The following discussion is based upon the major weather features appearing on Monday night's surface weather maps:
QUIET WEATHER ACROSS THE EAST -- High pressure centered over the lower Mississippi Valley and southern Plains was responsible for relatively tranquil weather across the most of the region east of the Mississippi on Monday evening. Partly cloudy skies were found across most of the region. Afternoon high temperatures were at or above the long-term average highs for early February. The largest temperature anomalies (differences between actual and average highs) were found across the Northeast and Midwest, where highs were 10 to 15 Fahrenheit degrees above average. High temperature records were tied on Monday in the Northeast at Binghamton, NY (50 degrees) and at Burlington, VT (50 degrees).
Generally quiet weather should remain across the East on Tuesday as high pressure would remain across the Southeast. A weak cold front that stretched across the St. Lawrence Valley and the northern Great Lakes should move southward. With dry air across the region, this front was relatively to remain relatively quiet.
SHOWERS ACROSS THE SUNSHINE STATE -- Scattered light rainshowers continued into late Monday evening across the Florida Peninsula. These showers were associated with a trough of low pressure that extended across south Florida. The low pressure trough triggered shower and thunderstorm activity across the Sunshine State for most of Monday. By late evening, the thunderstorms had moved off northern Florida's Atlantic coast and were located over the western North Atlantic east of Jacksonville and Daytona Beach. Radar-estimated rainfall for Monday indicated most of the Florida Peninsula had received more than a few hundredths of an inch of rain, with a more than one inch of rain falling at few locations along the Atlantic coast and across northern interior sections near Ocala. The rain was welcome, as Florida has been under moderate to severe drought conditions.
Although skies ranged from partly to mostly cloudy and rainshowers fell, the afternoon high temperature at Tampa, FL reached 84 degrees, tying the previous high temperature record for the date,
Remnants of the low pressure trough were expected to remain across Florida on Tuesday. Rainshowers and isolated thunderstorms could develop across south Florida during the morning, primarily along the Atlantic coast. Nearly one half of an inch of rain was forecast to fall over the Miami metropolitan area during the 24 hours ending on Tuesday evening.
COOL AIR MOVES INTO THE NORTHERN PLAINS -- A chilly air mass was spreading southward from the Canadian Prairie Provinces into the Dakotas and eastern Montana on Monday evening. This chilly air mass was associated with a large area of high pressure that was centered over northern Saskatchewan. The southern extent of the cold air was marked by the cold front that had moved as far south across the Plains as Nebraska. Late evening temperatures across eastern Montana, the Dakotas and northwestern Minnesota were between 10 and 20 Fahrenheit degrees lower than what they had been at the same hour on Sunday night before frontal passage.
The high pressure system over Saskatchewan was forecast to move to the south-southeast on Tuesday, reaching northeastern South Dakota by Tuesday evening. Cool and quiet weather conditions should be expected across the region on Tuesday.
WINTRY WEATHER SPREADS ONTO CENTRAL PLAINS -- Scattered areas of precipitation that included rain and snow developed across the western Plains of Kansas and eastern Colorado on Monday evening. This precipitation was associated with a weak surface low pressure system that had organized along the eastern slopes of the Rockies in southern Colorado. A disturbance in the upper tropospheric wind pattern circulating around a pool of cold air aloft over the Great Basin and the western slopes of the Rockies in Colorado was responsible for developing this surface low pressure feature. Cold air moving southward across the Plains also helped keep the precipitation in the form of snow.
The low pressure center over southeastern Colorado was forecast to move eastward on Tuesday morning and then merge with the cold front moving southward across the central Plains. Snow should fall across the central Plains during the morning, extending from the eastern slopes of the Rockies in Colorado and Wyoming eastward into Kansas and southern Nebraska. By late afternoon, most of the snow would turn to rain as the area of precipitation would reach the mid-Mississippi Valley. In addition to the snow, strong winds should also accompany the system as it moves eastward.
A winter weather advisory for snow and blowing snow was posted for southwestern Kansas and sections of the Oklahoma and Texas Panhandles that would run through late Tuesday afternoon. Up to three inches of snow were expected to fall and north winds gusting to 40 mph could create blowing snow conditions that would limit visibility to less than one half mile at times.
UNSETTLED WEATHER FOR CALIFORNIA -- Rain was spreading on to the northern and central coasts of California on Monday evening. This rain was in advance of a warm front that was approaching to within approximately 200 miles off the coast. The warm front was accompanying a storm moving northward across the eastern North Pacific toward the Gulf of Alaska. A cold front followed to the west of the warm front.
A secondary low pressure system was to develop off the California coast early Tuesday near the point where the warm and cold fronts would meet. This new low pressure system was forecast to travel southeastward along the coast, reaching western Mexico by late Wednesday. As this new storm moves southeastward offshore of the coast, light to moderate rain should fall along the California coast, while light snow could fall over the higher elevations of the mountains in southwestern California. Over one inch of liquid-equivalent precipitation was forecast to fall along the California coast during the 24 hours ending late Tuesday afternoon. Some high terrain locations along the coast could receive sufficiently intense rain to result in local flooding in the coastal valleys.
Sufficiently cold air should accompany the new storm so as to cause snow levels to fall from above 8000 feet to around 5000 feet across southwestern California. Therefore rain could change to snow at high elevations of the mountains from near Santa Barbara and around the Los Angeles basin. Consequently, a winter weather advisory was to run from midday Tuesday through midmorning Wednesday for the mountains surrounding the Los Angeles Basin. Between three and seven inches of snow were expected to fall above elevations of 6000 feet.
In addition to the locally heavy rain and mountain snow, the storm was expected to be accompanied by strong and gusty winds. A high wind warning and a wind advisory were to remain in effect through midafternoon on Tuesday across sections of southwestern California, extending from the San Joaquin Valley south of Bakersfield across the Tehachapi Mountains and the mountains around Santa Barbara. Winds could gust to 60 mph in the area under the warning and to between 40 and 50 mph in the advisory area.
While most of the precipitation would move southward into southern California, some light rain associated with remnants of the old frontal boundary was expected to spread northward into southern Oregon by late Tuesday night and into Wednesday.
QUIET WEATHER ACROSS THE NORTHWEST -- Skies were partly cloudy across Washington and Oregon on Monday evening because of an elongated ridge of high pressure that stretched from the interior Northwest into the Great Basin.
The presence of high pressure across the interior Northwest maintained sunny skies and an offshore flow across the Pacific Northwest and northern California. Consequently, relatively warm weather was found across the region. The temperature at Eureka, CA reached 73 degrees on Monday, which broke the high temperature record for the date.
Relatively tranquil weather should continue across the Northwest on Tuesday as high pressure was forecast to maintain a presence across the region. However, poor air quality and low visibility will present a problem in some locations because of the nearly stationary high pressure system.
The light surface winds and stable atmospheric conditions caused by a temperature inversion (temperatures increase with ascent through the atmosphere) would continue to trap atmospheric pollutants near the surface across some of the valleys of southeastern Washington and northern Oregon. An air stagnation advisory was to remain in effect through midmorning on Tuesday across the Columbia Basin and the foothills of the Blue Mountains in Oregon and Washington.
The lack of clouds across the interior Northwest should result in nighttime air temperatures to fall toward the dewpoint temperatures, resulting in saturation of the air with respect to water vapor. Consequently, dense fog would form as visibility would fall to under one quarter of a mile. Since surface temperatures would be below freezing, fog droplets would freeze upon contact with these cold surfaces, resulting in slick, icy road surfaces. Therefore, freezing fog advisories were posted across southeast Washington and sections of northeast and central Oregon through midmorning on Tuesday.
TEMPERATURE EXTREMES IN THE LOWER 48 -- The lowest temperature on Monday was 22 degrees below zero (Fahrenheit) at Wisdom, MT, while Monday's highest temperature was 87 degrees at MacDill AFB Tampa, FL.
ALASKAN WEATHER -- A large band of clouds were moving to the northwest across central and western mainland Alaska on Monday. Satellite imagery showed skies across eastern Alaska were beginning to clear. The cloud band was associated with a large storm that was moving to the north-northwest across the Bering Sea on Monday (Alaskan time). By late afternoon, the storm's low pressure center was situated over the Gulf of Anadyr, just off the coast of Far East Russia's Chukchi Peninsula. A warm front extended to the north-northeast across the Peninsula and the Chukchi Sea before curving to the east along Alaska's Arctic coast. A cold front stretched to the south-southeast across the Bering Sea, passing to the east of the Pribilof Islands. Southerly winds brought relatively warm and humid air into southern Alaska, which resulted in rain across Kodiak Island, the Kenai Peninsula and the northern sections of the southeastern Alaska Panhandle. In colder air, snow fell across western Alaska, extending from Bristol Bay northward across the Seward Peninsula to the Arctic coast. The presence of a large ridge of high pressure over northern Canada helped clear skies across eastern Alaska. Little significant precipitation was reported across interior or eastern Alaska. A tight pressure gradient over western Alaska between high pressure over eastern Alaska and low pressure over Far Eastern Russia generated strong winds that gusted to between 30 and 40 mph along the Chukchi Sea coast.
Snow associated with the cold front over the Bering Sea was forecast to continue across southwestern Alaska. A winter weather advisory for snow was posted for the western sections of the Alaska Peninsula that would extend through late Tuesday night. Anticipated snowfall totals would range between six and twelve inches. Some locations could experience a change from snow to rain during the late evening.
The state's lowest temperature on Monday morning was 17 degrees below zero at Northway. The highest temperature across Alaska as of midafternoon on Monday was 47 degrees at Annette Island and Klawock.
HAWAIIAN WEATHER -- Satellite and radar imagery revealed a large band of clouds and showers covering the western islands of the Aloha State on Monday afternoon. The showers were moving across Kauai, Oahu and Molokai. While the band was slowly progressing eastward along the island chain, individual cloud and shower elements were moving to the northeast, carried along by a general southwesterly flow across the western islands. These clouds and showers were out ahead of a midlatitude cold front that was approaching the 50th State from the northwest. This approaching front would be the second front to affect the islands over the last day. Earlier Monday, the western end of a cold front had moved to the southeast across the islands. A weak ridge of high pressure following this front passed across the islands on Monday. By late afternoon, the axis of this ridge was located near the Big Island. The new cold front was approximately 700 miles to the northwest of Kauai. Consequently, the winds to the west had become southwesterly.
The second cold front located to the northwest of Kauai late Monday afternoon was expected to pass southeastward across the islands beginning Tuesday afternoon and continuing into the late evening. With frontal passage, the southwesterly winds should become gusty before shifting to the west and then to the northwest. Shower activity should also increase with the arrival of the front. Since the air mass across the islands was stable, significant shower and thunderstorm development was not anticipated. The showers were to dissipate on Wednesday as the prevailing winds would become northerly. The southwest winds that would remain across the islands on Tuesday were not limited to the surface, but would extend upward through the low troposphere. Therefore, a high wind warning was in effect across the summits of the Big Island's Mauna Loa and Mauna Kea through early Wednesday night. Since strong winds were expected on Maui's Haleakala Summit, a high wind watch was posted for this summit. Ocean swell generated by storms over the North Pacific northwest of the Hawaiian Islands was expected to continue producing high surf along the coasts of the islands. One round was affecting the islands late Monday, which would be followed by a second and much larger round late Tuesday. The first round should peak at the time of high astronomical tide. High surf warnings were to continue through early Thursday evening for the north and west facing coasts of the western islands, while a high surf advisory would also continue for the west facing coasts of the Big Island.
PUERTO RICO/U.S. VIRGIN ISLANDS WEATHER -- Skies ranged from partly cloudy to variably cloudy across Puerto Rico, Culebra, Vieques and the Virgin Islands late Monday night. Satellite imagery showed clusters of low-level clouds moving westward across the islands and surrounding waters. Radar detected isolated to scattered showers associated with these clouds moving to the west across the region. While most of the showers were found across the local Atlantic and Caribbean waters, a few showers were affecting the windward or eastern sections of the individual islands. By late afternoon, some locations in Puerto Rico and the Virgin Islands had received as much as one-half inch of rain. The low clouds and accompanying rainshowers were embedded in the easterly trade wind flow in the lower troposphere. The surface winds across the islands had speeds ranging from 10 to 20 mph, with slightly higher speeds over the surrounding waters. These trade winds were on the southerly flank of an elongated ridge of high pressure stretching across the western North Atlantic approximately 1000 miles to the north of the region.
The moderate easterly trade winds should prevail across the islands on Tuesday as high pressure was forecast to remain across the western North Atlantic. Scattered low clouds and showers should pass across the region. Moderate trade winds with speeds to over 20 mph should continue producing high seas around the islands. A small craft advisory was in continued for the local waters of the Atlantic and the local passages.
FEBRUARY FULL MOON -- The moon will reach the full moon phase this afternoon (officially, at 2154Z on Tuesday, 7 February or 4:54 PM EST, 3:54 PM CST, etc.). The February full moon is traditionally known as the "Wolf", "Snow" or "Hunger Moon."
Meteorological satellites are our "weather eyes in the sky". The perspective of space is unique; a satellite image can often provide views of broad-scale weather systems in their entirety. A geosynchronous satellite, high above the equator at an altitude of 23,000 miles and revolving in the same direction as the earth rotates, remains fixed over the same scene on earth. Individual views of the planet below or a rapid sequencing of such images as animation can display surfaces and clouds associated with weather systems.
Weather satellite sensors are basically tuned to two types of radiation: visible light and infrared. Visible light views are like black-and-white television. Dark surfaces reflect little sunlight and appear dark, while clouds and snow cover are highly reflective, appearing bright. However, clouds, fog, and surface features (forests, mountain ranges, and major rivers) are usually visible from space only during daylight hours.
Infrared (heat) radiation is emitted by a surface at a rate directly proportional to its temperature. Consequently, thermal infrared images can be interpreted as temperature maps of the underlying surfaces and clouds. Because heat emissions are continuous, these satellite images are available day and night. Water and ground surfaces are generally warm and appear dark while middle level clouds are cool and look gray. The highest, coldest clouds such as thunderstorm tops are bright white. These temperature ranges may be enhanced by assigning various color schemes for television and computer display.
Specially tuned infrared sensors can even detect invisible water vapor in the middle troposphere. Regions of the atmosphere with little water-vapor content appear dark on "vapor channel" images while high vapor content areas are milky white. Clouds also show as bright white in vapor images.
To view satellite images, and for more details concerning satellite imagery, turn to the satellite views and the Tuesday Supplemental Information…In Greater Depth available on the DataStreme Atmosphere website.
To be submitted on the lines for Tuesday on the Study Guide, Week 3 Chapter Progress Response Form, under section B. Daily Summary.
From the files of the Aviation Weather Center, Kansas City, MO and Intellicast
Return to DataStreme Atmosphere website
Prepared by Edward J. Hopkins, Ph.D., email hopkins@meteor.wisc.edu
© Copyright, 2012, The American Meteorological Society.