Friday, August 15, 2014

New Climate Model Outlooks Fix Errors; Cool, Snowy Winter Possible

Long range climate model projections of the upcoming winter season, the same ones we discussed a little while back, have been updated. The latest models still retain errors, but two models have come in with drastic improvements.
Bear in mind the typical caveats with long range forecasts still apply.

The image above shows a compilation of multiple long range outlooks, projecting the El Nino-Southern Oscillation phenomenon from the present to next spring. In this chart, we can see the majority of models favoring an immediate commencement to the El Nino expected to form later this year. The issue here, which we elaborated on in the link above, is that these models want to make the El Nino start immediately, something unlikely to happen. Complicating the situation further is the fact that these models want to bring the El Nino to Moderate (+1º to +1.5º above normal) or even Strong (over +1.5º above normal) levels by this winter. Again, this is unlikely to happen. Consequentially, we have been forced to discard these forecasts, as the incorrect SST projections then ruin the remainder of the forecasts.
The new update to these models came in to me today, and I was surprised to find two models that have changed their tune. In the chart above, instead of all models going up and up with the El Nino, the GFDL (turquoise colored line) and GFDL_FLOR (beige line) prefer either an ENSO-Neutral situation, where the El Nino is unable to form, or a weak El Nino, which is what my preference is for this winter. It finally seems as if we have two models that may stand a chance at verifying this winter.

Without further ado, let's review the forecasts from these two models for this winter.

 The first model we will review for the temperature outlook is the GFDL_FLOR. The image above shows projected temperatures across the United States for December-January-February 2014-2015. In this graphic, we see that the model keeps the majority of Alaska and western Canada warm, which can be indicative of persistent ridging over the area. Whether that is the case, we don't know, but such a feature would help chances for a cold Central/East US winter. Now looking at the United States, we find the majority of the nation experiencing average temperatures for the winter, with the Plains experiencing slightly below normal anomalies.
This is a rather substantial shift from earlier forecasts of a blowtorch (excessively warm) winter for the nation, which was due to the incorrect SST forecasts. It can be expected that models may project normal anomalies, because these forecasts are being made for months out. However, with this being the first forecast that is not retaining major SST flaws, things are looking up for those wishing for a cold winter.


Turning our attention to the GFDL model, we find a slightly different temperature forecast in store. Much of the Central and Western US is experiencing average to slightly below average temperatures, while the Great Lakes, Southeast and East US in general experiences a warm winter. We see this warmth extend into northeast Canada and towards Greenland, which makes me think that we may need to watch for ridging building off the East Coast if this forecast is correct (which, as we know by now, is not a given).

We now turn our focus on the precipitation outlooks from the two models. The GFDL model, pictured above, shows a wide swath of above-normal precipitation extending from Texas to south-central Canada, bringing the heaviest anomalies to the southern Midwest and western Ohio Valley regions. Wetter than normal conditions are also observed across the Eastern Seaboard, while dry weather prevails into the West Coast.
I'm not willing to say much on this outlook just yet, but since this is the first forecast that doesn't have that dreadful SST flaw, this sort of precipitation pattern may bear watching for this winter. If it did verify, it could spell disaster for California and other drought-affected regions.

Taking a look at the GFDL_FLOR model, we see a somewhat similar outlook as the one portrayed by the GFDL system. In this outlook, the December-January-February period features a very dry West US, remarkably drier than the GFDL model outlook. Slightly above normal precipitation anomalies extend from the Southern Plains and Gulf Coast into the Midwest and Great Lakes. The Central Plains is also included in this wet trend.
Again, though there's not much else to say here, it could bear watching.

Lastly, we'll take a look at the model-projected upper air pattern for the coming winter. The image above shows the Z200 outlook over December-January-February from the GFDL model. We want to maintain focus more on the contour lines than the color shades for this post. Taking a look around North America, we find a ridging signal over the West Coast and into Alaska. As we've discussed extensively, persistent above-normal water temperature anomalies in the Gulf of Alaska may support such a scenario, which could then lead to another chilly winter. Looking downstream, we do see a slight suppression in the contour lines, potentially indicative of some stormy weather. We saw a similar outlook in the months leading up to last winter.
Something else to note is the suppressed contour lines over Japan. This could indicate stormy weather there, and if we apply the Typhoon Rule, it could then affect us here in a substantial way.

Finally, shifting to the Z200 outlook from the GFDL_FLOR guidance system, we still see a cold signal across North America. Eerily similar to outlooks from last year anticipating the winter of 2013-2014, we see strong ridging over the West Coast and into Alaska. This ridge looks to be of similar strength to the one observed last winter, which was the mechanism responsible for the polar vortex scraping the northern US. Once again, we see suppressed contour lines in Japan, again indicative of stormy weather. The most interesting feature, by far, is the depression of contour lines over eastern Canada and into the United States. This is definitely a cold weather signal, dare I say the same signal that eventually brought the polar vortex south. I'm not saying that whole episode will happen again, but if this model is right, cold weather becomes a significant possibility.

All of this looks pretty supportive of a cold and snowy winter, but when it comes down to it, remember that this all rests in the realm of possibility, not certainty. Things do look good from these error-corrected models, but we will have to wait and see if these solutions stick with the updated model forecasts next month.