Drought Monitor: Crops hindered by hot weather

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Weekly Weather Summary:  Despite scattered, locally heavy showers across the Midwest and Southeast, hot weather continued to have a detrimental impact on summer crops.  The heat’s effects were amplified in areas largely bypassed by showers, including a broad arc of farmland stretching from southern Iowa into western Ohio.  Meanwhile, an already dire situation continued to worsen across the south-central U.S., where the combination of an historic 10-month drought and a relentless summer heat wave left little hope for rain-fed commodities and placed significant stress on livestock and irrigated crops.  Farther west, an active monsoon circulation contributed to beneficial showers in the Four Corners States.  Elsewhere, Southeastern showers helped to offset the effects of hot weather, especially in the central Gulf Coast region and parts of the southern Atlantic States, while Tropical Storm Don—which made landfall in Deep South Texas on July 29—was a tremendous disappointment with minimal rainfall.

The Midwest and Northeast:  Patchy agricultural dryness (D0A) continued to develop from the Midwest into the Northeast, with some pockets of drought (D1A) beginning to appear.  In many areas, persistent heat aggravated the effects of short-term dryness.  For example, Detroit, Michigan, set a record for its hottest month (79.3°F; previously, 79.0°F in July 1921 and 1955).  Meanwhile in Indiana, Ft. Wayne not only set a record for its hottest month, but also experienced a record-high number of 90-degree days in July (22; previously, 21 days in 1983).

In Pennsylvania, nearly one-third (31%) of the corn crop was rated in very poor to poor conditions at the end of July.  Not far behind were Missouri (28% of the corn very poor to poor) and Indiana (21%).  Pastures continued to “burn up,” with more than half reported in very poor to poor condition on July 31 in Pennsylvania (58%) and Maryland (55%).  Topsoil moisture was rated 85% very short to short in Maryland; end-of-July values in other states included 78% in Pennsylvania, 69% in Missouri, 66% in Delaware, 64% in New York, and 63% in Indiana.

Ironically, some areas received heavy rain.  For example, daily-record totals in Michigan for July 27 reached 3.49 inches in Grand Rapids and 2.15 inches in Lansing.  On July 28, Wisconsin locations such as Wisconsin Rapids (3.20 inches) and Green Bay (2.25 inches) tallied daily-record amounts.  Dubuque, Iowa, was hammered by 10.62 inches of rain in a 24-hour period on July 27-28, establishing an all-time record.  Previously, Dubuque’s highest 24-hour rainfall had been 8.96 inches on August 21-22, 2002.  Dubuque also experienced its wettest calendar day on record (7.47 inches on July 27), shattering its former mark of 6.28 inches set on July 1, 1961.  In fact, Midwestern monthly rainfall totals were extraordinarily variable, with Dubuque (16.01 inches) experiencing its wettest month on record and Indianapolis, Indiana (0.47 inch), weathering its driest July.

The Southeast:  Locally heavy showers kept drought intensification at bay in some areas and resulted in some additional drought relief in the central Gulf Coast region.  In fact, New Orleans, Louisiana, received daily-record rainfall amounts on July 25 and 28 (2.34 and 3.52 inches, respectively), and ended the month with 13.00 inches of precipitation (210 percent of normal).  However, even rain-affected locations had to deal with record-setting heat.  In North Carolina, Wilmington (101°F on July 30) tied an annual record with its seventh day of triple-digit heat.  Wilmington originally set its annual record of seven 100-degree readings in 1952.

By July 31, more than half (56%) of South Carolina’s pastures were rated in very poor to poor condition.  South Carolina also led the Southeast with topsoil moisture rated 77% very short to short.  Nearly one-third (32%) of the cotton was rated very poor to poor by the end of July in Alabama and Georgia.  Peanuts (30% very poor to poor) were struggling in Alabama.  Nearly one-half (45%) of North Carolina’s corn was rated very poor to poor.

The Central and Southern Plains and The Mid-South:  Tropical Storm Don—which made landfall on July 29 between Brownsville and Corpus Christi—was a mighty disappointment for parched Texas.  Scattered showers, totaling mostly less than an inch, were limited to Deep South Texas, as the storm literally disintegrated upon moving inland.  Meanwhile, a record-shattering string of 100-degree readings continued into August across parts of the Lone Star State.  Tyler, TX, posted a 36-day streak (and counting) of triple-digit heat from June 28 – August 2, nearly doubling its former mark of 20 days set from July 15 – August 3, 1998.  Dallas-Ft. Worth registered highs of 100°F or higher on 32 consecutive days (and counting) from July 2 – August 2, second only to a 42-day stretch of triple-digit heat from June 23 – August 3, 1980.  With an average temperature of 89.2°F, July 2011 was the hottest month on record in Oklahoma City, Oklahoma, smashing its Dust Bowl-era record of 88.7°F set in August 1936.  Childress, Texas (90.2°F), also demolished its long-standing “hottest month” record, previously set with 89.0°F in July 1934.  Elsewhere in Texas, Wichita Falls (92.9°F) edged its July 1980 standard of 91.9°F.  For the second consecutive month, Lubbock, TX, experienced its hottest month on record (85.9°F in June and 86.0°F in July; previously, 85.4°F in July 1966).  Adding insult to injury was the ongoing historic drought.  For example, Midland, Texas, completed another month without measurable precipitation (rainfall greater than a trace last fell on May 20).  Midland also endured its driest 10-month period on record, with just 0.18 inch falling from October 2010 - July 2011.  The previous record-low precipitation for any 10-month period in Midland was 2.60 inches from October 1950 - July 1951.

The coverage of Texas rangeland and pastures in very poor to poor conditions stood at 93% on July 31, according to USDA.  The rangeland and pasture situation was nearly as bad in Oklahoma (86% very poor to poor), Arkansas (79%), and Kansas (57%).  Oklahoma’s row crops were in particularly bad shape, with USDA rating 88% of the cotton and 74% of the sorghum in very poor to poor condition.  By month’s end, topsoil moisture was reported to be 100% very short to short in Oklahoma, 97% in Texas, 89% in Arkansas, and 73% in Kansas.

The Southwest: An active monsoon circulation continued to generate scattered showers and thunderstorms across the Four Corners States.  July ended wetter than normal at many Southwestern locations, including Douglas, Arizona (3.57 inches, or 114% of normal), and Grand Junction, Colorado (1.71 inches, or 259%).  However, recovery in drought-affected areas was slow, with rangeland and pastures struggling to rebound.  At the end of July, USDA rated 88% of New Mexico’s rangeland and pastures in very poor to poor condition, along with 64% in Arizona. 

Puerto Rico, Hawaii, and Alaska:  Tropical Storm Emily formed southeast of Puerto Rico on August 1 but contributed to an overall wet pattern in early August across the Greater Antilles.  Meanwhile, lackluster summer showers across Hawaii’s Big Island led to expanded coverage of dryness (D0) and drought (D1 and D2).  In particular, moderate drought (D1) coverage increased due to increased irrigation demands and deteriorating pasture conditions.  Farther north, heavy precipitation fell across much of southeastern Alaska in late July, leading to a reduction in the coverage of abnormal dryness (D0).  July 24-30 rainfall totaled 2.33 inches in Juneau, boosting its monthly sum to 3.51 inches (85 percent of normal).  Nearly two-thirds (2.54 of 3.86 inches) of Yakutat’s monthly rain fell from July 24-30.

Looking Ahead:   During the next 5 days (from August 4-8), excessively hot conditions will persist across the south-central and southeastern U.S., while cooler air will overspread the Midwest.  Little or no rain will fall in the Far West and the drought-devastated south-central U.S.  However, most other areas—including the northern and central Plains, Midwest, and East—can expect 1 to 2 inches of rain, with locally higher amounts.  Most forecast guidance suggests that Tropical Storm Emily will turn away before reaching the U.S. mainland, although a weekend landfall along the southern Atlantic Coast cannot be ruled out.

The CPC 6- to 10-day outlook for August 9-13 calls for below-normal temperatures along and near the Pacific Coast and from the Midwest into the Northeast, while hotter-than-normal weather will prevail from the Four Corners region into the Southeast.  Meanwhile, below-normal rainfall in California and across the nation’s southern tier will contrast with wetter-than-normal conditions from the northern Plains to New England, including the Midwest.

Author: Brad Rippey, U.S. Department of Agriculture

Dryness Categories
D0 ... Abnormally Dry ... used for areas showing dryness but not yet in drought, or for areas recovering from drought.

Drought Intensity Categories
D1 ... Moderate Drought
D2 ... Severe Drought
D3 ... Extreme Drought
D4 ... Exceptional Drought

Drought or Dryness Types
A ... Agricultural
H ... Hydrological

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