WEATHER OVER THE WEEKEND -- Tropical Depression 11, which formed on Thursday near the Yucatan Peninsula, moved northeastward across the Gulf of Mexico over the weekend and intensified to hurricane status by early Saturday. As the seventh named tropical cyclone, this system became known as Gordon. By Sunday morning this Category 1 hurricane (on the Saffir-Simpson Hurricane Intensity Scale) had come close to the west coast of the Florida peninsula. By late Sunday afternoon, Gordon was downgraded as winds fell below the 75 mph minimal threshold for hurricanes.
On Sunday afternoon an unconfirmed tornado was reported just off I-95 between Ft. Lauderdale and Miami, causing some roof damage to a mobile home park. Tornadoes are frequently found associated with the outer bands of a hurricane or tropical storm as it makes landfall. Heavy rains fell over the Florida Peninsula, with some locations receiving more than 4 inches of rain. Flash flood watches were posted for part of the day on Sunday.
While the Southeast prepared for Gordon, tranquil weather dominated the rest of the country. A cool air mass progressed from the Northern Plains early Friday across the Great Lakes States on Saturday morning, reaching the Ohio Valley by Sunday morning. The cool air mass, together with the clear skies and weak winds permitted rapid overnight cooling. Consequently, numerous record low temperatures were reported on Saturday and Sunday mornings across the Ohio Valley and portions of the Southeast. On Sunday morning the temperature at the Tri Cities Airport (Bristol, Johnson City and Kingsport), TN fell to 37 degrees, marking the lowest temperature for so early in season. Record lows were also reported in Texas at Houston and Austin. Even under relatively sunny skies, relatively cool conditions were found across the Southeast on Sunday afternoon as high temperatures ranged from 5 to 10 degrees below average for mid-September.
In the West a persistent large ridge of high pressure maintains the abnormally warm and dry conditions. Much of the nation to the west of the Mississippi River experienced a relatively warm Sunday. Across the western high Plains, afternoon high temperatures ranged from 20 to 25 degrees above the long-term average highs for this time of year. Numerous record high temperatures were set on Saturday and Sunday from northeast Montana southward into western Kansas. Rapid City, SD had a record high of 101 degrees, which also marked the latest date that a triple digit temperature was reached. The record high of 95 degrees at Denver, CO is the 61st day with a 90 degree or higher reading, which also constitutes a record number of 90 degree days at the Mile High City. Record high temperatures were also set in Southern California.
As of Sunday, Dallas-Ft. Worth was continuing its record streak of 79 consecutive days without measurable precipitation.
WEATHER FOR THE START OF THE NEW WEEK -- The following highlights of the national weather have been extracted from the surface weather map for late Sunday night.
A large area of precipitation associated with Tropical Storm Gordon was found across northern Florida, Georgia and portions of South Carolina. As of 03 Z (11 PM EDT), Gordon had made landfall near Cedar Key in the northern portion of the Florida Peninsula. Three hours later the center of this storm system was located 30 miles west-northwest of Gainesville, and moving to the northeast at 12 mph. Central pressure was 995 mb (29.38 inches of mercury). Winds had weakened from 70 mph at landfall to 50 mph at the later time.
Gordon is expected to continue to move to the northeast on Monday, reaching southeast Georgia near Brunswick by morning and the South Carolina coast between Charleston and Mrytle Beach by evening. Some weakening of the winds is anticipated as this system continues to move across land. However, east winds could cause waves to pile up along the Atlantic coast, causing flooding. As of early Monday morning, tropical storm warnings remained in effect for the Gulf coast of Florida between Saint Marks and Anclote Keys, and along the Atlantic coast from Flagler Beach, FL to Little River Inlet, SC. These tropical storm warnings indicate that a tropical storm with winds ranging from 39 to 74 mph will affect the warned region within the next 24 hours. A tropical storm watch, indicative of the possibility of tropical storm winds in the next 36 hours, was in effect for the entire North Carolina coast, to include all bays and sounds behind the barrier islands. A slight risk of severe thunderstorms is expected beginning on Monday morning for the coastal sections of the Carolinas as Tropical Storm Gordon continues moving northeastward.
A stationary front curved around the northern edge of Gordon on Sunday night. This midlatitude feature was not associated with Gordon, a system of tropical origin. The stationary front separated the tropical air mass over the Gulf and the Florida Peninsula from the cooler and drier air mass associated with high pressure centered over the Middle Atlantic States. Fronts do not typically emanate from a tropical low pressure system since the tropical air surrounding the tropical system is relatively homogeneous.
A weak region of low pressure moved out into the western Plains of South Dakota on Sunday night. This system was accompanied by scattered rainshowers that were found across the central Rockies. The rainshowers extended across Utah, Idaho, Wyoming, Colorado and Nebraska. This system is expected to move eastward on Monday.
Elsewhere, relatively quiet weather prevailed. A weak cold front was found over the northern Great Lakes with little precipitation, the result of little available moisture
TEMPERATURE EXTREMES ACROSS THE LOWER 48 -- On Sunday, the lowest temperature reported in the continental U.S. was 30 degrees at Jefferson, NC, while Sunday's highest temperature was 118 degrees at Death Valley, CA.
ALASKAN WEATHER -- A large and elongated ridge of high pressure extended from one high pressure center over the central Bering Sea to another center over the Beaufort Sea on Sunday afternoon. This ridge was responsible for relatively cloud-free skies across much of Alaska to include the western Mainland and Alaska Peninsula. A weak region of low pressure with an associated front located over Southeast Alaska produced clouds and precipitation along the eastern interior, Southeast Alaska and the Panhandle. Light rain was reported at Juneau, while snow fell in the eastern Tanana Valley and the Copper River Basin. Snow changed to rain at Northway. Clouds were also found across the central Aleutians as the result of a large storm system moving across the North Pacific Ocean to the south of the island chain. Onshore winds gusting to over 20 mph along the Arctic Coast also produced cloudy skies at coastal communities, with light snow at Barrow and Wainwright. Wind-chill equivalent temperatures fell to below zero along the Arctic coast.
The lowest overnight temperature in Alaska as of Sunday was 16 degrees at Anaktuvuk Pass, and the midafternoon highest statewide temperature was 62 degrees at Kodiak and Valdez.
HAWAIIAN WEATHER -- The easterly trade winds across the islands began weakening on Sunday as the ridge of high pressure located to the north of Hawaii drifted northward and weakened. Wind speeds should be on the order of 10 to 15 mph. These winds began to turn to more of a southeasterly direction over Oahu and Kauai, while the winds remained easterly across the Big Island. As a result, some trade showers were found across the northern islands. A front moving southeastward and located approximately 800 miles to the northwest of the islands is expected to stall before reaching the 50th State.
EYE ON THE TROPICS -- In addition to the intensification a tropical depression into Hurricane Gordon in the Gulf of Mexico during this weekend, several other tropical weather systems remained active. Tropical Storm Florence continued to move northeastward across the North Atlantic from near Bermuda. As it moved northeastward, it accelerated. By late Sunday afternoon when the National Hurricane Center issued its last advisory on it, Tropical Storm Florence was 45 miles to the northeast of Cape Race, Newfoundland and moving to the north-northeast at approximately 38 mph. Sustained near-surface winds were estimated at 60 mph.
In the Eastern Pacific, Tropical Depression 15-E formed off the west coast of Mexico on Friday and became a tropical storm on Saturday. As the twelfth named tropical cyclone, this system was identified as Tropical Storm Miriam. However Miriam was short-lived since after lingering off Baja California for a day, it moved onshore and dissipated approximately 100 miles northwest of Cabo San Lucas, Mexico on Sunday afternoon.
OLYMPIC WEATHER HIGHLIGHTS -- Sel Kerans, Coordinator of Project Atmosphere Australia On-line (a weather education outreach program modeled after the American Meteorological Society's Project Atmosphere), encourages visiting their homepage http://www.schools.ash.org.au/paa and inspecting the page entitled "Weather and Sport Activities: Sydney 2000 Olympics". Students and teachers from any country may email paa-data@rite.ed.qut.edu.au to take part "Link-up" associated with Project Atmosphere Australia Online.
SO YOU WANT WEATHER DATA? A national network of several thousand weather observation stations continually monitors the near surface weather conditions across the country. You can access essentially current weather data from around your state or the United States from the portion of the DataStreme Homepage marked as State Surface Data-Text. Consult the Monday optional Supplemental Information for additional information as to the data and how you can interpret these data.
From the files of the Aviation Weather Center, Kansas City, MO and Intellicast
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URL: datastreme:/learn/m_sum.html
Prepared by Edward J. Hopkins, Ph.D., email hopkins@meteor.wisc.edu
© Copyright, 2000, The American Meteorological Society.