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Mid-April Post Frontal Transition

PostPosted: Tue Apr 18, 2017 3:53 pm
by sd
Tuesday afternoon look at the Post Frontal Transition

Today is a bit windy at altitude, and the lapse rate is only so-so down lower. It calms down overnight for a possible window Wednesday before building back stronger from the north on Thursday as it clocks around to come from the east (Santa Anna) on Friday.

Not a lot of instability associated with the broken cold front that passed through this morning. Wednesday starts out weak but the lapse rate improves during the day. The wind is also forecast to build some, but hopefully manageable. The timing could be important as to which gets here first, the better lapse rate or the west wind? We don’t block a west very good, so even a little west wind could be problematic and tear at the thermals if they are too weak.

Recommend launching high, Wednesday and not too early? The lapse rate is better up high, so there is an argument to try and go to OTB, but I think it might be better to attempt clawing through the low zone behind Summerland. If you can reach Powerline Ridge then the terrain starts to climb with more protection from the ocean. Should be a tailwind over Casitas Pass, if you can get that far. If you can, then conditions should be better through Ojai, but not stellar. With both the lapse rate and west flow increasing through the afternoon, there is potential to go past Fillmore if you can get past Summerland. The west wind pushes up the Santa Clara River, but not too strong.

There might be a low marine inversion on Wednesday, but no mid-level capping inversion. Coupled with a weak lapse rate, max altitudes will likely follow the terrain height. So… low behind Summerland, but better over Casitas Pass and through Ojai.

On Thursday, the lower level lapse rate looks good with a capping inversion around 4K in SB and 6K in Ojai. There is quite a bit of north wind above the inversion, perhaps too much for the mountains, but the inversion might limit the vertical mixing for a while and permit early low launches? It will likely blow too strong in the afternoon.

By Friday, the wind should clock around to come from the east as a moderate Santa Anna event on the east end of the course. Might be a good day for an out and return from the Nuthouse to SB and back. The inland temps should be quite hot yielding good late day conditions in the Ojai Valley, but likely too much Santa Anna east flow down the Santa Clara River to reach the bus stop in Fillmore? A good play might be to plan your route to be at the Topa Bluffs late in the day. Santa Barbara should be protected from the east flow below about 5K on Friday, but the lapse rate is weaker than Ojai. If you fly from the Nuthouse try to stay high on the westbound leg then lower on the eastbound return leg. Altitudes in Ojai look ok but not stellar, maybe 6Kish.

Re: Mid-April Post Frontal Transition

PostPosted: Fri Apr 21, 2017 3:08 pm
by gracecab
Hey Tom did you fly this week? It looked interesting at times in different places...

Re: Mid-April Post Frontal Transition

PostPosted: Mon Apr 24, 2017 8:58 am
by sd
gracecab wrote:Hey Tom did you fly this week? ...
Chris, no, I did not fly last Wednesday. I posted because Neal and Mitch requested my input on Monday evening for pending post frontal on Wednesday. Don’t know if anybody flew locally on Wednesday, but from Carpinteria it appeared to play out as forecast? Mitch opted to go to Marshall for better potential and flew to Chiriaco Summit, 102 miles. I didn’t review the weather down south, but based on Mitches flight track it seems like their skew-t profile was likely similar to our local area? Further inland, so more heating and a better lapse rate than SB. Without a capping inversion in the skew-Ts across the forecast area, max altitudes followed the terrain height. Mitch posted what you might think are big altitude numbers in places, but he was often below ridge line. San Gorgonio is 11.5K and Anderson Peak is just under 11K.

Had I flown with Mitch on Wednesday, I don’t know that I would have followed him along the north side of the San Gorgonio high terrain below ridge line because I don’t have the same hiking capability, but there was a reachable road below him during much of that critical phase, so maybe? We all need to strive to stay within our own personal limitations. Mitch’s athletic capabilities enable him to take deeper lines than many of us. There were also other sections of his flight were I likely would have been angling further out front which might not have offered as much protection from lower altitude stability?