The following charts depict monthly sequences that we have identified as an anomalous climate pattern for the coming spring and summer of 2007. There are several indicators that we are tracking to determine the probability of a High Plains drought in July 2007. The first is that if the current El Nino shifts into a La Nina or cooling pattern in the eastern Pacific in March that is an indicator of drought in the Midwest in the following summer. We will be looking for low snow-pack in Northwestern Mountains. This is an indicator of how much moisture will be available for the formation of thunderstorms in the Corn Belt later in the early summer.

The 1988 analog to this was the failure of snow-pack in PNW and Dakotas in late winter of that year. This was an early warning of emerging drought pattern for the High Plains.

March temperature

March precipitation

April 2007-

We will look for anomalous cooling of E Pacific in April. If a cool pool is off of Peru in the spring we will look for this to move west towards the end of April.

The analog to this was April 1988 when a strong anomalous negative SST ( La Nina) event off of Peru occurred. During this event a very cold body of water was found along the equator in the eastern Pacific. The strong La Nina supported the drought cycle for the summer of 1988 in the Midwest.

April temperature

April precipitation

May temperature

May precipitation

June 2007
In late June/ early July we will be watching the onset of the summer southwest monsoon. In this pattern also known as the American monsoon, the storm track migrates north on the continent at the solstice. Major Midwestern drought episodes are associated with an amplification of the upper troposphere monsoon ridge starting at this time. This usually signals a stronger than usual monsoon. The monsoon ridge is normally centered over the continental divide. If this is strong at the solstice, look for associated changes including a weakening of the western end of the Bermuda High in the Gulf of Mexico and the failure of the Great Plains low-level jet centered in the longitude of Brownsville, Texas. These key indicators will allow the ClimaTrends researchers to lock in on a drought prognosis.

June temperature

June precipitation

Finally, we will be watching for a triple cell high pressure pattern starting in summer 2007, as a sure drought signal. This is a pattern of three simultaneous strong highs, one over the eastern Gulf of Alaska, one over the western states and one over Greenland. We expect this pattern to arise in July 2007 and continue until the end of the month or even later.

July temperature

July precipitation