Here is the Virginia Water Central News Grouper’s monthly water-status report on precipitation, stream flow, and drought, as of end of November 2018. 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). For previous monthly water status reports, please see this link: https://vawatercentralnewsgrouper.wordpress.com/?s=Water+Status.
Here are National Weather Service (NWS) preliminary (still needing verification) precipitation totals for November 2018 at 12 Virginia or near-Virginia locations, along with the “normal” (three-decade average) for this month of the year at each location. Also shown are the precipitation totals at each location for the previous 12 months and the annual precipitation normals for each location. The values are in inches.
|Location||November 2018 Observed||Monthly Normal||December 2017-November 2018 Observed||Annual Normal|
|Reagan National Airport4||7.57 RH||3.17||60.96||39.74|
RH = record monthly high for the location and month of the year.
*NWS reported nine days of data missing at Danville in January 2018.
1 – The Bluefield location is the Mercer County, W. Va., airport, near the Va.-W.Va. state line.
2- The Bristol location Tri-Cities Airport in Tenn., about 20 miles from Bristol, Va./Tenn.
3 – The Charlottesville location is the Charlottesville-Albemarle Airport.
4 – Reagan National Airport is in Arlington County.
5 – Wallops Island is in Accomack County.
6 – Washington-Dulles Airport is in Loudoun County.
Precipitation sources: Climate pages of the following National Weather Service Forecast Offices:
Blacksburg, Va. (https://w2.weather.gov/climate/index.php?wfo=rnk);
Morristown, Tenn. (https://w2.weather.gov/climate/index.php?wfo=mrx);
Baltimore-Washington (https://w2.weather.gov/climate/index.php?wfo=lwx); and
Wakefield, Va. (https://w2.weather.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 High Plains Regional Climate Center at https://hprcc.unl.edu/maps.php?map=ACISClimateMaps), where you can find maps of total precipitation and percent of normal precipitation for the past 7, 30, 60, or 90 days for all U.S. regions; 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 preliminary maps of the percent-of-normal precipitation for the southeastern United States for the previous 30 days, 60 days, and 90 days, through December 4, 2018. Please note that the scale is different for the 30-day map.
According to the U.S. Geological Survey WaterWatch for Virginia (online at https://waterwatch.usgs.gov/index.php?m=mv01d&r=va&w=map), monthly average stream flow values for November 2018 at 158 stream gages in Virginia and just beyond the state border were as follows, compared to the historical range for each given gage:
within the normal historical range – one gage;
above normal – about 4% of gages;
much above normal (or higher) – about 96% of gages.
Shown below is the color-coded, flow-percentile map for this period, accessed at the Web site given in the paragraph above. The chart below the map shows the color codes/percentile classes used by USGS to compared flows to historical records for the month.
An overall look at Virginia streamflow conditions is provided in the USGS WaterWatch summary plot of daily average streamflow conditions, compared to historical records for any given date. Below is the summary plot for 88 Virginia sites during the 45-day period ending December 2, 2018, accessed on December 5, 2018, at https://waterwatch.usgs.gov/index.php?id=pa01d&sid=w__plot&r=va.
Information on current groundwater levels in Virginia monitoring wells is available from the U.S. Geological Survey’s National Water Information System, online at http://waterdata.usgs.gov/va/nwis/current/?type=gw; and from the USGS Climate Response Network, online at http://groundwaterwatch.usgs.gov/net/ogwnetwork.asp?ncd=crn (at that page, you can find a national map showing the status of groundwater monitoring wells compared to historical values).
DROUGHT IN VIRGINIA
The weekly U.S. Drought Monitor map from the University of Nebraska-Lincoln (http://droughtmonitor.unl.edu/) for November 27, 2018, categorized Virginia as drought-free. The Commonwealth has been essentially drought-free since the June 5, 2018, Drought Monitor report, except for a 0.57% abnormally dry rating in the July 17 report and a 0.01% abnormally dry rating in the June 26 report.
Drought Monitor categories are as follows:
D0 = abnormally dry;
D1 = moderate drought;
D2 = severe drought;
D3 = extreme drought;
D4 = exceptional drought.
The Drought Monitor notes that it “focuses on broad-scale conditions [and] local conditions may vary.”
For comparison, here are Virginia ratings from previous Drought Monitors from about one month, two months, three months, and one year ago:
10/30/18 – drought-free;
9/25/18 – drought-free;
8/28/18 – drought-free;
11/28/17 – 44.1% abnormally dry or worse; 3.9% moderate drought.
In early June 2018, the Virginia Drought Monitoring Task Force (DMTF), a collaboration of state and federal agencies, issued its most recent report. At that time, the DMTF stated that is would monitor conditions and meet again when conditions warrant another report. A link to the June 2018 report, along with other current drought-status information, is available online at http://www.deq.virginia.gov/Programs/Water/WaterSupplyWaterQuantity/Drought.aspx. The DMTF’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. Shown below is a map identifying the Drought Evaluation Regions used by the DMTF.
The November 27, 2018, U.S. Drought Monitor categorized about 29.4% of the United States (including all or parts of 26 states plus Puerto Rico) as being abnormally dry or worse. The Drought Monitor categorized about 9.9% of the country (including parts of 11 states), as being in severe drought or worse (categories D2, D3, and D4. (The highest percentage in the severe-or-worse categories reported by the Drought Monitor since it began in 2000 was 38.5% of the country for the week of August 7, 2012.)
The nationwide percentages for abnormally dry or worse (categories D0-D4) and severe or worse (categories D2-D4) in the previous three months and one year ago were as follows:
10/30/18 – 31.5% abnormally dry or worse; 10.8% severe drought or worse;
9/25/18 – 41.4% abnormally dry or worse; 14.9% severe drought or worse;
8/28/18 – 47.5% abnormally dry or worse; 16.2% severe drought or worse;
11/28/17 – 35.7% abnormally dry or worse; 4.1% severe drought or worse.
The following states had 50% or more of their land area categorized by the November 27 Drought Monitor in severe-or-worse drought:
Colorado – 55%;
Oregon – 86%;
Utah – 76%.
Following are some comments from the November 27, 2018, Drought Monitor on conditions in several regions.
“Enough precipitation fell [in the past week] to reduce long-term deficits along the New York-Vermont state line, where D0 was pulled back. But no change was made to the other D0 remaining in northern New York and northern New England due to lingering long-term (3 months or longer) deficits.”
“Precipitation deficits existed along the Georgia and South Carolina coasts from 1 week to 12 months, with the exact locations varying depending on time scale. …[D]ryness in southern Florida was reflected by several indicators, including streamflow, percent of normal precipitation, the Standardized Precipitation Index (SPI), the Standardized Precipitation Evapotranspiration Index (SPEI), soil moisture models and USDA soil moisture reports, groundwater estimates, and the VegDRI vegetation-based drought index. Expansion of D1 in southern Florida can be expected to occur in the weeks ahead if the dryness worsens.”
“…[M]ost of Texas and Oklahoma received no precipitation this week, and have been drier than normal for most of the last 4-7 weeks. Mounting dryness over the last 3-6 months prompted expansion of D0-D1 in northeast Oklahoma into northwest Arkansas, with some D0 expanding into adjacent southwest Missouri and bleeding slightly into adjacent southeast Kansas.”
“The precipitation [in the past week] was not enough to affect the D0-D1 lingering in northeast Kansas. Even though the week was drier than normal in north central Montana, the D0 there was trimmed to reflect a reassessment of the impact of precipitation in recent weeks. The D0-D1 in the Dakotas reflected lingering long-term dryness.”
“[During the past week, the] Pacific weather systems brought beneficial rain and snow to coastal Washington and Oregon, and parts of central to northern California and the Sierra Nevada range. Widespread amounts of 2-4 inches occurred, with locally up to 5 inches in parts of northern coastal California and the Sierra, and 5-10 inches in the Olympic Peninsula of western Washington. Some parts of the Sierra Nevada measured more than a foot of new snow. The rain helped firefighters contain the Camp wildfire and snow improved mountain snowpack. But it wasn’t enough to overcome precipitation deficits which have built up over many months.”
90-DAY DROUGHT OUTLOOK
For a look ahead, the National Weather Service/Climate Prediction Center’s “U.S. Seasonal Drought Outlook” is available at http://www.cpc.ncep.noaa.gov/products/expert_assessment/sdo_summary.php. Shown below is the outlook map available on November 1, 2018.