WELCOME TO DATASTREME - The Daily Summary file will describe the current weather pattern across the U.S. The Tuesday and Thursday files will also contain the "Concept of the Day" with a question to be answered on the weekly Chapter Response Form. Additional Supplemental Information Files will provide optional background material.
The following highlights of the national weather have been extracted from the surface weather map for Tuesday night:
SEVERE WEATHER MOVES ACROSS THE NORTHEAST -- A cold front moving eastward from the Great Lakes on Tuesday helped trigger thunderstorms across the Northeast. These thunderstorms were fed by the warm and humid air mass found across the East. Some of the thunderstorms that moved across Pennsylvania and New Jersey became severe. Strong winds caused damage, to include a roof being torn off a building near Lewisburg in central Pennsylvania and several reports of trees and power lines being toppled near Reading and some of the suburbs of Philadelphia in the southeast corner of the Keystone State. Large hail, with 0.75 to 1.00 inch diameters, fell in near Chester, PA and Somerset, NJ.
By late Tuesday evening thunderstorms were continuing across Downeast Maine and across southern New Jersey, Delaware Bay and the Del-Mar-Va Peninsula. These thunderstorms were found along and just to the east of the cold front that stretched from a low pressure center off the Labrador coast south-southwestward across the Maritime Provinces, New England and the Middle Atlantic States before curving westward to cross the Appalachians and parallel the Ohio Valley before reaching the mid-Mississippi Valley.
A cool, Canadian high pressure cell centered to the north of the Great Lakes in Ontario on Tuesday night was expected to spread southeastward across the eastern Great Lakes in the wake of the cold front. By sunrise on Wednesday the northern portion of the front is forecast to have moved out to sea. Southern sections of the front should be located across the Virginias, where it is forecast to become stationary by evening. Several tenths of an inch of precipitation is anticipated to fall along the front across coastal New England.
RAIN CONTINUES ACROSS THE SOUTH -- Locally heavy scattered rain and embedded thunderstorms continued across a large portion of the South on Tuesday. Much of the rain was concentrated across Texas, along the central Gulf coast of Louisiana and Mississippi and over Florida, southeastern Georgia and South Carolina.
The heavy precipitation across the southern Plains was associated with a distinct counterclockwise circulation regime that extends upward through the atmosphere to an altitude of approximately 20,000 feet. Only a weak trough line across Texas is the surface reflection of this upper level feature. Thunderstorms moving across western Oklahoma near Weatherford generated winds that had speeds between 60 and 65 mph. Some locations in the Houston metropolitan area have received more than 14 inches of rain within the last ten days. This system has been slow to move, with continued rain anticipated through Wednesday. An additional 2 inches of rain could fall across east Texas in the 24 hours ending on Wednesday evening. Consequently, flash flood watches were in effect for much of eastern Texas, extending from the Red River Valley, through Dallas-Fort Worth, Austin, San Antonio and Houston to the Gulf Coast and the lower Rio Grande Valley. Some roads were flooded on Tuesday.
Numerous thunderstorms were across Florida. Some wind damage was sustained from thunderstorms to the north of Daytona Beach. Lightning injured a woman and a child in separate incidents in St. Petersburg on Tuesday evening. More thunderstorm activity is forecast for Wednesday. Between 0.5 to 0.7 inches of rain could fall across the Florida Peninsula by Wednesday evening.
UNSEASONABLY WARM WEATHER ACROSS THE PLAINS -- Several factors have contributed to the unseasonably warm weather that has been found across the Plains recently. Cloud-free skies have permitted the sunshine to rapidly heat the relatively dry surface and overlying dry air during the day. In addition, winds descending onto the high Plains from the Rockies compress and heat as they move downslope. Tuesday afternoon high temperatures were above the long-term average highs for the first week of September over a large area extending from the Mississippi River westward to the Sierras. The largest departures were found across the Dakotas, where highs on Tuesday were on the order of 25 degrees above average. In fact, daily high temperature records were tied on Tuesday afternoon at Aberdeen and Huron with 105 degrees and 100 degrees, respectively, and near Wheatland, WY (101 degrees).
MOISTURE SPREADS NORTHWARD ACROSS THE ROCKIES -- A flow of moisture northward across the Rockies and the Intermountain West has caused widely scattered thunderstorms to spread northward from the Four Corners Region (of Arizona, New Mexico, Utah and Colorado) into Idaho and Montana. A tornado was reported near Milford in southwest Utah on Tuesday. No injuries or damage were sustained from this tornado.
A cold front that stretched southwestward from a complex low pressure system over the northern Rockies to northern California on Tuesday evening was contributing to producing thunderstorms across Montana and Idaho. This front is expected to continue to move eastward on Wednesday. A slight risk of severe thunderstorms is anticipated across the high Plains of Montana east of the Divide and adjoining portions of neighboring states through Wednesday. As much as 0.3 inches of rain could fall by Wednesday evening in the mountains of western Montana and the chimney of northern Idaho.
While the increased atmospheric moisture and the possibility of precipitation is welcomed by those fighting the wildfires across the West, especially near Glacier National Park in northwest Montana, they remain concerned that lightning from some of these thunderstorms could start additional fires. Too often these high-based "dry" thunderstorms do not have sufficient rainfall to quench the fires that the lightning starts. In addition, the accompanying winds could fan the fires.
YESTERDAY'S TEMPERATURE EXTREMES ACROSS THE CONTINENTAL US -- Tuesday morning's lowest temperature was 34 degrees at Stanley, ID, while the highest temperature on Tuesday was 110 degrees at Phoenix, AZ.
ALASKAN WEATHER -- A strong storm system that moved across the Bering Sea and into Norton Sound was spreading clouds, rain and winds across much of Alaska late Tuesday afternoon. This storm system was accompanied by a frontal system that extended southeastward across southwestern Alaska and over the Kenai Peninsula and Kodiak Island. While the rain was relatively widespread across Alaska, the heaviest rain was concentrated in the south central portions of the state. Saint Paul, Delta Junction and Bethel experienced gusts to 40 mph, while Anchorage, Barrow and Cold Bay had gusts to near 35 mph. A stationary front was found along the Brooks Range. Afternoon temperatures along the North Slope to the north of the front were in the 30s, while to the south of the front, some locations in the interior were in the 60s.
The state's lowest overnight temperature on Tuesday morning was 27 degrees at Snowshoe Lake. The highest temperature by mid afternoon of Tuesday was 66 degrees at Eielson AFB, Fairbanks, Wainwright and Annette.
HAWAIIAN WEATHER -- An elongated ridge of high pressure remained to the north of the Hawaiian Islands on Tuesday. As a result, the islands continued to experience northeast trade winds with speeds ranging from 10 to 20 mph. These relatively persistent winds from the northeast circulate out of the equatorward flank of the high pressure cells that typically reside over subtropical latitudes. Some increase in moisture from the south was expected by the end of the week. Until then, relatively pleasant weather with moderate northeast trade winds should continue across the islands as high pressure is forecast to remain relatively stationary.
EYE ON THE TROPICS -- Tropical Storm Erin continued its westward movement across the tropical North Atlantic. As of late Tuesday night Erin, with 50 mph sustained winds, was approximately 425 miles to the east of Antigua and it was moving to the west-northwest at 16 mph.
The tropical eastern Pacific was becoming more active again. The eighth tropical depression of the season intensified to become Tropical Storm Gil, the seventh named storm of the season in the Eastern North Pacific. As of Tuesday evening, Gil had wind speeds of 65 mph and was moving to the west at 5 mph. Its evening position was 1100 miles to the west-southwest of Cabo San Lucas, on the southern tip of Mexico's Baja California. Meanwhile, the ninth tropical depression of the season, identified as TD-9E, also had developed. On Tuesday evening, TD-9E had estimated wind speeds of 30 mph and was moving to the west-northwest at 16 mph along the Mexican coast approximately 380 miles to the south-southwest of Cabo San Lucas.
From the files of the Aviation Weather Center, Kansas City, MO
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Prepared by Edward J. Hopkins, Ph.D., email
hopkins@meteor.wisc.edu
© Copyright, 2001, The American Meteorological Society.