Friday Daily Summary

DATASTREME ATMOSPHERE DAILY SUMMARY

Friday, 20 November 2009

MIDWEST STORM FINALLY ON THE MOVE
PLEASANT WEATHER SPREADS ACROSS NATION'S MIDSECTION
SOGGY WEATHER ALONG THE WESTERN GULF COAST
NORTHWEST BRACES FOR MORE STORMY WEATHER
UPPER AIR
TEMPERATURE EXTREMES ACROSS THE CONTINENTAL US
ALASKAN WEATHER
HAWAIIAN WEATHER
PUERTO RICO/US VIRGIN ISLANDS WEATHER
EYE ON THE TROPICS
A REMINDER
HISTORICAL WEATHER EVENTS

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

MIDWEST STORM FINALLY ON THE MOVE -- Clouds and rain associated with a slow moving Midwestern storm spread eastward into the Northeast on Thursday evening. After a nearly four-day trip across Missouri, the storm finally accelerated to the north-northeast on Thursday. By evening, the storm's primary low-pressure center was located over Michigan's Upper Peninsula. An occluded front curved southeastward across the eastern Great Lakes and the Appalachians from the low-pressure center. Farther to the southeast, a secondary low pressure center that formed near the storm's point of occlusion over Georgia late Wednesday moved offshore and was located along the coast of the Carolinas near Wilmington, NC by Thursday evening.

Most of the precipitation associated with this large storm system as of late Thursday evening was to the east of the occluded front, extending across the Eastern Seaboard and the eastern Great Lakes. A few thunderstorms continued into late evening over the Middle Atlantic States, from Chesapeake Bay northward into the Delaware Valley of eastern Pennsylvania. Buffalo, NY received 1.49 inches of rain on Thursday, which represented a daily maximum precipitation record for the date.

The storm's primary low pressure center was forecast to take a track to the northeast across Ontario and Quebec on Friday, forced eastward by a cold front that was sweeping southeastward from northwest Ontario. By evening the low pressure center should have reached the lower St. Lawrence Valley of eastern Quebec. The frontal system accompanying this storm should move eastward across the eastern Lakes and New England, along with the precipitation associated with this storm and associated fronts. Precipitation totals of nearly one inch during the 24 hours ending Friday evening were forecast across northern Upstate New York and adjoining sections of New England.

PLEASANT WEATHER SPREADS ACROSS NATION'S MIDSECTION -- Except for a few clouds traveling eastward across the Plains, skies cleared across the nation's midsection on Thursday in the wake of the Midwestern storm. Several areas of high pressure were responsible for the return of tranquil weather. One area of high pressure was located across the Cumberland Plateau and Tennessee Valley in the Southeast. Farther to the west, high pressure was located over the Rockies and the high Plains as of Thursday evening. Some clouds associated with the remnants of a cold front were traveling across the northern Plains. Like the cold front, these clouds were beginning to dissipate as they approached the upper Midwest.

The area of high pressure located over the Southeast was expected to remain relatively stationary on Friday. The high-pressure ridge over the Rockies and the high Plains was forecast to spread eastward across the mid-Mississippi and Ohio Valleys by Friday evening. The eastward movement of this high should signal a return to more pleasant weather conditions for the start of the weekend than what the region experienced during much of this workweek with the cutoff storm.

SOGGY WEATHER ALONG THE WESTERN GULF COAST -- Rainshowers and thunderstorms had spread northeastward across coastal and southern sections of Texas on Thursday as one part of a two-part weather system that was evolving across the Lone Star State. Farther to the northwest and west, another area of rainshowers was moving across western and central sections of Texas as the other part of the system.

A surface low-pressure system that had developed over the eastern slopes of the southern Rockies in New Mexico late Wednesday traveled eastward across the Texas Panhandle on Thursday. By evening, this low- pressure center was located over southwestern Oklahoma. As the low pressure organized during its eastward travels, southeasterly winds strengthened and brought warm and humid air from the western Gulf of Mexico northward across Texas. A warm front developed along the boundary of this warm air.

Moderate to heavy rainshowers along with a cluster of thunderstorms continued into the late evening along the lower Texas Gulf coast north of the warm front.

The low-pressure system located over the Red River Valley of southern Oklahoma was expected to dissipate on Friday. However, farther to the south, a low-pressure center was forecast to develop along the western sections of the warm front over the northwestern Gulf of Mexico. An onshore flow of humid air from off the Gulf of Mexico should contribute to locally heavy precipitation totals in showers and thunderstorms. With sufficiently humid air flowing into coastal Texas, thunderstorms could develop across the region on Friday. Some of the thunderstorm cells could produce hail or even spawn a tornado. Twenty-four hour precipitation forecasts valid for Friday evening indicate that rainfall totals exceeding five inches could occur along the Texas coast between Corpus Christi and Galveston. Because of the anticipated heavy rain, flash flood watches were in effect along the Texas coast.

NORTHWEST BRACES FOR MORE STORMY WEATHER -- Coastal and low elevation rain along with mountain snow had spread across western Washington on Thursday evening in association with a warm front that was ahead of another approaching storm. Earlier during the predawn hours of Thursday, a cold front had reached Washington's Olympic Peninsula, but dissipated as it moved inland. This cold front had been associated with a storm that reached the central British Columbia coast.

By early Thursday evening, the storm total rainfall commencing early Wednesday morning that was associated with the series of storms exceeded four inches across the Olympic Peninsula. Snowfall totals for the storm were as much as a foot in Washington's North Cascades and to five inches in northern Idaho. Early in the storm event, wind gusts of 107 mph were reported at Hurricane Ridge in Olympic National Park.

The new storm affecting the Pacific Northwest early Thursday evening was located 300 to 400 miles off the coast of British Columbia's Vancouver Island. A warm front accompanying this storm had moved into western Washington during the afternoon. A cold front trailing southwestward from this storm was approximately 300 miles of the Washington and Oregon coasts.

The storm's low pressure center was forecast to travel to the northeast crossing northern Vancouver Island before reaching the Coast Mountains of British Columbia on Friday. The trailing cold front should move onshore along the Washington and Oregon coasts during the predawn hours of Friday. By evening, northern sections of the cold front were to have moved across the interior Northwest, reaching the western slopes of the mountains of northern Idaho. Southern sections of the cold front were to travel eastward and southward, moving into Nevada and across northern and central sections of California.

Between two and three inches of precipitation were forecast for coastal sections of Washington, Oregon and northern California including the western slopes of the Coastal Ranges during the 24 hours ending late Friday afternoon. Flood warnings and watches were in effect across western Washington through early Saturday because of this anticipated rain falling on already saturated ground. Very cold air aloft in the westerly winds following the frontal passage would result in unstable atmospheric conditions and some isolated thunderstorms along the coast on Friday.

The arrival of the warm front caused snow levels to rise to 4500 feet across the northern and central Cascades of Washington late Thursday. However, cold air following behind the cold front should cause snow levels to drop to between 2000 and 3000 feet by late Friday. Therefore, a winter storm watch was posted for the northern Washington Cascades from Friday afternoon through late Friday night, as up to 18 inches of snow could fall. Winter weather advisories were in effect from mid Friday morning through early Saturday morning for the Cascades of Oregon and southern Washington. With snow levels falling to approximately 3000 feet, up to a foot of snow was anticipated. Farther south, winter storm warnings were posted for the Sierras in California.

In addition to the heavy rain and snow, the cold front that will approach the coast will be accompanied by strong winds. High wind, gale and storm warnings were in effect along the coast and the coastal waters of Washington and Oregon. Inland, wind advisories were posted across sections of northern California and the Intermountain West.

The recent heavy snow, combined with warm air and strong winds has maintained dangerous avalanche conditions across the mountains of western Washington. Consequently, an avalanche warning was continued through Friday morning for Cascade Crest and the Olympic Mountains.

UPPER AIR -- Both the 500 and 300-mb charts for 00Z Friday continued to show the large counterclockwise circulation feature associated with the cold air column extending upward through the troposphere from the Midwestern storm. Like the surface storm center, the centers of the upper-tropospheric height troughs had shifted to the northern Great Lakes.

TEMPERATURE EXTREMES ACROSS THE CONTINENTAL US -- Thursday's lowest temperature was 2 degrees below zero at Laramie, WY. Thursday's highest temperature was 86 degrees at Miami (Kendall-Tamiami), FL and Indio, CA.

ALASKAN WEATHER -- A cold arctic air mass had spread across much of mainland Alaska on Thursday, accompanying a ridge of high pressure that was centered over the central interior sections of the state. Midafternoon temperatures were below zero across the interior sections of the state. Partly to mostly cloudy skies were found across this region. Some clouds were moving northward across the Panhandle and southeastern Alaska due to a large area of low pressure with multiple low-pressure centers that remained across the northern Gulf of Alaska. Rain and snow fell across the Panhandle on Thursday. A cold front powerful storm traveling to the northeast across the western Bering Sea was responsible for clouds, fog, rain and windy weather conditions across the western Aleutians. Shemya reported wind gusts to 67 mph.

The lowest overnight temperature in Alaska on Thursday morning was 46 degrees below zero at Bettles, while the mid-afternoon highest statewide temperature was 45 degrees at Atka.

HAWAIIAN WEATHER -- Fresh to strong easterly trade winds prevailed across the Aloha State on Thursday afternoon because of a large surface high pressure system was passing approximately 800 miles to the north of Honolulu. In addition to the strong winds, low cumuliform clouds and scattered showers embedded in the trade wind flow were traveling westward and affecting the usual windward and mountainous locations on the islands. Some showers were carried across to the leeward sides of several smaller islands because of the strength of the trades. The trades should decrease slightly over the weekend as the high-pressure cell moves to the northeast of the islands and weakens. A decrease in the precipitable water, or the bulk water vapor content in an air column, across the islands, together with an increase in the strength of the trade inversion, should limit the development of convective clouds and showers.

PUERTO RICO/US VIRGIN ISLANDS WEATHER -- Skies were variably cloudy across Puerto Rico, Culebra, Vieques and the Virgin Islands late Thursday night as scattered to numerous rainshowers along with isolated thunderstorms continued across the region. These showers and thunderstorms developed during the afternoon and continued into the late evening. Radar-estimated precipitation totals through mid evening ranged from two to four inches across sections of Puerto Rico, including Old San Juan. While most of the precipitation had moved offshore to the west northwest by late evening, St. Thomas and St. Croix, along with some locations across Puerto Rico continued to experience shower activity. A weak surface trough of low pressure located across the Anegada Passage east of the Virgin Islands was responsible for the shower activity. Surface winds across the islands were relatively light and generally from the east. The trough was expected to travel to the west-northwest during the early morning hours of Friday, resulting in a continuation of the scattered showers and thunderstorms across the islands and surrounding waters. With sufficient humidity available, daytime heating and local effects should result in the typical afternoon development of convective shower and thunderstorm activity.

EYE ON THE TROPICS -- No organized tropical cyclones were detected across the North Atlantic or the eastern North Pacific basins on Thursday evening; no cyclone development was anticipated through Saturday.

A REMINDER -- To All DataStreme Participants:

Next week is Thanksgiving Week recess. The DataStreme Atmosphere Daily Summary will contain only the selected Historical Weather Events for each day during Thanksgiving Week. Current weather data will be available on the website as usual. If you are looking for an alternative description of daily weather, you could try: http://www.usatoday.com/weather/default.htm (USA Today) or http://www.weather.com/newscenter/fcstsummary.html (The Weather Channel). The DataStreme Atmosphere Daily Summaries and Current Weather Studies files will resume Monday, 30 November 2009.

Have a Happy and Safe Thanksgiving!

Ed Hopkins

HISTORICAL WEATHER EVENTS - 20 November

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

...1869...A second great windstorm in three days struck Vermont and New York blowing railroad trains off their tracks. (David Ludlum)
...1900...An unusual tornado outbreak in the Lower Mississippi Valley resulted in 73 deaths and extensive damage across Arkansas, Mississippi and Tennessee. Two F4 tornadoes accounted for most of the deaths. (David Ludlum) (Intellicast)
...1914...The high temperature of 28 degrees at Atlanta, GA was their earliest daily high below the freezing mark. (The Weather Channel)
...1979...A blizzard struck Cheyenne, WY producing a record 19.8 inches of snow in 24 hours, and a record to tal of 25.6 inches in forty hours. Strong winds created huge drifts stopping all transportation. (19^th-21^st) (The Weather Channel)
...1987...Blustery northwest winds created snow squalls in the Great Lakes Region and the Upper Ohio Valley. Snowfall totals in Upper Michigan ranged up to 18 inches at Paradise. Lake City, MI received 9.5 inches of snow in four and one-half hours. Up to a foot of snow blanketed Oswego County in western New York State. Strong winds produced wind chill readings as cold as 22 degrees below zero at Duluth, MN. (The National Weather Summary) (Storm Data)
...1988...Thunderstorms developing ahead of a fast moving cold front produced severe weather in the Upper Ohio Valley and the Middle Atlantic Coast Region during the afternoon and early evening. Thunderstorm winds gusted to 69 mph at Kennedy Airport in New York City, and winds along the cold front itself gusted to 56 mph at Cincinnati, OH. The same storm produced snow in Kansas, Missouri and Illinois, with eight inches reported at Rolla, MO. (The National Weather Summary) (Storm Data)
...1989...Low pressure brought thunderstorms in an unusual out-of-season severe outbreak across the Northeast that featured 193 reports of damaging thunderstorm winds in New York State, Pennsylvania and New Jersey. Tornadoes touched down near Seaside Park, NJ and McAlevys Fort, PA. In New York State, thunderstorm winds gusted to 94 mph at Newburgh and 92 mph at Poughkeepsie, while in Pennsylvania, Harrisburg had an 86 mph gust and in New Jersey, Hammonton had gusts to 86 mph. High winds in the Washington, DC area gusted to 73 mph, resulted in one death. (Storm Data) (The National Weather Summary) (Intellicast)

21 November

...1798...A four-day storm (the "Long Storm") was in progress in the northeastern U.S. The storm dropped a 18 inches of snow on New York City, more than a foot of snow New Haven, CT and as much as three feet in Maine and New Hampshire. The snowstorm ushered in a long and severe winter, in some places the ground remained covered with snow until the following May. (David Ludlum)
...1967...Excessive rains in southern California caused the most severe flooding and the most damaging mudslides in 33 years. Downtown Los Angeles received 7.96 inches of rain, and 14 inches fell in the mountains. (David Ludlum)
...1984...Over 4 inches of rain fell in less than 4 hours making for a wet Thanksgiving at Palm Beach, FL. Much street and urban flooding occurred. (Intellicast)
...1985...Hurricane Kate made landfall during the evening hours near Mexico Beach FL. Wind gusts to 100 mph were reported at Cape San Blas, FL. This was the sixth landfalling storm in the U.S. that year, a record and it was the latest known hurricane to hit the U.S. so far north. (The Weather Channel) (Intellicast)
...1987...Squalls in the Lower Great Lakes Region and the Upper Ohio Valley produced 14 inches of snow at Snowshoe, WV, and nearly eight inches at Syracuse, NY. Eleven cities in the eastern U.S. reported record low temperatures for the date. Record lows included 21 degrees at Pinson, AL, 9 degrees at Syracuse, NY, and 8 degrees at Binghamton, NY. Gale force winds lash the Middle and Northern Atlantic Coast, and the strong northwesterly winds produced wind chill readings as cold as 30 degrees below zero. Winds gusting to 60 mph at Trumansburg, NY toppled a chimney onto a nearby truck. (The National Weather Summary) (Storm Data)
...1988...High winds accompanied rain and snow in the northeastern U.S. Caribou, ME received eight inches of snow in six hours, and Fort Kent, ME was blanketed with a total of fourteen inches of snow. (The National Weather Summary) (Storm Data)
...1989...The storm which produced thunderstorms and high winds in the northeastern U.S. the previous day, produced snow and high winds in New England, with blizzard conditions reported in Main e. Winds gusted to 55 mph at Boston, MA, and reached 58 mph at Augusta, ME, and hurricane force winds were reported off the coast of Maine. Snowfall totals ranged up to 18 inches at Vanceboro, ME, with 17 inches at South Lincoln, VT. There were thirty-five storm-related injuries in Maine. (The National Weather Summary) (Storm Data)
...1992...Severe thunderstorms spawned six tornadoes within 70 minutes in the Houston metro area. At one time, there were three on the ground in Harris County. The strongest, an F4, tracked 20 miles through the eastern suburbs of Houston destroying 200 homes and damaging 1000 more. In total, 23 tornadoes struck Mississippi and Alabama. An F4 tornado killed 12 on a 128-mile track through seven Mississippi counties. (Intellicast)

22 November

...1641...An observer at Boston, MA recorded a "great tempest of wind and rain from the southeast all night, as fierce as a hurricane, and thereupon followed the highest tide which we have seen since our arrival here". (David Ludlum)
...1957...Extremely destructive Santa Ana winds blew from Oxnard to San Diego and inland parts of southern California. The high winds produced a 28,000-acre brush fire on a 40-mile front west of Crystal Lake. People were ordered off streets in some areas due to flying debris. (21^st-22^nd) (The Weather Channel)
...1987...Eight cities in the eastern U.S. reported record low temperatures for the date. Elkins, WV reported a low of 5 degrees above zero. Gale-force winds continued along the Northern Atlantic Coast. (The National Weather Summary)
...1988...Wet and windy weather prevailed across the western U.S., with heavy snow in some of the higher elevations. Winds gusted to 62 mph at Vedauwoo, WY, and reached 75 mph at Tillamook, OR. Shelter Cove, CA was drenched with 4.37 inches of rain in 24 hours. (The National Weather Summary) (Storm Data)
...1989...Strong northerly winds produced squalls along the shore of Lake Michigan, with heavy snow in extreme southeastern Wisconsin. Milwaukee received nine inches of snow, and in Racine County, there were more than one hundred automobile accidents. (The National Weather Summary) (Storm Data)
...1992...Forty-five tornadoes touched down in the Tennessee and Ohio Valleys. Georgia was hard hit with two F4, one F3 and three F2 tornadoes that killed six people and injured 144. Indiana had a total of 15 tornadoes on this day to set a record for an outbreak in November and for the month of November. One, an F4 multiple-vortex type, cut a 22-mile path through extreme southeastern Indiana and northern Kentucky. (Intellicast)