California and National Drought Summary for July 19, 2016

Summary

July 21, 2016 - This week’s USDM period (ending on July 19) was characterized by typical hit and miss summer-time shower activity across the country, punctuated by extreme heat in the Southern Plains and the Northeast. The heaviest rains fell in southern Minnesota, southwest Iowa, much of Indiana and eastern Illinois, western Kentucky, eastern North Carolina, along the Gulf Coast and Florida. Below normal precipitation was observed in eastern Texas, northern Wisconsin, Pennsylvania and New England. A strong ridge over the southern Plains contributed to abnormally warm temperatures in New Mexico and Texas during the period. Daily maximum temperatures soared well into the triple digits, as much as 10 degrees F above normal in the area. While not as intense, temperatures 6-8 degrees F above normal were observed in the Northeast. Cooler-than-normal temperatures encapsulated much of the Northwest and High Plains.

Northeast

Another mostly below normal precipitation week in the Northeast as only light rain fell later in the USDM period. Convection affected areas which have been wetter rather than the drier areas. The driest areas were concentrated in western New York and Pennsylvania, and much of Massachusetts, Connecticut, and Rhode Island. For the last 30 days, precipitation is below 25 percent of normal. Stream flows at all levels (1-, 7-, 14-, and 28-day) are reaching into the tenth percentiles. Moderate to Severe drought (D1-D2) was expanded to cover these high impact areas. Media reports of problems due to the dry weather are becoming common in the region and New York issued the first statewide drought watch since 2002. Massachusetts was also issued a drought watch.

Impacts are far reaching across the region as many farmers are using irrigation methods as the dry conditions hindered growth and stressed crops. It was reported that pastures were stunted and corn was curling in parts of central New York. Soil moisture deficits, which have been deteriorating since this past winter, have forced some farmers to irrigate around the clock.

Much of Massachusetts was in moderate and severe drought, leading to more than 120 towns statewide adopting mandatory water restrictions. Several farms in northeastern Massachusetts reported crop losses due to non-irrigated fields being too dry to plant or because the seed sprouts did not emerge after planting. A fungus that kills gypsy moth caterpillars needs springtime moisture to grow. Without adequate rainfall, the caterpillar population thrived and in turn decimated tree foliage in Massachusetts, Rhode Island, and Connecticut. Defoliated trees, caused by an abundance of caterpillars that thrive in dry conditions, has also heightened fire danger.

In Connecticut, the year-to-date period ending in June was the state’s ninth driest on record and the 12-month period (July 2015-June 2016) was the fourth driest. The local water company asked its customers to conserve water and reduce non-essential outdoor water use because rainfall was below normal while water demand was extremely high, putting local reservoirs and wells below normal capacity.

Southeast

Much of the Southeast experienced scattered rain showers this past USDM week. Some areas were winners while others were losers. Eastern North Carolina, parts of southwest and eastern South Carolina, the Georgia/Florida border, west central Alabama, southern Mississippi and southeastern Louisiana all experienced above normal precipitation for the 7-day period. The majority of other locations were at or below normal in terms of precipitation. Average daytime temperatures for the region were generally above normal. The most intense heat was focused in western South Carolina where anomalies were as great as 4 degrees F above what is typically expected during the time period. Below average temperatures, associated with the cloud cover, were centered along the Gulf Coast.

Warm temperatures, combined with a lack of precipitation, exasperated drought conditions in the region. Degradations were made across Georgia where precipitation was 50 percent of normal or less. An area of Extreme Drought was introduced in Cherokee County and stretching into Bartow County, Georgia where a stream flow gauge was measuring below 2 percent. D0 was stretched south and east covering the quickly deteriorating conditions. Reported impacts are mixed across Georgia but include: loss of corn crops, no grass to feed the cattle resulting in the use of hay to supplement, daily irrigation was not enough to supply plants what they need to survive. On a more positive note, one farmer reported they had a record watermelon harvest season.

Southern Plains

Much of the Southern Plains suffered as stifling heat baked the soils while precipitation was non-existent. Recent rains over the northern half of Oklahoma did warrant some improvement, but there was huge disparity in the south central and southeast part of the state. A single-category degradation was needed due to the 30-day precipitation departures. In Texas, temperatures were for the most part 4 degrees F above normal during the period. The most intense heat was in western Texas where anomalies were around 8 degrees F above normal. According to the USDA, 64 percent of topsoil moisture conditions are in the very short to short category. Deterioration occurred in the north, southwest and eastern parts of the state.

Midwest

Scattered showers affected the region from Minnesota eastward into Ohio. As much as 4 inches of precipitation was observed in southern Minnesota, eastern Illinois and western Indiana. Below average precipitation was reported in much of Missouri, Wisconsin and the Upper Peninsula of Michigan. A large disparity in temperatures occurred from Minnesota and Iowa eastward to Ohio. Temperatures were 3-5 degrees cooler than normal in the west and 3-5 degrees warmer than normal in the east. Drought conditions improved in Iowa, but expanded in Ohio. It was reported by a farmer near Toledo that the lack of rain has slowed crop growth and he has relied on his pond for irrigation, but the pond’s water level was dropping rapidly.

High Plains

Precipitation in the High Plains this period ranged from greater than 300 percent in much of Montana to well below 10 percent along the North and South Dakota state border. Temperatures were muted across the region as anomalies were as much as 6 degrees below normal. Conditions continue to be drier than normal in the western South Dakota/eastern Wyoming area. Less than half of what is normally expected, in terms of precipitation, has fallen in that area during the last 30 days. 28-day stream flows are measuring in the 5-10 percent category and lower. All other indicators, including model based and satellite derived, are pointing to an extreme localized drought in the area. Ranchers and farmers in the area are experiencing no hay production at all and the cattle are already on winter pastures. There are not only water quantity issues, but also as the stock ponds and dams dry up, the water quality is suspect. Some ranchers have to haul water in every day. Wildfires are also a large concern. Based on all the indicators and impacts, all categories of drought were expanded in the area.

West

Precipitation was virtually non-existent in much of the Western region during the period. Light rain (0.5 inch) did fall in central Oregon and norther Washington. The southwest monsoon provided some relief to parts of Arizona, albeit only light amounts fell. Temperatures were cooler than normal in the Northwest, but slightly above normal for the desert southwest. The cooler than normal temperatures during July have helped suppress many new wildfires from emerging. This is the dry season for the West Coast, so changes to the drought monitor are very rare this time of year.

Alaska, Hawaii, and Puerto Rico

In Alaska, percent of normal precipitation along the south and the entire panhandle is at 5 percent through the last 2 weeks. Meanwhile, temperatures are 8-10 degrees above normal during this 7-day USDM period. Wildfires are spreading across southern Alaska and streamflow’s are low in parts of the southwest and much of the southern panhandle. In the panhandle, fish and game authorities are starting to see some small fish die offs at the fisheries due to the high water temperatures while the low water levels are keeping the salmon in the ocean where the water is cooler. Due to these conditions, D0 was added to the entire panhandle. No changes were made in Hawaii and Puerto Rico this week.

Looking Ahead

The next 3-7 days will bring above normal temperatures for much of the CONUS with the warmest anomalies forecasted for the Midwest and along the East Coast. Negative temperature anomalies will be confined to the Northwest. The High Plains, parts of New England, the Southeast, and Florida have the best chances of greater than normal precipitation.

The CPC 6-10 day outlook calls for the greatest chances of above normal temperatures in California and the Great Basin, as well as the East Coast. The probability is high that below normal precipitation will occur in the Northwest, especially in Washington and Oregon, and the Midwest, while odds are in favor of above normal precipitation in the Southeast and East Coast.

Author(s):
Chris Fenimore, NOAA/NESDIS/NCEI

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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

S ... Short-Term, typically <6 months (e.g. agricultural, grasslands)

L ... Long-Term, typically >6 months (e.g. hydrology, ecology)
Source: National Drought Mitigation Center