Plains, Northeast, and southern Florida. Abnormal dryness or drought expanded in other parts of the West and southern Plains, parts of Puerto Rico, and much of Hawaii. As a result, the USDM-based national moderate-to-exceptional drought footprint across the CONUS contracted from 21.9 percent of the CONUS at the end of December to 16.5 percent of the CONUS at the end of January (from 18.7 percent to 14.3 percent for all of the U.S.). According to the Palmer Drought Index, which goes back to the beginning of the 20^th century, about 18.5 percent of the CONUS was in moderate to extreme drought at the end of January, decreasing about 3.5 percent from the 22.0 percent at the end of December.

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 January 29^th, 2019 USDM map, included the following core drought and abnormally dry areas:

• A large area of abnormal dryness (D0) to moderate (D1) drought stretched across the West, with centers of severe (D2) to extreme (D3) drought in the Pacific Northwest and severe to exceptional (D4) drought in the Southwest (Four Corners States). According to the USDM, about 41 percent of the West was experiencing moderate to exceptional drought at the end of January. This is a decrease from last month's 53.3 percent. The percent area of the West (from the Rockies to the West Coast) in moderate to extreme drought (based on the Palmer Drought Index) also decreased to 56.5 percent compared to 67.6 percent at the end of December.
• Abnormal dryness to severe drought continued in Alaska.
• Abnormal dryness and moderate drought expanded, and severe drought developed, in Hawaii.
• Areas of moderate drought covered a few parts of the northern and southern Plains, southern Florida, and much of Puerto Rico.

Palmer Drought Index

The Palmer drought indices measure the balance between moisture demand (evapotranspiration driven by temperature) and moisture supply (precipitation). The Palmer Z Index depicts moisture conditions for the current month, while the Palmer Hydrological Drought Index (PHDI) and Palmer Drought Severity Index (PDSI) depict the current month's cumulative moisture conditions integrated over the last several months. While both the PDSI and PHDI indices show long-term moisture conditions, the PDSI depicts meteorological drought while the PHDI depicts hydrological drought. The PDSI map shows less severe and extensive drought (as well as wet spell conditions) in some parts of the country than the PHDI map because the meteorological conditions that produce drought and wet spell conditions are not as long-lasting as the hydrological impacts.

Used together, the Palmer Z Index and PHDI maps show that short-term dry conditions continued in January in the Pacific Northwest over areas that were in drought at the end of December, maintaining or intensifying long-term drought. Short-term near-normal to wet conditions occurred across much of the Southwest, reducing or eliminating previous areas of long-term drought. Short-term near-normal to wet conditions occurred across much of the country from the Plains to East Coast, maintaining or intensifying previous areas of 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.

The SPI maps illustrate how moisture conditions have varied considerably through time and space over the last two years. Wet conditions dominate much of the CONUS east of the Rockies at all time scales. As far as dry conditions are concerned, dryness dominates the Pacific Northwest at the 1- to 12-month time scales, and much of Oregon at the 24-month time scale, and the northern to central Rockies from 2 to 12 months. Dryness extends into northern California at 6 to 24 months. Parts of the Southwest are dry at 6 to 12 months, and much of the Southwest is dry at 24 months. Parts of the central Plains and southern High Plains have dry conditions at the 1-month time scale. Parts of southern Florida are dry at 6 months. A large portion of the northern Plains shows dry conditions at the 24-month time scale.

Regional Discussion

Hawaii:

Drier-than-normal conditions dominated the Hawaiian Islands during the last 1, 2, and 3 months. Honolulu had the fifth driest November-January in the station's 1940-2019 record. October 2018 was wetter than normal across the state, but the severe dryness of the last three months still resulted in widespread below-normal precipitation at the 4-month time scale. Wetter-than-normal conditions are evident at longer time scales (last 6, 7, 10, 12 months). Wet conditions still dominate at the 24- and 36-month time scales, although stations on the Big Island show evidence of drier-than-normal rainfall totals at these time scales. Streamflow was above normal at many stations, but below-normal streamflow was beginning to appear at some stations. Drought and abnormal dryness expanded on the January 29^th USDM map, with moderate to severe drought covering about 39 percent of the islands.

Alaska:

February was drier than normal in interior to south coastal Alaska, but wetter than normal in the drought-stricken southern panhandle and in parts of the west and far north. Dryness persists in parts of the interior for the last 2 to 4 months and is evident in the west and panhandle. Wet conditions dominate at longer time scales, except in the panhandle where precipitation deficits become more severe (low elevation station precipitation maps for the last 1, 2, 3, 4, 6, 7, 10, 12, 24, and 36 months) (gridded precipitation percentile maps for the last 1 and 3 months) (climate division precipitation maps for the last 1, 3, 6, 12 months) (Leaky Bucket model precipitation percentile map for January). Temperatures during January were warmer than normal except in the southern and eastern interior regions. Warmer-than-normal temperatures dominated at longer time scales, with record warmth in the west for the last 12 months (low elevation station temperature maps for the last 1, 2, 3, 4, 12 months) (gridded temperature percentile maps for the last 1 and 3 months) (climate division temperature maps for the last 1, 3, 6, 12 months) (Leaky Bucket model temperature percentile map for January). Snow pack was below average in much of the south due to the warmer-than-normal conditions. Streamflow (for those streams that weren't frozen over) was mostly near to above normal. Abnormally dry to severe drought conditions continued in the panhandle. About 5.8 percent of the state was in abnormally dry to severe drought conditions on the January 29^th USDM map.

Puerto Rico:

January 2019 was drier than normal in central Puerto Rico to the northern coast and in parts of the southwest, and wetter than normal along the west coast. Drier-than-normal conditions were widespread for the last 2 to 3 months, and still dominated the island at the 4-month time scale (October 2018-January 2019). The central to eastern sections, and the southern coast, were drier than normal at the 6-month time scale. Soils were dry along the southern coast, towards the interior, and in parts of the northwest, and some streams had below-normal flow. As seen on the January 29^th USDM map, moderate drought expanded to cover about 9 percent of the island, with abnormal dryness to moderate drought extending across three-fourths (76%) of Puerto Rico.

CONUS State Precipitation Ranks:

With above-normal precipitation across much of the CONUS during January, most of the states had near-average to above-average precipitation ranks. Those five states with significant areas drier than normal — Oregon, Washington, Idaho, Montana, and Nebraska — ranked in the dry third of the historical record.

This spatial pattern held for most of the last 12 months. Only the three states in the Pacific Northwest ranked in the dry third of the historical record for the last three months (November 2018-January 2019); five states in the Pacific Northwest and northern Rockies ranked in the dry third of the historical record for the last six months (August 2018-January 2019); and six states (all in the West) ranked in the dry third of the historical record for the last 12 months (February 2018-January 2019). Only Oregon had a top ten driest rank, and that was ninth driest February-January.

Agricultural Belts

January 2019 was warmer than normal across the Primary Hard Red Winter Wheat agricultural belt, with parts of the region wetter than normal and parts drier than normal. The month ranked as the 46^th wettest and 33^rd warmest January, regionwide, in the 1895-2019 record.

October marks the beginning of the growing season for the Primary Hard Red Winter belt. October 2018-January 2019 was wetter and cooler than normal across the region. The 4-month period ranked as the second wettest and 53^rd coolest October-January, regionwide.

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), January 2019 was drier than normal at Koror, Saipan, Kosrae, Kwajalein, Majuro, and Pago Pago, and wetter than normal at Yap, Guam, Chuuk, Lukonor, Pohnpei, and Kapingamarangi.

It was a dry month in terms of drought at Saipan (Marianas); Woleai (FSM); and Ailinglapalap, Jaluit, Kwajalein, Majuro, Utirik, and Wotje (RMI), with rainfall amounts below the minimum thresholds (4 or 8 inches) required to meet most monthly water needs. 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.

The dryness in the RMI was widespread and, in some locations, becoming significant. Ailinglapalap had the fifth driest January in a data record spanning 36 years, and Jaluit was second driest (out of 36 years of data) (although instrument exposure may have contributed some to the low rainfall totals at Jaluit). January 2019 was the eleventh driest January at Wotje (out of 36 years of data) and Utirik (21 years of data) and 16^th driest at Kwajalein (67 years). Kwajalein also had the seventh driest September-January (67 years) and Ailinglapalap the seventh driest February-January (33 years). In the FSM, Woleai had the fifth driest September-January (30 years), Nukuoro the fourth driest March-January (34 years), Lukonor the second driest April-January (22 years), and Kosrae the second driest September-January (35 years). At the other extreme, the last 12 months (February 2018-January 2019) were the wettest such 12-month period at Kapingamarangi (out of 14 years of data) and second wettest at Saipan (30 years), Pohnpei (67 years), and Kwajalein (66 years).

As measured by percent of normal precipitation, Kosrae has been drier than normal in the short term (January and the last 3 months [November 2018-January 2019]) and drier than normal in the long term (last 12 months [February 2018-January 2019]). Kwajalein, Majuro, and Saipan have been drier than normal in the short term and wetter than normal in the long term. Koror and Pago Pago were drier than normal for January but wetter than normal for the other two time periods (the 12-month time period was missing for Koror). Guam was drier than normal for the last 3 months, but near to wetter than normal for January and the last 12 months. Lukonor was wetter than normal for January, but drier than normal for the other two time periods. Chuuk, Kapingamarangi, Pohnpei, and Yap were wetter than normal for all three time periods.

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 January 2019, September 2018-January 2019 (the last 5 months), and February 2018-January 2019 (the last 12 months). Some stations have a long period of record and their dataset is fairly complete, while other stations have a shorter period of record and the dataset has some missing data.

Station	Jan 2018 Rank	Jan No. of Years	Sep 2018- Jan 2019 Rank	Sep- Jan No. of Years	Feb 2018- Jan 2019 Rank	Feb- Jan No. of Years	Period of Record
Jaluit	2	36	1	34	MSG	33	1981-2019
Koror	37	68	35	68	MSG	66	1951-2019
Woleai	20	37	5	30	11	23	1968-2019
Yap	64	68	48	68	50	67	1951-2019
Majuro	27	65	14	65	58	64	1954-2019
Mili	17	35	18	32	MSG	31	1981-2019
Ailinglapalap	5	36	8	34	7	33	1981-2019
Kosrae	23	49	2	35	11	29	1954-2019
Lukonor	26	35	7	33	3	22	1981-2019
Saipan	10	39	23	31	29	30	1981-2019
Pohnpei	55	68	32	68	66	67	1951-2019
Kwajalein	16	67	7	67	65	66	1952-2019
Kapingamarangi	27	29	19	19	14	14	1962-2019
Chuuk	66	68	62	68	51	67	1951-2019
Guam	28	62	36	62	46	61	1957-2019
Nukuoro	13	37	15	35	8	34	1981-2019
Pago Pago	21	53	37	53	47	52	1966-2019
Wotje	11	36	12	33	MSG	32	1981-2019
Utirik	11	21	6	10	4	4	1985-2019

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

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