Long Range Lookout: East Asia Entering Very Stormy Pattern

This is the GFS Ensemble 500mb height anomaly forecast for November 27th. While there is a deep stormy pattern across the central part of Canada into the north and central Plains, we are going to pay attention to the upper left hand corner of this image. In the upper left hand corner, we find East Asia.

This forecast for East Asia has two strong storm systems located over the region, with one of these troughs placed on the coastal region of East Asia. When you get storm systems near East Asia, there is a 6-10 day gap between what happens in East Asia and what then happens on the East Coast of the US.

This stormy pattern over East Asia looks like it will be very persistent, which tells me that there will be a stormy pattern over the East Coast about 6-10 days later, which puts us at the December 4 - December 8 timeframe. This will likely not be a train of storms, more-so a storm system that develops either near or offshore of the East Coast and stays in place for a prolonged period of time.

The GFS model did show this system developing well offshore, so that is a possible solution.

Andrew

November 27-29 Potential Winter Storm Discussion (11/22)

Please note that yesterday's first call is now void, as I realized the data I was watching is incorrect. This post now includes my best thoughts on the situation.

Rather than clog up this post with a ton of images, here's my own manual analysis of the models as of the most recent 0z run. As you can see, the GFS, ECMWF ENS, GGEM, GGEM ENS, NOGAPS, NOGAPS ENS, ESRL ENS, NAEFS ENS, UKMET models and ensembles are all in agreement of a North Camp solution, where the storm system goes north and impacts the Midwest, Ohio Valley and eventually New England. The GFS ENS appear to be in the 'Middle Ground' in between the North Camp and South Camp (The South Camp goes through the South and goes up the East Coast), while the JMA, FIM and FIMZ models are unavailable for the time of analysis.

Curiously, the ECMWF is the only one going for the South Camp. I can't say I disagree entirely, as there will be a negative NAO in place. However, this negative NAO will be east-based, which, as the image above details, brings a stormy and cold pattern to the Midwest, Plains and Great Lakes, whereas a west-based negative NAO supports the cold and snow for the East Coast. For those of you wondering, an East-Based negative NAO literally means that the ridge of high pressure that causes the negative NAO is east of Greenland. In the west-based negative NAO, the ridge is west of Greenland.

Models are supporting the idea of an east-based negative NAO, which is why the heavy majority of models and ensembles are in favor of this North Track.

What the models are really having trouble diagnosing is the strength of this storm system against a ridge of high pressure which will be in place over the Southeast. If the low pressure system is weaker, the ridge will deflect it north. However, the ECMWF believes that the system itself is stronger, and that the Northeast is destined for this storm. While it has happened before where the ECMWF has been the only one to correctly predict such a scenario, nearly all of the ensembles (including the NAEFS and ESRL PSD) are going for the North track.

At the moment, I now favor the North Camp, not only thanks to the models, but as I described with the east-based negative NAO and ridge in the Southeast.

PDO Showing Signs of Transition

The Pacific Decadal Oscillation, or PDO, is showing signs of changing its phase as we move through the last month of fall.

The above image shows changes in sea surface temperatures (SST's) from September 2012 to October 2012. The blues signify a cooling temperature trend, while reds display warming of the waters. If we take a look at the north central Pacific in whole, we see a stark cooling trend coming around from east Asian waters to the waters south of the Aleutian Islands. Also, notice a slight warming trend focused in and to the north of the Aleutian Islands to the west coast of Canada, as far south as Baja California. This warming then moves west, forming a backwards 'C' around the cold pool.

PDO Phases

What we are seeing here is a vaguely textbook example of a positive PDO. In a positive PDO, a cold pool of water extends from East Asia and across much of the north Pacific. Warmer waters encompass this cold pool, as I described above as a backwards 'C'. In the negative PDO, the temperature anomalies change places, with cold waters forming a backwards 'C' around a warm pool.

Because the PDO is so complicated, I'll put the effects as simple as possible. A positive PDO tends to bring cooler than normal temperatures to much of the nation, while a negative PDO brings warmer than normal temperatures to the Lower 48. So, if we do have this PDO switch from its current negative phase to a positive phase, we could see a cooler winter than I had accounted for.

Exciting times ahead!

Andrew

Positive AMO Losing Grip

The positive Atlantic Multidecadal Oscillation (AMO) appears to be losing its grip on the waters near Greenland in the past month.

Above shows a side-by-side comparison of water temperatures on October 17th and November 14th. If we look on the left side (October 17), we see a wide swath of above normal water temperatures stretching from Greenland, through northern Canada and to the waters south of Greenland. The waters off the East Coast also showed heavy warming during that time period. If we look to the right image, taken on November 14th, we now see neutral water temperatures in place around much of Greenland and in Northern Canada. However, waters remain warm to the east of eastern Canada, and have actually intensified off the coast of the Northeast US.

What is setting up here is something called the Atlantic Tripole. In a nutshell, the Atlantic Tripole is shown by cool waters off the coast of the Northeast and East Coast, warm waters in the Gulf of Mexico, Caribbean and southeast Atlantic, and warmer than normal water temperatures in the Greenland waters. Below are temperature and precipitation anomalies during the Atlantic Tripole.

Temperature Anomaly

Precipitation Anomaly

Andrew

November 27-29 Storm: First Call

This is my first call on the November 27-29 potential winter storm system. Let's start with the factors that are going into my first call.

This is the latest ECMWF model. This is valid for the morning of November 26th. It shows our storm system currently in southwestern Oklahoma, with a minimum pressure of 1006 millibars- a pretty weak system overall. Notice the cold air far up in the North Plains. If that were to be pulled south by this storm system, many locations could see absolutely frigid temperatures.

2 days later, on the morning of November 28th, the storm system has moved due east and is now out to sea, hugging the East Coast. Considering we will be in a negative NAO, this is not surprising, but the due east movement of the storm is pretty sketchy, especially considering the ECMWF has been supporting a North Camp (system affects Midwest, Great Lakes) solution for so long.

By the way, so you know, the North Camp was described above. The South Camp is for models that take the system through the South US and up the East Coast. They are called 'camps', because the models will group together for some time (like a camp of people) under one forecast solution (like a group of people with a common cause).

Here's the run-down of the models for camps.

North Camp: GGEM, GGEM ENS, NAEFS ENS
South Camp: ECMWF, GFS, GFS ENS

Based on how the models are treating the system heading out of the Rockies, and the 4 day lag between observed NAO conditions and effects on North America, the system should be forced south, providing a rainy scenario for the region. However, when the storm shoots north and strengthens a bit near New England, this precipitation will turn to snow. Best accumulation will occur nearest the Great Lakes as cold air behind the system brings about lake effect snow potential.

Andrew