DATASTREME DAILY SUMMARY

Monday, 3 September 2001


WELCOME TO DATASTREME - This Daily Summary represents one of the products that you will routinely use in the DataStreme Project. We - to include myself and those at DataStreme Central - would like to welcome all the participants to this exciting project. I will be responsible for producing this Daily Summary File that describes current and recent weather features of note. On Tuesdays and Thursdays, this file will also contain a "Concept of the Day", which will develop some weather topic in further detail. Two questions related to that topic will appear at the end of this feature for you to answer as part of the weekly materials that you will submit to your LIT mentor by fax. On occasion, I will post a Supplemental Information File. As its name indicates, this file will contain supplementary background material or resource information.
Sincerely,
Ed Hopkins

00Z Weather Systems


HAPPY LABOR DAY!

WELCOME TO SEPTEMBER AND AUTUMN -- The name September appears to be derived from "Septem", the Latin word for the number seven, representing the seventh month of the year in the old Roman calendar that started with the month of March.

Saturday was also the first day of meteorological autumn, the three-month (September, October, November) interval that meteorologists frequently use for record keeping processes. Additional information will be presented in the next several weeks concerning meteorological seasons and the astronomical seasons, such as the familiar autumn that begins on the autumnal equinox in three weeks (Saturday, 22 September 2001).

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

PLEASANT WEATHER ACROSS THE NORTHEAST -- A large area of high pressure centered over the Middle Atlantic and New England States was responsible for relatively pleasant conditions extending from New England westward into the Great Lakes, with cloud-free skies, weak winds and afternoon high temperatures that were within several degrees of the long-term average highs for the start of September. However, the presence of the high pressure system, with its clear skies and weak winds, produced a chilly start to Sunday morning as these conditions permitted considerable radiational heat loss to space. Record low temperatures for the date were established on Sunday morning at Trenton, NJ (50 degrees) and at Scranton and Wilkes-Barre, PA (43 degrees).

The high pressure system is expected to drift eastward off the Atlantic Coast on Monday. As this high pressure system departs, the clockwise wind circulation around the high will cause winds from the southwest to spread warmer air into the Northeast, along with increased clouds associated with a cold front advancing into the Midwest.

RAINS SOAK PORTIONS OF THE SOUTH -- Widely scattered rainshowers and imbedded thunderstorms continued in the warm and humid tropical air that extended inland across the South from the Gulf of Mexico. Most of the precipitation was found to the south of an east-west stationary front that extended westward from the Atlantic Coast across the Carolinas and Tennessee to the Bootheel of Missouri in the mid-Mississippi Valley. This stationary front separated the moisture-laden warm Gulf air from slightly drier and cooler air associated with the high pressure system that had moved into the Northeast.

Thunderstorms with winds reaching 60 mph toppled trees in northeast Florida near Jacksonville. At least one tornado was spotted near New Madrid in southeastern Missouri on Sunday afternoon. No damage was reported. Some locations across the Gulf Coast States, extending from Texas into Alabama, received from 1 to 2 inches of rain by early Sunday evening.

The stationary front is expected to remain in essentially the same position through Monday evening. To the south of this front, heavy rains are expected to continue over some portions of the South, to include the southern Appalachians, the Tennessee River Valley and the Lower Mississippi Valley. As much as 2 inches of additional rain is anticipated in the 24 hours ending on Monday evening in some locations across northern Alabama. As a result of this anticipated rain, coupled with the rain that has already fallen, a variety of flash flood watches were in effect across the southern Appalachians of the western Carolinas and northeast Georgia, as well as across the Gulf Coast from central Alabama southwestward into Louisiana and east Texas.

A COLD FRONT MOVES INTO THE UPPER MIDWEST -- A relatively dry cold front with little accompanying precipitation was moving southeastward from the Northern Plains into the Upper Mississippi Valley on Sunday night. This cold front, representing the leading edge of cooler and drier Canadian air, trailed southwestward from a low pressure center along the Ontario-Manitoba border across northwest Minnesota before curving westward and then northwestward over South Dakota and Wyoming. Winds to the south and east of the front were carrying warm air northward. Afternoon high temperatures across the Plains were 10 to 20 degrees above the long-term average high temperatures for the first week of September. Behind the southeastward advancing front, winds were from the northwest, with temperatures that were on the order of 10 degrees lower than air in advance of the front.

The cold front is expected to continue moving to the south and east on Monday. By sunrise, the front should extend southwestward across the Great Lakes and Mississippi Valley from the low pressure center which is forecast to have reached James Bay in Ontario. By sunset, the low should continued into Quebec, while the cold front is forecast to extend across Lower Michigan and northern Illinois into Iowa before curving northwestward across the Plains. A cooler high pressure system is expected to follow behind the front, moving southeastward from the Prairie Provinces and reaching the eastern Dakotas by evening. Some rain and thunderstorms could develop along and ahead of the front as it crosses the upper Mississippi Valley into the western Great Lakes on Monday as moisture is brought northward from the Gulf on southerly winds.

SEVERE WEATHER IN THE PLAINS -- Thunderstorms associated with a trough of low pressure moved southward across the western Plains on Sunday evening. Some of these thunderstorms produced winds of at least 60 mph, resulting in downed power lines near Great Bend in central Kansas during the late afternoon and early evening hours. Some of these thunderstorms also produced large hail with diameters ranging between 0.75 and 1.75 inches in diameter near Russell, KS. Large hail also fell across northern portions of the Texas Panhandle.

More thunderstorms are forecast for the southern and central high Plains on Monday.

DRY WEATHER CONTINUES ACROSS THE WEST -- Except for some afternoon thunderstorms in the southern Rockies, much of the West remains warm and dry. This extended drought has contributed to the numerous wildfires that have occurred across Washington, Oregon, Idaho, Montana and California. High winds earlier over the weekend helped spread a major wildfire in northwest Montana into Glacier National Park. However, slightly higher humidities on Sunday helped firefighters battle the blaze.

Some precipitation associated with an approaching cold front could reach the Olympic Peninsula of western Washington State by late Monday afternoon. Locally isolated afternoon thunderstorms could produce upwards of 0.3 inches of rain across portions of southern Nevada and southeast California, while 0.2 inches were anticipated in the mountains of New Mexico and southern Colorado.

TEMPERATURE EXTREMES ACROSS THE LOWER 48 -- On Sunday, the lowest temperature reported in the continental U.S. was 32 degrees (Fahrenheit) at Saranac Lake, NY, while Sunday's highest temperature was 115 degrees at Death Valley, CA.

ALASKAN WEATHER -- Much of Alaska experienced cloudy skies late Sunday afternoon. A weakening low pressure system in the northeastern Gulf of Alaska near Yakutat brought heavy rainshowers and strong winds to much of the Panhandle on Sunday. Petersburg received 2.03 inches of rain in the 24 hours ending on Sunday afternoon, while Sitka reported 1.16 inches. Earlier on Sunday, winds gusted to over 50 mph at Sitka. Another low pressure system was developing over the Gulf approximately 500 miles southwest of Ketchikan. An east-west stationary front stretching along the Brooks Range separated cooler arctic air north of the front from milder air to the south. Midafternoon temperatures were in the 30s and 40s along the Arctic coast and the North Slope, while in the 50s and 60s in the interior. A ridge of high pressure extended northward from the North Pacific across the Aleutians and Bering Sea into the Chukchi Sea. Farther west, another low pressure system was developing in the western Pacific near Russia's Kamchatka Peninsula. This developing storm system was expected to bring strong winds to the western Aleutians.

The lowest overnight temperature in Alaska as of Sunday was 30 degrees at Barrow and the midafternoon highest statewide temperature was 66 degrees at McGrath.

HAWAIIAN WEATHER -- An elongated area of high pressure extended across the central Pacific Ocean to the north of the Hawaiian Islands. Winds spiraling out of the southern flank of this high pressure cell are called trade winds. These trade winds were relatively strong over the weekend, but had weakened slightly by Sunday afternoon. The wind direction of these trade winds has been from the northeast or east-northeast. While relatively cloud-free skies have been experienced across much of the islands, some trade type showers have been experienced, especially on the windward northeast slopes of the high terrain on some of the islands. With a weakening of the northeast trade winds, the small craft advisories that had been in effect on Sunday were canceled during the early evening.

EYE ON THE TROPICS -- On Sunday morning the sixth tropical depression (a region of low pressure that forms over the tropical oceans) of the current 2001 hurricane season in the North Atlantic Basin became organized and intensified into Tropical Storm Erin when sustained near surface winds reached 39 mph. As of late Sunday night, Erin, the fifth named tropical system (including tropical storms and hurricanes), was moving west-northwestward at about 16 mph across the tropical Atlantic approximately 1200 miles east of the Lesser Antilles. Surface winds were estimated to be approximately 50 mph. Intensification to hurricane status, with sustained winds of at least 75 mph, is not expected before Tuesday morning.

REPORT FROM THE FIELD -- Faye McCollum, DataStreme LIT Leader from Columbus, GA reported that much of the recent rains experienced across the South have missed southwest Georgia where the continued effects of the extended drought remain. Farmers in the region are concerned with the negligible soil moisture and its affect upon the peanut crop which is near harvest. The clouds have held down temperatures, but have not produced significant precipitation. However, she did caution that while rains from a tropical system would be welcome, she does not want to see excessive precipitation rates, since the heavy rain would runoff rather than infiltrate into the dry soil.

AN INVITE -- If you witness some interesting weather phenomena or would like to share some weather-related experience with others in the DataStreme Project, we cordially invite your contributions. Please email these to the address appearing below. Some of these may appear in the section titled "Reports from the Field"


HISTORICAL WEATHER EVENTS - 3 September

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.