DATASTREME DAILY SUMMARY

Friday, 26 October 2001


00Z Weather Systems


The following highlights of the national weather have been extracted from the surface weather map for Thursday night:

A MAJOR STORM CONTINUES -- The potent storm system that brought severe weather, heavy rain, snow and blizzard conditions to the nation's mid-section on Wednesday drifted slowly to the northeast on Thursday. As of Thursday evening this occluding storm system had a primary low pressure center that was located over the eastern end of Lake Superior, having moved less than 200 miles. However, in the process of occluding, the accompanying cold front that had been responsible for the much of the severe weather had moved rapidly eastward on Thursday and was located off the Eastern Seaboard in the western Atlantic. An occluded front extended northeastward to secondary low pressure centers located at a point of occlusion over the lower St. Lawrence Valley and northern Maine. A warm front extended eastward across the Maritimes, while a cold front stretched southward over the open waters of the Atlantic before curving southwestward and crossing the Florida Peninsula and the Gulf of Mexico.

The primary low pressure system is expected to move northeastward across Ontario into Quebec on Friday, weaken and finally dissipate. The southern portions of the cold front are expected to move southward across Florida.

THE EAST SPARED FROM ACTIVE WEATHER -- With more than 550 reports of severe weather, to include 20 reports of tornadoes, more than 420 reports of high thunderstorm winds and approximately 100 reports of large hail, Wednesday gained the dubious distinction of having one of the largest outbreaks of severe weather in the last decade. Several deaths and numerous injuries were also the result of the thunderstorms. The severe thunderstorms formed along a line that preceded the advancing cold front as it moved eastward across the Mississippi and Ohio Valleys on Wednesday. However, much of the severe thunderstorm activity dissipated by early Thursday as the cold front moved toward the eastern Lakes and the Appalachians. Isolated thunderstorm wind damage continued into early Thursday in southern West Virginia, southwestern Virginia, western North Carolina and northwestern Georgia as the cold front passed. However, most of the damage was relatively minor, confined mainly to downed trees and power lines.

As the cold front moved eastward, southerly winds ahead of the front were responsible for warm-air advection, resulting in high temperatures along the Eastern Seaboard that were between 10 to 15 degrees above average. Record high temperatures were either tied or established in Florida at Daytona Beach (89 degrees), Miami (88 degrees) and Jacksonville (87 degrees); in Georgia at Savannah (87 degrees); in South Carolina at North Myrtle Beach (88 degrees); in North Carolina at Wilmington (87 degrees) and New Bern (86 degrees); in Virginia at Norfolk (83 degrees); in Delaware at Georgetown (81 degrees) and Wilmington (79 degrees); in New Jersey at Newark and Atlantic City (both 79 degrees) and in Connecticut at Bridgeport (76 degrees). A record high low temperature was also set at Tampa (75 degrees).

A BLUSTERY DAY ACROSS THE MIDWEST -- While the storm system drifted slowly toward the north and east, the primary low pressure center had deepened slightly, resulting in the maintenance of an exceptionally tight pressure gradient over the Midwest. The packing of the isobars on Thursday night's surface weather analysis charts reflects this tight pressure gradient. Tight pressure gradients produce strong gradient winds. With colder air moving across warmer surfaces, the resulting convection produces gusty winds. La Crosse had a wind gust to 64 mph and Leland, MI had 57 mph gust on Thursday. A variety of high wind warnings and wind advisories were in effect for much of Thursday because of these strong gradient winds that were circulating around the western and southern flanks of the storm system. High wind warnings were continued from Thursday night into Friday for the lakeshore counties in Michigan's Upper Peninsula, western Lower Michigan, northern Ohio, northwest Pennsylvania and western New York State. Wind gusts at some locations along the lake shores and on the lakes could reach speeds of 55 mph.

Passage of the cold front brought a marked drop in the temperatures from the previous day across a large portion of the Midwest. High temperatures across the northern Plains and Upper Mississippi Valley were on the order of 10 to 20 degrees below the average highs for late October. Rochester, MN had a high temperature of only 34 degrees, which established a new low high temperature record for the date.

Lake-enhanced and lake-effect snow fell across portions of the Midwest that were downwind of the Great Lakes. With northwesterly winds carrying cold air across the relatively warm surface waters of the lakes, snow fell across the western Lakes, while rain was found over the eastern lakes. As of Thursday night, 6 inches of snow had fallen across the snow belt of northern Wisconsin. Some electric power outages had occurred in northern portions of the Badger State because snow covered tree branches have snapped and fallen onto power lines. Record snow fell at Duluth (1.7 inches).

As the storm continues to move away from the Lakes, northwesterly winds are still expected to continue through Friday. Consequently, a variety of winter storm warnings, winter storm watches and winter weather advisories remained in effect from northwest Wisconsin to eastern Upper Peninsula of Michigan as 6 to 10 inches of snow could fall by early Friday. Northwesterly winds gusting to 40 mph were expected to continue through midday on Friday, with 3 to 8 inches of snow by late Friday night.

RAINY WEATHER CONTINUES ACROSS THE SUNSHINE STATE -- A persistent flow pattern over Florida has meant a continuation of the rainshowers and thunderstorms across the Peninsula. Melbourne received a record 1.45 inches of rain on Thursday. In Brevard County near Cape Canaveral, a waterspout that had formed over the Indian River came onshore, crossed US Highway 1 as a tornado and damaged several houses before lifting.

Continued rain is expected along the Florida Keys and south Florida on Friday with more than one inch expected during the 24 hours ending on Friday evening.

A COOL NIGHT AHEAD IN THE SOUTH -- High pressure spreading into the South Central and Southeastern states behind the cold front is expected to produce a chilly night across the region. Freeze warnings and advisories were in effect across the Cumberland Plateau of east Tennessee and along the Ohio River from southern Indiana across southern Illinois and western Kentucky into the Missouri Bootheel. Frost advisories were posted for the Piedmont and higher terrain of western South Carolina and northwest Georgia. Farther west, frost advisories were also in effect for eastern Kansas and southwestern Missouri.

LARGE DIURNAL SWINGS IN THE WEST -- A relatively dry air mass associated with high pressure over the West has produced large variations in temperature from morning to afternoon. A record low temperature was reached at Eureka, CA (38 degrees). Afternoon high temperatures across the Southwest and into central California were on the order of 10 degrees above average.

As of late Thursday evening, dense fog was beginning in southern California Valleys.

TEMPERATURE EXTREMES ACROSS THE CONTINENTAL US -- Thursday's lowest temperature was 4 degrees at Big Piney, WY. Thursday's highest temperature was 95 degrees at Thermal, CA.

ALASKAN WEATHER -- Low pressure located over the southern portion of the Gulf of Alaska continued to produce windy weather across southern Alaska. Sand Point and Whittier both reported wind gusts to 40 mph, while Kodiak had gusts to 30 mph. Snow was falling at Yakutat. A stationary front paralleled the north Gulf Coast, separating warm air to the south from colder air in the interior of the state. Arctic high pressure located over the Arctic Ocean and the Chukchi Sea spread cold air southward across the state. Several stations along the North Slope reported subzero afternoon temperatures, with Deadhorse reporting the lowest temperature with 9 degrees below zero. Deadhorse, Nuiqsut and Wainwright had reduced visibility in freezing fog. High pressure was located over the central Aleutian Islands. Relatively cloud-free skies were found across southwestern Alaska. Snow was falling across the interior.

The lowest overnight temperature in Alaska on Thursday morning was 17 degrees below zero at Deadhorse, while the mid-afternoon highest statewide temperature was 47 degrees at Adak.

HAWAIIAN WEATHER -- A trough of low pressure that had passed westward across the Aloha State produced convective showers over some of the islands. Two inches of rain fell over portions of Oahu on Thursday afternoon. As the trough line departs on Thursday evening, light trade winds along with drier air are expected to return for the later nighttime hours and for Friday. A wind shear line which was located approximately 600 miles to the north of the islands is expected to arrive on Saturday. This shear line, representing the remnants of a midlatitude cold front, should be followed by a large high pressure cell that should increase trade winds.

REPORT FROM THE FIELD -- Mark Seeley, a LIT member and University of Minnesota climatologist, reported on the early winter storm that brought record snow to the Red River Valley on Wednesday. He said that the North Dakota Weather Service Office named this storm "Blizzard Al". In addition to the record October snowfall at Grand Forks, ND (10.8 inches), monthly snowfall records were also established at several locations in Minnesota, to include Argyle (14 inches), Thief River Falls (8 inches) and Roseau (8 inches). He also noted that this storm was similar in strength to the famous blizzard that struck the Red River Valley with 10 to 19 inches of snow on 19-20 October 1916. This early blizzard was at the start of one of the snowiest winters of the 20th Century in the state of Minnesota.

"FALLING BACK" THIS WEEKEND -- On this Sunday morning most of the nation will revert back to Standard time after roughly 7 months of observing Daylight Saving Time. Since Arizona, Hawaii, Puerto Rico and the eastern time zone sections of Indiana do not observe Daylight Saving Time, no time change will be needed in those parts of the country. Time changes have been mandated by the U.S. Congress. Following the old adage of "spring ahead, fall behind", you will need to turn your clocks back by one hour to conform with the local time observance. An informative web site http://deil.lang.uiuc.edu/web.pages/holidays/DST.html explains the history involved with the institution of Daylight Saving Time not only in the United States but in other countries. This site has the potential for use in the classroom since it also has links to other items of interest, including the history of calendars and time.

What does this time change mean to you (other than earlier sunsets)? A change from Daylight Saving to Standard Time does not deduct an extra hour of daylight from the day nor does it affect weather patterns. While the weather will not change because of the time change, the times when you will be able to obtain weather charts will now be one hour earlier. The reason for this earlier time is that the National Weather Service always operates on "Z time" (variously called Greenwich Mean Time or Universal Coordinated Time) which does not observe Daylight Saving Time. Thus, the charts are still produced and transmitted at the same Z time.

As a reminder, do not forget to change, if necessary, the internal clock on your computer from Daylight Saving to Standard Time.


HISTORICAL WEATHER EVENTS - 26 October

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

27 October

28 October


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