August/Summer 2012 Climate and Hydrology Summary

August & Summer 2012

Tulsa: August 2012 was the 44th warmest (82.9°F, tied with 1991, 1988; since 1905) and the 52nd wettest (3.32"; since 1888) August on record.

Fort Smith: August 2012 was the 35th warmest (83.8°F, tied with 1929; since 1882) and the 56th driest (2.18"; since 1882) August on record.

Fort Smith: Daily records set or tied this month include a record warm mean temperature.

Fort Smith had 12 consecutive days with high temperatures at or above 100° ending on 08/08/2012. This ranks as the 9th highest number of days (tied with 8/9/1970, 7/18/1954, 8/3/1896) since records began in 1882.

Using the radar-derived estimated observed precipitation from the RFCs, rainfall totals for August 2012 ranged from around a meager 0.50” in isolated areas to near 8” in a few spots. Most of the HSA received 2”-4”. Localized rainfall this month meant that some areas of eastern OK and northwest AR received near to above normal rainfall for August, but many areas only received 25-75% of the normal August rainfall. Portions of central Osage County only received 10-25% of the normal August rain.

The remnants of Hurricane Isaac (which made landfall near the mouth of the Mississippi River in Louisiana at 645pm CDT on Aug. 29, 2012 with sustained winds of 80 mph) affected far eastern OK and northwest AR beginning the evening of the 30th and continuing for much of the 31st before moving north into the Midwest. The center of the low pressure moved northward across western AR, with the highest rainfall totals occurring along and east of the track. Rainfall totals across western AR ranged from near 0.25” to around 2” from Isaac, while little rain affected eastern OK. The exception was far northeast OK, where around 1” of rain fell, and across a few localized areas of east central OK.

Significant deterioration in drought conditions occurred during August 2012. According to the Drought Monitor from August 28, 2012, all of eastern OK and northwest AR were in drought conditions. Exceptional drought (D4) included portions of Osage, northern Pawnee, Ottawa, and northern Delaware Counties in northeast OK and Benton, eastern Washington, Carroll, Madison, and eastern Franklin Counties in northwest AR. Extreme drought (D3) was affecting the remainder of the HSA, with the exception of Pushmataha and Choctaw Counties in southeast OK, which were in Severe (D2) drought.

Summer (June-July-August) 2012

Tulsa: Summer 2012 was the 6th warmest (84.2°F; since 1905) and the 45th driest (8.99"; since 1888) Summer on record.

Fort Smith: Summer 2012 was the 6th warmest (84.8°F; since 1882) and the 44th driest (7.66"; since 1882) Summer on record.

Outlook

The Climate Prediction Center CPC outlook for September 2012 (issued August 31, 2012) indicates a slightly enhanced chance for above normal temperatures and an equal chance for above, near, and below median rainfall across eastern OK and northwest AR. This outlook was based primarily on short-term dynamic computer models and very low soil moisture effects.

For the 3-month period Sep-Oct-Nov 2012, CPC CPC is forecasting an enhanced chance for above average temperatures and equal chances for above, near, and below median precipitation across the region (outlook issued August 16, 2012). This outlook is based on dynamic computer model output, long term trends, and initial soil moisture conditions.

According to CPC, ENSO neutral conditions continued through August. Equatorial sea-surface temperatures continue to warm and there is an increasing chance El Niño conditions to develop during the Sep-Oct-Nov period.