DATASTREME DAILY SUMMARY

Thursday, 8 November 2001


00Z Weather Systems


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

THE WARM WEATHER CONTINUES -- Unseasonably mild weather continued across much of the country on Wednesday. High pressure located across the Southeast maintained a southerly wind flow across the southern Plains and Mississippi Valley. As a result, high temperatures across the nation's midsection were once again above average, the largest departures were found across the western Corn Belt, with some stations in Iowa and Nebraska reporting highs that were 25 degrees above average. Daily record high temperatures were equaled or exceeded in Kansas at Russell (80 degrees) and Topeka (79 degrees); in Missouri at St. Joseph (78 degrees); in Nebraska at Omaha (77 degrees); in Iowa at Waterloo (78 degrees), Webster City (77 degrees), Mason City (75 degrees) and Spencer (74 degrees); in Minnesota at Rochester (73 degrees) and in Indiana at South Bend (68 degrees). To the southeast, Raleigh-Durham, NC also set a record high temperature (76 degrees). The daily low temperatures at Phoenix, AZ (66 degrees) and at Grand Junction, CO (47 degrees) set daily high minimum records.

A cold front moving southeastward across the northern Plains is expected to signal an end of the warm weather across the Midwest on Thursday.

A COLD FRONT MOVES ACROSS THE PLAINS -- A cold front trailing from a low pressure center over the Upper Mississippi Valley near Minneapolis/St. Paul, MN was bringing markedly colder weather southward across the Plains. Strong northerly winds in the Dakotas to the west of the low pressure system were causing temperatures to fall. As of 10 PM CST on Wednesday night, the temperature in Des Moines, IA, which was to the east of the front, was 62 degrees with light winds from the west-southwest. Roughly 400 miles to the west and on the other side of the front, North Platte, NE had a temperature of 43 degrees with strong northerly winds.

Gusty northerly winds were found behind the cold front. Wind advisories were in effect for Wednesday night across eastern North Dakota and northwest Minnesota. With strong northerly winds with speeds to 35 mph and gusts to 45 mph following the passage of the cold front, wind advisories have been posted through mid morning for western Kansas. As the western sections of the front move southward into west Texas, continued strong winds are expected. A high wind watch was posted for Guadalupe Pass in west Texas on Thursday as north winds were expected to reach 45 mph with gusts to 55 mph.

A long band of rain was found on the cold side of the front stretching from northwestern Wisconsin to northwest Kansas. A large area of rain also was found across northern Wisconsin and Michigan's Upper Peninsula to the north and east of the surface low pressure system.

On Thursday the storm system is expected to move toward the east-northeast, with the low pressure center forecast to be centered near Sault Ste. Marie, MI by sunrise and near Ottawa, ON by evening. The cold front trailing from the low is expected to move eastward and southward. By evening the northern portions of the front should have moved across the eastern Lakes and the Ohio Valley while southern portions of the front should have pushed southward to the Rio Grande Valley of west Texas.

SNOW IN THE ROCKIES -- Snow was falling across the mountains of southern Wyoming and northern Colorado as cold air was moving southward behind the cold front. Several inches of snow had fallen across the central Rockies by evening.

Snow should spread southward across the southern Rockies as the cold front continues moving southward. A snow advisory was in effect for Wednesday night and Thursday along the east slopes of the Sangre de Cristo Mountains of northern New Mexico, as 3 to 5 inches of snow could fall above 8000 feet.

CHILLY WEATHER IN THE NORTHWEST -- A relatively dry air mass accompanied high pressure that was situated over the Pacific Northwest. With clear skies and weak winds, record low temperatures were set on Wednesday morning at Klamath Falls, OR (15 degrees) and at Monterey, CA (41 degrees).

Radiational cooling across the interior portions of the Northwest was helping to form fog in the Columbia Basin of south central Washington and north central Oregon. As a result, a dense fog advisory was posted through Thursday morning.

BLUSTERY WEATHER CONTINUED ACROSS NEW ENGLAND -- A large storm system located between Newfoundland and Labrador continued to generate gusty northerly winds across New England on Wednesday. The winds were the result of a tight pressure gradient between high pressure in the vicinity of James Bay and the low pressure center of the Maritimes.

Relaxation of the pressure gradient by Thursday morning should decrease the winds. Until then, gale warnings for winds between 39 to 54 mph remained in effect along the Maine coast from Eastport to Stonington and along the Massachusetts coast from Merrimack River to Nantucket.

UPPER AIR -- The mid-tropospheric 500 mb constant pressure chart and the upper-tropospheric 300 mb chart for 00Z Thursday revealed a relatively zonal flow pattern across the country. This zonal flow meant that the prevailing winds were traveling from west to east with relatively small north-south departures.

TEMPERATURE EXTREMES IN THE CONTINENTAL U.S. -- Wednesday morning's lowest temperature was 12 degrees at Baker City and Burns, OR, while the Wednesday afternoon highest temperature was 90 degrees at Death Valley, CA.

ALASKAN WEATHER -- An arctic air mass remained stretched across most of Alaska on Wednesday in association with high pressure located over northwest Canada. Scattered to broken cloud cover was found across northern Alaska from the North Slope into the interior and south central portions of the state. Snow was falling at Barrow. The slight increase in temperatures across interior Alaska from subzero values on Tuesday represented a slow modification of the air mass. The southern boundary of this air mass was a stationary front that extended from the eastern Bering Sea along the Alaska Peninsula and the north Gulf Coast to the northern Panhandle before entering northern British Columbia. Warmer and more humid maritime air was situated to the south of the front. A storm system located over the Gulf of Alaska generated increased southerly winds across the Panhandle. These southerly winds spread clouds and precipitation across the Panhandle into southeast Alaska. Rain was falling across southern locations in the Panhandle, while snow was reported at Juneau and Northway. Another powerful storm was moving into the western Bering Sea from near the Kamchatka Peninsula. Strong winds and precipitation accompanying this storm were affecting the western Aleutians.

The lowest temperature in Alaska on Wednesday morning was 20 degrees below zero at Arctic Village and Ft. Yukon. The highest statewide temperature as of Wednesday afternoon was 48 degrees at Adak.

HAWAIIAN WEATHER -- The swirl of clouds and showers associated with the remnants of former Hurricane Octave were moving westward across the island chain. As of late afternoon this center of the swirl was several hundred miles south of Molokai. While radar indicated a general decrease in the showers, several isolated thunderstorms were forming northeast of Maui. The showers are expected to diminish on Thursday, followed by clearing of the clouds by Friday. Moderate trade winds remained across the islands as a ridge of high pressure was situated to the north of the state.

Ocean swell generated by a major storm system east of the Kamchatka Peninsula at the start of the week has propagated southeastward across the North Pacific and should arrive in the vicinity of the islands on Thursday. This swell may produce high surf along the northwest facing islands. The storm currently east of Kamchatka should generate slightly smaller swell that would reach the state by Sunday.


CONCEPT FOR THE DAY - UPPER AIR and JET STREAMS

Television weathercasts are often not complete without an arrow or two indicating the position of the "jet stream". What are jet streams?

Prior to World War II little was known of atmospheric conditions above the Earth's surface. A few instrumented airplane and kite measurements had been made but cloud patterns proved the most complete guide. Combatants during the war first encountered high speed winds at great altitudes on bombing missions. Reid Bryson, a wartime meteorologist on Saipan in the Pacific in November 1944 (and later noted climatology professor at the University of Wisconsin-Madison), first predicted 175 mph winds near the 30,000-foot flight level based on arguments similar to those presented in the DataStreme Pressure Blocks Activity 5B. Aircraft actually encountered those winds, confirming the forecast! Carl-Gustav Rossby named these winds the "jet stream" after high speed jets of water that had been studied in the laboratory. Knowledge of these winds is obviously critical for aircraft operations!

Decades of radiosonde data and more recent computer models of atmospheric flows have confirmed that the strength and location of what has become known as the Polar Front jet stream in upper level motions are linked to the formation, movement, and evolution of the Highs and Lows of the surface weather maps. The polar front is the boundary between the cold air masses of high latitudes and the warm air masses of lower latitudes. For more detail on some of these relationships, see the optional Thursday Supplemental Information.

QUESTIONS:

To be submitted on the lines for Thursday on the Study Guide, Part B, Applications', Week 9 Chapter Progress Response Form, under section B. Daily Summary.

  1. The polar front jet stream can be found above regions where [(weak) (strong)] horizontal temperature gradients exist; that is, regions where warm and cold air masses come in contact.
  2. The upper tropospheric jet stream was discovered in about the [(1900s) (1940s) (1960s)].

HISTORICAL WEATHER EVENTS - 8 November

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


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