National Weather Service Huntsville, AL -- September 2012 Climate Summary

September Climate Summary for Huntsville and Muscle Shoals

Temperatures...

Average temperatures were below normal for the month of September, for the 2nd month in a row. Back to back months with below normal temperatures hasn't occurred at Huntsville or Muscle Shoals since September and October of last year. The large scale pattern became much more amplified during August and continued into Setember, leading to more intrusions of cooler airmasses of Canadian origin into the Tennessee Valley and surrounding regions. Although temperatures averaged below normal for the month as a whole, temperatures began a little warm. In fact, the only temperature records set during the month were for overnight record warm minimums, including a low of 77 at Muscle Shoals on the 1st and a low of 74 degrees at Huntsville on the 4th. While temperatures averaged above normal for the first week, conditions changed abruptly at the start of the second week, with a series of cold fronts bringing drier and cooler weather into the region. Daytime highs remained in the 80s for the most part, but some days saw highs in the 70s, while overnight lows were generally in the 50s and 60s. Morning lows even fell into the 40s at many locations on the 19th and 20th, for the first time since early May at Huntsville, and since late April at Muscle Shoals. At the close of September, temperatures averaged around one to two degrees below normal for the month.

Annual update: despite below normal temperatures for both August and September, overall temperature averages are still well above normal through the first nine months of 2012. In fact, to date, it is still the warmest year on record at Muscle Shoals, while the ranking has slipped to 2nd place at Huntsville. Below are the top 5 warmest January - September periods at both locations:

Huntsville

Muscle Shoals

Rank	Avg Temperature	Year	Rank	Avg Temperature	Year
1	67.9	1925	1	68.1	2012
2	67.7	2012	2	67.0	1925
3	66.5	1927	3	66.8	1998
3 (tie)	66.5	2007	4	66.7	1921
5	66.4	1922	5	66.5	2006

Daily Temperature Graphs for the month of September for each location (click on the images for a larger version).

Huntsville - Sep 2012 Temperature Graph	Muscle Shoals - Sep 2012 Temperature Graph

Temperature Statistics for the Month of September at Huntsville and Muscle Shoals. All temperatures are in degrees Fahrenheit.

September Statistics	Huntsville	Muscle Shoals
Average Monthly Temperature	71.5	72.1
Normal Temperature*	73.7	73.2
Deviation From Normal	2.2 Below Normal	1.1 Below Normal
Monthly Ranking**	30th Coolest	34th Coolest
Warmest September	83.5 (1925)	82.2 (1925)
Coolest September	68.2 (1975)	65.3 (1918)
Max Temperature	91 (Sep 6th/7th)	93 (Sep 7th)
Min Temperature	44 (Sep 24th)	43 (Sep 24th)
All-Time Max Temperature	108 (Sep 7, 1925)	108 (Sep 8, 1925)
All-Time Min Temperature	37 (Sep 29, 1942) (Sep 30, 1967)	35 (Sep 30, 1901)
Record Highs	74 on the 4th (High Minimum)	77 on the 1st (High Minimum)
Record Lows	None	None

Precipitation...

Early in September, rounds of showers and thunderstorms developed in the area as a moist and humid airmass enveloped the region. The remnants of once Hurricane Isaac combined with a strong upper-level system to help with the rainfall production. Rainfall totaled just over 0.75 inches at Huntsville and over 1.50 inches at Muscle Shoals for the first five days of the month. More impressive totals around 3 to 5 inches were reported over southern portions of the Huntsville forecast area, from parts of the Bankhead National Forest through Cullman into southern Marshall County. However, more widespread heavier rains moved across the area on the 17th in association with a strong low pressure system from the Gulf. Rainfall totaled around 2 to 5 inches across a broad swath of northern Alabama and middle Tennessee during just a one day period. The rainfall was sufficient to produce some flooding, mainly in northwestern portions of Alabama. The one day totals of 3.69 inches at Huntsville and 3.09 inches at Muscle Shoals broke daily rainfall records for September 17th. At Huntsville, this was the 5th wettest September day on record and the wettest single day since the remnants of Tropical Storm Lee drenched the airport location with 4.42 inches on September 5, 2011. By the end of the month, precipitation totaled 5.43 inches at Huntsville, and 5.71 inches at Muscle Shoals, which was above the normal for both locations.

Radar Precipitation Estimates and Departures from Normal for September for the Huntsville Forecast Area (amounts are in units of inches).

Radar Precipitation Estimates	Radar Precipitation Departures from Normal

September Precipitation Statistics for Huntsville and Muscle Shoals (amounts are in units of inches).

September Statistics	Huntsville	Muscle Shoals
Monthly Precipitation	5.43	5.71
Normal Precipitation	3.72	3.72
Departure from Normal	1.71 Above Normal	1.99 Above Normal
Monthly Ranking	18th Wettest	19th Wettest
Wettest September	12.48 (1906)	10.13 (1979)
Driest September	0.00 (1897 & 1916)	0.00 (1897)
Wettest Calendar Day	3.69 (Sep 17th)	3.09 (Sep 17th)
Record Wettest Day	5.95 (Sep 13, 1929)	5.71 (Sep 13, 1979)

The Monthly Outlook for October from the Climate Prediction Center...
The one month temperature outlook indicates higher chances for below normal temperatures for the central Tennessee Valley climatic zones, based on the 3-tiered categories. The probabilities are as follows...

Above Normal....~24%
Near Normal......33%
Below Normal......~43%

The one month precipitation outlook indicates equal chances for above, near or below normal precipitation for the central Tennessee Valley climatic zones, based on the 3-tiered categories. The probabilities are as follows...

Above Normal....33%
Near Normal......34%
Below Normal....33%

What is normal for October? ...Huntsville daily normals and records / Muscle Shoals daily normals and records

* Normal temperatures and precipitation are based on the 1981-2010 climatological period. All temperature data are expressed in degrees Fahrenheit.
** Temperature data for Huntsville go back to 1907, while precipitation data are available since 1894. Any months that contain missing daily temperature or precipitation data are not counted in the rankings.

*** Temperature and precipitation data for Muscle Shoals go back to 1893, however sporadic outages of data occur especially in the 1910s and again from September 1995 through May 1997. Any months that contain missing daily temperature or precipitation data are not counted in the rankings.

Note...all data above are preliminary and have not undergone final quality control by the National Climatic Data Center (NCDC). Therefore, these data are subject to revision. Final and certified data can be accessed at the NCDC at the following location... http://www.ncdc.noaa.gov

One month and seasonal temperature and precipitation outlooks may be obtained from the Climate Prediction Center at the following location...http://www.cpc.ncep.noaa.gov

KDW

National Weather Service Weather Forecast Office