Tuesday, September 27, 2011

Surfin' U.S.A.
- Timeless 1963 single by the Beach Boys 

12:40 PM EDT 9/27/11  Waves of 15 to 18 feet along the Pacific Northwest coast today, as projected by the Seattle National Weather Service, are the first phase of what our team believes will become a major change in the atmospheric pattern over much of North America. These high surf conditions are being caused by a strong cyclone approaching from the Gulf of Alaska, containing the remnants of Super Typhoon Roke which struck Japan last week. We first reported on Roke's potential impact to the U.S. weather pattern in our "Here We Go Again" post from 9/19. It is a surfin' safari for those skilled enough to brave the rough conditions, or just safely surf Pacific coast web cams. Still dreaming of surfin' summer waves? Hang with the Beach Boys in this Youtube video.  

A second influence in the long range pattern should also be the remnants of Hurricane Hilary, shown as the little red and orange ball on this Northeast Pacific enhanced satellite image (Flash loop). The National Hurricane Center, and our Long Range Team,  expects Hilary to turn north and send upper level energy and moisture into the U.S. southwest. We believe downstream impact of both Hilary and the energy from Roke will fuel a significant pattern change across the entire U.S. for the first 2 weeks of October. Possible outcomes, as indicated by the Climate Prediction Center, include major amplication of the ridge-trough arrangement. In the week ahead, the western U.S. trough should sharpen, leading to a major ridge developing in the central U.S. By October 10, a large area of the Eastern U.S. could be facing a major post-summer warmup with possible above normal precipitation in the Northeast U.S. 

ANY EFFECT ON THE WINTER PATTERN? Plenty, my fellow powderhounds, plenty. For starters, a major fall warmup may wreak significant havoc on the development of Arctic cold reservoir.  It could delay the buildup of the reservoir, holding back a kickoff of winter in the Eastern U.S. or it may end up fueling a "blocking" regime over northeast Canada to Greenland. Granted we are very concerned and closely monitoring the near-record melt off of Arctic Sea Ice (TIME) reported to be the second lowest since NOAA began tracking the data in 1979. However snow and ice will reform as winter approaches, and cold air will build up over the Arctic. An imbalance of warm and cold out of season could create another  "Rubber Band Effect" our team refers to in times of changing patterns. A rapidly arriving warm-up in mid-October could snap back like a rubber band with a sharp cool down by late October and early November. See what is happening? The upper level pattern would get thrown out of balance again, creating an earlier arrival to winter despite Arctic sea ice. 

SO HOW MIGHT ALL THIS PLAY OUT? We hypothesize the influence of Hurricane Hilary and the Pacific Northwest storm may produce a long term change in the pattern, and re-energizing the apparent 45- to 60-day sequence of high impact events which seem to be in place. A major cold outbreak by late October may allow a mid-November warmup at a time when cold air is beginning to build across Canada. One or two traditional Alberta clippers right around Thanksgiving could easily unlock all that cold air-- and the Eastern U.S. receives an early winter drubbing similar to the famous White Thanksgiving  and subsequent Arctic invasion of December 1989.  

LET ME GET THIS STRAIGHT: You all are saying a September Hurricane in the East Pacific could lead to a White Thanksgiving in the central and eastern U.S.? No, not exactly. We are saying that the long range impacts of two major systems influencing the pattern, plus La Nina similarities between this time of year in 2011, 1995 and 1989, are possibilities to be considered. That's what we do on this site...we map out the parameters and possibilities, then we analyze the data stream and see how things play out.  We think a new cycle is about to start, so go ahead and mark your calendars and we'll watch it happens together. (Forecasters Foot, Nic R. and the Long Range Team)