Drought - November 2012
NCDC transitioned to the nClimDiv dataset on Thursday, March 13, 2014. This was coincident with the release of the February 2014 monthly monitoring report. For details on this transition, please visit our public FTP site and our U.S. Climate Divisional Database site.
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
Detailed Drought Discussion
November 2012 marked a return to the warmth and dryness which characterized much of the year, ranking as the 20th warmest and eighth driest November (based on data back to 1895) when weather conditions are averaged across the country. Like the last several months, cool fronts swept across the country (weeks 1, 2, 3, 4), bringing below-normal monthly temperatures to most areas east of the Mississippi River. High pressure (High, or upper-level ridge), centered over the Southwest and Central Rockies, dominated the West and Great Plains with its descending air ("subsidence"), resulting in a monthly pattern of anomalous warmth there. The associated circulation pattern dumped above-normal precipitation across parts of the West from California to the Northern Rockies and northern High Plains, but it also reduced precipitation across the rest of the country (weeks 1, 2, 3, 4). The wet weather in the West nibbled away at the edge of the drought areas in the Pacific Northwest and northern High Plains, but dry weather expanded drought in the Southeast, Southern Plains, and Hawaii. Nationally, the moderate to exceptional (D1-D4) drought footprint increased to about 52.4 percent of the country, compared to last month, while the percentage in the abnormally dry to exceptional drought category increased to about 71.2 percent. About 16.8 percent of the country was in the worst drought categories (D3-D4, extreme to exceptional drought), a bit more than last month. The Palmer Drought Index, whose data go back 113 years, is relied upon for drought comparisons before 2000. The November 2012 Palmer value of 59.5 percent in moderate to extreme drought is an increase of about 7 percent compared to last month, and the percent area in severe to extreme drought increased to about 44.8 percent.
By the end of the month, the core drought areas in the U.S. included:
- a large area of moderate (D1) to exceptional (D4) drought stretching from the western High Plains, across the Northern to Southern Plains, into the Upper Midwest and Mid-Mississippi Valley;
- a persistent area of moderate to exceptional drought in the Southeast to Mid-Atlantic;
- an area of moderate to extreme (D3) drought across much of the West; and
- much of Hawaii, where moderate to extreme drought persisted.
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.
Used together, the Palmer Z Index and PHDI maps show that the November short-term drought conditions exacerbated long-term drought conditions across the nation's drought areas (November PHDI compared to October PHDI), resulting in an increase in the percent area under drought. The November short-term dryness essentially neutralized the areas of October moistness that had developed in the Northeast to Ohio Valley. The areas that received above-normal precipitation were mostly in the Northwest, which was for the most part drought-free.
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 1-month SPI map shows the area of November dryness covering most of the country east of the Mississippi River, the Southern and Central Plains, and the Central Rockies to Southwest. Near normal to wet conditions stretched from northern California, across the Northwest, to the Northern High Plains. Much of the Northwest (especially coastal sections) shows up as wet at all time scales. The Northeast is dry at the 1-month time scale but near normal to wet at the 2- to 24-month time scales. Dryness dominates in the Southeast at all time scales, except wet conditions are evident at 6 to 12 months along the Gulf Coast. The Ohio Valley has evidence of wet conditions at 3 and 24 months, but dry conditions at 2, 6, 9, and 12 months. Dry conditions dominate at all time scales across the Southwest to Southern and Central Plains, spreading into the Northern Plains and Midwest on the 6- to 12-month SPI maps.
Agricultural and Hydrological Indices and Impacts
Drought conditions were reflected in numerous agricultural, hydrological, and other meteorological indicators, both observed and modeled.
Based on end-of-November (November 26th) U.S. Department of Agriculture (USDA) reports, winter wheat emergence was hampered by drought in several central states, with 65 percent of the winter wheat in drought. Overall, 26 percent of the winter wheat was rated in poor to very poor condition (compared to 15 percent a month ago), although that number was much higher in South Dakota (64 percent), Nebraska (46 percent), Oklahoma (44 percent), and Texas (40 percent). About 65 percent of the domestic hay acreage and 73 percent of the domestic cattle inventory were in an area experiencing drought.
- NOAA Climate Prediction Center (CPC) modeled soil moisture anomalies and percentiles for the end of the month, and soil moisture anomaly change compared to previous month;
- CPC's Leaky Bucket model soil moisture percentiles;
- NLDAS (North American Land Data Assimilation System) modeled soil moisture percentiles for the top soil layer and total soil layer;
- VIC (University of Washington Variable Infiltration Capacity macroscale hydrologic model) modeled soil moisture percentiles, and soil moisture percentile change compared to previous month;
- Vegetation Drought Response Index (VegDRI);
- the NOAA/NESDIS satellite-based Vegetation Health Index (VHI);
- USGS observed streamflow;
- VIC 1-, 2-, 3-, and 6-month runoff percentiles;
- NLDAS modeled streamflow anomalies and percentiles;
- NLDAS model runoff anomalies and percentiles;
- USGS groundwater observations (real-time network, climate response network, total active network);
- USDA snow water content observations for the West (SNOTEL station percentiles, SNOTEL station percent of normal, SNOTEL basin percent of normal and percent of average) and Alaska (SNOTEL station percent of normal, SNOTEL basin percent of normal);
- VIC modeled snow water content percentile;
- USDA statewide reservoir storage as percent of capacity;
- total precipitation (plotted by the USGS, NOAA National Weather Service [NWS], and NOAA High Plains Regional Climate Center [HPRCC]);
- percent of normal precipitation and precipitation percentiles (NWS, CPC, HPRCC station observations, Leaky Bucket model), precipitation anomalies (CPC);
- NCDC statewide precipitation ranks;
- USGS number of days with precipitation and maximum number of consecutive dry days;
- temperature departures from normal (CPC, HPRCC) and temperature percentiles (CPC, Leaky Bucket);
- NCDC standardized temperature departures and statewide temperature ranks; and
- number of record warm daily low temperatures, record daily high temperatures, record daily low temperatures, and record cool daily high temperatures, set during the month (from NCDC's daily records analysis).
Hawaii: November 2012 was another very dry month for the Hawaiian Islands. The pattern of below-normal rainfall was evident at most time periods (especially the last 2 months, but also the last 3, 6, 8, 12, and 36 months, year-to-date, water year-to-date, and, for the southern islands, the last 24 months), and streamflow was below normal across the islands. Moderate to extreme drought affected 54 percent of the state, a little more than last month.
Alaska: Most of the stations in Alaska were drier and cooler than normal during November. The dryness is widespread at 2 months (water year-to-date). But the pattern shifts at longer time scales, with dryness evident from the southeast panhandle to interior southeast stations (at 3, 6, and 8 months) then becoming mixed (at the year-to-date and 12-, 24-, and 36-month time scales). An area of abnormal dryness covered the northern areas to south central Alaska on the USDM map.
Puerto Rico: Southeastern Puerto Rico was drier than normal during November with a mixed precipitation pattern across the rest of the island. The pattern of dryness in the southeast is evident at longer time scales (2 months [water-year-to-date] and year-to-date, but especially the last 3 to 6 months). Except for a few gauges in the east, November monthly streamflow was generally near normal. The November 27th USDM map was free of any drought or abnormally dry areas.
Over a third of the U.S. was very dry (the driest ten percent of the historical record) during November 2012, marking the driest November since 1976 by this measure. On a statewide basis, November 2012 ranked in the driest third of the historical record for November for 22 states — mostly east of the Mississippi — with five states (Connecticut, Florida, New Hampshire, Vermont, West Virginia) second driest in the 1895-2012 record.
|The spatial pattern of dryness at the three-month time scale was centered from the Southwest to Upper Midwest and in the Southeast. Three states (Nebraska, South Dakota, and Minnesota) fell in the top ten driest category for September-November 2012, while another 14 ranked in the driest third of the historical record for November.|
At the six-month time scale the Central Rockies to Central Plains were the epicenter of dryness, with Nebraska and Wyoming having the driest June-November in the 1895-2012 record. Eight other states (from the Southwest to the Upper Midwest) were in the top ten driest category and an additional twelve states (from the West to Midwest and in the Southeast) ranked in the driest third of the historical record for June-November.
The spatial pattern of dryness for the year-to-date was similar to that for the twelve-month time scale, with dryness stretching across the country from the Intermountain Basin to the East Coast. A large epicenter of dryness was located from the Central Rockies to the Midwest, with smaller ones in the Southeast and Mid-Atlantic Coast.
Colorado had its driest January-November during 2012, and Nebraska and Wyoming had both their driest January-November (NE, WY) and December-November (NE, WY) in the 1895-2012 record. Eight other states ranked in the top ten driest category for the year-to-date (January-November) and another 19 were in the driest third of the historical record. A total of eight states were in the top ten driest category for the last twelve months (December-November) and another 21 were in the driest third of the historical record.
As noted earlier, 26 percent of the winter wheat crop was rated in poor to very poor condition, a jump of 11 percent compared to last month. November 2012 ranked as the 13th driest November in the 1895-2012 record averaged across the Winter Wheat agricultural belt, with April-November third driest and the year-to-date eighth driest. For the smaller Primary Hard Red Winter Wheat belt, November 2012 ranked 23rd driest, October-November tenth driest, April-November second driest, and the year-to-date third driest (behind January-November 1956 and January-November 1910). The aggregate PDSI for the Primary Hard Red Winter Wheat area reached the lowest value since the 1950s, while the PDSI for the broader Winter Wheat area was far less extreme since this larger area encompassed counties that have seen wetter conditions during 2012. While the PDSI for the Primary Hard Red Winter Wheat belt is the worst in over 50 years, the PDSI values for the droughts of the 1930s and 1950s were much more severe.
|Pacific Northwest||18th wettest|
|Great Basin||19th driest|
|Lower Colorado||18th driest|
|Rio Grande||12th driest|
|Texas Gulf Coast||49th driest|
|Lower Mississippi||47th driest|
|Upper Mississippi||8th driest|
|Great Lakes||41st driest|
|South Atlantic-Gulf||41st driest|
|New England||56th wettest|
Several river basins have experienced unusually dry conditions during 2012, with the Upper Colorado having the driest January-November in the 1895-2012 record. As noted by the Midwest Regional Climate Center, drought has contributed to low water issues from the Great Lakes to the Missouri and Mississippi rivers, with navigation on the Mississippi River becoming a growing concern as levels continued to drop through November. The Missouri River basin had the third driest January-November in 2012 (behind 1936 and 1934), the Upper Mississippi had the eighth driest January-November, and the Ohio River basin ranked 16th driest. For the Mississippi River and all of its tributaries north of Memphis, Tennessee, January-November 2012 ranked as the third driest January-November on record, again, behind 1936 and 1934. For comparison, January-November 1988 ranked fourth driest for this basin. The aggregate PDSI for the Missouri basin reached the lowest value since the 1950s, while the aggregate PDSI for the broader Mississippi and its tributaries was the lowest since only 1988.
Percent area of the Western U.S. in moderate to extreme drought, January 1900 to present, based on the Palmer Drought Index.
Like last month, beneficial precipitation fell in the northern parts of the West this month, while much of the rest of the West was drier than normal. Widespread above-normal temperatures caused the precipitation to fall more as rain than snow, resulting in a pattern of above-normal precipitation but below-normal snow water content at the high elevation (SNOTEL) stations in the north. Precipitation for high elevation and low elevation stations in the south, as well as snow water content for the high elevation locations (stations, basin averages), was generally below average. The Southwest was especially dry, both in the short term (October-November water year-to-date) and long term (last 12 months, December-November). Reservoir storage was below average, statewide, in most of the western states, but near to slightly above average in Montana and Washington where beneficial precipitation has fallen. According to the USDM, 73 percent of the West was experiencing moderate to exceptional drought at the end of November, a three percent decrease compared to October. The Palmer Drought Index percent area statistic was about 67 percent, an increase compared to last month.
Drought has affected the nation for most of 2012. The year began with 27.5 percent of the contiguous U.S. in moderate to extreme drought (based on the Palmer Drought Index) with separate drought epicenters in the Southwest to Southeast and parts of the Northwest and Upper Midwest. Drought expanded to 61.8 percent of the country by July and stretched from California to the Carolinas, and Texas to North Dakota. The percent area has stayed above 50 percent since the summer, ending at 59.5 percent in November. Although every drought is different, historical analogs to the current drought can be determined by comparing the spatial pattern and intensity of various climate indicators using statistical tools such as the correlation coefficient and mean absolute difference. In the table below, the conditions for January-November 2012 were averaged and compared to the January-November average conditions for all past years in the 1900-2012 national drought record. The top five years for each of four criteria are listed in the table, with the four criteria being:
|Rank*||Precipitation||PHDI||Percent Area**||Palmer Z Index|
|January-November 2012 Statewide Precipitation Ranks||January-November 2012||January-November 2012 (47.7%)||January-November 2012|
** (Average percent area in moderate to extreme drought for January-November of the given year.)
Two years are common in each criteria: 1955 and 1956. The average percent area in drought for these two years is almost identical to the average percent area in 2012, and the spatial pattern and intensity of the dryness (as measured by precipitation, PHDI, and Palmer Z Index) during these two years are a close match to that of 2012.
|Nov. 2012 PHDI||Nov. 2012 PHDI|
|Nov. 1955||June 1955|
|Nov. 1956||March 1957|
|Nov. 1933||May 1955|
|Nov. 1934||April 1955|
|Nov. 1939||June 1956|
The spatial pattern of drought (PHDI) for November 2012 was compared to the spatial pattern of drought (PHDI) for all other months in the historical record using the mean absolute difference statistical tool. In the table to the left, the top five Novembers having the closest match to November 2012 are listed in the first column, and the top five months of any of the twelve months (January-December) are listed in the second column. Again, the 1950s have the closest match, with November 1955 and November 1956 being the closest November analogs.
(January-November) Temperature (and Jan-Nov temperature rank, average percent area in drought)
Statewide Temperature Ranks
|1998 (3rd warmest, 8.9%)|
|2006 (4th warmest, 31.5%)|
|1921 (10th warmest, 12.8%)|
|1990 (5th warmest, 31.7%)|
|1953 (13th warmest, 32.6%)|
The dryness during the 2012 drought was accompanied by record heat. The spatial pattern of January-November average temperature for 2012 was compared to the spatial pattern of January-November average temperature for all other years in the historical record using the mean absolute difference statistical tool. The table to the right lists the top five years having the closest spatial pattern match to 2012. The year having the closest spatial pattern to January-November 2012 average temperature was 1998, which was the third warmest, nationally, for January-November (behind 2012 and 1934). Most of the country, except for the Southwest, had January-November 1998 average temperatures above to much above average. But 1998 was not a drought year on a national scale, with only an average 8.9 percent of the country experiencing moderate to extreme drought. The year with the next closest spatial pattern of January-November average temperatures was 2006, which was a drought year, nationally. Like 1998, most of the country in 2006 was warmer to much warmer than average, except for the Southeast. Next was 1921, which had widespread record heat in the midwestern and eastern states, but it was not a drought year, nationally. The fourth and fifth closest spatial matches, 1990 and 1953, had widespread drought. The warmth during those two years was as widespread as in 2012, although not quite as warm. It is interesting to note that the second warmest year nationally, 1934, was a drought year — in fact, it had the greatest average January-November percent area in moderate to extreme drought (65.7%) — with record heat in the western and central states. But most of the Northeast was colder than average, which is significantly different from the 2012 spatial pattern. The sixth through ninth warmest years nationally — 2005, 2000, 1999, and 2007, respectively — had widespread warmth, but the magnitude of the warmth, spatially, was not as severe as 2012 or the other years.
A more detailed drought discussion, provided by the NOAA Regional Climate Centers and others, can be found below.
West — Upper Colorado River Basin — Pacific Islands
As described by the High Plains Regional Climate Center, November 2012 was warm and dry across the majority of the High Plains region. Temperatures for the year continued to be among the warmest on record for locations in each state of the region. Precipitation totals for November were well below normal across the majority of the region. A large swath extending from Colorado and Kansas up into southern North Dakota received as little as 25 percent of normal precipitation. In addition, some locations did not receive any measurable precipitation. For instance, Goodland, Kansas received just a trace of precipitation this month and tied with 1959, 1939, and 1932 for its driest November on record (period of record 1895-2012). Goodland has been experiencing exceptional drought conditions (D4) since the end of July. A few areas of the region did get ample precipitation this month including northern and central North Dakota and north-central Wyoming. Although drought conditions were downgraded in parts of North Dakota where beneficial precipitation fell, the drought continued to have impacts elsewhere. For example, the Fern Lake Fire in Rocky Mountain National Park has burned for more than 6 weeks due to the combination of high winds and dry conditions. According to the Coloradoan, by the end of the month, more than 3,500 acres had burned since the fire started on October 9th. Even though the harvest season has come to a close, the dry weather continued to impact agriculture across the region as well. The major concerns were the condition of winter wheat and the replenishment of soil moisture. According to the United States Department of Agriculture (USDA), the winter wheat ratings across the U.S. were the worst since 1985. Winter wheat emergence was still just behind the 5-year average in Colorado, Nebraska, and South Dakota. The two hardest hit states were Nebraska and South Dakota, where the percentage of the winter wheat crop rated in good condition was only 14 and 2 percent, respectively. Neither state's crop was rated in excellent condition.
According to the USDM, drought conditions remained widespread over the past month. Overall, about 94 percent of the region was still in moderate (D1) to exceptional (D4) drought. This was down slightly from the end of last month when 98 percent of the region was in D1-D4. Although Nebraska had a very slight improvement over last month, it was still the hardest hit state in the region, with 77 percent in the D4 designation. Wyoming had a slight increase in D4 in the eastern portion of the state as well. Unfortunately, there were slight improvements in only limited parts of the region. North Dakota received beneficial precipitation which led to improvements in the north-central part of the state where much of the D1 was downgraded to abnormally dry conditions (D0). By the end of the month a couple of areas of western and central North Dakota were completely drought free.
As explained by the Southern Regional Climate Center, November was a very dry month for the entire Southern region, with a strong majority of stations averaging less than half of the monthly normal precipitation total. Collectively, it was the fourth driest November on record (1895-2012) for the region, which averaged only 0.93 inch (23.62 mm) of precipitation. November temperature averages in the Southern region were split longitudinally down the middle, with the western half of the region experiencing a warmer than average month, while the eastern half experienced a colder than average month. The dry conditions in the Southern region have not allowed for much improvement in drought status. The significant lack of November precipitation led to widespread extreme and exceptional drought in Oklahoma and northwestern Texas. In addition, an area of severe drought was now present in the western panhandle of Texas. A one category improvement did occur in western Tennessee and northeastern Arkansas. The area, which was classified as severe drought, was now classified as moderate drought.
In Texas, one of the biggest concerns this time of year is the winter wheat crop, and the lack of rain in the short term is taking its toll: between 40 and 45 percent of all Texas winter wheat is rated as poor or very poor and that number is increasing rapidly. Additionally, grasslands continue to dry out, making it difficult for ranchers to put their herds out. On the positive side, pecan farmers are expected to have above normal harvests this year: 67 million pounds compared to the 52 million pound average (Information provided by the Texas Office of State Climatology). Surface water declines have driven many meetings and symposiums in Texas, as water supplies continue to decline during a period of recharge or maintenance, such as in Corpus Christi, whose total water supply is at 40.6 percent. The city of El Paso currently is planning to drill nine new wells to meet water demands at a cost of $3.5 million. Other plans include a new pipeline between Stillhouse Hollow and Belton Lakes, estimated to cost approximately $500 million, diverting water from the Colorado River that would normally be reserved for rice farmers, and instituting water restrictions (Information provided by the Texas Office of State Climatology).
As summarized by the Midwest Regional Climate Center, November precipitation was below normal across the Midwest. Only small pockets of northern Minnesota and Upper Michigan reached normal for the month while all nine states had areas with less than 25 percent of normal. Most of the southeastern half of the region received less than half of their normal precipitation in November. Statewide totals in Ohio (4th), Indiana (4th), Kentucky (5th), and Michigan (7th) all ranked among the 10 driest Novembers since 1895. Fall precipitation totals ranged widely from southern Illinois and northern Ohio with over 150 percent of normal to most of Minnesota with less than 50 percent of normal for the three-month period. Year-to-date statewide precipitation totals ranged from 70 percent to 95 percent of normal. Iowa (8th) and Missouri (9th) ranked among the top 10 driest January to November periods since 1895. November temperatures in the Midwest were moderate with departures ranging from 2 degrees F (1 C) along the Iowa-Minnesota border to as much as 5 degrees F (3 C) below normal in parts of eastern Kentucky. Two warm spells during the month, the first coming on the 10th to the 12th and the second on the 22nd and 23rd, were responsible for most of the 600 plus daily temperature records. Just dozens of record lows were recorded. Fall (September to November) temperatures ranged from near normal to below normal across the region. Kentucky ranked as the 6th coolest fall dating back to 1895 with temperatures 2.2 degrees F (1.2 C) below normal. The cooler November and fall temperatures have cooled the year-to-date temperatures slightly but all nine states remain among the five warmest January to November periods dating back 118 years.
Drought remained a serious issue in the western half of the Midwest. Moderate drought extended across most of the western half of the region with areas of extreme drought in Minnesota and Iowa at the end of the month. A little over half (55 percent) of the Midwest was in drought and 9 percent was in extreme drought as November came to a close. The drought has contributed to low water issues from the Great Lakes to the Missouri and Mississippi rivers to lakes and farm ponds. Navigation on the Mississippi River is a growing concern as levels continued to drop through November. In Iowa near Des Moines, Saylorville Reservoir fell to within inches (cm) of its record low stage. Recharge of soil moisture also is a concern with the low precipitation totals.
As noted by the Southeast Regional Climate Center, November was an exceptionally dry month across the Southeast, as over 100 locations recorded one of their top five driest Novembers on record. Many of these locations recorded less than 2 inches (50.8 mm) of precipitation for the month, or less than 50 percent of normal. The driest locations were found across Florida, where monthly totals were less than 10 percent of normal in many places. Two locations in Florida (Moore Haven Lock and Inverness) did not record any measurable rainfall for the month. Monthly precipitation was also below normal across most of Puerto Rico and the U.S. Virgin Islands. Mean temperatures in November were below normal across most of the Southeast region, except across Puerto Rico and the U.S. Virgin Islands, where monthly temperatures were between 1 and 3 degrees F (0.5 and 1.6 degrees C) above normal. The warmest weather occurred during the first half of the month, with temperatures exceeding 80 degrees F (26.7 degrees C) across parts of Alabama, Georgia, and South Carolina from the 3rd to the 5th of the month. Temperatures reached 70 degrees F (21.1 degrees C) as far north as northern Virginia from the 11th to the 13th of the month. A cold spell occurred in between these periods over a large portion of region, with subfreezing temperatures recorded as far south as southern Alabama from the 6th to the 8th of the month. Over 200 daily low maximum temperature records were tied or broken across the region during this three-day period. The coldest weather of the month occurred over Thanksgiving weekend, with subfreezing temperatures recorded as far south as central Florida on the 25th of the month.
The lack of rainfall in November resulted in an expansion of drought conditions across the Southeast. By the end of the month, nearly 70 percent of the region was classified as abnormally dry or in drought according to the USDM, up from 40 percent at the end of October. The biggest changes were an expansion of moderate drought (D1) into central North Carolina and Virginia and the re-emergence of abnormally dry (D0) and moderate drought conditions across the Florida Panhandle. Areas of severe to exceptional drought (D2 to D4) across central Georgia expanded slightly across the state and into parts of eastern Alabama by the end of the month. The persistent dryness across Georgia continued to place stress on water supplies. Lake Lanier, which is the primary water supply for Atlanta, reached its lowest level since March 2009. The U.S. Army Corps of Engineers reported a drop of almost 4.5 feet (1.4 m) in November, which is the largest one month decline in more than five years. Releases from several reservoirs were modified in response to the dryness across North Carolina and mandatory water restrictions began to be implemented. Although the dry weather aided farmers in completing their harvests for the season, the lack of rainfall and cool temperatures affected the growth of cool season forages, and several small grain crops have been slow to germinate due to the lack of moisture. Some farmers were concerned that these crops may have difficulty surviving the winter if their growth remains stunted.
As explained by the Northeast Regional Climate Center, despite a mid-month warm up, the Northeast was cooler than normal for November 2012. Even though it was a wet start to the month for several states, November 2012 went into the record books as the 2nd driest since 1895. With an average of 1.04 inches (26.42 mm), the region received only 27 percent of normal precipitation. The record driest November was 1917 when the Northeast received only 0.88 inch (22.35 mm) of precipitation. All states were drier than average. Departures ranged from 16 percent of normal in Connecticut, their 2nd driest November, to 37 percent of normal in New Jersey, their 11th driest. The Northeast was slightly drier than average for autumn with 11.36 inches (288.54 mm) of precipitation (98 percent of normal). The region was split down the middle with half of the states drier and half the states wetter than normal. The USDM issued November 27 indicated abnormal dryness continued in upstate New York while a new area of abnormal dryness popped up near the Vermont-New Hampshire border and in central/southern West Virginia.
As summarized by the Western Regional Climate Center, while most of the conterminous United States remained drier than normal this month, several systems delivered above-average precipitation to portions of the Northwest. Over the last few days of November, a series of atmospheric rivers (narrow filaments of high water vapor transport with subtropical origins) brought heavy precipitation to northern and central California as well as parts of Oregon and Idaho. Throughout the West, average monthly temperatures remained above normal with many locations reporting a positive anomaly of at least 3.0 F (1.6 C).
Dry and warm conditions prevailed for much of the Southwest this month. Phoenix, Arizona saw its second warmest November on record at an average 68.4 F (20.2 C). Records at Phoenix began in 1895. In Colorado, Denver airport received only 1.7 in (43 mm) of snowfall this month, 20 percent of its normal 8.7 in (223 mm). In the Great Basin, Las Vegas, Nevada recorded its 3rd warmest November at 60.1 F (15.6 C) in a record dating back to 1937 and Ely, Nevada logged its 4th warmest November at 39.8 F (4.3 C), 6.1 F (3.4 C) above normal. Tonopah, Nevada tied 1995 for warmest autumn on record with a September-October-November average of 56.0 F (13.3 C). Records in Tonopah began in 1902. Throughout New Mexico, year-to-date average temperatures have been some of the highest on record. The January-November average temperature in Albuquerque was 62.0 F (16.7 C), the warmest such period in a record beginning in 1914. Roswell and Clayton also saw near-record year to date average temperatures. In addition, Clayton experienced its driest January-November period, receiving only 7.4 in (188 mm) so far this year and no precipitation this month. Normal January-November precipitation at Clayton is 15.43 in (392 mm) and records began in 1896.
The Northwest was dominated by wet and warm conditions. Between November 28-30, 3-day precipitation totals farther south at windward locations in California's Coast Range between Big Sur and the San Francisco Bay Area were over 6 in (152 mm). This event brought monthly totals to over 200 percent of normal at some locations. Farther inland, some of the highest 3-day totals in the southern Cascades and northern Sierra Nevada were over 8 in (203 mm). Several long-standing daily precipitation records were surpassed in northern California and Oregon. Seattle, Washington recorded its 4th wettest November on record with a total of 9.17 in (233 mm) and also its 9th warmest at an average 47.4 F (8.6 C) for the month. Several other western Washington locations also recorded top 10 warmest November temperatures. Above-normal monthly precipitation totals were also observed throughout Montana, providing relief from persistent dry conditions this year. For the year-to-date, 2012 was the warmest on record at Billings with an average 53.3 F (11.8 C) and also the driest at a total 6.86 in (174 mm). Records at Billings began in 1934. Miles City, Montana and Sheridan, Wyoming also experienced top 10 warmest and driest conditions year-to-date on record.
Dry conditions persisted in Hawaii. Following its driest October in a record beginning in 1950, Lihue, Kauai received only 0.58 in (14.7 mm) this month and tied 1968 for the driest November on record. Stations throughout the state recorded below normal precipitation, with percentages of normal as low as 9 percent in Honolulu. At the end of November, the USDM classified 54 percent of the state as experiencing some level of drought and the rest of the state abnormally dry.
Upper Colorado River Basin: As reported by the Colorado Climate Center, the December 4th NIDIS (National Integrated Drought Information System) assessment for the Upper Colorado River Basin (UCRB) indicated that, for the month of November, most of the UCRB received below average precipitation. The Wasatch and Uintah ranges in Utah received between 2 and 3 inches for the month, while much of the higher elevations of western Colorado and southwest Wyoming received between 0.5 and 1.5 inches. This is below normal for this time of year though and most of the basin saw between 10 percent and 50 percent of average precipitation. East of the basin, the rest of Colorado was very dry, with most of eastern Colorado receiving less than 0.5 inch for the month and between 0 percent and 25 percent of the normal moisture received for November. Accumulated snowpack was much less than average on the east side of the UCRB and slightly below average on the west side of the basin. Sub-basins in western Colorado and along the Colorado River valley in eastern Utah are all between 15 percent and 45 percent of average snowpack. Northeast Utah and southwest Wyoming basins are around 80 percent to 100 percent of average snowpack. For the month of November, all of the UCRB saw warmer than average temperatures. With warmer than average temperatures, there is a risk that the snowpack that has built up could possibly melt back down.
As of December 2nd, about 27 percent of the USGS streamgages in the UCRB recorded normal (25th to 75th percentile) to above normal 7-day average streamflows. About 45 percent percent of the gages in the basin are recording much below normal or low (i.e. lowest on record) streamflows, and only one gage recorded above normal flows. Much below normal flows are concentrated around the Colorado River headwaters in Colorado and along the lower San Juan River. The best conditions (near normal) are concentrated around the Upper Green River. Many of the gages are under frozen conditions and the number of reporting sites has decreased from 130 gages one month ago to 73 gages.
The VIC soil moisture model shows dry soils through most of Wyoming, with soil dryness below the 20th percentile in northeast Utah and northwest Colorado. When modeled soil moisture is combined with snowpack, northwest Colorado shows dryness below the 5th percentile, while northeast Utah shows dryness below the 10th percentile. Dry soils also show up in southeast Colorado with near normal soil moisture in north-central Colorado and in the San Luis Valley in southern Colorado. Last month, many of the major reservoirs in the UCRB saw smaller volume decreases than what is normal for this time of year, with Flaming Gorge staying near steady and Lake Granby seeing a slight increase. Dillon, Lake Powell, and McPhee saw larger decreases than what is normal for this time of year. Most of the reservoirs are between 60 percent and 80 percent of their early December averages and around 60 percent to 80 percent of last year's volumes.
Pacific Islands: According to reports from National Weather Service offices, the Pacific ENSO Applications Climate Center (PEAC), and partners, conditions varied across the Pacific Islands.
As noted by the National Weather Service office in Honolulu, in October and November, record low precipitation totals occurred at several locations in the state. Fortunately for Kauai, the first week of December produced 2 to 4 inches of rainfall which should help bring some drought relief but the rest of the state has thus far remained dry. The drought depiction for Kauai remained unchanged over the past month. This includes extreme drought, or D3 category conditions in the USDM map, over the southeastern portion of the island, and severe drought, or the D2 category, over south Kauai from Koloa to Waimea. It is too soon to tell how much improvement the recent rains will bring though it is estimated to be about one D-category worth of change. Extreme drought also remains in place over the southwest slopes of Lanai, western Molokai and southwest Maui from Kihei to Makena. Big Island extreme drought continues to cover most of the south Kohala district, the Pohakuloa region of the Hamakua district, the north-facing slopes of Hualalai in the north Kona district and the lower elevations of southwest Kau. Severe drought persists in Maui county on central and northeastern areas of Lanai, the lower leeward slopes of the west Maui mountains, and the western slopes of Haleakala from Haiku to Kaupo. On the Big Island, the main area of severe drought is in the Humuula Saddle. Moderate drought, or the D1 category, expanded into the south Hilo and Puna districts in recent weeks.
Some drought impacts impacts in Hawaii include the following:
KAUAI. NO SIGNIFICANT CHANGES SINCE THE NOVEMBER 8 UPDATE. PASTURES NEAR KOLOA AND MAHAULEPU IN THE SOUTHEASTERN PORTION OF THE ISLAND HAVE ALREADY BEEN DESTOCKED. CATTLE WEIGHTS HAVE ALSO BEEN SIGNIFICANTLY REDUCED DUE TO POOR PASTURE CONDITIONS. OAHU. NO SIGNIFICANT CHANGES SINCE THE NOVEMBER 8 UPDATE. PASTURES AND GENERAL VEGETATION REMAIN IN POOR CONDITION OVER THE LEEWARD WAIANAE RANGE. WEST OAHU RANCHERS HAVE DESTOCKED PASTURES DUE TO POOR GRAZING CONDITIONS. DESPITE THE RECORD DRY CONDITIONS...THE WATER SUPPLY IN THE WAIMANALO RESERVOIR REMAINS ABOVE PRE-DROUGHT LEVELS. A VOLUNTARY 10 PERCENT REDUCTION IN WATER USE REMAINS IN PLACE AS A PRECAUTION. MOLOKAI. NO SIGNIFICANT CHANGES SINCE THE NOVEMBER 8 UPDATE. PASTURES AND GENERAL VEGETATION CONDITIONS REMAIN VERY POOR WEST OF KAUNAKAKAI. THE WATER LEVEL IN THE KUALAPUU RESERVOIR REMAINS VERY LOW. THUS...THE STATE OF HAWAII DEPARTMENT OF AGRICULTURE HAS CONTINUED A MANDATORY 30 PERCENT REDUCTION IN IRRIGATION WATER CONSUMPTION. LANAI. NO SIGNIFICANT CHANGES SINCE THE NOVEMBER 8 UPDATE. THE MIDDLE AND LOWER ELEVATIONS OF THE ISLAND...ESPECIALLY ALONG THE NORTH-...EAST- AND SOUTH-FACING SLOPES...REMAIN VERY DRY AND PLANTS AND ANIMALS IN THESE AREAS HAVE BEEN STRUGGLING TO SURVIVE. EVEN DROUGHT-RESISTANT PLANTS AND TREES SUCH AS KIAWE WERE STRUGGLING UNDER THE DRY CONDITIONS. MOUFLON SHEEP...AXIS DEER AND GAME BIRD POPULATIONS HAVE BEEN REDUCED. MAUI. RECENT RAINFALL OVER SOUTH MAUI NEAR ULUPALAKUA AND KEPUNI HELPED IMPROVE DROUGHT CONDITIONS BUT ONLY IN SMALL AREAS DUE TO THE HIGHLY LOCALIZED NATURE OF THE SHOWERS. THERE HAVE BEEN NO ADDITIONAL IMPACTS RECENTLY BECAUSE THE PASTURES IN THE WORST DROUGHT AREAS HAVE ALREADY BEEN DESTOCKED. PRODUCTION AT THE OLINDA WATER TREATMENT FACILITY REMAINED BELOW NORMAL DUE TO A LOW WATER SUPPLY. THE MAUI COUNTY DEPARTMENT OF WATER SUPPLY CONTINUED ITS LONG STANDING REQUEST FOR A 5 PERCENT REDUCTION IN WATER USE FOR UPCOUNTRY RESIDENTS. THE REQUEST FOR A 10 PERCENT REDUCTION IN WATER USE BY CENTRAL AND SOUTH MAUI RESIDENTS ALSO REMAINED IN EFFECT. BIG ISLAND. BELOW NORMAL RAINFALL HAS FORCED SOME FARMERS TO HAUL WATER IN THE NORMALLY WET PUNA DISTRICT. ALTHOUGH RAINFALL IS ALSO BELOW NORMAL ALONG THE LOWER NORTHEASTERN SLOPES...RECENT REPORTS INDICATE THAT THERE APPEARS TO BE SUFFICIENT RAINFALL TO MEET NEEDS AND THAT VEGETATION IN MOST AREAS IS STILL GREEN. CONDITIONS REMAIN VERY POOR FOR PASTURES AND NON-IRRIGATED AGRICULTURE IN MOST OF THE KAU AND LEEWARD KOHALA SECTIONS OF THE ISLAND.
On other Pacific Islands (maps — Micronesia, Marshall Islands, basinwide), November was drier than normal for Guam and Koror, and much drier than normal for Kwajalein and Saipan. November rainfall amounts at Guam, Kwajalein, and Saipan were below six inches. Kwajalein has been well below normal for the last three months and Koror has been below normal for the last two months. Total rainfall for the last 12 months (December 2011-November 2012) was above normal for all stations except Koror, Kwajalein, Majuro, and Pohnpei.
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.):
|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.|
|Contiguous United States|
- Palmer Drought Indices
- Standardized Precipitation Index
- long-term (36 to 60 month) percent of normal precipitation maps
- airport station percent of normal precipitation maps
- statewide precipitation rank maps
- Cooperative station percent of normal precipitation maps
- percent of average maps for the SNOTEL stations in the western mountains provided by the Western Regional Climate Center
- satellite-based observations of vegetative health
- National Weather Service model calculations of soil moisture, runoff, and evaporation
- National Weather Service model calculations of soil moisture using the Leaky Bucket Model
- Midwest Regional Climate Center model calculations of soil moisture
- topsoil moisture conditions observed by the USDA and mapped by the Climate Prediction Center
- pasture and range land conditions observed by the USDA and mapped by the Climate Prediction Center
- streamflow maps maintained by the USGS
Contacts & Questions