STILL Not Much to Hang a Hat On for the WinterNovember 15th, 2012 at 8:36 pm by Don Paul under 4 Warn Weather
The Climate Prediction Ctr has updated its Winter Outlook and its Monthly (December) Outlook today. If you were looking to the CPC–or me–or anyone else to reduce the uncertainty about a winter outlook, you’ll be disappointed. CPC is maintaining its EC/Equal Chances status for much of the east. They’re reasoning is partially tied to the lack of predictability of the phase of the AO/Arctic Oscillation or the NAO/North Atlantic Oscillation beyond a couple of weeks. The MJO/Madden-Julian Oscillation is briefly mentioned but, not much was said about its current active phase due to that lack of predictability. On the matter of time scales CPC put a little more emphasis on the role of the PDO/Pacific Decadal Oscillation, which is in a Cool/Negative phase. Before anyone gets excited about what that might mean, PDO phases tend to run on the order of 20-40 years, as opposed to the typical 30-60 days for the MJO. They seemed to imply that the negative PDO, which weakened in October but is expected to strengthen again by summer next year, may have been enough to kill off what would have only been a weak el nino and keep ENSO neutral.
I might have expected them to give more weight to the current active phase of the MJO, which favors above average temperatures in the central and eastern U.S. Since this active phase has run only 2-4 weeks, that would still leave it with at least several weeks more time in this phase, which could weight the start of winter with above average temps in the central & ern U.S. In my mind, that might have tilted the odds toward a positive temperature anomaly for December, with the emphasis on the first couple of weeks.
Now that I’ve said all that, I do not have the tools and experience of the long range specialists of CPC, and I have very little experience balancing the PDO with shorter term oscillations. That is not false humility. That is a statement of fact. If the MJO returns to the normal longevity for its phases, we could well see a notable flip in the overall pattern later next month. The length of active phase time the MJO took on last winter was highly anomalous, and didn’t follow the rules. Could that happen again? No one knows. If it does not happen again, we may see a return to more variability in 4-6 weeks.