NATIONAL STORM SUMMARY

 

SEPTEMBER 2012

 

1^st-8^th…Wet weather persisted for the East on Labor Day as the remnants of Isaac slowly into the Ohio River Valley. The system merged with a frontal boundary to the north, and created heavy rain showers from the Ohio and Tennessee Valleys, through the Mid-Atlantic states. Heaviest rainfall in the region was reported at Wilmington, Ohio with a mid-day total of 1.24 inches of rain. Some areas of the Ohio River and surrounding tributaries saw flooding as the remnants of Isaac slowly moved eastward throughout the day. There was a slight risk of severe weather development across Alabama and Mississippi as the southern side of Isaac pulled more moisture onshore. This kicked up moderate to heavy showers and thunderstorms with strong winds and heavy rains. Heaviest rainfall was reported in Birmingham, Alabama with a mid-day total of 2.60 inches. Strong winds with gusts from 30 to 40 mph were reported across the Eastern Valleys.

Heavy rain and thunderstorms developed in the Northeast as a low pressure system moved through New England and an associated cold front extended southwestward across the Upper Mid-Atlantic. Rainfall totals of up to 2.85 inches were reported in the Northeast this afternoon, while lighter and more scattered precipitation developed in the Upper Mid-Atlantic. To the south, an area of low pressure located along the coast of the western Florida Panhandle kicked up rain near the northeastern Gulf Coast.

 

9^th-15^th…Wet weather activity continued across the Four Corners on Wednesday as ample monsoonal moisture remained over the region with several weather disturbances. This setup translated into showers, periods of heavy rainfall and thunderstorms during the morning and afternoon. Flood Advisories and Flash Flood Watches and Warnings were issued for areas of southern Utah and southern Colorado in response to today and this week's significant rainfall. In the afternoon, precipitation, winds, and thunderstorm activity began to pick up across eastern Colorado, New Mexico, and western Texas as a cold front dropped across Colorado and the Southern High Plains. A Winter Weather Advisory was issued for elevations above 11,000 feet in the southern and northern Sangre de Cristo Mountains, the western Mosquito Range, and eastern Sawatch Mountains in anticipation of potential snowfall associated with this storm. Total snow accumulations were expected to range between 4 and 8 inches today with local 10 inch snow amounts possible at the highest elevations.

 

16^th-22^nd…Heavy rain drenched the South and East, while dry weather covered the western half of the nation. Weekly precipitation totaled 4 inches or more in parts of the Appalachians. Nearly all of the week’s precipitation highlights occurred across the East on September 17-18. In Tennessee, Knoxville received a September 17-18 total of 6.10 inches, highlighted by daily-record amounts on both days (2.94 and 3.16 inches, respectively). Other daily-record totals for September 17 included 3.09 inches in Muscle Shoals, AL; 2.95 inches in Tupelo, MS; and 2.37 inches in Evansville,

IN. The following day, record-setting amounts for September 18 reached 5.41 inches in Mt. Pocono, PA; 3.65 inches in Chattanooga, TN; 3.28 inches in Asheville, NC; and 3.19 inches in Albany, NY. By the night of September 21-22, the season’s first snowflakes were noted in portions of the upper Great Lakes region. On September 22, Wisconsin Rapids, WI, reported a trace of snow, while Duluth, MN (0.1 inch), tallied a daily-record amount. Powerful, early-autumn storms pounded south-central Alaska, resulting in high winds, heavy precipitation, and flooding. Weekly rainfall totaled 13.92 inches in Valdez, aided by daily-record amounts on September 16, 19, and 20 (3.86, 2.59, and 4.27 inches, respectively). Valdez also set a monthly record with 21.95 inches through the 23rd. Prior to this year, the wettest September in Valdez had occurred in 1982, with 16.69 inches, while the wettest month had been November 1976, with 20.59 inches. Record flooding developed along the Resurrection River, where the crest at Exit Glacier Bridge exceeded the October 2006 high-water mark by nearly 1½ inches. Significant flooding was also reported in the Susitna Valley. Wind gusts in Palmer were clocked to 56 mph on September 15-16 and 54 mph on September 18-19. On the Harding Icefield, the two storms produced gusts to 96 and 91 mph, respectively. High winds even reached interior Alaska, where Delta Junction recorded a gust to 71 mph during the September 15-16 storm.

 

23^rd-30^th…Heavy rains continued across Texas on Saturday, while showers and thunderstorms moved into the Carolinas. A low pressure system strengthened as it moved over Texas and spread tropical moisture across the state. At the same time, the system pulled moisture in from the Gulf of Mexico, which kicked up heavy rainfall across most of central and northern Texas. The system moved eastward throughout the day and approached the Lower Mississippi River Valley. Heaviest rainfall was reported in Abilene, Texas with a mid-day total of 3.84 inches of rain. Thus, flash flood advisories were issues throughout the region. Strong winds also accompanied this strong low pressure system with gusts from 40 to 50 mph across parts of Texas and the Lower Mississippi River Valley.

 

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