2009

Just a quick weather update this evening–more will follow this weekend.

After a quiescent period across the state of California, the weather pattern over the Eastern Pacific will become decidedly more active over the coming week. Most obviously, a rather large upper-level low is currently spinning far SW of the CA coast. This low has just begun to tap copious mid and upper-level moisture from soon-to-be-former Hurricane Linda. The forecast models do not have a good handle on this moisture entrainment nor the depth of the low. I expect an increasing amount of moisture to be drawn up from the remnants of the tropical system as the low moves towards the Central/Northern CA coast on Saturday. As this low moves inland, there will be a considerable amount of elevated instability, and it now appears that there may well be a substantial moisture source, as well. A significant nocturnal/high-based convective outbreak is possible on Saturday throughout much of NorCal north of about Santa Barbara. Again, the models are not keying in on this completely, but the parameters certainly appear to be favorable for this to occur. It is also worth noting that mid-September is nearly the peak of climatological likelihood for this type of event to occur in CA, so it is certainly not out of the realm of possibility. This may be one of those scenarios where watching satellite pictures may be more useful than following the explicit model output…

Another potentially very interesting event will occur around next Monday as the base of an unseasonably strong Pacific trough cuts off west of CA and slowly drifts ashore. This low will have substantially more moisture and even cold air aloft, so there is perhaps even a better chance of showers and thunderstorms across the northern 2/3 of the state early next week. The models are explicitly indicating precipitation over much of NorCal attm. Again…stay tuned. There remains the possibility that either of these two events may have impacts further south than currently anticipated.