Wednesday, July 11, 2012

PDO Spike May Be On The Horizon

Data from the Earth System Research Laboratory (ESRL) indicates that the Pacific Decadal Oscillation may be trying to head for a turn around. Values from January to April of the PDO (pictured above) have been steadily increasing until April, when a major jump occurred towards the positive PDO phase.
Sea surface temperatures indicate a warm body of water is entrenched in the north central Pacific Ocean, with an opposing cool body of water just to the east of the warm anomalies. Both bodies of water appear to be fighting for their spot in the ocean.

A traditional positive phase PDO has cool temperature anomalies in the northern Pacific, with warm anomalies in the equatorial Pacific. This would make for a correlation between a positive PDO and El Nino, as well as a negative PDO and La Nina.
If an El Nino is forming, it is definitely conceivable that the Pacific Decadal Oscillation will try and make a move to a positive phase, which would enhance winter precipitation.

Seeing as there is a large warm body of water in the North Pacific tells me there remains a lot of work to be done, but there are some signs that a positive PDO may be trying to get going.


Drought May Worsen for Midwest This Winter

The latest US Drought Monitor update includes drought conditions covering much of the country, including the Midwest, Rocky Mountains, and portions of the Southeast. According to the latest indications, this drought may not be letting up for the Midwest. While it will likely be dented in the Southeast and Southwest, the Midwest usually does not fare well in precipitation during an El Nino.

During El Ninos in the winter, we see warm conditions overspreading much of western Canada and the northern US in general. Cool and wet conditions are observed across much of the southern US, while the Ohio Valley and Midwest tend to be on the warm and dry side of things.

My concern rests on the latest heat wave and associated worsening of drought conditions over much of the Central US. I find it likely that an El Nino regime will set up going into fall, and if this were to happen, we could see much of the Great Lakes/Midwest region continuing to spiral into worsening drought conditions.

There remains a lot of the atmosphere that could very well change things for the wetter in these areas, however a typical El Nino will usually frown upon much of the Great Lakes and Midwest for precipitation. This scenario will have to be closely watched as we enter the fall season and find out more information on what the atmosphere is thinking of doing this winter.


Hurricane Emilia About to Hit Dry Air

Hurricane Emilia, currently a Category 2 hurricane, is about to hit a wide swath of dry air, which should be the final blow for this hurricane, which managed to reach Category 4 strength.

Emilia has winds reaching 115 MPH, and a central pressure reading of 960 millibars. There are no buoys near Emilia, making confirmation of this very difficult. Regardless, the weakening process will begin as Emilia continues to trudge on a westward course. There is little doubt in my mind that this is indeed the end of the road for Emilia. However, the National Hurricane Center believes Emilia will keep on keepin' on and stay at tropical depression strength through the next few days, and possibly onwards.


Upper Troposphere Not Showing El Nino Conditions

Courtesy AMSU Temps Website
The upper troposphere is not showing a significant correlation to the oncoming El Nino, as the chart above of 400 millibar temperatures shows.

There are three lines of values on the chart- 2008 (purple), 2010 (orange), and 2012 (light green). I am using 2008 and 2010 as basically defining boundaries between an El Nino and La Nina, with El Nino seeing warmer 400mb temperatures, and a La Nina observing cooler than normal temperatures in the upper troposphere.

At this time, the upper troposphere is pretty much in the middle of both benchmarks at this point in time. If we want to see an El Nino really get going (which should happen soon), I would expect to see a warming trend in the 400 millibar level to prove that the atmosphere is prepared for an El Nino.

You may ask why I see these two as good benchmarks. If you look towards the beginning of the year, you will see 2012 values in 2008 level temperatures. However, as of recent, the 400mb level has warmed considerably, but not to the point that I am convinced that the atmosphere is primed for an El Nino.