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NATIONAL STORM SUMMARY

 

SEPTEMBER 2009

 

1st-5thPlenty 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.

Active weather continued to develop in the eastern half of the nation on Wednesday. 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.

 

13th-19thThe 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 spread 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. 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.

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.

 

20th-26thSeveral 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.

27th-30thA 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.

 

27th-30th...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.

 

 

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



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