A MAJOR STORM MOVES TOWARD THE GREAT LAKES -- An intense storm system moved into the northern Great Lakes from the Upper Mississippi Valley on Wednesday night accompanied by severe weather, strong gradient winds, heavy rain, snow and blizzard conditions. This occluding storm consisted of a primary low pressure system with a central pressure of 985 mb located over eastern Lake Superior, an occluded front that extended to a secondary low pressure center over the Mackinac Straits, where a warm front extended eastward into Ontario and a cold front bowed southward to the Texas Gulf Coast. A secondary cold front trailed southwestward from the vicinity of the storm's center across the Mississippi Valley into the central Plains.
The intense storm system was accompanied by strong gradient winds (to distinguish from thunderstorm winds) that resulted from the tight pressure gradient surrounding the low pressure center as indicated by the packing of isobars on Wednesday night's surface analysis charts. Strong southerly winds were found along the Appalachians and across the eastern Great Lakes. As a result of this southerly flow, high temperatures to the east of the Mississippi River, were on the order of 15 to 20 degrees above average. Record high temperatures were either tied or set in Texas at Del Rio (98 degrees), Corpus Christi (94 degrees) and College Station (93 degrees); in Louisiana at New Orleans (88 degrees); in Alabama at Montgomery (88 degrees); in Florida at Palm Beach (89 degrees) and Orlando (88 degrees); in South Carolina at Columbia (89 degrees), Charleston (87 degrees) and North Myrtle Beach (84 degrees); in North Carolina at New Bern (88 degrees), Raleigh-Durham (87 degrees), Wilmington (87 degrees), Greensboro (84 degrees) and Asheville (81 degrees); in Kentucky at London (82 degrees); in Virginia at Richmond (86 degrees), Norfolk (86 degrees), Roanoke (85 degrees), Lynchburg (83 degrees) and Blacksburg (80 degrees); in West Virginia at Beckley (78 degrees) and Bluefield (75 degrees); at Washington DC (84 degrees at both National and Dulles); in Maryland at BWI near Baltimore (82 degrees); in Wilmington (82 degrees) and Delaware at Georgetown (81 degrees); in New Jersey at Newark (83 degrees); in New York at Central Park in New York City (79 degrees); in Pennsylvania at Philadelphia (83 degrees), Harrisburg (80 degrees), Reading (81 degrees), Allentown (81 degrees) and Wilkes-Barre/Scranton (77 degrees) High minimum temperature records were also set at Tampa, FL (75 degrees) and Portland, ME (55 degrees).
Strong northwesterly gradient winds swept around to the west of the storm. Consequently, many locations across the northern Plains to the west of the developing storm system experienced high temperatures that were on the order of 20 degrees below average.
The storm is expected to intensify slightly as it drifts slowly toward the northeast on Thursday. By sunrise the primary low pressure center should be located to the northeast of Lake Superior, with the occluded front stretching eastward to a point of occlusion that is forecast to be located over the Ottawa River Valley. A warm front is expected to continue eastward across northern New England, while a cold front should stretch southward from the point of occlusion along the Eastern Seaboard. By evening the primary low is anticipated to remain relatively stationary, while the occluded front bows northward with the point of occlusion forecast to be located over northern Maine. The cold front should have moved off the East Coast. However, strong winds are expected to continue across the Great Lakes as a tight pressure gradient is forecast to dominate the region.
SEVERE WEATHER IN THE NATION'S MIDSECTION -- The cold front was extremely active as a line of strong to severe thunderstorms extended nearly the entire length of the front from Lower Michigan south to northern Louisiana well into the late hours of Wednesday night and Thursday morning. Severe thunderstorms spawned tornadoes, generated damaging winds and produced large hail across the Mississippi and Ohio Valleys into the Great Lakes States, encompassing an area that extended from northern Mississippi to Lower Michigan and from western Missouri to West Virginia. By early Thursday morning, as many as 20 tornadoes were reported to the Storm Prediction Center from Missouri, Illinois, Indiana, Michigan, Ohio and Tennessee. One fatality is attributed to a tornado that destroyed a house near La Porte in northern Indiana. Many of the tornadoes caused damage to homes and businesses, along with uprooted trees. In addition to the tornadoes, numerous (405) reports of damaging thunderstorm winds were also made. At least 2 fatalities were attributed to the thunderstorm winds. A tree crushed a pickup truck and killed its driver in central Michigan north of Lansing. A child was killed when thunderstorm winds caused major damage to a home in east Tennessee near Chattanooga. Numerous injuries were caused by the thunderstorm winds, with 10 injuries reported when a commercial building partially collapsed near Warsaw in Indiana. An additional wind-induced injury was reported in Indiana, 4 injuries in Michigan, 2 injuries in Tennessee and 1 injury each in Kentucky and Missouri. Large hail also fell from these thunderstorms, with diameters ranging from 0.75 inches to 2.75 inches.
In addition to the severe weather, the thunderstorms produced heavy rains that resulted in daily rainfall records at Grand Rapids, MI (2.24 inches), Indianapolis, IN (1.52 inches).
A high risk of severe weather is expected to continued into the night across Ohio and the lower Great Lakes, with a moderate to slight risk found across a large portion of the Ohio Valley and the Southeast along and ahead of the cold front. On Thursday, northern New England was expected to experience a slight risk of severe weather as the cold front approaches the region with potentially severe thunderstorms.
WINTRY WEATHER ACROSS THE NORTHERN PLAINS -- Heavy snow fell in the cold air to the north and west of the low pressure center. North Dakota was particularly hard hit as Grand Forks received 10.8 inches of snow on Wednesday, which set not only a daily snowfall record but also the monthly record for October. The liquid water equivalent precipitation was 0.92 inches, also a daily record. Fargo received 4.9 inches of snow, far short of a record snowfall for the date, but the liquid equivalent precipitation total of 0.80 was a daily record. Snow continued to fall across portions of the eastern Dakotas and northern Minnesota. Strong gradient winds from the northwest produced blizzard conditions across the region.
A blizzard warning had been posted for northeastern North Dakota and adjacent sections of northwestern Minnesota as northwesterly winds gusting to 45 mph could reduce the visibility in blowing and drifting snow. Winter weather advisories were in effect across southeastern North Dakota, northern Minnesota and northern Wisconsin, where several inches of snow coupled with strong northwesterly winds were anticipated. Winter storm watches were also issued for portions of north central Wisconsin and the eastern half of Michigan's Upper Peninsula, where 6 to 10 inches of lake-enhanced snow is expected by Thursday night, along with the strong winds. A high wind warning was in effect across much of Michigan and adjacent counties in northern Indiana and northwest Ohio, as strong winds with gusts to 60 mph are expected, especially in the Upper Peninsula. A wind advisory was in effect across Wisconsin.
OF NOTE ELSEWHERE -- Locally heavy rain in Florida produced a daily record rainfall at Melbourne (1.13 inches).
High pressure located over the Pacific Northwest was responsible for record low temperatures that were established on Wednesday morning in Oregon at Burns (14 degrees) and Klamath Falls (15 degrees) and in California at Eureka (38 degrees). Relatively low temperatures are expected on Thursday morning across the West. Freeze warnings were posted for portions of northwest Kansas and east central Utah.
TEMPERATURE EXTREMES IN THE CONTINENTAL U.S. -- Wednesday morning's lowest temperature was 10 degrees at Big Piney, WY, while the Wednesday afternoon highest temperature was 100 degrees at Laughlin AFB at Del Rio, TX.
ALASKAN WEATHER -- A large low pressure system located over the northeastern Gulf of Alaska continued to dominate the weather across much of Alaska on Wednesday. Except for relatively cloud-free skies across portions of southwest Alaska, much of the state experienced cloudy skies. The low pressure center was located within 200 miles south of Cordova, with a central pressure of approximately 998 mb. Southerly winds to the east of the low brought warm air with temperatures in the mid 40s and rainshowers across the Panhandle. To the north of the low easterly and northeasterly winds were found across south central and interior Alaska. Snow was reported at Bethel and Delta Junction. Strong northwesterly winds were reported across southwestern Alaska, the Alaska Peninsula and the eastern Aleutians. The strength of these winds was enhanced by the tight pressure gradient resulting from a high pressure center located over the central Aleutians and the low in the Gulf. Whittier reported gusts to 46 mph, while Dutch Harbor and Seward had gusts to 36 mph. Another high pressure cell was located over the Arctic Ocean and the Chukchi Sea to the northwest of Alaska. Arctic air associated with this high kept midday temperatures along the North Slope near zero. Anaktuvuk had a temperature of 8 degrees below zero. Several stations had subzero wind-chill equivalent temperatures.
The lowest temperature in Alaska on Wednesday morning was 8 degrees below zero at Anaktuvuk Pass and Gulkana. The highest statewide temperature as of Wednesday afternoon was 48 degrees at Adak.
HAWAIIAN WEATHER -- Light winds were found across the Aloha State on Wednesday afternoon as the result of a surface trough of low pressure that stretched across the central islands. An increase in the low level moisture because of the trough plus a decreased atmospheric stability associated with a cold pool of air in the upper troposphere produced heavy rainshowers and isolated thunderstorms across the Big Island. The showers were expected to continue there through the night before spreading across the other islands on Thursday and Friday. A flood watch was in effect for all islands.
EYE ON THE TROPICS -- The former Hurricane Narda weakened to tropical depression status as it moved westward from the eastern into the central North Pacific Ocean. As of late afternoon when the Central Pacific Hurricane Center in Honolulu issued its last official advisory on Narda, this tropical depression had maximum sustained winds of 35 mph, and it was located 680 miles east-southeast of Hilo on Hawaii's Big Island with a forward motion of 13 mph to the west.
Question: What do meteorologists, police and television baseball announcers have in common? Answer: Doppler radar, for one thing.
Radar, RAdio Detection And Ranging, uses a pulse of microwave energy sent out and echoed back by a distant target. Using radar, we can spot targets at various distances and directions. Tracking airplanes was the first goal of radars. Meteorologists have long used radar to spot the locations, intensities and movements of precipitation that are associated with storm systems. Recently the National Weather Service installed a network of new radar units across the U.S. that can also detect motions of raindrops, snowflakes, and hail using the Doppler principle. When a moving target echoes back part of the radar pulse, the frequency of the electromagnetic energy is shifted slightly from the original signal value. The amount of shift relates to the speed of target movement directly toward or away from the receiver. With a weather radar this means we can infer the wind speeds and directions that move the raindrops and other particles in the storm.
Police agencies have also used Doppler radar units in enforcing speed limits. A traffic radar aimed at a moving car will tell the car's speed directly toward or away from the unit. The sports media have been quick to use this technology to impress viewers with the speed of a baseball pitch or tennis serve. While the speed of a pitch from the mound to home plate can be "measured" because it travels toward the radar, a throw from third to first base would not because it is moving across the radar beam. So Doppler weather radar interpretation is much more complex than baseball and chasing speeders. Storm motions are scanned across the entire atmosphere surrounding the radar site for hundreds of kilometers out and several kilometers up, with no "seventh inning stretch"!
Another additional feature of the new Doppler radar units operated by the National Weather Service is the capability to estimate the accumulated rainfall over a given area near the radar unit and then alert the radar operator to the possibility of flooding if some critical threshold were reached. As a result, flash flood watches and warnings can be issued more promptly.
For more information describing interpretation of DataStreme radar summary products, you may consult Thursday's electronic Supplemental Information .
To be submitted on the lines for Thursday on the Study Guide, Part B, Applications', Week 7 Chapter Progress Response Form, under section B. Daily Summary.
From the files of the Aviation Weather Center, Kansas City, MO and Intellicast