Happy Monday and welcome to another edition of Beyond the Forecast!
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Rainy days since the start of summer means flooding is more prevalent than drought right now, but before the rain, some places were particularly dry. One of the best ways to determine where and how bad droughts are is by using the U.S. Drought Monitor.
The USDM is a broad analysis of different factors that when combined paint a picture of how dry the country is. In 1999, the National Drought Mitigation Center in Lincoln, Nebraska joined the National Oceanic and Atmospheric Administration and the US Department of Agriculture to develop the USDM and it’s been in use ever since.
The Drought Monitor uses a wide variety of data points to determine how dry different parts of the country are compared to average and then sorts each area into one of five classifications each week.
The data ranges from looking at the amount of precipitation over the previous week to how much water is in streams and mountain snowpack to how much water crops are able to hold onto. The NDMC works with experts across the country to determine how the monitored water levels affect people living in different areas to specify the drought conditions for particular regions.
The classifications on the Drought Monitor range from D0 through D4:
- D0 means that an area is abnormally dry, which can mean rain is lacking in the area and it is going into a drought or that rainfall is picking up and the area is coming out of a drought but still beneath normal levels.
- D1 to D4 are the different drought types themselves, which include:
- Moderate
- Severe
- Extreme
- Exceptional
Those classifications do not have a specific threshold that is the same all across the country; instead, it compares the average water levels in a particular location to the current conditions there. That means that a severe drought in New Mexico has a different absolute water amount in the ground than in Virginia.
The USDM also describes what each drought level means for each state in terms of impact. In Virginia, a D1 Moderate Drought means some crops are stressed, rivers and streams run low and fire danger increases.
In Washington state, a D1 drought can cause dust storms, and in Maine, honey production begins to decline. On the more extreme end impacts vary as well. A D3 Extreme Drought causes scarce hay and nearly dry lakes, while in Washington state the river levels are so low that it’s hard for certain fish to reach their spawning areas.
Data from the Drought Monitor is archived so you can compare current conditions to previous years to find out which was drier. You can even view a graph of the total percentage of the country that was in a particular drought level through the start of the record. These tools can help people compare how they dealt with dry conditions previously and give an indication of the necessary steps to take for the next dry stretch.
Monday is another cloudy day with afternoon rain and some storms, but there is a dry stretch for most of us through the middle of the week. You can download our weather app for information on storms as they develop and get Meteorologist Chris Michaels’ latest updates online.
You can always get specific forecast details for your zone, whether it’s the Roanoke Valley, Lynchburg area, the New River Valley or elsewhere around Southwest and Central Virginia, anytime at WSLS.com/weather. Know your zone!
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-- Marshall Downing
