DATASTREME DAILY SUMMARY

Tuesday, 11 December 2001


00Z Weather Systems


The following discussion is based upon the major weather features appearing on Monday night's surface weather maps:

WELCOME RAINS ACROSS THE SOUTHEAST -- A large precipitation shield to the north of a low pressure system spread welcome rain across portions of the dry Southeast on Monday. As of late Monday evening the low pressure center was located off the South Carolina coast. A warm front extended eastward from the low pressure center while a cold front trailed to the southwest across northern Florida toward a stationary front that continued across the Gulf of Mexico. Most of the precipitation extended northward from coastal Georgia and South Carolina to the Del-Mar-Va Peninsula and westward to eastern Kentucky. The clouds and rain kept afternoon highs across the Carolinas below the average highs for this time of year. Strong thunderstorms were found off the Florida coast late Monday afternoon and off the coast of the Carolinas late Monday night.

The storm system is expected to move northeastward over the western Atlantic Ocean, paralleling the East Coast on Tuesday. By morning the storm system is forecast to be off the Middle Atlantic Coast near the Del-Mar-Va Peninsula. The precipitation shield is expected to move northward in association with the movement of the storm. Between 0.5 and 1.4 inches of rain are expected to fall in the 24 hours ending by Tuesday evening along the Eastern Seaboard from the Grand Strand of South Carolina northward to Delaware Bay.

AHEAD OF THE FRONT -- A cold front moving across the Upper Midwest was bringing slightly cooler air southeastward from the northern Plains. The area to the south and east of the front, to include the central Plains, the Upper Mississippi Valley and Great Lakes, experienced a relatively warm Monday with high temperatures between 10 to 20 degrees above average. A record high temperature was reached at Marquette, MI (40 degrees). Essentially no precipitation was found along the front because of the lack of sufficient available moisture.

The western portion of the cold front, which had stalled and become a stationary front, is expected to move back northward across the Plains as a warm front on Tuesday.

WINTRY WEATHER IN THE WEST -- A cold pool of air was situated across the Great Basin, where high temperatures were between 10 to 15 degrees below the average highs for the date. A cold storm system that extended up through the troposphere was moving across the Four Corners area of the Southwest. Several surface low pressure centers were found over New Mexico and northern Arizona. Light snow was falling across western Colorado, southern Utah, northern Arizona and northern New Mexico, while light rain was detected over southern Arizona and southeastern California. As of late Monday night, 8 inches of new snow had been reported near Wolf Creek Pass in southwestern Colorado.

The diffuse surface lows are expected to drift eastward on Tuesday accompanied by several areas of precipitation. Several tenths of an inch of liquid equivalent precipitation are anticipated to fall across the Four Corners area by Tuesday evening. Snow advisories were posted for the mountains of southwestern Colorado to include the San Juans, where 4 to 8 inches of snow are expected by Tuesday morning. Additional snow advisories were in effect through Tuesday for the Mogollon Rim in central Arizona, where snow accumulations between 5 to 10 inches are anticipated at elevations above 5000 feet.

Cold air was being drawn southward over California on northerly winds in the wake of the storm system and in advance of high pressure building into the area. Because the air mass is cold and relatively dry, overnight low temperatures are expected to fall to the low 30s in the sheltered areas of central and southern California. As a result, frost warning and advisories were posted for the Sacramento and San Joaquin Valleys in central California and some of the sheltered valleys of Ventura County near Los Angeles. However, along the California coast northerly winds are sufficiently strong to require gale warnings from Point Arena to Santa Cruz Island. In addition, heavy surf advisories were also in effect along the California coast from Pigeon Point to Santa Cruz Island and for the Pacific Northwest between Cape Flattery, WA to Florence, OR.

UPPER AIR -- Both the 500 and 300 mb charts for 00Z Tuesday have a large height trough across the Great Basin and the Southwest, reflecting the cold pool of air that extends upward through the troposphere. Northerly winds at each of these constant pressure surfaces are found along the West Coast, traveling southward around the west limb of the trough. Southwesterly winds are located on the east limb of the trough across the Rockies.

TEMPERATURE EXTREMES IN THE LOWER 48 -- The lowest temperature on Monday was 18 degrees below zero at Wisdom, MT, while Monday's highest temperature was 84 degrees at Fort Myers and Lakeland, FL.

ALASKAN WEATHER -- A ridge of high pressure extended northwestward across eastern Alaska from one high pressure center located over northwestern Canada to another center over the Arctic Ocean. As a result, arctic air remained across much of mainland Alaska. Most stations across interior Alaska reported afternoon temperatures that were below zero, with the lowest reading at Northway (24 degrees below zero). An east-west oriented stationary front separated the arctic air mass from warmer air to the south. This front ran from northern British Columbia westward along the Gulf coast and the Alaska Peninsula to the southern Bering Sea. A large area of low pressure was located over the Gulf of Alaska. Rain fell at Ketchikan (1.97 inches) and Annette (1.07 inches). A trough of low pressure extended across western Alaska. Snow fell at Dillingham. A freezing rain watch was posted through Tuesday for the vicinity of Bristol Bay, to include King Salmon. Another storm system was located across the central and eastern Aleutians.

The state's lowest temperature on Monday morning was 40 degrees below zero at Fort Yukon. The highest temperature across Alaska as of midafternoon on Monday was 43 degrees at Annette and Metlakatla.

HAWAIIAN WEATHER -- A strong high pressure system remained relatively stationary to the northeast of the Hawaiian Islands. This high continued to generate strong and gusty trade winds over the islands. The subtropical high is expected to remain essentially stationary with little change in intensity through midweek, resulting in the continuation of the strong trade winds. An increase in atmospheric moisture is also expected by Wednesday, resulting in a greater chance of showers. With strong trade winds, a gale warning was posted for the Alenuihaha Channel and high surf advisories were continued for the east-facing shores of the islands. Small craft advisories also remained in effect for state waters.

AN INTERESTING EDUCATIONAL RESOURCE SITE -- The Southeast Regional Climate Center (SERCC) maintains a weather and climate education page called "Climate Kids" at http://www.sercc.com/education/education.html. They have recently posted a new feature called "Hurricane Name Game".


HISTORICAL WEATHER EVENTS - 11 December

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



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