Here is the Virginia Water Central News Grouper’s monthly water-status report on precipitation, stream flow, and drought, as of the end of April 2015. The Virginia Water Resources Research Center thanks the agencies mentioned below for providing the data and maps used in this post. Icons for precipitation, stream flow, and drought are by George Wills of Blacksburg, Va. (https://www.etsy.com/people/BlacksburgArt).
Here are National Weather Service (NWS) preliminary (still needing verification) precipitation totals for April 2015 at 11 Virginia or near-Virginia locations, along with the normal for this month of the year. Also shown are the precipitation for the previous 12 months and the normal annual precipitation for each location. All values are in inches, rounded to the nearest 0.1 inch from NWS values.
May 2014- April 2015 Precipitation
Normal Annual Precipitation
|Bluefield (Merc. Co. airport, near Va.-W.Va. state line)||5.3||3.3||42.4||39.6|
|Bristol (Tri-Cities Airport in Tenn., about 20 miles from Bristol, Va.-Tenn.)||5.0||3.3||42.5||41.0|
|Charlottesville (Char.-Albemarle Airport)||4.7||3.4||36.1||42.7|
|Wallops Island (Accomack County)||3.8||3.1||40.3||40.8|
|Washington-Dulles Airport (Loudoun County)||2.5||3.5||39.5||41.5|
Precipitation sources: Climate pages of the following National Weather Service Forecast Offices:
Blacksburg, Va. (http://www.nws.noaa.gov/climate/index.php?wfo=rnk)
Morristown, Tenn. (http://www.weather.gov/climate/index.php?wfo=mrx
Baltimore-Washington (http://www.nws.noaa.gov/climate/index.php?wfo=lwx); and
Wakefield, Va. (http://www.nws.noaa.gov/climate/index.php?wfo=akq).
The normal values used by the National Weather Service (NWS) in these provisional reports are based on the period from 1981 to 2010. The National Climatic Data Center released these normal values in July 2011. For information on the normal values, see the National Climatic Data Center Web page at http://www.ncdc.noaa.gov/data-access/land-based-station-data/land-based-datasets/climate-normals.
For graphs of precipitation, visit the Southeast Regional Climate Center (Chapel Hill, N.C) at http://www.sercc.com/climateinfo/precip_maps, where you can find maps of total precipitation and percent of normal precipitation for the past 7, 30, 60, or 90 days; or the NWS’ Advanced Hydrologic Prediction Service at http://water.weather.gov/precip/ for a map of precipitation nationwide or by state, with capability to show county boundaries, and archives available for specific days, months, or years. Shown below are the Southeast Regional Climate Center’s provisional (still needing verification) maps of the percent-of-normal precipitation for the previous 30 days, 60 days, and 90 days, through April 30, 2015. Please note that the scale is different for the 30-day map.
According to the U.S. Geological Survey WaterWatch for Virginia, average stream flow values for April 2015 at 152 stream gages in Virginia and just beyond the state border were in the normal range at about 52 percent of gages, below normal at about 3 percent, above normal at about 45 percent (with much-above-normal readings for the month a few gages in western Virginia). The color-coded, flow-percentile map for this period is shown below. The color codes/percentile classes used by USGS to compared flows to historical records for the month are shown in the chart below the map.
The weekly National Drought Monitor map from the University of Nebraska-Lincoln (http://droughtmonitor.unl.edu/) for April 28, 2015, showed Virginia as drought-free, which has been the since the Drought Monitor report for April 21, 2015. Before that, some area of Virginia had been categorized as at least “abnormally dry” since the Drought Monitor report for April 22, 2014.
The Drought Monitor notes that it “focuses on broad-scale conditions [and] local conditions may vary.” The Drought Monitor categories are as follows:
D0 = abnormally dry;
D1 = moderate drought;
D2 = severe drought;
D3 = extreme drought;
D4 = exceptional drought.
For comparison, here are Virginia ratings from previous Drought Monitors from about one month, two months, three months, and one year ago:
3/31/15 – 14 percent abnormally dry;
3/3/15 – 31 percent abnormally dry;
1/27/15 – 10 percent abnormally dry;
4/29/14 – 0.1 percent abnormally dry.
The Virginia Drought Monitoring Task Force, a collaboration of state and federal agencies, issued its most recent Drought Status Report on March 17, 2015. A link to the report, along with other current drought-status information, is available online at http://www.deq.virginia.gov/Programs/Water/WaterSupplyWaterQuantity/Drought.aspx. The next report is scheduled for May 2015. The Task Force’s reports typically include information from some or all of the following agencies: University of Virginia Climatology Office, U.S. Geological Survey (USGS), and the Virginia departments of Agriculture and Consumer Services, Health, and Environmental Quality.
The Drought Monitoring Task Force also produces a daily map rating drought-status indicators. Shown below is the May 1, 2015, map. The status-indicator abbreviations on that map are as follows: GW = groundwater levels, Prcp = precipitation deficits, Res – reservoir storage, and Flow = stream flow conditions. For each region of Virginia, the indicators are color coded for “normal,” “watch,” “warning,” or “emergency conditions.” Any given day’s current map and more information on drought status in Virginia are available the Task Force Web site listed above.
The April 28, 2015, U.S. Drought Monitor rated 48.5 percent of the United States (including all or parts of 39 states) as being abnormally dry or worse, and it rated 16.7 percent of the country (including all or parts of 15 states), as being in severe drought or worse (categories D2, D3, and D4). (On August 7, 2012, 38.5 percent of the country was in the three worst categories; that was the highest percentage in these categories reported by the Drought Monitor since it began in 2000.)
The nationwide percentages for abnormally dry or worse (D0-D4) and severe or worse (D2-D4) in the previous three months and one year ago were as follows:
3/31/15 – 54.0 percent abnormally dry or worse; 16.0 percent severe drought or worse;
3/3/15 – 49.4 percent abnormally dry or worse; 13.1 percent severe drought or worse;
1/27/15 – 43.4 percent abnormally dry or worse; 14.1 percent severe drought or worse;
4/29/14 – 41.3 percent abnormally dry or worse; 22.4 percent severe drought or worse;
In the following states, over 50 percent of the state was categorized by the April 28 report as being in severe-or-worse drought:
California – 93% (with 67% in extreme or exceptional drought; California has had over 90 percent of its area categorized in severe-or-worse drought every week since February 11, 2014, and the Golden State had 100 percent in those categories from May 13—July 29, 2014);
Nevada – 87% (with 49% in extreme or exceptional drought);
Oregon – 63% (with 34% in extreme drought).
For a look ahead, the National Weather Service/Climate Prediction Center’s “U.S. Seasonal Drought Outlook” for the next 90 days is available at http://www.cpc.ncep.noaa.gov/products/expert_assessment/sdo_summary.html. Shown below is the outlook map available on May 1, 2015.
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