4th weekend in October (the 25th-27th), 2019

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4th weekend in October (the 25th-27th), 2019

Postby DTM » Thu Oct 24, 2019 3:09 pm

Weather forecasting discussion as of Thursday, October 24th at 4pm:

This weekend looks to have some decent XC potential, and below I'd like to share what I'm seeing in case it benefits our community in making flight plans in the coming days.

We are already approaching the end of October and we have yet to see the cooler temperatures here in Santa Barbara that we typically associate with fall flying. Nevertheless, this past week has produced some decent XC days, due largely to the fact that even though it hasn't been very cold at altitude, it has still been unusually warm down on the coastal plain (i.e. "in town"), allowing for a usable lapse rate to set up.

Fast forward to today and this weekend, and we may be starting to see a shift. While the temps on the ground down in town are not predicted to cool down too much, we do have a significant amount of wind at altitude (even at advisory levels) that represents a colder air mass moving in. When wind blows from a region of colder air to a region of warmer air, it is called cold air advection. When this happens at altitude, it can oftentimes set up a very nice lapse rate. We may benefit from this during the weekend, as winds aloft are predicted to be fairly strong and from the N and W, while winds at more modest altitudes (below 5k) are predicted to be relatively light and variable.

This may set up a situation where our mountains are permitted to heat up nicely with blue skies predicted and little wind present down low to scour the heat. If the air aloft that is blowing in ends up being much colder than the warm air we've been enjoying for the last several days, then we may have some very high thermal heights.

How much our thermals can stand up to the wind higher up is still uncertain, but the situation does look promising to me at the moment.

Friday looks like a nice day to perhaps launch relatively early (10am-ish) and head eastbound toward Ojai. Winds aloft will be blowing from the N and W, so you should get a push downrange even if you climb well above 4k... Always a nice consolation if there is any wind.

NE Santa Ana winds coming down the Santa Clarita River valley may make it difficult to get past Fillmore. Upper Ojai seems like a reasonable goal for our seasoned XC pilots.

Saturday looks like another day to launch early in SB and be making your way eastbound before noon. Winds aloft at 5k and above are mostly from the N and are strong but not too severe, likely being in the low- to mid-teens (mph). I suspect that the anabatic flow from the Santa Ynez mountains will block this wind enough at our relevant altitudes to make it a fine XC day, if perhaps a bit turbulent at the uppermost thermal tops. There is not the same Santa Ana flow predicted in the afternoon, so I think it's possible to see flights beyond Fillmore on Saturday.

Sunday is an interesting day on paper right now. The wind conditions looks quite favorable (light and variable) below 5k, nevertheless the wind gets ballistic (30mph+) from the WNW up around 6k, so we'll have to see how much that affects the airmass below it (that we would be flying in). I simply don't know.

There is also predicted to be a cloud bank out over the coast on Sunday. I don't know if this will affect us in the mountains, but it's possible the LZs get socked in early in the morning and delay our launch. I'm optimistic on this though, and would bet that the low cloud bank won't throw our flying plans off much at all.

We are predicted to have a nice amount of solar exposure all three days, so I'm hoping that the solar heating, in conjunction with the colder airmass moving in at altitude, will yield us a good lapse rate. Nevertheless, I am quite novice at predicting lapse rates, so this is still a large uncertainty in my mind. I welcome thoughts from our more experienced weather forecasters.

Here's hoping that we'll all get some good flying in! 8)
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Postby sd » Fri Oct 25, 2019 12:37 pm

Great write up Derek. Good to see you and Chris raising a torch to shed some light. I try to learn by being open to differing perceptions. No forecast is perfect, so we need to be willing to be always a little wrong, and sometimes completely off the mark, but our aim will continue to improve as we tune in on all the variables of the ever-increasing data available.

I did a quick review and concur with most of Derek’s perceptions, but would likely have preferred to launch from Ojai on Friday (which is Monday morning quarterbacking about Derek’s Thursday forecast after I’ve had the luxury of viewing Friday’s midday observations), then by Saturday SB seems like the better call to maximize XC potential? Sunday seems to be switching back to an offshore Santa Anna influence.
Friday 2 PM Skew-T for Santa Barbara
Friday 2 PM Skew-T for Ojai
Saturday 2 PM Skew-T for Santa Barbara
Saturday 2 PM Skew-T for Ojai
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