NATIONAL STORM SUMMARY

 

AUGUST 2012

 

5th-11^th…A long cold front moved through the eastern third of the country on Monday, producing the most active weather in the country. The front began the day stretched from Arkansas through western New York before moving slowly eastward. There was not a tremendous amount of moisture associated with this front, but scattered showers and thunderstorms were triggered throughout the Southeast and Mid Atlantic. These thunderstorms developed particularly in the afternoon.Early morning rain and thunderstorms also moved through New Jersey, but these thunderstorms had pushed out into the Atlantic Ocean later in the morning.

Showers and thunderstorms developed across the eastern U.S. as a low pressure system lingered over the Great Lakes. This system created a warm front that extended northeastward into Maine, while a cold front stretched south of this system and moved through the Eastern Valleys. These systems pulled abundant moisture in from the Gulf of Mexico and Atlantic Ocean, which allowed for showers and thunderstorms to develop over most of the eastern U.S. Heavy rains developed in the North, from Michigan to Maine with heaviest rainfall reported in Belmar-Farmingdale, New Jersey. Some of these storms turned severe with strong winds and hail. Multiple trees and power lines were blown down from New York through Massachusetts.

 

 

19^th-25^th…The most active weather in the country occurred along a front that stretched from the Gulf Coast through North Carolina. This front allowed moisture to stream along it, producing areas of heavy rain and thunderstorms through the panhandle of Florida. This represented the only significant rain in the country as several inches of rain fell. Some rain did fall along the eastern seaboard from North Carolina through Delaware, but this precipitation was not widespread in nature. Additional scattered showers and thunderstorms did develop in New England in the afternoon. Meanwhile, monsoon moisture streamed into the Southwest and produced a few thunderstorms in the Four Corners region. More thunderstorms were expected into the afternoon, as is typical this time of year. Coastal clouds along the West Coast kept the immediate coast cool, while inland areas of the Southwest once again warmed up to the 90s and some 100s. Cooler weather is on the way as a low pressure system from the Gulf of Alaska approaches the West. The Northeast rose into the 70s, while the Southeast saw temperatures in the 70s and 80s for the most part. The Southern Plains rose into the 80s and 90s, while the Northwest saw temperatures in the 60s, 70s, and some 80s with the coolest temperatures at the coast.

 

19^th-25^th…Active weather returned to the Plains on Wednesday as a trough of low pressure moved off the Northern Rockies and into the Northern Plains. This system pushed a frontal boundary eastward and kicked up scattered showers and thunderstorms across the Dakotas and Minnesota throughout the day. Some of these storms have turned severe with large hail and gusty winds. One inch in diameter hail was reported in Stewart, Minnesota, while 1.25 inch in diameter hail was reported in Dassel, Minnesota. Strong winds ahead of this front increased fire danger across the Central Plains, due to prevailing hot and dry surface conditions. In the South, a frontal boundary lingered over northern Florida and the Southeast and triggered more heavy rainfall with strong thunderstorm development. These storms have not yet turned severe but a mid-day total of 2.69 inches of rain was reported at Perry, Florida.

Multiple areas of active weather developed across the nation on Friday. A low pressure system moved through the Northern Plains and pushed a warm front through the Dakotas and Upper Midwest, while a cold front developed behind the system across the High Plains. To the south, another area of low pressure moved off the Central Rockies and into the Central Plains. This pushed a warm front eastward into the Mid-Mississippi River Valley, which created periods of heavy rain and strong thunderstorms. Thus, showers and thunderstorms developed across most of the Plains on Friday as these weather features moved off the Rockies. In the South, areas of wet weather developed from Texas through the Southeast. Onshore flow from the Gulf of Mexico created heavy rains and scattered thunderstorms from eastern Texas through the Lower Mississippi River Valley. Heaviest rainfall was reported in Lake Charles, Louisiana with a mid-day total of 2.59 inches. In the Southeast, a frontal boundary slowly moved offshore and into the Atlantic Ocean. However, this triggered a few more showers and thunderstorms across parts of Florida as well as eastern North Carolina and South Carolina.

Isaac continued to lash Louisiana, Mississippi, and Alabama with extremely heavy rain, strong wind, and life-threatening storm surge and flooding as it weakened from a category 1 hurricane to a tropical storm in the afternoon. As of Wednesday afternoon, Isaac was located about 50 miles southwest of New Orleans, Louisiana and continued on a northwestward track with maximum sustained winds near 70 mph. Storm surge values of about 8 feet were reported at Shell Beach, Louisiana and Waveland, Mississippi, while dangerous surf and rip current conditions continued along the West Coast of Florida and the northern Gulf Coast. In regards to rainfall, rain totals from Monday through this afternoon have been quite significant. For this time period, New Orleans Lakefront Airport reported a rainfall total of 9.26 inches, Boothville, Louisiana reported 6.58 inches, and Gulfport, Mississippi reported 5.05 inches. Isolated tornadoes also remained a concern along the central Gulf Coast region and parts of the Lower Mississippi River Valley.

Isaac reduced to a tropical depression on Friday with maximum sustained winds less than 39 mph. The system lost energy and strength as it slowly moved northward and further inland over Arkansas and Missouri. Flow around this system continued to pull abundant moisture in from the Gulf of Mexico and produced extremely heavy rains for the Mid- and Lower Mississippi River Valley. Mid-day rainfall totals for Friday ranged from 2 to 4 parts of Arkansas and Missouri, with the heaviest rainfall was reported at 5.17 inches in Alexandria Esle, Louisiana. Strong winds persisted in the vicinity of the storm with gusts up to 54 mph at Tin City, Arkansas. Since Monday, rainfall totals have reached up to 20.08 inches in New Orleans, Louisiana, 17.04 inches in Kiln, Mississippi, and 16.60 inches in Vero Beach, Florida. Thus, the mid and lower Mississippi River Valley remained under severe flooding conditions.

 

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