A spectacular near-miss

Filed in Uncategorized by on August 28, 2009 111 Comments

A very late-night update (this morning?). The remnants of former Tropical Storm Ignacio have been caught up in the deep southerly flow ahead of an unseasonably strong trough off the West Coast. Widespread deep convective activity (like I have never seen this time of year) over the ocean has been ongoing both in the tropical moisture plume and along the cold front further north and west. The plume has just started to ease onto the far NorCal coast this evening…and a band of heavy showers and probably some thunderstorms is readily apparent on Eureka radar attm. Much more intense thunderstorm activity appears to be occurring just another 1-2 hundred miles offshore. The trouble in this instance is that the flow is TOO easterly–weak southeast flow aloft, usually a boon in moisture surges, is actually keeping most of the deep moisture offshore. There is a phenomenal amount of moisture offshore–over 2.5  in. PW–and it is very close to the coast. Unfortunately, steering flow is almost due southerly in the plume, and so most of the convective activity will miss CA entirely and head right into Oregon! There is one caveat, however. The plume has been much deeper…much wider…and a little further east than the models were earlier indicating that it would be. A shift of only 50-100 miles further east would bring convective chances as far south as the Bay Area tomorrow. Therefore…the situation is certainly worth keeping an eye on. Stay tuned.

Today was also extremely hot in SoCal…with a number of 110+ records broken by several degrees. Expect another very hot and dry day tomorrow, highlighted by the ongoing Red Flag Warnings.

After the weekend, the weather should temporarily quiet down some. By Tuesday or Wednesday, however, new E Pac tropical systems will have the potential to bring moisture to CA depending on the location of an even deeper trough and associated cutoff low that is expected to develop offshore. The models are having a very hard time with this scenario right now…and it would be very unusual to have such a deep low so far south so early in the year. Therefore: stay tuned. The potential for tropical systems to have an effect on CA will be much higher than the background level, that’s for sure…