The Ridge Saga

This is my first posting ever on something like this. Because of time, I will have to keep these writings extremely brief. At some point we (Dr. Klaus Weickmann(PSD) and myself) hope to post more detailed weather-climate discussions weekly (at least) on the MJO experimental web site hosted by PSD at

http://www.cdc.noaa.gov/MJO/Forecasts/climate_discussions.html


Up to now, these have only been done as time permits. These postings do include week 1-3 outlooks primarily for the lower 48 states based on our research developing a subseasonal synoptic-dynamic model (pdf version of submitted MWR paper at http://www.cdc.noaa.gov/MJO/Predictions/ (section 8c); this paper is currently under revision for final submission).

Right now the main issue for week 1-2 predictions is how will the circulation across the Pacific-North American sector (PNA) evolve. Numerical models have struggled with problem for at least the past week, and our uncertainty continues to be very high.

Tropical convective forcing has been intensifying centered ~0/120E for the past few days, while a weaker signal has propagated into the western hemisphere. We feel that this tropical convection will remain in place for at least the next 1-2 weeks, possibly even shift slightly to the west.

Thus, the extended polar jet now across the central and western Pacific is expected to break through the current ridge during the Monday-Wednesday time frame of next week, with a subsequent discontinous retrogression to of the ridge ~140W being most probable by days 10-14. Downstream effects should include a trough developing across the Rockies, possibly extending off the California coast. This trough may interact with additional subtropical jets, and possibly lead to storm development across the Rockies and Plains during that time. In any event, monitoring is critical.