NATIONAL WEATHER SUMMARY

 

SEPTEMBER 2009

 

1^st-5^th…Plenty of active weather persisted throughout the nation on Wednesday. In the East, unsettling weather developed in areas of the Southeast as a frontal boundary remained stretched across portions of the western Atlantic, the northern Florida Peninsula, and the Gulf of Mexico. Moist, easterly flow swept in behind this front and supported scattered showers with isolated thunderstorms throughout areas of the northern Florida Peninsula and the nearby coastal waters of the Southeast. To the south, scattered showers with areas of brief heavy downpours, thunderstorms, and gusty winds of up to 35 mph developed across the southern half of the Florida Peninsula. Meanwhile, eastern Oklahoma and portions of the Ozarks saw decreasing showers and isolated thunderstorms through the morning and afternoon as a warm front moved through the Central and Southern Plains. Elsewhere, atmospheric conditions in northeastern and southeastern Texas remained favorable for producing high levels of ozone air pollution. Tranquil weather conditions developed in the northeastern quadrant of the nation due to a dominant ridge of high pressure. In the West, a heating event persisted throughout the the Southwest and southern California due to a strong ridge of high pressure over the Southwest. Daytime temperatures reached to above seasonal averages and continued to pose health hazards for persons outdoors, especially the elderly and children, as well as pets.

A relatively calm day in the country was headlined by the weakening of Tropical Storm Erika as it entered the eastern Caribbean Sea. This weakening basically ended any major threat the storm posed for the country. The most active weather occurred in the Plains as some moisture produced scattered areas of showers and thunderstorms. The heaviest of these thunderstorms swept through northern Texas, while another area moved from Kansas through Missouri. Both of these areas of precipitation weakened as the day progressed. A high pressure system stretched across the Great Lakes and into the eastern half of the country, providing a dry and pleasant day preceding the Holiday weekend. The West Coast remained dry even as a low pressure system approached the Northwest from the Gulf of Alaska. Temperatures were not extremely hot in California, allowing fireifghters an advantage in fighting the massive fires in the state.

The Northeast rose into the 70s and 80s, while the Southeast saw temperatures in the 80s. The Southern Plains rose into the 80s and 90s, while the Southwest saw temperatures in the 80s, 90s, and some 100s.

 

6^th-12^th…Heavy rain and strong thunderstorms popped up in the Central and Northern Plains on Tuesday, while an area of low pressure off the East Coast pushed scattered showers over New England. A low pressure system developed over the Canadian Rockies and created a cold front that swept through the Plains. The system pulled moisture in from the Gulf of Mexico and triggered heavy rain with scattered thunderstorms over Kansas and Oklahoma while the Dakotas saw only a few scattered showers. These storms have not yet turned severe with 1.96 inches of rain reported in Wichita, Oklahoma and 1.05 inches reported in Amidon, North Dakota. The north remained cool with highs in the 60s and the Southern Plains saw another warm day in the 90s. In the East, a low pressure system had low potential for tropical storm development as it spun off the coast of the Carolinas. This storm pushed ample moisture over the Northeast coast as it slowly moved northward up the East Coast throughout the day. Light rain with less than a tenth of an inch was reported over the Virginias. Coastal flooding threatened the region with wind gusts up to 20 mph, which created dangerous surf with high tides and low level floods. South of this storm, the Gulf states saw drier conditions with a few patchy clouds and highs in the 90s. Meanwhile, out West, high pressure brought dry and sunny conditions to the West Coast while a low pressure system and associated frontal boundary approached the Pacific Northwest. This pushed a few clouds over Washington but has not yet triggered any precipitation. The north only saw highs near 60, while California remained in the 70s.

Active weather continued to develop in the eastern half of the nation on Wednesday. In the Central US, areas of showers and thunderstorms popped up across Kansas and the northern Ozarks as a warm front lifted into the Central Plains. Excessive rainfall put areas in southeastern Kansas at risk for flash flooding. As the warm front progressed, moisture from the Gulf of Mexico spread across the Gulf Coast, heightening instability throughout southeastern and central Texas as well as the Louisiana coast. This activity translated into numerous showers and thunderstorms throughout the afternoon. Meanwhile, atmospheric conditions in northeastern Texas became favorable for bad ozone production, creating unhealthy air quality for sensitive groups. Elsewhere in the East, low pressure over the Ohio Valley produced locally heavy rainfall with strong isolated thunderstorms across areas of the Eastern Valleys and the inner Mid-Atlantic as the system shifted into the Southeast. Some of these storms turned severe during the afternoon and produced areas of penny to golf ball sized hail (0.75 to 1.75 inches in diameter) and damaging winds. Finally, high pressure centered over Quebec ushered an area of low pressure located along the Virginia coast into the Atlantic Ocean today. As the system exited the immediate coast, wrap around moisture continued to spark a few showers across the nearby coastal regions of the northern Mid-Atlantic. Quieter weather activity developed in the West on Wednesday. The Pacific Northwest saw a few pockets of light showers as a cold front in the Eastern Pacific trekked toward the Pacific Northwest Coast. Meanwhile, moisture from the south kicked up a few patches of light rainfall in the Southwest.

There were a few areas of active weather in the country on Friday.

First, a low pressure system tracked through the Northern Plains and toward the Upper Midwest. This storm initially produced areas of rain and thunderstorms in the Dakotas, but this precipitation quickly diminished into showers from Nebraska through North Dakota. Second, an abundance of moisture streamed into the Southern Plains and Lower Mississippi Valley and instigated widespread showers and some thunderstorms from Texas through Alabama. Third, a low pressure system approached the Mid-Atlantic coast and pushed moisture into the Northeast. Thus, precipitation fell from Maryland through Vermont. In between these active areas were dry. Conditions remained dry through the West as clear skies dominated. Low clouds along coast did provide cool conditions near the immediate coast.

The Northeast rose into the 70s, while the Southeast saw temperatures in the 70s and 80s. The Northwest rose into the 70s and 80s, while the Southwest saw temperatures in the 90s and 100s.

The Southern Plains and Lower Mississippi River Valley was pounded with periods of heavy rainfall again on Monday. A low pressure system over the northwestern Gulf of Mexico slightly moved northward and advected further over land. On Monday, this system hovered over eastern Texas, Arkansas, and Louisiana and persistently pulled warm and moist conditions in from the south. Thus, a warm front developed over the eastern portion of the system and extended over Georgia and Florida. Heaviest rainfall was reported along this front and in the center of the low with 1.25 inches of rain reported in Stephens, Arkansas. The back side of this system, in the Southern Plains, saw windy conditions with lighter rainfall. Oklahoma and Texas saw rainfall totals up to a half of an inch with wind gusts up to 17 mph in Calumet, Oklahoma. Meanwhile to the north, high pressure dominated the weather over the Great Lakes and Mississippi and Ohio River Valleys. This allowed for mostly sunny skies and warm conditions. Highs reached into the 80s in most areas of the North again on Monday. However, in the West, a low pressure system moved eastward into the Rockies from the West Coast. This system that previously brought scattered showers and thunderstorms over northern California has intensified as it has moved over the Sierras into the Great Basin. These storms have turned severe with strong winds up to 60 mph gusts in Wendover, Utah. Rainfall amounts remained less than a half of an inch in most places, with 0.31 of an inch reported in Ely, Nevada. The West Coast remained in the 70s with scattered clouds.
The Southeast continued to see showers and thunderstorms on Thursday as low pressure continued to drift rather aimlessly across eastern Texas. A warm front ahead of the low pulled abundant moisture off the Gulf of Mexico, which allowed some very heavy downpours to develop. Rainfall rates over 2 inches per hour were reported from Texas to Georgia. Less intense precipitation was reported throughout the Southwest as separate monsoon moisture flowed into the region from the Pacific. In the Northeast, a few clouds lingered over the coast as high pressure built over the Great Lakes and pushed the majority of clouds off the coast.

In the West, a ridge of high pressure began to strengthen towards the coast bringing clear skies to the entire West Coast. Some morning fog had been reported in the region, but burned off relatively early everywhere except for isolated stretches of the Southern California coastline.

A low pressure system along the Gulf Coast moved very slowly into the Lower Mississippi Valley and provided the most active weather in the country on Friday. A large amount of tropical moisture streamed into the Southeast and into the Tennessee Valley and instigated fairly widespread scattered showers and thunderstorms through the Southeast and farther to the north. Meanwhile, a high pressure system stretched from the Great Lakes through southern New England and provided dry conditions that not only encompassed these areas, but also into the Plains. A cold front progressed through eastern Canada and produced some rain in western New England in the afternoon. Dry conditions transpired in the West even as a low pressure system progressed toward the West Coast from the Pacific Ocean. A high pressure system behind this low will move into the area over the weekend and begin a strong heat wave through much of the West. The Northeast rose into the 60s and 70s, while the Southeast saw temperatures in the 70s and 80s. The Northern Plains rose into the 70s, while the Southwest saw temperatures in the 90s and some 100s.

 

20^th-26^th…Several main weather features produced active weather across the nation on Monday. In the Central US, widespread clouds and areas of fog covered much of the Plains as a deep trough of low pressure supported waves of energy moving through the region. Waves of low pressure along a cold front that extended from western Minnesota through the Southern Plains interacted with a plume of rich gulf moisture to produce numerous showers with locally heavy precipitation and thunderstorms. Stronger thunderstorms in Nebraska, Kansas, and Missouri were accompanied by areas of nickel to ping-pong ball sized hail (0.88 to 1.50 inches) and strong winds. Excessive rainfall created risk for local flash flooding, while gusty winds created powerline damages in St. Clair, Missouri. In the East, a storm system centered over the Upper Great Lakes kicked up another round of scattered showers and thunderstorms across the Eastern Valleys and the Southeast. Heavier and persistent rainfall put the northern regions of Mississippi, Alabama, and Georgia at risk for flash flooding. Meanwhile, deep easterly flow kept areas of the Florida Peninsula under scattered showers and thunderstorms. In the West, a building ridge of high pressure brought warmer and drier weather to the West Coast states. Low relative humidity levels coupled with warmer temperatures and light offshore winds increased the risk of fire weather danger in the Pacific Northwest and the northern and southwestern regions of California.
A deep trough in the Jet Stream continued to sit over the central U.S. bringing some cool weather to the Plains and wet weather to the South and Southeast. The majority of precipitation fell over the Ohio Valley and western Appalachian mountains, good news for residents of the Southeast who have been hard hit by floods over the past week. While the trough was unusually strong for this time of year, it failed to produce any extreme weather, in fact most of the rain from this storm on Thursday fell in regions that needed the precipitation. While the trough dominated the center of the country, high pressure was noted along the coasts. The East coast saw generally clear skies and temperatures were relatively warm. Similar conditions were reported in the West where a very large ridge of high pressure centered over the Northwest kept skies clear, and temperatures hot, especially across the interior. While the rest of the West was hot, coastal regions were blanketed with fog that rolled in off the Pacific, keeping temperatures significantly lower than just a few miles inland. Some locations around the San Francisco Bay Area saw highs in the mid-50s.

A low pressure system in the eastern third of the country provided the most active weather in the country on Friday. The associated cold front draped itself from the Gulf Coast through the Tennessee Valley and instigated rain mainly along the frontal boundary. Another front extended into the Plains and produced more widespread precipitation from South Dakota through Wisconsin and the Upper Mississippi Valley. An additional front thrust toward the Southeast Coast and provided another area of scattered showers and thunderstorms in the Southeast. A high pressure system anchored over eastern Canada spread into the Northeast. Those, thus region remained mostly dry. The West remained dry as well and low coastal clouds have kept coastal areas cool, while inland areas warmed.

The Northeast rose into the 60s, while the Southeast saw temperatures in the 70s and 80s. The Northern Plains rose into the 60s and 70s, while the Northwest saw temperatures in the 60s, 70s, and some 80s. The Southwest rose into the 90s and 100s.

 

27^th-30^th…A deepening trough of low pressure in the northern Great Lakes brought a cloudy and chilly day of weather to much of the Midwest and western New England on Monday. Strong flow over the warm lakes gave way to numerous showers and thunderstorms from the Upper Great through western New England. Gusty winds ushered in cooler temperatures throughout the region and caused minor power line and property damages in northwestern New York. An associated cold front also sparked scattered rain showers and thunderstorms near the Gulf Coast as it extended through the Mid-Atlantic, Southeast, Lower Mississippi Valley, and the Southern Plains. The heaviest storms occurred in southeastern Texas and southwestern Louisiana. Meanwhile, the West Coast also kicked off the work-week with breezy and cooler weather conditions as low pressure settled in over the coastal states. Increased onshore flow returned to the region with low clouds and morning fog as a cold front pushed across the Pacific Northwest Coast and a warm front meandered into the Northern Intermountain West. Gusty winds and low humidity levels put much of Oregon, northwestern California, and portions of Nevada at risk for fire danger. Finally, scattered showers persisted in the southern region of the Florida Peninsula, while fairly quiet weather developed elsewhere.

Wednesday's main weather event occurred in the Intermountain West and the Southwest as a strong autumn storm system from the Pacific trekked through these regions. Significant moisture and energy accompanied the system during it's progression and yielded to areas of mixed precipitation and strong winds with gusts up to 60 mph. Snow showers draped the higher elevations of the western mountains, while areas of scattered showers and isolated thunderstorms developed throughout the lower elevations. Heavy snowfall in the higher elevations of the Wasatch and western Uinta mountains created dangerous traveling conditions with snow packed roads and limited visibility. These areas remained under a Winter Storm Warning through the afternoon. In addition to mixed precipitation, the storm system dropped a much colder airmass into the aforementioned regions, dragging afternoon highs to below average temperatures. Meanwhile, warmer temperatures and drier weather crept back into the coastal states of the West as high pressure began to build into the eastern Pacific. In the East, scattered showers developed in the Northeast as a cold front exited into the Atlantic. Meanwhile, an unrelenting, blustery northwest flow produced another day of chilly weather in the Upper Great Lakes, Ohio Valley, Appalachians, and the Northeast. To the south, dry and warm weather persisted throughout the majority of the Southeast. Low humidity levels in much of northern Florida created a risk of fire danger.

 

Jim G. Munley, jr.
http://www.goecities.com/jimmunleywx