Going into the winter we were in an ENSO neutral pattern and the consensus thinking, of which I agreed, was that this would mean below normal precipitation for the Southwest this winter. The middle to later part of December brought stormy weather at least to parts of the area and hopes were lifted that maybe it was not going to be too bad. Then January has returned to drier than normal weather pattern and the huge ridge offshore has brought completely precipitation free conditions for days now which is likely to persist into early next week. Therefore drier than normal conditions have increased as this dry spell is coming smack in the middle of the middle part of the stormiest time of the year.
Here are percentages of normal precipitation for various cities in the Southwest from October 1 through January 17.
San Luis Obispo-62%
A look at the latest conditions show that ENSO neutral conditions continue. Over the last month below normal sea surface temperatures were as much as 0.5 degrees Celsius below normal in the far eastern Pacific and above normal in the western Pacific and Indian Ocean.
These conditions have actually increased in coverage over the last several weeks as well.
Modeling data are very consistent in showing that ENSO neutral conditions persists the rest of the winter and into the spring.
The combination of the current departures from normal and a continuation of ENSO neutral conditions point toward below to much below normal precipitation for the entire winter into spring. One must remember this does not mean there will not be any storms. This does mean that over the long term the amount of storms and precipitation they bring will not be normal.
These is the possibility that another surge of tropical moisture could move into Arizona and Southern California by the middle of next week.
I still believe the greatest amount of rain, at least partially relating to Norbert, occurs from southeast California to Arizona
The effects on Southern California are very much in question.
With low wind shear and warm water in its path for a while longer, it is likely that Norbert intensifies into at least a Category 2 storm.
For much of the last week the monsoon moisture flow into the Southwest has been completely shut down by dry westerly winds. This is about to change.
A big pattern change is underway, one that will completely shut down any chance of showers and thunderstorms for an extended time period.