DATASTREME DAILY SUMMARY

Wednesday, 25 October 2000


00Z Weather Systems


THE RAINS CONTINUE ACROSS THE SOUTHERN PLAINS-- Southerly winds across the Plains transported warm, humid Gulf air northward on Tuesday night to maintain a large region of rain and thunderstorms. The southerly winds were to the east of a cold front that stretched southward from a low pressure system located in northeastern Wyoming to west Texas. This cold front marked the transition between the warm air over the Plains and the colder air across the southern Rockies and the Four Corners area of Colorado, Utah, Arizona and New Mexico. A warm front that extended eastward from the low pressure center across the Dakotas into the upper Mississippi Valley marked the northern advance of the warm Gulf air.

Rainshowers and thunderstorms were found in the "warm sector" of this low pressure system, which is a region to the southeast of the low bounded by the warm and cold fronts. The precipitation stretched from south Texas northward to the Canadian border in the Dakotas. Thunderstorms were found just to the east of the cold front across west Texas, Oklahoma and southern Kansas. Substantial amounts of rain fell across the region. In Kansas, Russell and Salina had set daily rainfall records of 0.66 and 0.53 inches, respectively, as of mid evening. Severe thunderstorms continued to move across west Texas, where dime sized hail was reported near Cotton Center, Texas, and Woodward, Oklahoma, had winds that reached 60 mph. Hail was also reported near Albany, WY.

The low pressure system is forecast to move toward the northeast on Wednesday, while the bulk of the precipitation is expected to shift northward and eastward over the Plains into the Mississippi Valley. Between 0.5 and 1.5 inches of rain are expected across a large portion of Texas and Oklahoma during the 24 hours ending on Wednesday evening. As a result of this anticipated rainfall on top of the recent heavy rains, flash flood watches were in effect for more than 80 Texas counties stretching from the Rio Grande northward into the northern Panhandle. A slight risk for severe thunderstorms continues until Wednesday morning in west Texas. During the subsequent 24 hours, this area shifts into the northern Plains.

A FOGGY NIGHT -- Large areas of dense fog developed across the Great Lakes States and the Ohio Valley on Tuesday night. Dense fog advisories were posted for portions of Wisconsin, Iowa, Illinois, Minnesota and Michigan as the fog was expected to reduce the visibility less than 0.25 miles. The fog resulted as nighttime cooling of the relatively humid air lead to saturation conditions. Much of the area affected was under the influence of high pressure that was situated over the Great Lakes, extending southward across the Ohio Valley to the Appalachians. The weak winds under the high pressure were not sufficiently strong to cause mixing of drier air downward to dissipate the fog.

MILD WEATHER CONTINUES ACROSS THE PLAINS -- Southerly winds across the Southern Plains and Mississippi Valley helped produce unseasonably warm weather across the region on Tuesday. High pressure situated over the Middle Atlantic and Great Lakes States helped maintain these southerly winds. Afternoon high temperatures ranged between 10 to 15 degrees above the climatological average highs for late October across nearly the entire Mississippi Valley. Record high temperatures were either tied or set on Tuesday afternoon in Kentucky at Paducah (86 degrees) and Louisville (82 degrees), in Tennessee at Memphis (85 degrees), Nashville (85 degrees), Jackson (83 degrees) and Dyersburg (82 degrees), at Huntsville, AL (83 degrees) and at Asheville, NC (76 degrees). In addition, several locations experienced record high minimum temperatures on Tuesday, to include Minneapolis-St. Paul, MN (59 degrees) and Sioux Falls, SD (55 degrees).

COOL WEATHER OVER THE SOUTHWEST -- A cool pool of air extending upward through the troposphere over the Four Corners area was responsible for the clouds, precipitation and cool weather. Afternoon high temperatures across the region on Tuesday were on the order of 10 degrees below the long-term average highs. Some light snow fell across the Colorado Rockies at elevations above 9500 feet. The 0.44 inches of rain that fell at Ely, NV on Tuesday set a daily record.

A new storm system off the Pacific Northwest coast is expected to move southeastward, crossing the northern California coast on Wednesday. This system should bring more chilly air into the West. Snow could fall across the higher elevations of the northern Sierras.

A SAFE LANDING -- Space Shuttle Discovery finally landed safely at Edwards AFB, CA on Tuesday afternoon. The landing had been delayed because of strong crosswinds at the Kennedy Space Center, the primary landing site at Cape Canaveral, FL.

Winds reaching 20 to 30 mph continued across Florida as the pressure gradient was maintained between the high pressure center over the Middle Atlantic States and a developing low pressure system near the Bahamas. Heavy surf advisories were in effect for the coast from Altamaha Sound, GA to Hallandale Beach, FL.

YESTERDAY'S TEMPERATURE EXTREMES ACROSS THE CONTINENTAL US --Tuesday morning's lowest temperature was 17 degrees at Leadore, ID, while the highest temperature on Tuesday was 89 degrees at Cottula and Kingsville, TX.

ALASKAN WEATHER -- A potent storm system moving eastward across the west central Bering Sea continued to produce high winds across western Alaska. The storm system consisted of a low pressure center with a central pressure that was deeper than 980 mb and an occluded front that stretched eastward across the Yukon-Kuskokwim Delta. A stationary front continued eastward across southern Alaska, passing across the Copper River Basin. Southeast winds gusted to 54 mph on St. Lawrence Island at Savoonga and Gambell, while earlier, Cold Bay and King Salmon had gusts to 48 mph. The strong winds were the result of the tight pressure gradient that developed over southwest Alaska between a high pressure ridge over interior Alaska and the low center in the central Bering Sea. Most of the precipitation was found across south central Alaska, the Alaska Peninsula and on St. Paul Island. At Cold Bay, 2.28 inches fell by Tuesday afternoon, pushing the annual total for the year to date to 57.00 inches, which is a new record annual precipitation total. In addition, the 9.00 inches received so far this month is also a record for the month of October at Cold Bay.

A ridge of high pressure extended from the Gulf of Alaska across interior Alaska to the Arctic Ocean, with the ridge axis running from Kodiak to Barrow. As a result, interior Alaska had clear to partly cloudy skies. Elsewhere, skies were cloudy.

The state's lowest overnight temperature on Tuesday morning was 15 degrees below zero at Anaktuvuk Pass. The highest temperature by mid afternoon of Tuesday was 50 degrees at Ketchikan, Klawock and Sand Point.

HAWAIIAN WEATHER -- Northeast trade winds with speeds of approximately 20 mph continued across the islands on Tuesday as a large subtropical high pressure cell was located to the northeast of Hawaii. Some increase in clouds was expected as a cloud mass moves toward the islands from the northeast.

PARTLY CLOUDY OR PARTLY SUNNY? You have probably wondered if a distinction exists. If you are curious, refer to the optional electronic Supplemental Information for Wednesday.

REPORT FROM THE FIELD -- Mark Seeley, LIT member from the Twin Cities and the extension climatologist for the University of Minnesota-Twin Cities, reported on the new highest minimum temperature records that were set across Minnesota on Monday, 23 October. He noted that these occurred with fog, low overcast and mist, reiterating the point that "water vapor is the ultimate greenhouse gas".


HISTORICAL WEATHER EVENTS - 25 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, 2000, The American Meteorological Society.