DATASTREME DAILY SUMMARY

Wednesday, 3 October 2001


00Z Weather Systems


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

UNSETTLED WEATHER MOVES TOWARD THE WESTERN LAKES -- While much of the country experienced relatively tranquil weather, a weak storm system was moving eastward from the Plains into the western Great Lakes, accompanied by some light rain. The low pressure system was located over southern Minnesota on Tuesday evening. A warm front extended to the southeast into northern Indiana from the low pressure center, while a cold front trailed to the southwest across Iowa and Nebraska. Most of the precipitation was to the north of the low pressure center and accompanying warm front, stretching eastward from the Arrowhead of northeast Minnesota across northern Wisconsin into Michigan's Upper Peninsula.

The counterclockwise circulation around the low pressure system influenced the temperature pattern across the Plains and Midwest. With southerly winds to the south of the low pressure system, temperatures on Tuesday night across the upper Mississippi Valley and Great Lakes were at least 10 degrees higher than they were 24 hours earlier. This increase in temperatures from one night to the next is the result of warm-air advection. However, to the west of the low pressure system, northerly winds caused temperatures to fall. As a result of cold-air advection, Tuesday night temperatures across the western Plains were on the order of 15 degrees lower than they were on Monday night.

The low pressure system is expected to move eastward across the northern Lakes on Wednesday, reaching northern Lake Michigan by sunrise and the Ottawa River Valley to the northeast of Georgian Bay by sunset. As much as 0.5 inches of rain could fall in the 24 hours ending on Wednesday evening along a band to the north of the storm track, extending from the Upper Peninsula across Ontario and into Quebec. Another cold front is expected to swing southeastward across the Canadian Prairie Provinces on Wednesday, reaching the Dakotas and northern Minnesota by evening.

WARM WEATHER ABOUNDS -- A large portion of the country experienced a relatively warm Tuesday, with high temperatures that were above the average highs for early October. The largest temperature anomalies (differences between the observed and average values) were across the Plains and into the upper Mississippi Valley where temperatures were on the order of 20 degrees above average. Since this region was to the south of the approaching storm system, it was experiencing warm air advection. Another region with large positive anomalies was in northern California and southern Oregon with 15 degrees above average. Record high temperatures were set in California at Sacramento (104 degrees at Airport and 102 degrees Downtown) and in Colorado at Glenwood Springs (87 degrees).

COOL CONDITIONS ACROSS THE SOUTH -- A large and elongated ridge of high pressure extended across the South, from off the Carolina coast westward to Alabama. The relatively clear skies, low humidity and weak winds have allowed for overnight temperatures to fall as a result of nighttime radiational cooling. Record low temperatures were either tied or set on Tuesday morning in Texas at Bergstrom Field in Austin (49 degrees) and in Florida at Daytona Beach (57 degrees), Melbourne (59 degrees) and Ft. Myers (61 degrees). Afternoon high temperatures were within several degrees of the average highs for this time of year. This high pressure is expected to remain over the region on Wednesday.

MORE RAIN FROM JULIETTE -- Widely scattered rainshowers continued to move across southern Arizona on Tuesday as a result of moisture being carried northward around former Hurricane Juliette. As of Tuesday night Tropical Depression Juliette continued to drift across the northern portions of the Gulf of California and Mexico's Baja California. At this time, Juliette had maximum sustained surface winds of 25 mph. Its location was 90 miles south-southeast of San Felipe Mexico and movement was to the south at 5 mph. Central pressure was estimated to be 1008 mb.

Rain associated with Juliette is expected to continue across southern Arizona and southwestern New Mexico through Wednesday, with as much as 0.3 inches falling across the region by evening.

YESTERDAY'S TEMPERATURE EXTREMES ACROSS THE CONTINENTAL US -- Tuesday morning's lowest temperature was 22 degrees at West Yellowstone, MT, while the highest temperature on Tuesday was 110 degrees at Death Valley, CA.

ALASKAN WEATHER -- A large, complex low pressure system was located across the eastern Aleutians. Southerly and southeasterly winds to the east of this system spread warm air across southwestern Alaska. A cold ridge of high pressure extended along the Arctic Coast, bringing cold arctic air southward across the North Slope. Snow fell across portions of northwest Alaska and the interior, to include Kotzebue, Bettles, Cantwell and Eagle. Bettles had one inch on the ground. A stationary front extended from the vicinity of Norton Sound in western Alaska eastward across interior Alaska to the Yukon Territory. This stationary front separated the cold arctic air north of the front from warmer air to the south of the front. High pressure located to the southwest of the Queen Charlotte Islands produced a westerly onshore flow across the Panhandle, resulting in clouds and rain across the region. Valdez reported 1.37 inches, while Cordova had 1.20 inches.

The state's lowest overnight temperature on Tuesday morning was 16 degrees at Arctic Village. The highest temperature by mid afternoon of Tuesday was 59 degrees at Elmendorf AFB.

HAWAIIAN WEATHER -- Remnant clouds and showers associated with the wind shear line that moved across the islands on Monday were beginning to dissipate late Tuesday afternoon. Most of the remaining clouds were found to the east of the Big Island. Cooler and drier air was moving southward across the islands on northerly winds. The low pressure system associated with the wind shear line was located to the northeast of the islands and was beginning to move toward the northeast. High pressure is expected to move into the region. As the high builds to the north, the northeast trade winds are expected to gradually strengthen through the end of the week. High surf advisories were continued for the north and northeast facing shores of the islands.

EYE ON THE TROPICS -- The tropical depression that had formed off the west coast of Mexico on Monday intensified to become Tropical Storm Lorena on Tuesday. As of Tuesday evening, Lorena was located 315 miles south-southwest of Manzanillo, Mexico and moving to the north-northwest at 15 mph. Maximum sustained surface winds were 45 mph.

MONITORING DEGREE DAY UNITS -- Cumulative heating and cooling degree day units are available on monthly basis for selected cities across the country. For additional information as to where these data can be obtained, see the optional Wednesday Supplemental Information .


HISTORICAL WEATHER EVENTS - 3 October

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


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