Drought is an extended period when a region notes a deficiency in its water supply whether surface or underground water.
A drought can last for months or years, or may be declared after a shorter period.
Generally, this occurs when a region receives consistently below average precipitation.
It can have a substantial impact on the ecosystem and agriculture of the affected region.
Although droughts can persist for several years, even a short, intense drought can cause significant damage and harm to the local economy.
California is in a period of drought.
Water years 2012 and 2013 were dry statewide, especially in parts of the San Joaquin Valley and Southern California.
Water year 2014, which began on October 1st, continues this trend.
Precipitation in some areas of the state is tracking at about the driest year of record.
Statewide reservoir storage going into our wet season was about 75 percent of average for this time of year, and impacts of two dry years on statewide groundwater levels are also evident.
On average, about half of California’s statewide precipitation occurs in December, January, and February, with only a handful of large winter storms accounting for the difference between a wet year and a dry one.
Some who study weather predict that 2014 will be the driest California water year in 500 years.
The cause of the drought is reported to be a vast zone of high pressure in the atmosphere off the West Coast, nearly four miles high and 2,000 miles long.
As recently reported in the San Jose Mercury News, "this high pressure zone is behaving like a brick wall, the mass of high pressure air has been blocking Pacific winter storms from coming ashore in California, deflecting them up into Alaska and British Columbia, even delivering rain and cold weather to the East Coast.
Similar high-pressure zones pop up all the time during most winters, but they usually break down, allowing rain to get through to California. This one, ominously, has anchored itself for 13 months, since December 2012, making it unprecedented in modern weather records and leaving researchers scratching their heads."
Rain is liquid water in the form of droplets that have condensed from atmospheric water vapor and then precipitated—that is, become heavy enough to fall under gravity.
Rain is a major component of the water cycle and is responsible for depositing most of the fresh water on the Earth. It provides suitable conditions for many types of ecosystem, as well as water for hydroelectric power plants and crop irrigation.
The major cause of rain production is moisture moving along three-dimensional zones of temperature and moisture contrasts known as weather fronts.
If enough moisture and upward motion is present, precipitation falls from convective clouds (those with strong upward vertical motion) such as cumulonimbus (thunder clouds) which can organize into narrow rain bands.
The Sacramento Bee reports that "Thursday will finally see the first rainfall in the Sacramento area this month, with a 40 percent chance of precipitation. The city may get as much as a quarter inch of rain from the storm."
If the National Weather Service is right, the Greater Sacramento Region is in for a wet week - Good News!