Saturday, September 20, 2014

JAMSTEC Model Predicting Harsh Winter Ahead

A popular weather model, the JAMSTEC climate model, is forecasting a harsh winter ahead... but will it verify?

The image above shows the December-January-February temperature anomaly forecast for the winter of 2014-2015, with the forecast made in August 2014. This forecast is made up of 27 ensemble members, which can enhance its credibility, so long as the forecast is within reason.

In this image, we can see strong below-normal temperature anomalies across nearly the entire United States. Canada and Alaska look to see above to well-above normal temperature anomalies, with the anomalies maximized over the far northern reaches of the country. Last winter, the core of the cold was displaced in the north-central US, but if this model is correct, it would be shifted into the Southern Plains.

On the precipitation side, the JAMSTEC model is forecasting a swath of above-normal anomalies to affect the Southeast US, even stretching west into the Texas/New Mexico region. These wet conditions look to extend up the East Coast, almost in typical El Nino fashion. The Pacific Northwest would see a rather dry winter if this solution were to verify, while the Southwest would see slightly below-normal to average precipitation anomalies.

Even though this model certainly is painting an ominous picture, is it a realistic one?

The graphic above once again shows an outlook for the December-January-February period, but now depicts sea surface temperature (SST) anomalies . In this image, I can identify two areas of concern, as far the forecast potentially not verifying.

First off, we see a moderate to borderline-strong El Nino evolving in the Pacific. SST anomalies of 1.2 to 1.5 degrees Celsius above normal might be a bit too strong for this winter, as I'm currently expecting only a weak to possibly-moderate El Nino. It would be quite a stretch for a strong El Nino to hit this winter.

Second, we see a pool of deep negative SST anomalies in the waters just south and west of Greenland, while well above-normal anomalies flourish on either side of the land mass just north of the cold pool. There isn't as much reasoning behind this one as there is a gut feeling; the alignment of SST anomalies looks odd to me, and I'm not so sure I would put stock in this forecast.

To summarize, the JAMSTEC model is indeed forecasting a very ominous winter to once again hit the United States. However, concerns with the sea surface temperature anomaly forecast for the coming winter could mean the forecast may be flawed.



Anonymous said...

Andrew can you please respond to this: (I know you can respond because you have to read to approve comments): If the southeast U.S. does indeed see a harsh winter again, (January 2014 parts of the Florida Panhandle had highs in the 20's with snow), can this be a possibility:

Frank-o said...

Very interesting.....What if....we do get a moderate to strong El-Nino.....

Anonymous said...

It's gonna be a bad one. All the nature signs point to it. I'm 65 years old and know how this works! Woolly worms are dark, that means a bad winter. Sounds funny, but trust me, it is a big part of a winter signal. Also, have you noticed all the acorns? Perhaps the best "model" in forecasting is nature signs!

Anonymous said...

This is the August update. The model will likely update again within the next couple of days (it usually issues the update for that month by the 23rd of a month). Hopefully you'll keep us in touch with the new forecast, especially if there's any big changes. :)

Andrew said...

Anonymous at 4:01: We would need to see quite a few things fall into place for such an event to happen. I'm not expecting it right now.

Anonymous at 11:19: I do plan on discussing the next update to the JAMSTEC when it comes out, yes.

Anonymous said...

(I'm Anonymous from 11:19) Thanks, also definitely as I said before look for it in the near future, probably any day now in fact. The 21st is I think the latest I've seen it take, so there may very well be a new forecast in as little as a day or two.

As for the August forecast, in the ENSO it appears to have the warmest anomalies in the right area I think, but I agree they are too warm. And I don't know what's going on around Greenland, that is strange, and it was doing it with last winter as well.

Rick said...

Andrew I believe you are misreading that model. The JAMSTEC model is showing a weak el Nino of about +0.8 or so. This graph of nino 3.4 SST depicts it well looking at the mean:

Anonymous said...

You have a great website! However, I feel you misinterpreted the 8/1/14 JAMSTEC SST map as regards Nino 3.4 for DJF. That's easy to do due to the similar colors of the various anomaly levels. I think it is actually showing only ~+0.90 as opposed to +1.2 to +1.5. You said, "SST anomalies of 1.2 to 1.5 degrees Celsius above normal might be a bit too strong for this winter, as I'm currently expecting only a weak to possibly moderate El Nino."

Keeping in mind Nino 3.4 covers 120W-170W from 5N to 5S, the warmest anomaly is a tiny area near the equator in a part of 120-125W. That means that tiny area is likely only barely into the +1.2 to +1.5 range per the legend (the 5th pink area as you head up). So, the warmest part of 3.4 is only ~+1.2 and over only ~1% of 3.4. The next warmest area (+0.9 to +1.2) covers ~45% & likely averages ~+1.025. The next warmest area (+0.6 to +0.9) covers ~50% & likely averages ~+0.775. Finally, ~4% is covered by the +0.3 to +0.6 category with an estimated average of +0.55. So, rough weighted avg is this:
(0.01 x +1.2) + (0.45 x +1.025) + (0.50 x +0.775) + (0.04 x +0.55) = +0.88 or ~+0.9.

The following link is to the 8/1/14 graph of ensemble members for 3.4 with the red line being the mean (note the ~+0.9 for the average of DJF as opposed to +1.2 to +1.5):