More on the El Nino and Pete /. Repeat Pattern

15 degress here in North Ashburn VA... two degress colder than IAD and 4 degrees colder than DCA. Does NOT suck


Let me start off with some new information about the current El Nino event. One of the things that Meteorologists should look at to figure out how a particular El Nino or La Nina is developing are the SUB sea surface temp anomalies -- SUB SSTAs.

The reasoning here it is that research has long showed that warming / cooling of SUB sea surface temperatures are good reliable pre-cusors of a developing El Nino or La Nina event. And the recent history shows is to be quite true. For example when the La Nian last winter collapsed in March the cold waters below the surface weakened first before the actual surface water temperature began to warm. Likewise...when the El Niño began to develop in July and August the warming in May & June at the subsurface SSTA again was a precursor to the actual event itself.

This first image is the Sub surface temps from NOV 22 with the numerical values being the temperature anomalies. As you can see there is a large area of very warm water extending across the equatorial Pacific from the dateline almost towards the Peruvian coast... there is a large area of +5c and even large areas of +4c SSTAs.
http://www.wxrisk.com/MODELFOLDERS/today/nov22.jpg


The 2nd image is the DEC 7 map... but we see some noticeable changes in the subsurface SSTA map. First the +5c area is gone from the CENTRAL PACIFIC and the +4c area has shifted to the east and has left the cental equatorial Paicfic ( NINO 4).
http://www.wxrisk.com/MODELFOLDERS/today/dec7.gif

Now what this data should be telling you is that the El Niño may have reached its peak. We'll have to wait another couple weeks to find out if this current trend is in fact the real deal or perhaps it's just a blip. For example it's quite possible that may be a second surgie of warm water developing in the sub-surface levels.... so at this point is still premature to say that the El Niño as reached its peak or that has begun to weakened. But we should know more --alot more in the next 2-3 weeks.

Now if we turn our attention to the overall pattern synoptically... what we have is Pete and his brother Repete. In other words I see the pattern repating over the next 10 to 12 days across most of North America... in a manner similar to what we saw the last 10 days of November. In case you can't quite remember... we saw a deep trough develop over the Western quarter of North America and a very strong Ridge over the Midwest and Southeastern states which bought about a series of very warm days of near record and record warmth. But more importantly keep in mind how the pattern developed in the medium-range.

When I started talking about the developing+PNA around November 16... and other meteorologists began to pick up on it by the 20th or 21st none of us ( myself included) thought that the cold shot that was coming through at the end of the month would last more than 3 days. The medium-range models showed no indication all several arctic HIGHs comign south and it was no indication by any of the medium-range models from NOV 22 NOV 24 Nov 26 at the cold pattern would last 7-9 days. None of the MR showed that!!!

But that is exactly what has happened... and as a result using that pattern I see a distinct repeat of the overall pattern evolution in the next 10 days across North America.

The next map is the operational European from D10... and we can see that the model has a pretty deep trough developed over Western North America.
http://www.wxrisk.com/MODELFOLDERS/today/ec240.gif


And the operational 240 hr 500 MB GFS at 0z ( shown here ) and 6z ( not shown) is very consistent and is a close match to the operational European.
http://www.wxrisk.com/MODELFOLDERS/today/gfs_500_240s.gif

Now again realize that 10 days out I am not forecasting specific storm tracks ot heavy snow areas or temperature boundaries. I am just using these oeprational Models to get an overall general idea of what the pattern is going to look like Dec 18-19. Obviously the strong Ridge over the Southeastern states is very similar to what we saw in the last week of November.

Next I have the 240 hrs 0z GFS ensembles. As you can see ALL members strongly support the idea of a large deep trough over the Western US and many of them show close low over the Southwest states. This are pattern supports a significant winter storm over the great Basin and the lower Rockies and this is a very good agreement for 10 date model ensemble.
http://www.wxrisk.com/MODELFOLDERS/today/f240.gif

By 300 hours out the pattern is beginning to shift but the models this morning dont really shot a cold looking pattern... Eventually the cold front sweeps eastward over the strong Ridge over the Southeastern but by then it has Nothing left and the most of the models show more energy coming in from the Pacific Northwest. Thus when one looks at the operational 0z or 6z GFS... your initial reaction should be OK it cools down little but because more Pacific energy... No Big deal and no sustained cold pattern.
http://www.meteo.psu.edu/~gadomski/ENSHGT_0z/f300.gif


Now while that might be correct again let me emphasize the point I made above which is that back in the period November 20 -25 NONE of the medium-range models showed any hint of prolonged +PNA pattern developing over North America. ALL the the MR Models showed was a very brief shallow short duration cold shot which came through and that is very similar to what the models are showing right now for the period after December 20-22.

For all I know these models may be correct... Perhaps this next cold shot which finally comes through the East around the 20th or 22nd is no big deal... perhaps Pacific pattern continues and we stay mild over the eastern half of the CONUS thru Christmas. But if the pattern does res-assert itself then it looks like the period from DEC 22-30 could turn out to be seasonally cold once again.