In our last forecast two days ago, 2/27/16 the absence or late return of el Niño was discussed and I mentioned the second week of March as a possible resumption of moisture flow to the San Juans. I corresponded with Joe Ramey, NWS forecaster in Grand Junction … here’s our email exchange.
On Monday, February 29, 2016 9:37 AM, Jerry Roberts <email@example.com> wrote:
Read this morning’s NWS forecast discussion and looked closely at the final line. What indicators are you guys looking at for the 4-corners lows to begin again?
“THE CPC FORECASTS WELL AND LOOKS REASONABLE AS WE EXPECT
THE `EL NINO` FOUR CORNERS LOWS TO START UP AGAIN SOON.” NWS
So since about February 7th, we have had a maleable ridge over the West Coast to Great Basin. Actually the larger pattern is a persistent trough in the Aleutians, ridge western U.S., trough over Hudson Bay-Midwest. Anyway, Pacific storms have been able to move the western ridge but they lose nearly all their energy as they pass here. Thus we are staying nearly fresh-snow free. This is the dry period I promised for January. What’s one month amongst friends? 🙂
What seems to happen on about 7 March, is a shift of the whole big trough-ridge-trough pattern eastward so that the ridge is pushed onto the Plains. This would open the door to more active weather here with the GFS producing a El-Nino-like closed low over New Mexico, Tuesday 8 March. The European model disagrees with that detail but also has us in an active trough. This type of pattern change is also expected during El Nino years, a snowy March-April.
What worries me is both models show a ridge rebuilding along the West Coast on 9-10 March. So I won’t be betting my 401k on the details at this point.
Other climate news, the weekly Nino 3.4 temperature anomaly is down to 2.1 which is the lowest value since October-ish? Strong El Nino is defined as >= 1.5, so we are still plenty strong. The latest outlook is still heading towards Neutral ENSO by early summer and La Nina by next fall.
Below, 500mb geopotential height analysis, taking us through Tuesday, March 9th.
500mb Geopotential Height – 12z GFS
A potential pattern shift sometime after the 1st week of March
The obvious feature appears in the March 7/8 time frame, in the form of a longwave trough across the west & closed UL low pressure south of Colorado. Barlometer