WELCOME TO DATASTREME ATMOSPHERE - This Daily Summary represents one of the products that you will routinely use in the DataStreme Atmosphere Project. We - to include those at DataStreme Atmosphere Central and myself - would like to welcome all the participants to this exciting project. I will be responsible for producing this Daily Summary File that describes current and recent weather features of note. On Tuesdays and Thursdays, this file will also contain a "Concept of the Day", which will develop some weather topic in further detail. Two questions related to that topic will appear at the end of this feature for you to answer as part of the weekly materials that you will submit to your LIT mentor. On occasion, I will post a Supplemental Information File. As its name indicates, this file will contain supplementary background material or resource information. I also produce the Weekly Weather and Climate News, another DataStreme Atmosphere product that includes links to various current news items I have found on the Web that pertain to weather and climate issues and events that occur around the world that are not typically associated with events covered in this Daily Summary.
Sincerely,
Ed Hopkins
The following highlights of the national weather pattern have been extracted from the surface weather map for late Sunday night:
THE LEGACY OF FAY -- Widespread clouds, rainshowers and several isolated thunderstorms continued across the South into Sunday evening due to Tropical Depression Fay. As of late Sunday, the low-pressure center that marked this former tropical storm was a located in southern Mississippi approximately 90 miles north of New Orleans, LA. In addition to the locally heavy rain, the counterclockwise circulation of air around the center of Fay produced sustained winds reaching 25 mph, with some wind gusts having higher speeds. The minimum central pressure was 1001 millibars (or 29.56 inches of mercury). The relatively tight packing of the isobars (lines of equal pressure) on Sunday night's surface weather analysis charts indicated a strong pressure gradient (difference in pressure) between the low-pressure center and the surrounding high-pressure area. This tight pressure gradient was responsible for the strong winds.
Some thunderstorm activity accompanied Fay on Sunday. Two unconfirmed tornadoes were spawned by the thunderstorms during the afternoon in central sections of Alabama to the northeast of Montgomery. No damage was reported from these tornadoes. Strong thunderstorm winds knocked down signs in northern Alabama and blew down trees and power lines in southern Louisiana late Sunday afternoon. As of late Sunday night, several isolated thunderstorms were found over northern Georgia and middle Tennessee, while a cluster of thunderstorms were detected over the Gulf of Mexico coastal waters offshore of Alabama, Mississippi and Louisiana.
During its travel across Florida and southern sections of Alabama and Mississippi during the past week, Tropical Storm Fay was known as a prolific rain-producing storm system. As of Sunday evening, Melbourne Beach along Florida's east coast had received 25.28 inches of rain from Fay, while nearby Cocoa Beach recorded 24.38 inches and Cape Canaveral 22.83 inches. Daily maximum rainfall records were set on Sunday in Louisiana at Baton Rouge (3.04 inches), in Mississippi at Tupelo (2.00 inches) and in Georgia at Columbus (2.11 inches) and Macon (1.58 inches). While some locations in Florida experienced serious flooding, the rain was generally welcome across the Southeast as much of the region has been experiencing severe drought conditions for more than a year.
Tropical Depression Fay was expected to remain relatively stationary through Monday, with gradual weakening. The system should continue to produce between three and six inches of rain across a large section of the Gulf Coast States, extending from the western Panhandle of Florida, all but northern Alabama, eastern and southern sections of Mississippi to southeastern Louisiana, including the Mississippi Delta and the New Orleans metropolitan areas. Consequently, flash flood watches were continued across this region.
ACTIVE WEATHER ACCOMPANIES COLD FRONT -- Thunderstorms continued into late Sunday evening along a cold front that pushed eastward from the Midwest into the eastern Great Lakes and Northeast. The thunderstorms stretched southeastward from the St. Lawrence Valley of Quebec across sections of northern Vermont, Upstate New York and western Pennsylvania. During the late afternoon, one of the thunderstorm cells produced strong thunderstorm winds that toppled some power poles in the Cincinnati (OH) metropolitan area. Some of the thunderstorms moving across the Ohio Valley produced an "outflow boundary" (as indicated on the accompanying fronts-satellite insert). This outflow boundary is leading edge of rain-cooled downdraft of air from a thunderstorm that has reached the surface and spread outward.
The cold front responsible for the active weather was the leading edge of colder air that was spreading eastward and southward from the Midwest. The front trailed southwestward across the Northeast and the Ohio Valley from a low pressure-center located in northern Quebec. Farther to the west, the cold front stalled to become a stationary front that stretched from the Bootheel of southeastern Missouri to a low-pressure center over southeast Colorado.
Northern sections of the cold front were expected to continue moving eastward across New England and the Middle Atlantic States on Monday. However, sections of the front over the Ohio and Mississippi Valleys were expected to remain relatively stationary.
A TASTE OF FALL -- A cool and dry air mass following behind the cold front spread across the northern Plains and into the Upper Midwest on Sunday. This chilly air mass was associated with a large sprawling high-pressure center that was located in southwestern Ontario to the north of Lake of the Woods and northern Minnesota. The clockwise circulation of air around the high-pressure center resulted in winds from the north and northwest on the eastern side of the high, while winds from the south and southeast on the high's western flank. Near the center of the high, calm conditions or relatively weak winds were found.
The combination of cool dry air from Canada and weak wind conditions helped cause significant nighttime cooling. On Sunday morning, temperatures at Grand Forks, ND fell to 39 degrees and at Marshalltown, IA to 50 degrees, which were daily low temperatures records for the date at both locations.
The center of the high-pressure system was forecast to drift eastward across Lake Superior on Monday. The ingredients for another chilly night were available. Freeze warnings were issued for early Monday across a large section of northeast Minnesota's Arrowhead as predawn temperatures could fall to the upper 20s or low 30s. Frost advisories were posted for the sections of northern Wisconsin and Michigan's Upper Peninsula as temperatures in the mid to low 30s were anticipated on Monday morning.
SEVERE WEATHER ALONG THE FRONT RANGE -- Thunderstorm cells developed along the eastern slopes of the Rockies in Colorado and Wyoming late Sunday afternoon. As many as eight unconfirmed tornadoes were reported in the Denver metropolitan area during the late afternoon and early evening. Up to one-inch diameter hail also fell from some of these early-evening thunderstorms along the Front Range in Colorado. Farther to the north, thunderstorms traveling across eastern Wyoming and the Black Hills of western South Dakota produced hail with diameters up to 1.75 inches.
The thunderstorm activity was associated with a trough of low pressure that developed along the Front Range of the Rockies in southern Colorado. Winds from the southeast brought sufficiently warm, humid and unstable air up the slope toward the mountains, resulting in the production of thunderstorms. As of late Sunday evening, isolated thunderstorms were detected across southeastern Colorado east of Pueblo and in the Nebraska Panhandle. Additional thunderstorms were scattered across the mountains of northern New Mexico.
Some thunderstorm activity could develop on Monday across the mountains and adjacent high Plains of Colorado southward to the Panhandles of Oklahoma and Texas.
WARM CONDITIONS ACROSS THE GREAT BASIN -- Sections of the Great Basin and the Northern Rockies experienced unseasonably warm weather on Sunday. A half-dozen record high temperatures were reached on Sunday in Utah, including 104 degrees at Hanksville and 99 degrees at Salt Lake City. A large area of high pressure located over the region was responsible for the warm and relatively quiet weather.
UNSETTLED WEATHER IN THE NORTHWEST -- Clouds and rainshowers were spreading eastward across Washington State and northwest Oregon on Sunday evening. These clouds and rainshowers were accompanying a cold front that came onshore along Washington's Olympic Peninsula during the late afternoon. By evening, the front was progressing eastward across the Cascades. The front was bringing cool and humid air from the North Pacific onshore into the Northwest. Quillayute Airport on the Olympic Peninsula received 1.10 inches of rain, which set a daily maximum precipitation record for the date.
The front was forecast to continue traveling eastward across the interior Northwest, passing across the northern Rockies late Monday afternoon. Rainshowers were expected to continue across the western slopes of the Olympics and the Cascades in western Washington and the northern Rockies of eastern Washington and northern Idaho. Rainfall totals should range from three-quarters of an inch to one inch during the 24 hours ending late Monday afternoon. The lifting of the onshore flow of humid Pacific air along the west facing slopes of the mountains would help generate rain.
TEMPERATURE EXTREMES ACROSS THE LOWER 48 -- On Sunday, the lowest temperature reported in the continental U.S. was 31 degrees (Fahrenheit) at Stanley, ID, while Sunday's highest temperature was 120 degrees at Death Valley, CA.
ALASKAN WEATHER -- Clouds were found across eastern and southern Alaska late Sunday afternoon due to a large complex area of low-pressure along with an accompanying frontal system found across southeastern Alaska, southern sections of the Yukon Territory of Canada and the nearby waters of the northern Gulf of Alaska. The low-pressure area consisted of three separate low-pressure centers. One center was located near Anchorage on the northern Kenai Peninsula, a second center was situated near Whitehorse in the Yukon Territory and the third low-pressure center was found over the north central Gulf of Alaska. Some rain fell along the Panhandle in association with the complex low-pressure system. Relatively cloud-free skies and dry conditions were found across southwestern and interior Alaska as a ridge of high pressure extended from northeast Alaska southwestward to the Bering Sea. A low-pressure system moving eastward across the North Pacific to the south of the central Aleutians brought clouds to this section of the island chain. Clouds were also found across northwestern Alaska in association with a cold front that stretched across the region. This cold front trailed southwestward from a low-pressure center near the North Pole across mainland Alaska from near Barrow to Nome on the Seward Peninsula. Before the front approached, Nome reached a high temperature of 70 degrees, which tied a high temperature record for the date.
The lowest overnight temperature in Alaska as of Sunday was 27 degrees at Eagle, while the midafternoon highest statewide temperature was 71 degrees at Manokotak.
HAWAIIAN WEATHER -- Typical trade wind weather was found across the Aloha State on Sunday because of a large ridge of high pressure that stretched across the North Pacific approximately 1000 miles north of the islands. Winds, which were from the east and east-northeast on Sunday evening, were the trade winds that are often found across the region. These trade winds with speeds ranging from 10 to 20 mph were circulating around the southern flank of the high -pressure ridge, which is typically found to the north of the islands. Some clouds and isolated showers embedded in the trade wind flow were reaching the windward (or east-facing) sides of the islands. The high-pressure ridge was expected to intensify on Monday, resulting in an increase in the speed of the trade winds. Moderate to strong trade winds were forecast to continue affecting the islands through much of the week.
With the anticipated increase in the trade winds, a small craft advisory was posted for Monday extending through late Tuesday afternoon for the Pailolo and Alenuihaha Channels, Maui's Maalaea Bay and the coastal waters southeast of the Big Island.
PUERTO RICO AND US VIRGIN ISLANDS WEATHER -- High level clouds had spread across Puerto Rico, Culebra, Vieques and the Virgin Islands on Sunday. By late Sunday night, that large area of rainshowers and isolated thunderstorms that were spreading northwestward across the Caribbean had reached the southern coast of Puerto Rico and across some of the Virgin Islands, including St. Croix. The clouds and precipitation were associated with a slowly intensifying area of low pressure that was found across the southern Caribbean (see discussion below in the "Eye on the Tropics" section). While the precipitation was moving toward the northwest, the surface winds remained from the east and northeast at speeds of less than 15 mph. These east to northeast trade winds were circulating in a clockwise direction around a large high pressure system centered over the central North Atlantic well to the northeast of the islands. Clouds, rainshowers and isolated thunderstorms were expected across the islands on Monday as the low pressure center located approximately 340 miles south of Ponce was forecast to move to the west-northwest. Some of the rain could be sufficiently heavy to cause localized flooding.
EYE ON THE TROPICS -- The National Hurricane Center was paying attention to broad area of low pressure with numerous thunderstorms over the southeastern Caribbean between Puerto Rico and the Netherlands Antilles. As of Sunday night, the low-pressure center was approximately 340 miles south of Ponce, PR. Winds at several thousand feet appeared favorable for development of a tropical depression on Monday or Tuesday. A reconnaissance aircraft could investigate the region if necessary.
Tropical Storm Julio, the tenth named tropical cyclone (low pressure system that forms over tropical waters and reaches the intensity of a tropical storm or hurricane) of the 2008 eastern North Pacific hurricane season, had formed late Saturday over the Pacific Ocean west of Mexico and traveled to the north-northwest. As of Sunday evening, satellite imagery indicated that the center of Tropical Storm Julio was located over inland sections of the Baja California Peninsula approximately 50 miles west-northwest of La Paz, Mexico. Maximum sustained surface winds were reaching 45 mph, as the system was traveling to the north-northwest at 13 mph. This storm was bringing heavy rains to southern Baja California, where a tropical storm warning was remained in effect. Current forecasts indicate that Julio would weaken to a tropical depression on Monday and continue traveling to the north over the Baja Peninsula and into the northern Gulf of Mexico by Tuesday. Between three to six inches of rain were expected over the southern and central sections of the Baja Peninsula.
For additional information concerning tropical weather systems from last week, please consult the Weekly Weather and Climate News.
AN INVITE -- If you witness some interesting weather phenomena or would like to share some weather-related experience with others in the DataStreme Atmosphere Project, we cordially invite your contributions. Please email these to the address appearing below. Some of these may appear in the section titled "Reports from the Field".
TOUR OF THE DATASTREME WEBSITE -- The DataStreme Atmosphere website contains a variety of weather information. To help you get an overview of this page, consult Monday's optional Supplemental Information.
From the files of the Aviation Weather Center, Kansas City, MO and Intellicast
Prepared by Edward J. Hopkins, Ph.D., email
hopkins@meteor.wisc.edu
© Copyright, 2008, The American Meteorological Society.