DATASTREME DAILY SUMMARY

Monday, 26 November 2001


00Z Weather Systems


WEATHER OVER THE WEEKEND -- A distinct change from relatively quite weather to a more stormy weather pattern occurred over the four-day Thanksgiving weekend. Much of the nation experienced a relatively warm Thanksgiving Day with high temperatures at or above the average highs for this time of year. Residents of the mid- and upper-Mississippi Valley had highs that were on the order of 20 degrees above average. High pressure over the Middle Atlantic States permitted the Macy's Thanksgiving Day Parade to proceed under relatively pleasant conditions in New York City. However the western third of the country had clouds and wide-spread precipitation on Thursday. A weak trough of low pressure was found along the east slopes of the Rockies and a major storm system had just reached the Pacific Northwest. Low elevation rain fell across portions of the Pacific Northwest, California and the Great Basin. Salt Lake City received 1.27 inches of precipitation on Thursday, which set both daily and monthly precipitation records; essentially all of the precipitation fell as rain, with only a trace of snow. As much as 2 inches of rain fell by early Thursday morning along the Washington and Oregon coasts, while upward of 10 inches of snow was reported in the Sierras of California. Several inches of snow fell in the Rockies, and the higher terrain of the Utah and Nevada. The snow was good news in Utah, where as much as 3 feet of snow have fallen during the last week on some of the ski resorts where some of the upcoming Olympic venues will be held. With the snow base, many of these ski resorts were planning to open on the Thanksgiving weekend. The storm produced heavy surf along the California and Oregon coasts. Non-thunderstorm winds had speeds that reached 114 mph in Indian Wells Canyon near the southern end of the Sierras in southern California. These winds also took the roofs off some buildings in Ridgecrest on Thursday morning. Some rain and freezing rain were also found across portions of North Dakota.

The cold front associated with the storm system that reached the Pacific Northwest early Thursday moved southeastward across the Rockies on Thanksgiving, and by early Friday morning, a low pressure center with a central pressure of approximately 989 mb had formed along the front on the lee slopes of the Rockies in the Texas and Oklahoma Panhandles. A warm front stretched southeastward from the surface low pressure center to western portions of the Florida Panhandle, while a cold front trailed southwestward across New Mexico, Arizona and southern California. A large shield of precipitation spread out across the Plains to the north of the low pressure center, while another area of precipitation developed along the Gulf Coast in association with the warm front. Rain was falling across the western high Plains, while snow was reported in the mountains of New Mexico, Colorado, Wyoming and Idaho. As much as 3 to 4 inches of new snow were reported in the mountains of Colorado.

While the eastern two-thirds of the country remained unseasonably warm on Friday, cold air was drawn into the western flank of the storm system. High temperatures across much of Colorado, northern New Mexico and portions of Utah were nearly 10 degrees below the long-term average highs. To the east of the storm, much of the Plains, the Mississippi Valley and Great Lakes had highs that were as much as 20 degrees above average. Oshkosh, WI reached a record high temperature of 58 degrees on Friday, while Marquette, MI reported both a record high temperature of 54 degrees and a record high minimum temperature of 37 degrees. Several other record high low temperatures were either tied or set on Friday to include the Kansas cities of Salina (47 degrees) and Russell (44 degrees).

By Friday evening the storm had moved toward the northeast into south central Nebraska. The cold front had swept eastward across the Texas Panhandle. Record rainfall was reported on Friday at Sioux Falls, SD (1.92 inches). In addition to setting a daily record, a November monthly record was set. On Saturday morning the storm had begun to occlude, as the low pressure center located over southeastern Nebraska had deepened slightly and an occluded front curved to the southeast across the Mississippi Valley to a point of occlusion. A cold front extended southward from the occluded front through the lower Mississippi Valley. This storm system drifted slowly toward the northeast, with the low pressure centered over western Iowa as of Saturday night, as the occluded front moved toward the northeast across the mid-Mississippi Valley. On Sunday morning the low had reached northwest Wisconsin and the occluded front had reached the Upper Peninsula. The cold front had moved eastward across the Ohio and Tennessee Valleys.

As the storm became organized in the Panhandle, a strong flow of warm moist Gulf air from the south provided some of the necessary ingredients for the development of thunderstorms in the warm sector of the storm. This warm sector was found between the warm front and cold front. Some of the thunderstorms turned severe from early Friday evening through early Saturday morning, spawning tornadoes, generating damaging winds and large hail. As many as 12 people were killed as a result of the thunderstorms, with several dozen injured. At least 13 tornadoes were reported to the Storm Prediction Center from various locations in Louisiana, Arkansas, Missouri and Mississippi from Friday into early Saturday. Tornadoes apparently killed three people in Arkansas and two people in northwest Mississippi. One injury was possibly caused by a tornado in Mississippi. Mobile homes, houses, farm buildings and trees were either destroyed or badly damaged by these tornadoes. A tornado that produced a 0.25-mile wide path of destruction along a four-mile track in southwestern Missouri near the Lake of the Ozarks was estimated to have been a strong F-2 tornado on the Fujita Tornado Intensity Scale. Straight-line thunderstorm winds, with some gusts measured to 70 mph, also caused damage across portions of eastern Oklahoma, southern Missouri, many locations in Arkansas and across west central Mississippi. Three injuries resulted from the thunderstorm winds that damaged or destroyed homes in Arkansas early Saturday morning. Large hail with diameters reaching as large as 2.75 inches fell across eastern Oklahoma, southern Missouri, Arkansas and west central Mississippi. The severe weather continued through Saturday and into early Sunday morning, with tornadoes, strong thunderstorm winds and large hail being reported across western Kentucky, western Tennessee, Mississippi, Alabama and Georgia. Five tornadoes were reported across east central Mississippi and central Alabama. Some damage was sustained by the tornadoes. Strong thunderstorm winds caused four injuries in western Kentucky. Thunderstorm winds also caused damage across Indiana. Thunderstorm winds caused some damage to trees in Middle Tennessee on Sunday, while thunderstorms dropped large hail across Montgomery County, MD, a suburb of Washington, DC, on Sunday afternoon.

High temperatures on Saturday were above average across the eastern half of the country, but slightly below average temperatures were found across the Rockies and the Intermountain West. Residents of the Great Lakes States experienced the largest temperature anomalies (or departures from average), with highs that were on the order of 20 degrees above the average highs. Record high temperatures were set at Montgomery, AL (81 degrees), Columbus, GA (80 degrees), Knoxville, TN (72 degrees), Parkersburg, WV (73 degrees) and Jackson, KY (70 degrees). Record highs were also reached in Ohio at Zanesville (69 degrees), Findlay (66 degrees), Toledo (66 degrees), Youngstown (65 degrees), and Mansfield (63 degrees) and in Lower Michigan at Detroit-Metro (62 degrees) and Muskegon (57 degrees).

Record precipitation totals were reported on Saturday in Illinois at Springfield (1.67 inches), Peoria (1.15 inches) and Moline (0.94 inches); in Minnesota at Duluth (1.30 inches), St. Cloud (1.07 inches), Minneapolis/St. Paul (1.06 inches) and Rochester (0.74 inches); in Wisconsin at Eau Claire (0.84 inches) and La Crosse (0.65 inches); and in Iowa at Sioux City (1.74 inches) and Dubuque (0.62 inches).

The Northeast and Southern Plains experienced an unseasonably warm Sunday as high temperatures ranged from 20 to 25 degrees above the long term average highs over the Northeast Plains and about 15 degrees above average over Oklahoma and north Texas. Record high temperatures were set on Sunday in New York State at Massena, NY (67 degrees), Syracuse (67 degrees), and Albany (64 degrees); in Vermont at Burlington (67 degrees) and Montpelier (55 degrees); in Connecticut at Bridgeport (63 degrees); in Michigan at Detroit (63 degrees) and in Ohio at Findlay (64 degrees). Interestingly, some of these records were broken during the morning hours as the result of warm-air advection on strong southerly winds to the east of the storm system. To the west, highs across the Great Basin and the Four Corners Region of the Southwest were on the order of 10 degrees below the long term average highs for the date.

The next storm system to affect the holiday weekend weather reached the northern California coast on Saturday morning. The storm system consisted of a low pressure center that moved on shore near Cape Mendocino, with a warm front that stretched to the southeast, while a cold front trailed southward. By Saturday night the low pressure center had moved inland to southern Oregon, with the cold front stretching southward across Nevada and southern California.

The cold front with the new system produced record rainfall across California on Saturday. In northern and central California records were set at Redding (1.74 inches) and Stockton (0.71 inches). In Southern California, between 0.5 and 2 inches of rain fell, with records set at Torrance (0.80 inches) and Cuyama (0.50 inches). Some thunderstorms produced pea-sized hail in San Francisco and vicinity.

Strong winds accompanied the cold frontal passage. Winds reached 50 to 60 mph on Saturday in central California near Monterey. The winds caused minor damage in San Francisco, Oakland and other locations in the Bay Area. One location on the eastern slopes of the San Bernardino Mountains reported wind gusts to 92 mph on Saturday afternoon, while other locations in the Southern California mountains had gusts exceeding 55 mph. A record low temperature was set on Sunday morning at Simi Valley, CA (37 degrees).

The low pressure center was located in the Chimney of northern Idaho on Sunday morning, with the accompanying occluded front stretching southward across the Great Basin into Utah, where it became a cold front that curved southwestward across Arizona into Baja California. Heavy snow fell across the central and southern Sierras, with 18 inches of snow reported during the 24 hours ending on Sunday morning at Donner Summit and the ski resorts at Squaw Valley and Mammoth in California. By Sunday morning between 4 to 12 inches of snow had fallen in the mountains of Idaho. At least 4 inches of new snow had fallen across portions of northern Nevada. With cold northwesterly winds crossing Great Salt Lake, as much as 8 inches of lake-effect snow were reported to the southeast of the lake in the southern suburbs of Salt Lake City. This lake-effect snow was also enhanced by orographic effects.

WEATHER FOR THE START OF THE NEW WEEK -- The following highlights of the national weather have been extracted from the surface weather map for late Sunday night.

Rain continued across the Middle Atlantic and the New England States ahead of the cold front associated with the first major storm system that moved across the country over the weekend. The cold front extended southward along the Eastern Seaboard from an occluding low pressure system that was located over Quebec. Southern portions of the cold front had become essentially stationary across the Southeast, where little precipitation was detected.

Northern portions of the cold front are expected to continue to move eastward, reaching the coast by midmorning on Monday. Between 0.1 and 0.5 inches of rain are anticipated across New England during the 24 hours ending on Monday evening. Southern sections of the front are forecast to begin moving northward as a warm front. Several hundredths of an inch could fall across portions of the Southeast. With relatively clear skies across the Southeast, fog was beginning to develop across the Southeast on Sunday night, necessitating the posting of dense fog advisories along the Gulf Coast in southern Alabama, Georgia and the Florida Panhandle. Dense fog advisories were also in effect for southern Pennsylvania, Maryland and northern Virginia, to include the Washington, DC metropolitan area.

A major storm system has begun to develop on the lee slopes of the Rockies over southeast Colorado. While rain was reported across the Oklahoma Panhandle, central Kansas and eastern Nebraska, snow was falling across Wyoming, Colorado, western Nebraska and South Dakota. Between 1 to 3 inches of snow had fallen by late Sunday night across the Black Hills of South Dakota. A cold front located across the northern Plains was supplying cold air to the system. Snow was also falling along the cold front across northern Iowa and southern Minnesota. Wind advisories were in effect across western Kansas, eastern Colorado and western Nebraska through Monday as northwest winds are expected to reach 45 mph with gusts to over 50 mph.

The storm system in Colorado is expected to move northeastward on Monday, reaching north central Kansas by daybreak and west central Iowa by evening. The cold front over the northern Plains is expected to push southward and then dissipate during the day. As cold air behind this cold front moves southward and is entrained into the storm system, widespread snow is expected to fall to the north of the storm track, in band across the Plains and into the Upper Mississippi Valley. Upward of 1.4 inches of liquid water equivalent are expected to fall in the 24 hours ending on Monday evening across portions of Nebraska, South Dakota and southern Minnesota. A variety of winter storm warnings, snow and winter weather advisories were posted though Monday to cover an area to the north of the storm track extending from the western slopes of the Rockies in Colorado northeastward across Nebraska and South Dakota to the southwest Minnesota. Some locations in the Colorado mountains could receive a foot of new snow by daybreak on Monday. Northwesterly winds with gusts to 60 mph could reduce visibility in blowing snow and cause wind-chill equivalent temperatures to fall to 30 degrees below zero. Between 5 to 18 inches of snow could fall across portions of central South Dakota. Some locations, especially close to the storm track could receive rain turning to ice pellets (sleet) and then to snow. Farther to the east, winter storm watches were posted for Monday night into Tuesday morning for northern Minnesota, northern Wisconsin and Michigan's Upper Peninsula. Northeast winds could produce as much as 10 inches of lake-enhanced snow across portions of the Upper Peninsula.

To the south of the low, the cold front is expected to move eastward across the southern Plains. Thunderstorms are expected to develop in the warm sector to the east of the cold front. As a result, the lower Mississippi Valley and the western Gulf Coast could experience a slight risk of severe thunderstorms on Monday.

Winter weather advisories were in effect for portions of Idaho and Montana, while a winter storm warning was posted for the Rocky Mountain Front in northwest Montana, where as much as 16 inches of snow could fall in the mountains by Monday morning.

UPPER AIR -- The 500 and 300 mb charts for 00Z Monday reveal that the surface low pressure system over southeastern Colorado is a feature that extends upward through the troposphere. Both upper air charts have a height trough over the central Rocky Mountains that reflect the cold air found to the west and north of the surface low pressure feature. A height ridge is found to the east of this system across the Plains and the Mississippi Valley associated with warmer air. A tight height contour packing and strong winds are found around the southern periphery of the height trough. The fanning of the height contours to the southeast of the trough would suggest upper tropospheric divergence, which would support and guide the strong surface low pressure system as it moves to the northeast.

TEMPERATURE EXTREMES ACROSS THE LOWER 48 -- On Sunday, the lowest temperature reported in the continental U.S. was 12 degrees at Fraser, CO and Bridgeport, CA, while Sunday's highest temperature was 85 degrees at Tampa and Brooksville, FL.

ALASKAN WEATHER -- Most of mainland Alaska was dominated by a cold arctic air mass associated with a ridge of high pressure that extended westward from northern Canada. Relatively clear skies were found across interior Alaska. Many locations across the interior reported early afternoon temperatures that were near zero degrees, with the lowest being at Fort Yukon with 24 degrees below zero. A stationary front that represented the western and southern extremities of the arctic air extended from the Lisburne Peninsula southward across the Seward Peninsula and western Alaska to Bristol Bay before turning eastward to cross the northern Alaska Peninsula and paralleling the north Gulf Coast to southeast Alaska, with a final southeastward extension along the Panhandle and into western British Columbia. A strong storm system located over the west central Bering Sea produced gusty winds and cloudy skies across the Aleutians, the Bering Sea and the Alaska Peninsula. St. Paul Island reported wind gusts to 59 mph on Sunday morning, Gambell on St. Lawrence Island had gusts to 46 mph, while Dutch Harbor experienced 51 mph from the southeast. Dutch Harbor also reported 0.85 inches of precipitation by early afternoon and was one of only a dozen stations in the state that had measurable precipitation. With strong southerly winds across the Bering Sea, the Aleutian Peninsula and the Aleutians experienced relatively mild conditions.

The lowest overnight temperature in Alaska as of Sunday was 27 degrees below zero at Arctic Village and Fort Yukon and the midafternoon highest statewide temperature was 45 degrees at Port Heiden.

HAWAIIAN WEATHER -- A storm system that developed along a cold front to the northwest of Kauai has produced a potentially heavy rainfall event for Hawaii and winds became southerly across most of the islands. These southerly winds have spread tropical moisture northward across the islands. A region of heavy rainshowers and isolated thunderstorms were approaching the Big Island. The low, which could become what is popularly called a Kona low, is expected to affect the state through Wednesday. Because of the approaching heavy rains, a flood watch was in effect for the Big Island. A small craft advisory was posted for the state waters.

Ocean swell is expected to increase the surf along the northwest facing shores of the islands overnight. With surf expected to reach 10 to 15 feet by Monday morning, a high surf advisory was posted for the northwest shores that was to remain in effect through Monday.

EYE ON THE TROPICS -- While the hurricane season is winding down in the North Atlantic, the second subtropical storm of the season was located approximately 560 miles south-southeast of Bermuda on Sunday night. This storm was moving toward the southwest at 9 mph. Maximum sustained winds were estimated to be near 70 mph, and central pressure was estimated to be 979 mb. This storm is expected to drift slowly westward, while intensifying. Ocean swells generated by this subtropical storm could reach the East Coast of North America and produce heavy surf along the coast during the next several days. Coastal flood watches have been posted for Monday and Tuesday covering the northern facing coasts of Puerto Rico and for some of the U.S. Virgin Islands as long-period ocean swells of 4 to 6 feet have reached these islands.

HOLD ON TO YOUR HATS -- The National Weather Service alerts the public to these windy conditions with special advisories, watches and warnings as described in Monday's optional Supplemental Information.


HISTORICAL WEATHER EVENTS - 26 November

From the files of the Aviation Weather Center, Kansas City, MO and Intellicast


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URL Address: datastreme/learn/m_sum.html
Prepared by Edward J. Hopkins, Ph.D., email hopkins@meteor.wisc.edu
© Copyright, 2001, The American Meteorological Society.