Latest Report to the Drought Monitoring Task Force from the University of Virginia Climatology Office:
 

REPORT FROM THE STATE CLIMATOLOGIST

May 19, 2006

Despite a persistent jet-stream pattern that would normally be conducive to above-normal rainfall, the statewide average rain from May 1-17 was 75% of normal, or 1.74 inches.  However, mid-term moisture status (since April 1) is largely within the normal range, with a statewide average of 96% of the long-term mean.

This mid-term moisture, along with cooler than normal temperatures for the first half of May, has minimized the direct agricultural effects that might normally be associated with the longer-term precipitation deficit.

It is probably appropriate to reference January 1, 2006, as the benchmark for the current situation, as rainfall in late 2005 was quite plentiful.  The statewide average since January 1 is 10.95 inches, or 66% of the long-term average of 16.57 inches. 

In terms of historical perspective, this is a shortfall rate that is not as severe as the rates that were maintained in the last major drought that began around the turn of the century.  However, the 5.5-inch shortfall is now superimposed upon a normal increase in evapotranspiration (which has been recently held in check by below-normal temperatures).

It is important to emphasize that the seasonal transition to more scattered precipitation has been somewhat delayed this year, but can certainly be expected to become more evident in coming weeks.  It will be very difficult to recover accumulated deficits in deep-layer soil moisture (despite fairly moist shallow-layer conditions as of this writing) as summer progresses.  In a normal year, there is only a 30% probability that mid-summer rainfall exceeds evapotranspiration, which is why agricultural drought can develop so rapidly in this region.  This year, because of the accumulated deficit, June and July rainfall would have to be both unusually uniform and in the 90th or higher percentiles of observation in order to prevent the appearance of at least circumscribed areas of significant agricultural deficit.

Long range weather forecasting models indicate normal rainfall averaged across Virginia through the first few days of June, about 1.75 inches.  However, even if this is realized, the distribution is likely to become increasingly scattered.