A CONTRAST -- A nearly stationary front extended southwestward across the nation's midsection from the Great Lakes to the Texas Panhandle. This front separated warm and humid air over the Southern Plains from the cooler air situated over the Rockies and the Great Basin. The minimum temperature at Amarillo, TX on Monday morning was 57 degrees, which was a record high low temperature. High temperatures on Monday afternoon across the Ohio and mid-Mississippi Valleys were as much as 15 degrees higher than the climatological average highs for this time of year. On Monday afternoon, record high temperatures were established at Jackson, TN (85 degrees) and Paducah, KY (84 degrees). The late season warmth was the result of southerly wind flow across the Gulf Coast States on the western flank of a high pressure ridge that extended along much of the Eastern Seaboard. High pressure across the East did allow a record low temperature reading at Massena, NY (22 degrees)
To the west of the front and extending across the southern Rockies into the Great Basin, afternoon high temperatures were as much as 10 to 15 degrees below the average highs. Earlier in the day, the presence of high pressure over the Pacific Northwest allowed nighttime temperatures to fall, with the low temperature of 28 degrees at Eugene, OR tying a record for the date.
ACTIVE WEATHER CONTINUES ACROSS THE SOUTHWEST -- Widespread precipitation in the form of rain, thunderstorms and mountain snow was found across the Southwest on Monday night, extending from Arizona eastward to Texas and northward into Kansas, Colorado and Utah. Some of this precipitation, especially that to the west over the Four Corners, was associated with a large pool of cold air that extended upward through much of the troposphere (to elevations above 20,000 feet) over Arizona. The balance of the precipitation was associated with the stationary front whose southern terminous was over the Texas Panhandle.
Thunderstorm activity continued late into Monday night in the warm air to the south and east of the surface front, across portions of Texas, Oklahoma and Kansas. Earlier, some of the thunderstorms turned severe. At least one tornado was spotted near Amarillo in the Texas Panhandle at midday on Monday. Some damage was sustained. Golfball-sized hail was also reported near Amarillo, and in west Texas near Alpine during the late afternoon.
Little movement of this frontal system is expected on Tuesday. A slight risk of severe thunderstorms continues through early Tuesday across eastern New Mexico and west Texas. On Tuesday, the area where a slight risk of severe thunderstorms is expected shifts eastward to cover the Texas and Oklahoma Panhandles, along with portions of adjoining states.
As much as 1.5 inches of rain is expected to fall across central Texas northward to southern Kansas. Because of this anticipated rain falling in locales where heavy rains had fallen, flash flood watches were in effect for much of south and central Texas, the Panhandles of both Texas and Oklahoma, and central Oklahoma.
WINDY CONDITIONS ACROSS FLORIDA -- A tight pressure gradient between the high pressure center over the Middle Atlantic States and a trough of low pressure over the Bahamas generated easterly winds that gusted to over 30 mph along the east coast of Florida. In addition, the onshore winds generated unusually heavy surf along the coast on Monday. Since this pattern is expected to persist into Tuesday, heavy surf advisories were issued for Monday night to include the Florida Atlantic coast from Deerfield Beach, FL to Altamaha Sound, GA.
WAVED OFF AGAIN -- Strong crosswinds at the Kennedy Space Center in Florida postponed the landing of Space Shuttle Discovery once again on Monday. Clouds and rain also prevented landing at Edwards AFB in California, the primary backup runway. An attempt at a landing at either of these sites, or at White Sands, NM will be made on Tuesday.
TEMPERATURE EXTREMES IN THE LOWER 48 -- The lowest temperature on Monday was 8 degrees at Wisdom, MT, while Monday's highest temperature was 89 degrees at Alice, TX.
ALASKAN WEATHER -- Strong winds were found across the Alaska Peninsula, the Aleutians and the Bering Sea as a result of tight pressure gradient that developed between a high pressure ridge over the Alaska Peninsula and a major storm system in the western Bering Sea. This storm system also had an occluded front that extended eastward and then southward across the Bering Sea and the central Aleutians. Southeast winds gusted to 48 mph at St. Paul Island and to near 40 mph at Cold Bay, Dutch Harbor and St. Lawrence Island. St. Paul Island also had rain and fog. A low pressure center along the Gulf coast near Cordova and an associated stationary front that extended eastward across the Copper River Basin into the Yukon Territory spread clouds and rain across southeast Alaska. Rain fell from southeast Alaska, where Yakutat had 1.20 inches in the 24 hours ending on Monday afternoon, into the Panhandle. Inland, Anchorage had a snowshower. Weak low pressure was situated near the Seward Peninsula over Norton Sound. Elsewhere, high pressure was building southward from the Arctic across the Brooks Range and the northern interior. Cloud-free skies were reported across the Susitna Valley. However, clouds and snow accompanied the onshore winds along the North Slope at Barrow and Deadhorse.
The state's lowest temperature on Monday morning was 13 degrees below zero at Anaktuvuk Pass and Arctic Village. The highest temperature across Alaska as of midafternoon on Monday was 52 degrees at Hydaburg and Klawok.
HAWAIIAN WEATHER -- Northeast trade winds across the Hawaiian Islands were maintained on Monday as a subtropical high pressure cell drifted slowly eastward across the North Pacific to the north of the 50th State. These trades, with wind speeds on the order of 20 mph, are expected to become more gusty on Tuesday night. Little shower activity was found across the islands. However, a low was expected to develop along a wind shear line (an elongated region where the winds change speed or direction over a relatively short distance) northeast of Honolulu. This low with showers, was expected to move to the southwest, approaching the islands on Wednesday. While the surf was beginning to diminish, high surf advisories were continued for the northwest facing shores of all the islands.
Clouds are composed of liquid water droplets or ice crystals. So why don't these cloud particles fall? They do! Actually, they fall slowly, and the air in which they exist is also moving. The water droplets and ice crystals are almost microscopic and fall slowly in still air. A typical size cloud droplet falls at a speed of about 0.003 meters per second (0.007 miles per hour) in motionless air. This droplet would take days to fall from normal cloud heights! Added to this hurdle is the fact that the droplet has formed because the air is rising (and cooling adiabatically) so that the droplet is falling against the flow. If the droplet ever fell below cloud base into air that often has relative humidities less than 100%, the droplet would begin to evaporate. As a result, clouds are forced to stay up there.
If the cloud droplet were favored to grow to raindrop size however, the resulting drop would contain the water content of a million cloud droplets. This size drop falls through still air at a rate of about 4 meters per second (9 mph). The larger the drop, the greater the fall speed. These fall speeds will overcome the rising flow of air and reach the Earth's surface - rain happens.
So when you see a cloud, you know the air in that region is rising. And the cloud is falling relative to the air flow, yet remains in the sky. In this way the atmosphere transports million of tons of water from the Earth's surface, first as vapor, then as water droplets or ice crystals in clouds, and finally as the never-ending resupply of precipitation.
For more information describing various aids that you can use in identifying clouds, you may consult the optional material in Tuesday's optional electronic Supplemental Information .
To be submitted on the lines for Tuesday 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