Extreme fire weather NorCal; Gustav a potential catastrophe

Last week’s heat has subsided over CA and temperatures are very near to climatological norms. An unseasonbly strong trough and associated dry cold front are currently moving to wards CA from the N/NW and will move over NorCal tomorrow. Behind the front–cold air advection aloft will bring about unstable and windy conditions to the northern half of the state. A few isolated thunderstorms will be possible over the mountains, but the main story will be the extremely high fire danger that will result from very gusty winds (especially in the Sacramento Valley and over higher terrain), very low humidities, very dry fuels, and warm afternoon temperatures. I do expect to see some wind-driven fires here over the next 72 hours, and this will unfortunately be a pattern that will be repeated several times over the next two weeks.

 A low to mid grade monsoonal surge will be strictly confined to the southern 1/3 of the state over the next 48 hours, with scattered to numerous mountain and desert storms and a slight chance of some convection nearer the coast (especially in San Diego County). Mostly, though, a fairly run-of-the-mill monsoon forecast…

All eyes, in the meantime, turn to the central Gulf Coast, where Hurricane Gustav will be making landfall within the next 48 hours. A strong category 4 storm when it made landfall in Cuba, Gustav weakened slightly to a category 3 storm as it re-emerged over the Gulf of Mexico. On its current path, Gustav will be passing over the highest heat content of the Loop Current for the next 12 hours or so, and rapid intensification is highly probable, at least back into solid category 4 territory (and about a 50-60% chance of attaining cat. 5 status at some point). Cooler ocean temps and possibly some upper-level wind shear may weaken Gustav to a category 3 or category 4 storm before landfall, but regardless of distinction on the Saffir-Simpson scale the damage wrought by this storm will likely be enormous and very possibly catastrophic. The forecast track as been shifting slightly eastward over the past 24 hours due to re-formation of the center of circulation and slight changes in the position and strength of the high pressure ridge exerting a moderate steering infleunce on Gustav. New Orleans will be within 150 miles of the eye of Gustav as it makes landfall, and possibly less than 50 miles. The city will also be on the northeast side of the storm, which is not only the strongest part of any tropical system but is also a position that will allow storm surge to impinge directly on the city. Even without a direct hit, New Orleans is in danger. If Gustav does track slightly (as in 20-40 miles) east of the current forecast track (which is well within the now-infamous NHC “cone of uncertainty”), New Orleans will likely experience damage comparable (and, perhaps, even worse) than experienced by Katrina. Much is still to be decided, however, and a last-minute shift to the west (or an unexpected weakening trend) could act to de-fuse some of Gustav’s potential impact. It does not, however, look very good for the city of New Orleans at the current time. Stay tuned…