More Uncertainty About May from CPC and ‘Yours Truly’April 22nd, 2013 at 9:25 pm by Don Paul under 4 Warn Weather
There is no real confidence any longer that early CPC outlooks for a milder than average spring will bear fruit in May. In the near term, although the CPC is giving us a somewhat positive anomaly for temperatures in the 6-14 Day Outlooks, it should be noted that the 3 indices will be trending in the wrong direction for significantly warm anomalies around here. The AO and NAO are both showing most of their ensemble members trending toward negative territory in May, while many PNA members trend upward. While these indices tend to have a little less impact climatologically as we move into mid-spring, this year that may not be so much the case. A major snow cover anomaly continues over much of the northern plains and nearby Canadian praries, assuring a colder pool of air. That, plus a large area of high soil moisture will also hold temperatures down. Whether these anomalies will still play a key role later in May is unknowable right now.
The MJO has become weaker, and its climatological impact also lessens as the month goes on. ENSO remains neutral, and is forecast by most models as likely to stay neutral through the autumn.
While these near term positive temperature anomalies are the first we’ve seen from CPC in probably a couple of weeks for us, the confidence level for both the 6-10 & 8-14 Day Outlooks is only 2 out of 5, and that may be tied partially to the indices’ trends I outlined above.
In any case, CPC has backed off from the weak warm anomaly it had for our region for May, and gone over to EC. And, since ensemble means are showing no rebuilding of an eastern ridge with any staying power in the next 14-16 days, I concur with that call.