DATASTREME DAILY SUMMARY

Wednesday, 17 October 2001


00Z Weather Systems


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

WET WEATHER CONTINUES ACROSS THE NORTHEAST -- A slow-moving occluded storm system located over the Great Lakes continued to bring clouds and rain across a large portion of the Northeast on Tuesday. The low pressure center was located in southern Ontario just to the west of Buffalo, NY. An occluded front curved first to the northeast before turning southward to become a cold front that stretched southward along the Eastern Seaboard from the Delaware Valley to northern Florida. A large area of steady rain was found along the front, stretching northward from the vicinity of Chesapeake Bay across Pennsylvania and New York State. More widely scattered rain was also wrapped around the low pressure center, stretching across Lower Michigan and northern Ohio. Some of this precipitation was lake-enhanced rain that resulted from cold air being carried across the relatively warm lake surfaces. Relatively mild weather was found to the east of the storm system, as southerly winds helped high temperatures across New England to reach readings that were on the order of 10 degrees above average.

Another low pressure system was situated off New York's Long Island and its accompanying stationary front paralleled the coast approximately 100 miles out to sea. This separate low pressure system developed along a cold front that had moved offshore early Monday and stalled. As the low pressure system moved northward along the stationary front from the Carolinas toward the New York Bight, rain was spread northward across southern New England.

The occluding storm system over southern Ontario is expected to move toward the northeast, reaching a position near Ottawa in eastern Ontario by Wednesday morning and to central Quebec by evening. Some deepening of the system is anticipated as the storm continues to occlude during its travel to the northeast. A wind advisory has been posted for Wednesday across western New York State as westerly winds are expected to range between 20 to 30 mph along with gusts to 45 mph. The cold front should sweep eastward, moving out of New England by sunrise. However, precipitation is expected to linger over the Northeast. Between 0.25 and 1.25 inches is expected to fall during the 24 hours ending on Wednesday evening across the Northeast, with the greatest amounts anticipated across New England, especially Maine.

RAIN ACROSS THE SUNSHINE STATE -- Rainshowers and embedded thunderstorms continued to move across Florida in association with the two fronts that stretched across the state. Precipitation is expected to continue into Wednesday, with several tenths of an inch possible by Wednesday evening.

COLD AIR INVADES THE SOUTH -- A large cold high pressure continued to drift toward the south and east behind the cold front spreading some of the coldest air of the season across the nation's midsection. On Tuesday morning record low temperatures were set at Valentine, NE (14 degrees), Liberal, KS (29 degrees) and in Texas at Lubbock (30 degrees), Abilene (34 degrees) and Midland (34 degrees). High temperatures across the mid and lower Mississippi Valley ranged from 10 to 15 degrees below the 30 year climatological highs for the date. Record low maximum temperatures were tied at Monroe, LA (65 degrees) and Lufkin, TX (67 degrees).

As of Tuesday evening the high pressure center was situated over southern Missouri and northern Arkansas. Another night of significant radiative cooling was expected across the Midwest and South as a result of the cold dry air, the lack of clouds and the weak winds near the center of the high. Temperatures on Tuesday night over the Ohio and Mississippi Valleys and Gulf Coast had dropped by 15 to 20 degrees from the same time on Monday night. Consequently, freeze warnings were posted across the mid-Mississippi Valley, to include the Mississippi River in eastern Iowa, northeast Missouri and northwest Illinois. Freeze warnings were also in effect for northeast Georgia. Frost advisories were in effect for southern Illinois, western Kentucky, southern Missouri, northern Arkansas and southeast Oklahoma.

UNSETTLED WEATHER ACROSS THE NORTHWEST -- A cold front moving across the Pacific Northwest continued to bring welcome precipitation. This front trailed southwestward from a low pressure center over Alberta across to northern Idaho, eastern Washington State, central Oregon and northern California. Most of the precipitation remained behind the front, primarily across Washington State. While cool and damp air was found following the frontal passage, ahead of the front southwesterly winds helped produce a relatively warm day. High temperatures across the Great Basin and the northern Rockies ranged from 10 to 15 degrees above the average highs for the date.

The low pressure center in Alberta is expected to move eastward, reaching northern Manitoba by Wednesday evening. Northern portions of the cold front should move across the Rockies and out into the Dakotas. Southern portions of the front are expected to slowly push south and east over the Rockies and the Great Basin. Several tenths of an inch of precipitation could fall across the mountains of northern Idaho and Montana.

YESTERDAY'S TEMPERATURE EXTREMES ACROSS THE CONTINENTAL US -- Tuesday morning's lowest temperature was 13 degrees at Williston, ND, while the highest temperature on Tuesday was 99 degrees at Borrego, CA.

ALASKAN WEATHER -- A strong storm system moving across the Bering Sea helped spread clouds, rain and strong winds across the Aleutians and the Alaska Peninsula. The low pressure center had a central pressure of approximately 969 mb and was located near the Pribilofs. An occluded front extended eastward into Bristol Bay where a warm front continued toward the southeast across the central portion of the Alaska Peninsula and into the western Gulf of Alaska, while a cold front curved southwestward across the western end of the Alaska Peninsula and into the North Pacific. By midafternoon, Cold Bay had received a 24 hour rainfall total of 1.34 inches. A high wind warning was in effect for Turnagain Arm for strong east winds with gusts reaching 65 mph. Because of the strong winds coupled with high astronomical tides, a coastal flood watch was posted for Wednesday afternoon for the Bristol Bay coast between Togiak and Point Heiden. A trough of low pressure was also located along the Gulf Coast in southeast Alaska. Rain associated with this trough was found across the Southeast. High pressure located over the Arctic Ocean was building across the Arctic Slope. An onshore flow from the high produced midday temperatures in the single digits over the Arctic Slope, along with light snow.

The state's lowest overnight temperature on Tuesday morning was 13 degrees below zero at Noatak. The highest temperature by mid afternoon of Tuesday was 57 degrees at Cold Bay and Dutch Harbor.

HAWAIIAN WEATHER -- The islands are expected to experience continued moderate to strong trade winds as a strong high pressure system remains well to the north of the Aloha State. A pool of cold air in the upper troposphere to the west of Hawaii has been spreading thin high cirrus clouds across the islands. Increased sunshine is expected by Thursday as the cold pool of air weakens.

EYE ON THE TROPICS -- In the eastern North Pacific, Tropical Storm Manuel continued its movement away from the Mexican coast. As of Tuesday evening, Manuel was 745 miles to the west-southwest of Cabo San Lucas, Mexico with a forward motion of 13 mph to the west-northwest. Maximum sustained surface winds were 50 mph.

A TORNADO RECORD -- On Monday the National Oceanic and Atmospheric Administration (NOAA) issued a press release reporting that 89 tornadoes occurred during the first half of this October, with 59 occurring between 9-13 October. Most of last week's tornado activity was found in nine central and southeastern states. Part of this large number of tornadoes may be the result of better detection methods, such as Doppler radar.


HISTORICAL WEATHER EVENTS - 17 October

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


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URL Address: datastreme/learn/w_sum.html
Prepared by Edward J. Hopkins, Ph.D., email hopkins@meteor.wisc.edu
© Copyright, 2001, The American Meteorological Society.