DATASTREME DAILY SUMMARY

Monday, 15 October 2001


00Z Weather Systems


WEATHER OVER THE WEEKEND -- Several storm systems moved across the country over the weekend producing severe weather across the South Central States and wet weather across the Midwest. However, some areas along the West Coast and across the Southeast experienced relatively tranquil weather.

On Friday morning one storm system was located over the western Great Lakes with a cold front that trailed southward along the Mississippi Valley to the Gulf Coast. Some rain fell across the Midwest. On Friday morning, the low temperature at Tupelo, MS was a record 67 degrees. To the east of the front southerly winds were responsible for a relatively warm afternoon, with high temperatures across the Northeast ranging between 10 and 15 degrees above the average highs for the date. This storm moved to the northeast and by Saturday morning, it was located in Ontario to the northeast of Lake Superior.

The next cold front to move across the nation was found across the Plains on Friday morning, extending from a low in the northern Prairie Provinces southward to the Texas Panhandle. Cold air associated with high pressure building into the Pacific Northwest was responsible for keeping afternoon high temperatures across the central and northern Rockies behind the front between 10 to 15 degrees below the average highs for mid October. Spokane, WA had a record 0.7 inches of snowfall.

By Friday evening the southern portions of the cold front had become quite active across Texas and the southern Plains. Severe thunderstorms moved across the southern Plains and western Gulf Coast on Friday, spawning tornadoes, generating high winds and producing large hail. Severe weather on Friday night either postponed or canceled many of the highly popular high school football games across north Texas. As many as a dozen tornadoes were reported across the Lone Star State on Friday. A tornado extensively damaged homes and a gas pipeline in Decatur to the northwest of Ft. Worth. In addition to the tornadoes, strong thunderstorm winds also produced considerable damage. Wind damage was also reported in southwestern Arkansas and across much of northern and western Louisiana. Large hail fell from thunderstorms that passed across central Texas and Oklahoma, with some of the largest hail just west of Ft. Worth having diameters reaching 2.75 inches.

This cold front continued eastward and on Saturday morning the front stretched southward from a low pressure center over western Iowa to the lower Rio Grande Valley of south Texas. By Saturday evening the low pressure center had moved northeastward into northern Wisconsin, while the trailing cold front had reached the Mississippi River. To the east of the advancing front, southerly winds brought warm and humid air northward. Afternoon highs across the eastern Great Lakes and portions of the Middle Atlantic States ranged from 10 to 20 degrees above the average highs for the date. Chilly air was found to the west of the front. On Saturday morning, Liberal, KS reached a record low temperature of 29 degrees. High temperatures across east Texas and the southern Plains were 10 degrees below average, partly a result of the widespread clouds and rain.

Widespread heavy rain fell across the Midwest in the vicinity of the low pressure center. Daily rainfall records were established in Chicago, IL (3.79 inches), Evansville, IN (1.74 inches) and Waterloo, IA (1.22 inches). Some localized street flooding was reported across northeastern Illinois as a result of the rain.

Thunderstorms were found farther south along the cold front. The region of severe weather had moved eastward into the central Gulf Coast on Saturday, with thunderstorms producing tornadoes and high winds from just after sunrise until evening. Nearly a dozen tornadoes were reported on Saturday across an area that stretched from Louisiana's Mississippi Delta eastward across southern Mississippi and Alabama to the western Florida Panhandle. A waterspout developed off the Florida Gulf Coast near Pensacola and moved onshore to become a tornado. Most of the tornadoes appeared to have caused little damage, except for the tornado that damaged trailer homes and other buildings in Venice, in the Louisiana Delta. However, the thunderstorm winds were responsible for many downed trees and power lines across a wide region stretching from Lake Charles in southwestern Louisiana eastward to southwestern Alabama. Thunderstorms also produced record rainfall at El Dorado, AR (2.51 inches) and Shreveport, LA (1.98 inches).

By Sunday morning the cold front had moved eastward, stretching southward from Canada across the Great Lakes and Ohio Valley into the Southeast. A large area of precipitation accompanied this front, stretching from northern Lower Michigan south to the western Florida Panhandle.

Once again, areas east of the front were relatively warm as the result of southerly winds. Portions of the eastern Lakes and Middle Atlantic States had high temperatures that were on the order of 10 degrees above average. Massena, NY reached a record high of 79 degrees. However to the west of the cold front, afternoon high temperatures across the northern Plains and northern Rockies were on the order of 10 degrees below average. The low temperature at Austin, TX was a record low of 43 degrees. Cold air was carried southeastward around the western and southwestern areas of the low pressure center over western Ontario. This cold air extended up through the troposphere. Since the near-surface air was being heated from below because of contact with the warm earth, convective showers developed across the western Great Lakes and the upper Mississippi Valley. Some of these convective showers developed into thunderstorms during the afternoon. Golfball-sized hail covered I-57 in Iroquois County in east central Illinois during the early afternoon.

High pressure across the Pacific Northwest at the beginning of the weekend helped produce an easterly wind flow across central and northern California. As a result of this offshore flow and the lack of cooler marine air along the coast, unseasonably warm weather developed across the region. On Friday Moffett Field tied a record high temperature at 87 degrees. On Sunday afternoon, high temperatures were set at San Francisco (93 degrees), Oakland (91 degrees) and Moffett Field (90 degrees). To the south, Big Bear Lake also reached a record high of 76 degrees.

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 cold front trailing southward from a low pressure center over southern Hudson Bay to northern Florida brought rain to the eastern Great Lakes and the Eastern Seaboard. Most of the precipitation was found in the relatively warm and humid air to the east of the front. This band of rain included imbedded thunderstorms especially over the Carolinas. Behind the cold front, widely scattered showers continued in the cold flow across the Great Lakes. Some of the precipitation was also lake-enhanced as the cold air traveled across the relatively warm Lakes.

The cold front is expected to move eastward on Monday, moving off the coast by sunrise. Most of the precipitation associated with this system should end by afternoon. Between 0.2 and 0.5 inches of rain could fall in the 24 hours ending on Monday evening across the Middle Atlantic States.

An area of precipitation spread across the western Plains and the central Rockies. Most of the precipitation was falling in the form of rain, while some fell as snow across the higher terrain of Wyoming. This precipitation was in association with a low pressure area over Colorado.

The low pressure system and accompanying precipitation is expected to move eastward across the Plains on Monday, reaching the Oklahoma Panhandle by sunrise and then to the vicinity of the confluence of the Ohio and Mississippi Rivers by evening. As much as one inch of rain could fall across Kansas and Missouri to the north of the storm track.

A storm system located well off the Washington State's coast is expected to approach the coast by Monday evening with some precipitation reaching the Olympic Peninsula.

Dense fog that developed along the southern California coast between San Luis Obispo to Los Angeles has prompted dense fog advisories to be issued and to remain in effect through Monday morning.

TEMPERATURE EXTREMES ACROSS THE LOWER 48 -- On Sunday, the lowest temperature reported in the continental U.S. was 18 degrees at Limon and Alamosa, CO, while Sunday's highest temperature was 101 degrees at Death Valley, CA.

ALASKAN WEATHER -- A broad trough of low pressure that extended from southwest Alaska to northwest Alaska spread clouds across much of the state on Sunday afternoon. Light precipitation was found across southern Alaska, while snow was found at Barrow, Bettles, Kaltag and McGrath. Bettles had 8 inches of snow on the ground. High pressure was located along the Alcan border and into the Yukon. Another area of high pressure was located across the western Bering Sea. With a trough over Alaska and high pressure near eastern Siberia, cold air was brought southward across western Alaska.

The lowest overnight temperature in Alaska as of Sunday was 8 degrees below zero at Deadhorse and Nuiqsut and the midafternoon highest statewide temperature was 50 degrees at Ketchikan, Klawok and Port Alexander.

HAWAIIAN WEATHER -- High pressure far to the northwest of the Hawaiian Islands is expected to move eastward, tighten the pressure gradient and strengthen the trade winds across the 50th State. Relatively pleasant trade weather is expected, with relatively cloud-free skies except on the windward sides of the islands where the typical night and morning trade wind showers may develop.

EYE ON THE TROPICS -- An apparent midlatitude storm system moving across the western North Atlantic near Bermuda developed into Tropical Storm Karen early Saturday morning. By Saturday afternoon this eleventh named storm system of the season (to include both tropical storms and hurricanes) became a minimal hurricane and then was downgraded to tropical storm status on Sunday afternoon when sustained surface winds dropped below 74 mph. As of late Sunday night Tropical Storm Karen was 245 miles south of Halifax, NS and moving northward at 12 mph. Maximum sustained winds were 60 mph.

In the eastern North Pacific Tropical Storm Manuel curved from its track toward the west-northwest and took a track more toward the west to west-southwest starting on Friday morning. Between Friday and Saturday afternoons Manuel had weakened and was downgraded to a tropical depression, only to re-strengthen to a tropical storm late Saturday. As of Sunday evening, Tropical Storm Manuel was essentially stationary at a location 650 mph to the southwest of Cabo San Lucas, Mexico. Maximum sustained winds were 40 mph.

WINTER WEATHER AWARENESS -- The states of Montana and Wyoming will observe their Winter Weather Awareness Week this coming week (15-19 October 2001). Last week (7-14 October 2001) was Winter Weather Awareness Week in Alaska. Residents of these states should become aware of the hazards associated with winter storms and other cold weather events by reviewing the material prepared by the local National Weather Service Office. Other states will be observing their own winter weather awareness events during subsequent weeks. Stay tuned for further announcements.


HISTORICAL WEATHER EVENTS - 15 October

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.