DATASTREME DAILY SUMMARY

Friday, 16 November 2001


00Z Weather Systems


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

MORE SEVERE WEATHER HITS TEXAS -- Thunderstorms associated with a mid and upper tropospheric disturbance (see below) spawned tornadoes, produced large hail and flooding rains across a large portion of Texas on Thursday. A relatively innocuous looking surface low pressure center is the reflection of the relatively strong upper level disturbance with counterclockwise circulation. At least thirteen tornado reports were filed with the Storm Prediction Center during the late afternoon and into the early evening.. Most of these tornadoes occurred between Austin and Corpus Christi. One injury was sustained by a tornado between Austin and San Antonio. Some damage was reported from the tornadoes on the outskirts of Austin. Some of the thunderstorms also produced large hail, with diameters to 1.75 inches. The slow moving thunderstorm cells coupled with the passage of multiple cells over the same area (called "training") produced heavy rainfall totals. Record rainfall totals were reported on Thursday at Austin (8.68 inches at Bergstrom Airport and 6.67 inches at Camp Mabry), San Antonio (2.18 inches), and Abilene (0.85 inches). Flooding was reported in the Austin and San Antonio metropolitan areas.

Continued rainshowers and imbedded thunderstorms curled northwestward from the Gulf Coast across much of Texas into New Mexico on Thursday night. This precipitation shield is expected to remain across the region through Friday. A slight risk of severe thunderstorms remains over south Texas through daybreak on Friday morning. Between 1 and 2.2 inches of rain could fall across southern Texas during the 24 hours from Friday to Saturday morning. As a result of the recent rain and the additional anticipated rain, flash flood watches were issued for a large portion of Texas, extending from the Gulf Coast westward to the Rio Grande and northward to the Red River, to include cities such as Corpus Christi, San Antonio, Austin and Del Rio.

A PESKY SYSTEM -- A storm system located off Florida's Atlantic Coast near Cape Canaveral continued to produce rain and windy conditions across portion's of the Sunshine State. Rain continued to fall from northern Florida into southeastern Georgia. In addition to the clouds and rain, which suppressed afternoon high temperatures across the Sunshine State, the storm also continued to produce relatively strong and persistent east to northeasterly winds along the state's central and northern Atlantic coast. This wind regime produced high surf and local coastal flooding, especially because of the high astronomical tides due to new moon.

The low pressure system is expected to drift slowly toward the east on Friday. However, because of the continued easterly winds, heavy surf advisories remain in effect along the coast from Sebastian Inlet, FL to South Santee River, SC. Coastal flood watches were also continued for the coastal communities of northern Florida and southern Georgia.

UNSETTLED WEATHER ACROSS THE NORTHWEST -- A cold front trailed southward across Washington, Oregon and northern California from a low pressure center located in central Alberta. Widespread precipitation accompanying this cold front was detected across much of the Pacific Northwest, extending eastward into northern Idaho. Since the air was sufficiently warm, most of the precipitation fell as rain rather than snow even across the mountains. The windy conditions that had necessitated gale warnings as well as high wind and heavy surf advisories along the coast earlier in the day had slackened by Thursday night.

Northern portions of the front are expected to move eastward, reaching the Rockies in northern Montana by Friday afternoon as the low pressure center moves eastward across Alberta. Southern portions of the front are forecast to move slowly southward across northern California. Nearly one half inch of rain is expected on Friday and early Saturday from northern Idaho southwestward to northern California.

MORE RECORD WARMTH -- Except those regions affected by clouds and rain in south Florida as well as west Texas and southern New Mexico, most of the country experienced another day of unseasonably mild weather. High temperatures from Washington and Oregon eastward to New England were at least 10 degrees above average. The largest departures were found from the plains of eastern Montana to the western Lakes, where highs were nearly 30 degrees above average. Record high temperatures were either tied or exceeded in Nebraska at Norfolk (78 degrees), Lincoln (76 degrees), Grand Island (76 degrees), Hastings (75 degrees) and Omaha (75 degrees at Eppley Field); in Iowa at Sioux City (75 degrees), Des Moines (73 degrees), Ottumwa (73 degrees), Lamoni (72 degrees) and Waterloo (68 degrees); in Wisconsin at La Crosse (70 degrees), Green Bay (68 degrees), Oshkosh (68 degrees), Wausau (66 degrees) and Eau Claire (65 degrees); in Illinois at Moline (72 degrees); in Minnesota at Rochester (67 degrees) and in Michigan at Alpena (65 degrees) and Marquette (65 degrees). In the Pacific Northwest, record highs were set in advance of the cold front across Washington at Walla Walla (69 degrees), Ephrata (65 degrees) and Ellensburg (56 degrees) and in Oregon at Pendleton (68 degrees).

UPPER AIR -- Both the 500 and 300 mb charts for 00Z Friday continued to show a cut-off low over the Southwest which was responsible for the widespread rain and thunderstorm activity across Texas and New Mexico. This cut-off feature is a closed counterclockwise circulation regime in the upper troposphere that surrounds a pool of cold air that is detached from the prevailing westerly wind regime farther north. Because this deep feature that extends upward through most of the troposphere is detached from the westerly flow, the feature typically is slow to move and often erratic in its forward motion. As a result, the showers and thunderstorms should continue across Texas through Friday.

TEMPERATURE EXTREMES ACROSS THE CONTINENTAL US -- Thursday's lowest temperature was 16 degrees at Craig, CO. Thursday's highest temperature was 84 degrees at Palm Springs and Borrego, CA.

ALASKAN WEATHER -- Arctic air remained across essentially all of mainland Alaska on Thursday. Midday temperatures ranged from subzero readings along the North Slope to single digits in the interior. A stationary front along the coast of south central and southeast Alaska marked the southern boundary of this arctic air mass. A storm system over the northern Gulf of Alaska was responsible for clouds and precipitation across south central and southeastern Alaska. Snow was reported at Homer, but rain and snowshowers were found across the Southeast. Petersburg had 1.24 inches of precipitation, while Yakutat had 1.02 inches. Haines Customs had an additional 12.9 inches of snow, bringing the snow depth to 47 inches.

A weak low pressure center was found along the Arctic coast near Deadhorse. Snow was falling at Barrow, Nuiqsut and Wainwright. Many interior locations also reported snow.

The lowest overnight temperature in Alaska on Thursday morning was 22 degrees below zero at Aniak, while the mid-afternoon highest statewide temperature was 45 degrees at Annette and Wrangell.

HAWAIIAN WEATHER -- The subtropical ridge of high pressure that usually remains sufficiently far to the north maintaining the typical trade wind weather across the Aloha State has essentially moved over the islands on Thursday and is expected to remain into next week. The typical trade winds have been replaced by light and variable winds across all the islands in the chain except for the Big Island where light trade winds remain. Sunny skies have produced afternoon highs in the mid 80s. With light winds local afternoon sea breeze regimes develop as the interiors of the islands are warmed, producing an onshore sea breeze. Afternoon convective clouds and showers develop on the mountain slopes. Nights are clear and cool, with lows in the 60s. A cold front has stalled to the north of Kauai.

DID YOU KNOW? -- Astronomers predict that within the next two days the earth should experience the Leonid meteor showers. The Leonid meteor shower usually occurs at this time of year, with an hourly rate that typically was between 10 to 15 meteors per hour. Peak viewing in eastern North America should before dawn on Saturday. A new moon means viewing should not be adversely affected. If the skies are clear and dark, look toward the east early tomorrow morning. The Leonid meteors should disperse across your local sky as the radiant point near the constellation Leo rises in the southeast.

The Islamic month of Ramadan starts today, Friday 16 November. The Islamic calendar is lunar based and a month begins with each new moon's visible crescent.

A REMINDER -- To All DataStreme Participants:

Next week is Thanksgiving Week recess. The DataStreme Daily Summary will contain only the selected Historical Weather Events for each day during Thanksgiving Week. Current weather data will be available on the homepage as usual. If you are looking for an alternative description of daily weather, you could try:

http://www.usatoday.com/weather/wlead.htm

Have a Happy and Safe Thanksgiving!

Ed Hopkins

HISTORICAL WEATHER EVENTS - 16 November

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

17 November

18 November


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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.