Drought - November 2008
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|Contents Of This Report:||
|The weather pattern during November generally consisted of a high pressure ridge in the upper levels of the atmosphere over the western U.S. and a low pressure trough over the East. This upper-air pattern was associated with warmer-than-normal weather in the West and cooler-than-normal temperatures in the East and provided the guiding currents for numerous Pacific weather fronts. Cold, dry air was pulled in behind the fronts as they moved across the central and eastern U.S. With this pattern, Gulf of Mexico moisture was cut off from most of the country, resulting in dry conditions from the southern Plains to the interior Northeast. As a result, there was little change in the drought pattern across the contiguous U.S., with the exception of some intensification in the core drought areas of south central Texas and the Southeast (December 2 USDM versus October 28 USDM).|
|November was drier than
normal across the southern and eastern portions of Puerto
Rico, with year-to-date
precipitation below normal in the southeastern portion, but no
drought was indicated for the island on the early December
USDM. Dry weather dominated the Hawaiian Islands during
November. The pattern of dry weather extended well into the
past year as seen on maps for the last
three months and
last 12 months. Weather conditions were drier than normal
across the southern portions of Alaska during November
and the interior stations during the last
Early December snowpack was generally below normal over
interior southeast Alaska.
By the end of November, the core drought areas included:
|A band of above-normal precipitation improved drought conditions from southern Georgia, across the eastern Carolinas, into eastern Virginia this month. But conditions remained drier than normal from the southern Appalachians into the Ohio and mid-Mississippi valleys. Persistent dryness in this area resulted in the seventh driest August-November for Kentucky and eleventh driest June-November for Kentucky and Tennessee. Drought was manifested in low streamflow, groundwater, and modeled soil moisture levels (CPC, LDAS root zone, LDAS total column). According to USDM statistics, about 29% of the Southeast was in moderate to exceptional drought.|
|The last four months have been persistently dry in the northwestern Great Lakes/Upper Mississippi Valley. Wisconsin had their ninth driest August-November in the 1895-2008 record. The dryness was apparent in low streamflow, modeled soil moisture levels (CPC, LDAS root zone, LDAS total column), and vegetative response indicators. According to USDM statistics, about 19% of the Midwest (which includes the northwestern Great Lakes down to the Ohio Valley) was in moderate to exceptional drought.|
|Persistent dryness has afflicted parts of Texas for the past several months, especially south central Texas (climate division 7). After unusually wet conditions for the first part of 2007, Texas climate division 7 had its sixth driest year-to-date (January-November) in 2008 and the third driest fall (September-November 2008). Drought was evident in low streamflow, modeled soil moisture levels (CPC, LDAS root zone, LDAS total column), and vegetative response indicators. National Weather Service assessments indicated that some weather stations in south central Texas had their third driest year-to-date behind the record drought years of 1954 and 1956. Calculated year-to-date inflows (from the Llano, Pedernales, San Saba, and Upper Colorado rivers) into the Highland Lakes in this region were the lowest amount recorded since 1942. To date, this year's low numbers were lower than the previous lowest inflows recorded back in 2006. According to USDM statistics, about 19% of the U.S. South region was in moderate to exceptional drought.||
|October marks the beginning of the hydrological year (October through the following September). The 2008-2009 hydrologic year (October-November so far) has started out on a dry note for much of the West, with below-average precipitation in many areas and widespread below-average snowpack (November 30 basin percent of normal, December 9 station percentiles, December 10 basin percent of normal). Several states have had the 30th driest, or drier, fall on record this year. If spring and summer dryness is considered, the precipitation rankings drop into the top ten driest for several states: March-November 2008 ranked as the third driest on record for Nevada and Utah, and California had the driest February-November on record. According to news reports, the San Diego City Council approved water conservation rules in November in response to continued dry conditions. The November snowfall of 2.5 inches at Flagstaff, Arizona was well below the monthly norm of 12.2 inches. In Missoula, Montana, there was not any measurable snowfall in October and November for only the second time in the last half-century (the other year this happened was 2002). Dry conditions were reflected in low streamflow (both modeled and observed), modeled soil moisture levels (CPC, LDAS root zone, LDAS total column), and vegetative response indicators.|
|Overall drought conditions in the western U.S. (Rockies westward) increased from September to October but changed only slightly from October to November. According to the Palmer Drought Index, about 54% of the region was in moderate to extreme drought at the end of the month, while the USDM had about 30% in moderate to exceptional drought and about 67% experiencing abnormally dry to exceptional drought conditions. The differences between the Palmer and USDM statistics are due to the extreme seasonality of precipitation in the West and other hydrologic components in the drought calculations.|
|A more detailed drought discussion, provided by the NOAA Regional Climate Centers and others, can be found below.|
According to the Southeast Regional Climate Center, there was much variability in the monthly precipitation totals across the region. Florida, with the exception of its western panhandle, recorded much below normal precipitation totals. In fact, portions of southern Florida received less than 25% of the normal precipitation for the month. Precipitation totals for the month were below normal across much of Alabama, western Virginia as well as drought stricken portions of northern Georgia, northwest South Carolina, and western North Carolina. Most of Puerto Rico recorded precipitation totals that were below normal for the month of November. In contrast, a region of above normal precipitation stretched from portions of southern Georgia northeastward across central South Carolina, eastern North Carolina, and southeast Virginia. Several locations within this region recorded monthly totals that exceeded 200% of normal.
There was very little change in the drought lingering across portions of the region. Exceptional drought (D4) continued to plague northwestern South Carolina and expanded into extreme northeast Georgia and extreme western North Carolina. Moderate drought conditions continued to affect central Georgia and extreme northeast Alabama as well as southwestern Virginia and northeastern North Carolina.
As noted by the Southern Regional Climate Center, precipitation was quite scarce during the month of November for most of the Southern Region. Only small pockets of above normal monthly precipitation values were observed, specifically in north central Louisiana, eastern Texas, and southeastern Mississippi. Western and central Texas observed the largest precipitation deficits for the month, with many stations reporting 5% or less of normal. Similar deficit values were also observed in western and southern Oklahoma. In Arkansas, most stations in the southernmost counties did receive as much as 50-70% of normal. However, elsewhere the bulk of the stations received only 25-50% of normal precipitation for the month. Similar values were also observed in southeastern Louisiana, western Tennessee, and northern Mississippi.
Drought conditions in the Southern Region changed slightly over the past month. Due to extremely dry conditions in central and southern Texas, the USDM recognized a small area of exceptional drought (D4) in the Austin, TX area. This is the highest level of drought that is recognized by the USDM. The area of D4 drought extended from just north of Austin, to just south of New Braunfels. It also extended east to an area just west of Bastrop, and west to an area just west of Johnson City and Blanco. Areas in Texas of lesser drought that surround the bullet of D4 changed little over the past month, indicating persistently dry conditions. Similarly, drought also continued to persist in eastern Tennessee. In Tennessee, there was a slight westward migration of extreme and moderate drought. Conditions in the western half of the state also deteriorated slightly from near-normal to abnormally dry.
According to media reports (Knoxville News Sentinel, 11/07), in early November, the USDA designated 39 counties in Tennessee as primary natural disaster areas for agriculture. Governor Phil Bredesen said: "Farmers in these areas have suffered crop losses for corn and soybeans ranging from 30 to 65%. Livestock producers are reporting low hay stocks going into the winter months due to parched pastures and significantly reduced hay yields this summer and fall."
As explained by the Midwest Regional Climate Center, a persistent band of northwesterly winds aloft over the Midwest kept much of the region dry during November. The heaviest precipitation was in the western portions of the region on the southern edge of the northwesterlies, and in the lake-effect snow areas. Cold frontal passages, followed by westerly and northwesterly surface winds bringing cold air over the relatively warm lake waters, produced frequent days with lake-effect snow. Precipitation for the month of November was above normal in northwestern Minnesota, central Iowa, and downwind of the Great Lakes in Michigan and northeastern Ohio. Elsewhere, precipitation was only 50 to 75% of normal, with an area from southern Missouri through central Illinois with less than 50% of normal precipitation.
Areas of drought in the upper Midwest and in Kentucky expanded during November. This marks the fourth consecutive month that most of Kentucky has been dry, although some parts of northern Kentucky have had below-normal rainfall since the spring. Extreme drought conditions continued over eastern Kentucky where November precipitation was 70% of normal. Eastern Kentucky communities such as Jackson and London were short roughly a foot of rain for the year-to-date, which makes 2008 potentially one of the driest years on record for this region. Drought conditions eased somewhat towards western Kentucky but many areas remained in moderate to severe drought.
As noted by the High Plains Regional Climate Center, areas that received above normal precipitation during November include North Dakota, the western half of South Dakota, and northwest Nebraska. Many locations in the drought area of western North Dakota received over 200% of normal precipitation. Dry locations included Wyoming, Colorado, Nebraska, Kansas and north central South Dakota, with less than 50% of normal precipitation. The Perry Stokes Airport in Trinidad, CO did not record any measurable precipitation and tied the record for its driest November (last set in 1965).
In general, thanks to abundant precipitation, drought conditions improved in western North Dakota as severe drought (D2) was downgraded to moderate drought (D1) and conditions were forecast to continue to improve. Moderate drought conditions persisted in southwest Wyoming and southeast Colorado. While conditions were expected to improve in southeast Colorado, a new area of abnormally dry conditions (D0) developed in southwest Colorado.
North Dakota: By the end of the month, drought conditions improved significantly, alleviating severe drought that had lingered around southwestern portions of the state since the spring of 2008. Based on the USDM assessment, 17% of the state was under at least moderate drought. Counties mostly affected by the moderate drought were McKenzie, Golden Valley, Billings, Dunn, Stark, Morton, Grant, Hettinger, Slope, Bowman and Adams counties. Some of the impacts of the long-term drought since last fall are yield loss in lentil and pea production.
As summarized by the Western Regional Climate Center, precipitation was a mixed bag, with extreme northwest Washington, southern California and portions of the northern Rockies recording wetter than normal conditions. With the warm conditions, however, mountain snowpack remained well below the December 1st average. The Lake Tahoe drainage was at 3% of normal snowpack on December 1st and fell to just 2 inches (5 cm) above its natural rim. An unusually wet system crossed southern California on the 26th, producing locally heavy rain and flooding in some areas. It was the wettest November on record in Yuma, AZ, with 2.22 inches, all of it falling on the 26th, and precipitation percentages of 500-1100% of monthly average noted in many places.
Alaska: According to National Weather Service reports (from information compiled and provided by Audrey Rubel at NOAA NWS Alaska Region Headquarters), temperature and precipitation anomalies varied across the state. Snowpack over south central Alaska was slightly above normal while Anchorage received 21.7 inches of snowfall (190% of normal). Snow totals for reporting stations in southeast Alaska were well below normal. However, total precipitation was a mixed bag. Northern and central outer coast locations recorded below normal precipitation for the month while central inner channel and southern locations posted above normal total precipitation. The biggest departures from normal, were northern locations (below normal) and southern locations (above normal). Precipitation was fairly uniformly spread throughout the month with the exception of the central inner channels which experienced two 4-day stretches or dry or nearly dry days during the second and third weeks of the month. These two 4-day periods coincided with the coldest daily highs and lows during the month.
In Fairbanks, snow during the month was frequent but very light. The total snowfall of 6.5 inches was less than half of normal. The snow melted down to just 0.28 inch of precipitation, which is barely a third of normal. Snowfall for the season through the end of November (July-November) totaled 20.5 inches, which is more than 8 inches below normal.
November preciptiation (0.53 inch) and snowfall (7.3 inches) were both below average for Kotzebue. In Nome, precipitation for the month was all snow with 9.1 inches of snowfall recorded. This was equivalent to 0.35 inch of liquid precipitation, which is 0.93 inch below normal for November. The total amount of precipitation for the year (January-November) is 9.92 inches, making 2008 the eighth driest year on record so far.
November was warm and wet in Barrow. The average temperature of 4.0 degrees F was 4.9 degrees above normal. Total precipitation was 0.32 inch which is twice the November normal. Total snowfall was 12.3 inches, which is almost four times the average amount of 3.2 inches. November 2008 ranks as the fifth snowiest November on record. The top five snowiest Novembers are: 1925 (19.0 inches), 2001 (17.5 inches), 2007 (14.4 inches), 1965 (12.8 inches), and 2008 (12.3 inches). For the period October 1-November 30, the snowfall total was 35.5 inches, which ranks as the second snowiest October-November on record, with only 1925 having more snow (40.2 inches).
Lake and river ice thickness across Alaska was 81-93% of normal for the first of December.
As noted by the Northeast Regional Climate Center, above normal precipitation totals were confined to Maine, eastern New Hampshire, coastal Massachusetts, Rhode Island, southern New Jersey, Delaware, the Eastern Shore of Maryland and a few areas downwind of Lakes Erie and Ontario. State precipitation departures ranged from 70% of normal in Pennsylvania to 155% of normal in Maine. The Northeast, as a whole, averaged 99% of the long-term mean.
According to the December 2, 2008 USDM, most of western Pennsylvania was abnormally dry, as was the northern half of West Virginia, the western panhandle of Maryland and southwestern Maryland. The southern half of West Virginia was in moderate drought and the extreme southern tip of the state was still in severe drought. The Pennsylvania Department of Environmental Protection issued a drought watch for 29 counties in western and central portions of the state. The state requested that water users in the affected areas reduce their non-essential water use by 5%.
For autumn (September-November), precipitation totals averaged close to normal, 103%, but there was a wider range throughout the Northeast. The New England states of Maine, New Hampshire, Massachusetts, Rhode Island and Connecticut had totals ranging from 122% (CT) to 139% (ME) of normal. West Virginia and Pennsylvania's seasonal totals were 66% and 87% of normal, respectively. The remaining states had totals that were near normal.
|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.):