DATASTREME DAILY SUMMARY

Monday, 3 December 2001


00Z Weather Systems


Welcome to the month of December, named from the Latin word "Decem", for the number ten, representing the tenth month of the year in an early Roman calendar that commenced at the vernal equinox in March.

WEATHER OVER THE WEEKEND -- The West experienced a relatively stormy weekend while those in much of the eastern half of the country had relatively tranquil weather. However, at the start of the weekend, the Midwest received widespread rain along with some winds on Friday as a storm system moved northward from the mid-Mississippi Valley to the Great Lakes on Friday. Winds on Friday caused some damage to mobile homes in northeast Ohio and to trees in eastern Tennessee. By Saturday morning this storm system had moved into eastern Canada. High pressure built into the Midwest behind the storm.

On Friday high temperatures ranged between 15 to 20 degrees above average along the Eastern Seaboard, especially in the Middle Atlantic States. On Friday afternoon record high temperatures were reached at North Myrtle Beach, SC (76 degrees) and Elkins, WV (73 degrees). Farther west, clouds and precipitation associated with the series of storms meant that high temperatures across the Great Basin were on the order of 10 degrees below the average highs for the end of November.

A major storm reached the West Coast on Saturday morning. A large area of heavy precipitation and windy weather spread across the Pacific Northwest and northern California as the storm system made landfall. By Saturday afternoon, 4 to 5 inches of rain fell within 24 hours in Marin County in the San Francisco Bay area. As a result, some roads were flooded. The cold front moved inland with the rain and high elevation snow southward and eastward across central California. Heavy snow fell across the mountains of Idaho, with some locations reporting between 24 to 36 inches of snowfall within 24 hours ending on Sunday morning.

High temperatures on Saturday across the West were near seasonal averages, while in the Northeast, highs were on the order of 25 degrees above the average highs for the start of December. Record high temperatures were either tied or set on Saturday in North Carolina at New Bern (79 degrees) and Asheville (70 degrees); in Virginia at Richmond (74 degrees), Roanoke (71 degrees) and Blacksburg (65 degrees); at Washington, DC (72 degrees at Dulles and 71 degrees at National); in Maryland at BWI Airport near Baltimore (71 degrees); in Delaware at Wilmington and Georgetown (both 73 degrees); in New Jersey at Atlantic City (72 degrees at Airport and 70 degrees at State Marina), Newark (71 degrees) and Trenton (69 degrees); in Pennsylvania at Philadelphia (70 degrees), Allentown (66 degrees), Harrisburg (65 degrees) and Reading (65 degrees); in New York State at Central Park in New York City (69 degrees); in Connecticut at Windsor Locks (70 degrees) and Bridgeport (64 degrees); in Rhode Island at Providence (71 degrees); in Massachusetts at Boston (71 degrees), at Blue Hill Observatory in Milton (70 degrees) and Worchester (64 degrees); in Maine at Portland (66 degrees) and Bangor (59 degrees); and in New Hampshire at Concord (65 degrees). Overnight lows remained relatively high, with Boston, MA (51 degrees) and at Providence, RI (49 degrees) setting high low temperature records.

Even as precipitation from the first storm system lingered over the Great Basin on Saturday afternoon, the next storm system was approaching northern California. A large area of precipitation and high winds preceded the storm. High winds, with sustained speeds of 45 to 50 mph, were reported across interior Oregon on Sunday. Farther east, 74 mph winds were reported from near Spearfish in the Black Hills of South Dakota.

Essentially the entire country experienced an unseasonably warm Sunday, as high temperatures were above average across all but several locations. The largest departures from the long-term average were across the central Plains and the lower Missouri Valley where highs ranged from 20 to 25 degrees above average. Clouds and rain helped hold highs down to slightly below average readings across southern Texas and portions of the West Coast and Intermountain West.

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.

A major storm system was located along the West Coast. This occluded system consisted of a primary low pressure center that was located off Cape Blanco on the southern coast of Oregon with an occluded front that curved northeastward into the interior of the Northwest before turning southward over the Columbia Basin. The occluded front continued southward as a cold front that eventually curved southwestward across Nevada and southern California. A large area of precipitation accompanied this storm system, with coastal and low elevation rain found from western Washington southward to southern California near Santa Barbara. Inland, snow was falling over the higher terrain of the Olympics, the Sierras and the mountains of northern Nevada, Idaho and western Montana.

Strong winds have accompanied this storm. Gale warnings were in effect for the coastal waters along the Oregon and northern California coasts from Cape Blanco, OR south to Point Arena, CA, and also along the coast of southern California from Point Piedras Blancas to Santa Cruz Island. The winds have generated ocean swells that have moved toward the coast to produce heavy surf. As a result, heavy surf advisories were in effect along the California coast from Cape Mendocino to Santa Cruz Island, along with a coastal flood watch for the San Francisco Bay area and portions of central California. A high wind warning was out for the Laramie Range in southeastern Wyoming, as southwesterly winds could gust to 65 mph.

The storm is expected to move to eastward into the interior Northwest by Monday morning. Wide spread precipitation is expected to spread inland. A variety of winter storm warnings and snow advisories were continued for the Oregon Cascades southward over the mountains of northern California and the Sierras, where as much as 20 inches of new snow could fall above 6000 feet. Additional winter storm warnings and snow advisories were posted for the mountains of Idaho, northwestern Montana, northeastern Nevada and northwest Wyoming. A winter weather advisory was in effect through Monday night for the mountains to the north of the Los Angeles Basin. Snow levels are expected to drop to less than 5000 feet, with as much as 8 inches of snow possible. Flood warnings were posted for some of the rivers in western Washington State.

An elongated ridge of high pressure was located over the Eastern Seaboard and Appalachians. As a result, mostly tranquil weather was found across much of the East. This high should remain relatively stationary through Monday.

An onshore flow of moist Gulf air on southeasterly winds continued to bring rain across south Texas. This widespread rain was also producing moderate flooding on some of the rivers. The rain should continue through Monday morning.

UPPER AIR -- The 500 and 300 mb charts for 00Z Monday indicate that the flow across the continent was relatively zonal, with little north-south deviation from the westerly wind flow. A slight height trough appears to be located off the West Coast, associated with the cold air following the storm system that was moving onshore. The strongest jet stream winds appear to be displaced well to the north, reflecting the unseasonably warm air across much of the country.

TEMPERATURE EXTREMES ACROSS THE LOWER 48 -- On Sunday, the lowest temperature reported in the continental U.S. was 2 degrees below zero at Del Norte, CO, while Sunday's highest temperature was 85 degrees at Ft. Myers Southwest Regional Airport, FL.

ALASKAN WEATHER -- Cold arctic air remained over much of mainland Alaska courtesy of a large ridge of high pressure that extends from over the Arctic Ocean to the northwest of Barrow southeastward across the Yukon. A few clouds were found across northern and interior Alaska. Most locations across interior Alaska reported subzero temperatures during the early afternoon, with the lowest reading of 32 degrees below zero at Northway. The southern periphery of this arctic air mass consisted of a front with several low pressure centers that stretched from the western Bering Sea across the Alaska Peninsula to the northern Gulf of Alaska and then southeastward to near the Queen Charlotte Islands. One of the low pressure systems was situated in the northeastern Gulf of Alaska just south of Prince William Sound. This low spread clouds along the south central Alaska and the Panhandle. A stronger low pressure center was located in the western Bering Sea. A relatively tight pressure gradient between a large ridge of high pressure in the central North Pacific Ocean and this low pressure center generated windy conditions across the Bering Sea, the Aleutians and portions of the Alaska Peninsula. Dutch Harbor and Cold Bay had southwesterly winds with gusts to near 40 mph. With sustained southwest winds expected to reach 50 mph along with gusts to 65 mph, a high wind warning was posted for the Aleutians west of Adak Island through Sunday night. Relatively little precipitation was found around the state. Snow was falling at Barrow, Deadhorse, Nuiqsut, Wainwright and Yakutat.

The lowest overnight temperature in Alaska as of Sunday was 41 degrees below zero at Northway and the midafternoon highest statewide temperature was 43 degrees at Sand Point.

HAWAIIAN WEATHER -- The islands experienced relatively strong trade winds as a result of a large and relatively intense high pressure system located to the north-northeast of the Aloha State. Some showers accompanying a wind shear line (remnants of a midlatitude front) were brushing past the northeast sides of the islands. The strong trade winds are expected to continue through the first half of this upcoming week as the high pressure cell drifts eastward and maintains its strength. Because of the strong winds, a high wind warning was in effect for the volcanic summits of the Big Island and gale warnings were posted for the inter-island channels. Small craft advisories continued for coastal waters. A high surf advisory was in effect for the east shores of the islands.

EYE ON THE TROPICS -- Tropical Storm Olga continued to take an irregular path across the western North Atlantic Ocean over the weekend. On Friday morning Olga weakened and was downgraded to tropical depression status as it moved to the southwest toward the eastern Bahamas. By late Saturday night, Olga turned and began moving to the north and northwest. It also intensified once again, to be upgraded to a tropical storm. As of late Sunday night Tropical Storm Olga had maximum sustained surface winds of 40 mph and it was located approximately 415 miles to the southwest of Bermuda. The storm was moving to the north-northwest at 8 mph.

WINTER AWARENESS -- Alabama and South Carolina will observe Winter Weather Awareness Week during the upcoming week of 3-7 December 2001. Residents of these states should review the winter weather safety rules issued by their local National Weather Service Offices.

HURRICANE SEASON REVIEW -- The official 2001 North Atlantic hurricane season ended last Friday, 30 November 2001 . As a quick review of this year's statistics consult Monday's optional Supplemental Information.


HISTORICAL WEATHER EVENTS - 3 December

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


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Prepared by Edward J. Hopkins, Ph.D., email hopkins@meteor.wisc.edu
© Copyright, 2001, The American Meteorological Society.