DATASTREME DAILY SUMMARY

Friday, 28 September 2001


00Z Weather Systems


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

A PESKY LOW LINGERS OVER THE LAKES -- Clouds and widely scattered areas of rain continued to rotate in a counterclockwise direction around a cold pool of air over the eastern Great Lakes. This cold air column extended upward through the entire troposphere (to altitudes in excess of 30,000 feet) from a surface low pressure system over eastern Lake Ontario. The low pressure center represented the remnants of an occluded storm system that moved eastward across the Northeast at the beginning of the week, resulting in heavy rain across the region as well as killer tornadoes in the Washington, DC metropolitan area. An occluded front extends eastward into New England before becoming a cold front that curves first southward and then westward across the Middle Atlantic States and into the Ohio Valley. Because of the cold pool of air coupled with clouds, Thursday's high temperatures around the eastern Lakes were on the order of 10 degrees below average highs for the date.

The low pressure center is expected to move off the Eastern Seaboard and dissipate on Friday. Between 0.1 to 0.2 inches of precipitation could fall in the 24 hours ending on Friday evening across the Northeast, to include New England and the eastern Lakes.

WET WEATHER CONTINUES ACROSS FLORIDA -- A stationary front was located across the Florida Peninsula. A broad area of rainshowers and embedded thunderstorms were along this front that had moved southward earlier in the week as a cold front and stalled over Florida. This front marked a boundary between tropical air to the south from modified polar air that had moved southward to the Gulf earlier. Some of the heavier precipitation was found to the south of the front across south Florida. Several waterspouts were spotted over the waters surrounding the Florida Keys and off the Atlantic Coast near Jacksonville and Jupiter Inlet.

This front is expected to remain across south Florida. Twenty-four hour rainfall totals by Friday evening could range from 2.5 to 2.9 inches. Consequently, flash flood watches were continued across Florida south of a line extending from Tampa Bay to Cape Canaveral.

ANOTHER COOL START IN THE SOUTHEAST -- Relatively cloud-free skies coupled with the cool and dry air contributed to another chilly Wednesday night and Thursday morning across the Southeast to the north of the stationary front over south Florida. Record low temperatures were either tied or set on Thursday morning in Tennessee at Bristol (37 degrees); in Alabama at Huntsville (42 degrees), Montgomery (43 degrees) and Mobile (50 degrees); in Georgia at Augusta (45 degrees); in South Carolina at Columbia (46 degrees), Florence (47 degrees) and North Myrtle Beach (52 degrees); in North Carolina at New Bern (48 degrees) and in Florida at Tallahassee (47 degrees).

The Southeast should experience another cool morning on Friday, however air mass modification should reduce the number of low temperature records.

UNSEASONABLY WARM WEATHER PERSISTS OVER THE WEST -- A large, warm high pressure system that extended upward through the troposphere continued the warm and tranquil weather across much of the West. High temperatures across the northern Rockies as well as portions of the western Plains and the Intermountain West ranged between 15 to 20 degrees above the average highs for late September. Denver, CO had a minimum temperature of 59 degrees, which was a record high low temperature for the date. Record high temperatures were either tied or set on Thursday afternoon in Arizona at Phoenix (106 degrees) and Page (90 degrees); in Utah at Zion National Park (97 degrees), Salt Lake City (91 degrees) and Blanding (87 degrees); in Nevada at Wells (87 degrees); in Colorado at Glenwood Springs (90 degrees) and Alamosa (80 degrees) in Wyoming at Worland (90 degrees), Lander (87 degrees), Cheyenne (85 degrees), Rawlins (82 degrees), Jackson (81 degrees) and Laramie (79 degrees); in Idaho at Pocatello (89 degrees) and in Montana at West Yellowstone (80 degrees).

This weather pattern is expected to persist through Friday.

UNSETTLED WEATHER CONTINUES ACROSS THE NORTHWEST -- A stationary front that stretched from northwest Montana into southeastern Oregon brought widely scattered rain across the Pacific Northwest. Temperatures across the Pacific Northwest were several degrees below the long-term average highs for the date.

This front is expected to remain relatively stationary through Friday. Several tenths of an inch could fall by Friday evening across the region.

TEMPERATURE EXTREMES ACROSS THE CONTINENTAL US -- Thursday's lowest temperature was 22 degrees at Wisdom, MT. Thursday's highest temperature was 113 degrees at Death Valley, CA.

ALASKAN WEATHER -- A nearly stationary low pressure system was located over the Gulf of Alaska south of the Kenai Peninsula with a weakening front that stretched to the southeast toward the southern tip of the Panhandle. Another low pressure center was located over the north central Bering Sea. These two systems spread clouds across south central, southeastern and western Alaska. Widely scattered light precipitation was found across the state. A weak ridge of high pressure was located over the Arctic Ocean just off the Alaska coast. Cold air associated with this ridge extended southward across the North Slope to a stationary front that extended from the Seward Peninsula eastward to the Alcan border. To the south of this front, another weak high pressure ridge was located across interior Alaska between Galena and McGrath. Nearly cloud-free skies were found across interior Alaska.

The lowest overnight temperature in Alaska on Thursday morning was 18 degrees at Cantwell, while the mid-afternoon highest statewide temperature was 59 degrees at Big River Lakes.

HAWAIIAN WEATHER -- A ridge of high pressure located to the north and northwest of the islands produced trade wind weather across the Aloha State, with trade winds from the northeast. Residual scattered clouds remained from the remnants of a defunct wind shear line. Most of these clouds should dissipate by Friday. Some scattered trade showers have been found during the night and early morning especially on the windward slopes of the islands. The trade winds are expected to diminish slightly over the weekend as the high pressure ridge is anticipated to weaken.

EYE ON THE TROPICS -- Off the coast of Mexico, Hurricane Juliette continued to weaken as it began a more northward track on Thursday. As of Thursday evening, Juliette had maximum sustained winds of 85 mph and was located approximately 50 miles west-southwest of Cabo San Lucas, Mexico. Movement was to the north at 9 mph. Estimated sea level pressure within the central eye was 977 mb. In addition to the heavy rains across southern Baja California, the high winds have generated heavy surf along the Mexican coasts. A variety of hurricane and tropical storm warnings were in effect along the Pacific and Gulf of California coasts of Baja California. Moisture for Juliette could reach the Southwest US by the beginning of next week. Satellite imagery shows that some of the high cloud shield above Juliette is being carried eastward across Mexico and passing over the lower Rio Grande Valley near Brownsville, TX.

In the North Atlantic Hurricane Humberto was downgraded to a tropical storm as its sustained surface winds fell below 75 mph. This system was also losing some of its tropical characteristics. As of late Thursday afternoon when the last official advisory for this storm was issued by the National Hurricane Center, Tropical Storm Humberto was located approximately 620 miles to the southeast of Cape Race, Newfoundland and moving to the east at 31 mph. Maximum sustained surface winds had fallen to 50 mph.


HISTORICAL WEATHER EVENTS - 28 September

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

29 September

30 September


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