MarylandWeather.com reader Paul Snyder asks: "The papers and newscasters say we are in a drought, but I notice Maryland is +1" above average rain fall for the year and the local reservoirs are full. What is the official definition of a drought?"

Officially-designated drought conditions are determined by a complex formula that takes into account measurements of soil moisture, streamflow, precipitation and the health of vegetation as measured by satellite imagery.

The data is fed into a computer, which crunches the numbers and spits out a drought "index," and the results are mapped to produce a weekly "drought monitor" map. That's what we were going by last week when The Sun published a story about the deepening drought, and the prospects for relief from the remnants of Tropical Storm Tammy.

Ask your note suggests, it is possible for some of the indicators, such as water levels in reservoirs, to be close to normal, while others are sufficiently low to push the region into the drought categories. In our case, the September drought was considered an "agricultural" drought, primarily affecting farming interests. It was not regarded as a "hydrological drought," because water supplies had not yet been seriously depleted.

The drought monitor calculations are done weekly. The most recent was dated Oct. 4, which showed most of Maryland in moderate drought. Those numbers will be updated shortly, and the results will be updated for Oct. 11, and will likely show that the drought has ended, thanks to the record-breaking rains from Tammy. The seasonal outlook, thanks to Tammy, looks brighter.