NATIONAL STORM SUMMARY

AUGUST 2011

1st-6th…Low pressure system spinning on the coast of the Carolinas,
pushed ample moisture onshore triggering heavy showers and
thunderstorms across the Mid-Atlantic States. Rainfall totals
associated with this system have been between half an inch to almost 5
inches, with the highest mid-day rainfall totals reported in
Charlotte, North Carolina at 2.49 inches. In the central U.S., a low
pressure system moved off the central Plains into the Mid-Mississippi
Valley bringing heavy rain and strong winds to the region and parts of
the Ohio, Tennessee, and Upper Mississippi Valleys. Heavy downpours
and strong winds were associated with these storms, with a strong wind
reports Tennessee and Illinois. To the west, a low pressure system
over Montana pushed a cold front through the Northern Rockies and
Northern Plains producing moderate to heavy showers. Wind gusts were
reported between 30 to 70 mph. In addition, monsoon moisture in the
Southwest triggered scattered showers over the Four Corners region and
Central Rockies.

14th-20th…The heaviest precipitation fell in New England as a storm
moved up the eastern seaboard and rotated into the Northeast. This
storm carried a significant amount of moisture that once again dumped
rain on New England as some cities received several additional inches
of rain to go along with the drenching precipitation from the weekend.
The cold front associated with this storm pushed through the Southeast
and off the coast of the Carolinas, greeting the area with very
welcomed cooler air.
Parts of the Midwest experienced active weather Wednesday as a weak
cold front dropped southeastward through Iowa and Wisconsin toward
northwestern Illinois. Showers and a few thunderstorms accompanied the
front in parts of Minnesota, Wisconsin, and Iowa during the morning
and afternoon hours. While some storms associated with this system had
the potential to produce damaging wind and hail, no events were
reported as of this afternoon. To the south, daytime heating kicked up
more showers and thunderstorms in central Florida as a frontal
boundary remained stationary across the Florida Panhandle,
Mississippi, and southern Arkansas. Stronger storms in this region had
the potential to produce damaging wind gusts.

21st-27th…Low pressure over Ontario pushed a frontal boundary through
the Great Lakes to the Central Plains. Showers and thunderstorms
developed along and ahead of this front over the Northern Appalachians
to the Central Plains. The highest mid-day rainfall totals were
reported in Toledo, Ohio at 1.43 inches. However, high pressure
brought mostly sunny and dry conditions for the Northern Plains and
Northern Rockies. In the South, ample moisture pulled onshore, which
triggering heavy showers and thunderstorms across the Lower
Mississippi Valley and parts of the Tennessee Valley. Rainfall totals
associated with these storms have ranged from 0.35 inches to almost
1.5 inches. In addition, strong winds were reported in several areas
in Arkansas and Louisiana, with wind gusts recorded at 58 mph in
Monroe, Louisiana.

28th-31st…The northern states saw plenty of active weather on
Wednesday. A strong frontal system moved through the Northwest, which
contributed to widespread moderate showers and thunderstorms over the
Intermountain West and Northern Rockies. Wind gusts associated with
this system ranged from 30 to 50 mph. At the same time, a large low
pressure system positioned over Canada pushed moderate to light rain
showers to the Upper Midwest, Great Lakes, and Northeast. Wind gust
reached 51 mph in Mt. Washington, New Hampshire. To the south, ample
available moisture pushed onshore, which triggered heavy showers and
thunderstorms over most of Florida and along the coast of the Gulf
States. Rainfall totals reached between 0.40 inches and 0.85 inches in
Florida, with the highest mid-day rainfall totals recorded in
Boothville, Louisiana at 1.11 inches. Meanwhile, an upper level ridge
of high pressure over the Southeast produced mostly dry conditions for
the South-Central US, and eastward to the Mid-Atlantic.
Most of the precipitation were tropical in nature, as Tropical Storm
Irene’s departure from the Northeast was soon followed by Tropical
Storm Lee’s arrival along the central Gulf Coast. In Irene’s wake,
extensive flooding struck the interior Northeast. Later, more than 10
inches of rain drenched parts of the central Gulf Coast region,
triggering local flooding. Lee made landfall in southern Louisiana on
the morning of September 4. Farther north and west, a strong cold
front sparked some heavy showers and thunderstorms from the northern
and central Plains into the western Corn Belt. Early in the week,
Irene continued to batter the Northeast. Despite being downgraded from
a hurricane to a tropical storm before reaching New York City on the
morning of August 28, wind gusts on that day were clocked to 81 mph at
the Blue Hill Observatory in Milton, MA; 67 mph at New York’s
LaGuardia Airport; 64 mph in Providence, RI; and 63 mph in Bridgeport,
CT. Meanwhile, record setting rainfall amounts for August 28 reached
5.22 inches in Newark, NJ; 4.83 inches in St. Johnsbury, VT; 4.69
inches in Albany, NY; and 4.13 inches in Mt. Pocono, PA. Wilmington,
DE (6.94 inches on August 27-28), experienced its fifth-highest 2-day
rainfall on record. Record flooding affected numerous river basins
from New Jersey northward. On August 28 in New Jersey, high-water
marks from Hurricane Floyd in September 1999 were broken along the
Millstone River at Griggstown (14.21 feet above flood stage) and
Blackwells Mills (12.24 feet). Along the Passaic River at Pine Brook,
NJ (5.12 feet above flood stage on August 30), the river level
exceeded the high water mark established on October 10, 1903. In
Vermont, Otter Creek at Rutland climbed 9.21 feet above flood stage on
August 29, easily surpassing the record of 5.45 feet set in the
aftermath of a hurricane on
September 22, 1938. In North Walpole, NH, the Connecticut River (3.36
feet above flood stage on August 29) climbed to its highest level
since September 22, 1938.
Tropical Storm Lee made landfall on Sunday morning, September 4, near
Intracoastal City, LA. At landfall, Lee’s maximum sustained winds were
near 45 mph, mostly in squalls over the northern Gulf of Mexico. On
September 3, prior to Lee’s arrival, a few wind gusts to near 60 mph
were reported in southern Louisiana as far inland as New Orleans. A
gust to 51 mph was clocked on September 3 in Gulfport, MS. In
addition, a 4-foot storm surge was noted in southern Louisiana
locations such as Shell Beach and Lake Pontchartrain. However, Lee’s
most significant impact was heavy rain. Official September 1-5 totals
reached 11.64 inches in Mobile, AL; 11.15 inches in both Gulfport and
Jackson, MS; 11.05 inches in New Orleans, LA; 9.80 inches in
Chattanooga, TN; and 7.97 inches in Birmingham, AL. However, much of
Lee’s heavy rain fell in drought-affected areas, helping to limit
flood severity.