How long for thermals to start working after rain?

[Bruno[_2_]]

I am looking out the window of my office in Salt Lake City, Utah right
now to rain falling. Tomorrow is expected to be in the mid to upper
60's and sunny with fairly low humidity. Might be a decent soaring
day. How long does it take the ground to dry up enough after rain for
thermal soaring conditions to get good again? I am sure the answer
might be different when the temps are in the 60's and 70's compared to
80's and 90's summer time. What have you all experienced?

Thanks,
Bruno - B4

[cernauta]

On Fri, 23 Apr 2010 08:30:41 -0700 (PDT), Bruno
> wrote:

I am sure the answer
>might be different when the temps are in the 60's and 70's compared to
>80's and 90's summer time. What have you all experienced?

Geology (terrain composition in the different layers) also strongly
affects the time needed to restart the thermal cycle.
I think geology is also relevant to the max thermal height and to the
formation of convective clouds.

Not to mention airmass humidity, wind, elevation and so on.

AldoCernezzi

[mattm[_2_]]

On Apr 23, 11:30*am, Bruno > wrote:
> I am looking out the window of my office in Salt Lake City, Utah right
> now to rain falling. *Tomorrow is expected to be in the mid to upper
> 60's and sunny with fairly low humidity. *Might be a decent soaring
> day. *How long does it take the ground to dry up enough after rain for
> thermal soaring conditions to get good again? *I am sure the answer
> might be different when the temps are in the 60's and 70's compared to
> 80's and 90's summer time. *What have you all experienced?
>
> Thanks,
> Bruno - B4

I've found it to depend on the soil type. When I was a student pilot
the simplified wisdom I received was "the day after a cold front."
Then, after I got my license I would start to take days off to go soar
but wound up spending my vacation time looking at overcast skies
or (at best) grinding around in weak thermals. I started doing my
own weather forecasting after that and found that usually the second
day after the cold front was best where I lived (characterized by
forested hills and clay soil). My instructor, meanwhile, had
moved to New Jersey (characterized by sandy soil) and noted that
the first day after the front was best.

So, my answer is that "it depends". Since you live in a fairly
arid climate zone, I would expect that very soon after the front
would be best (especially with orographic lift available).

-- Matt

[Frank Whiteley]

On Apr 23, 9:30*am, Bruno > wrote:
> I am looking out the window of my office in Salt Lake City, Utah right
> now to rain falling. *Tomorrow is expected to be in the mid to upper
> 60's and sunny with fairly low humidity. *Might be a decent soaring
> day. *How long does it take the ground to dry up enough after rain for
> thermal soaring conditions to get good again? *I am sure the answer
> might be different when the temps are in the 60's and 70's compared to
> 80's and 90's summer time. *What have you all experienced?
>
> Thanks,
> Bruno - B4

Just stay out of the valleys.

During the Open Class Nationals in the UK in '93 or '94, it was
raining and gray as the pilots' meeting started at 10am. All assumed
it would be a rest day, but were astonished when CD Ken Sparkes called
a grid time of 12:30pm. He'd been consulting with Tom Bradbury who
was forecasting for the 15m Nats up country. Tom said there was a gap
coming, and it would be soarable in the gap. We had Meteosat images
and a contact out west who confirmed when the gap had arrived there,
and indeed it was soarable in the gap. The gap slowed and arrived
about 30 minutes late. The field launched and started, heading into
the gap, dog-legged south to the second TP, back to TP3, and home
again to Enstone as the gap closed. It was raining again as they were
putting the gliders away. IIRC 37 of the 45 competitors finished the
task. A few didn't start and one or two landed out. One of the UK's
top senior pilots complimented Ken saying 'gutsiest call I've ever
seen'. He was very proud to have called a contest day when no one
else would have dared.

Frank Whiteley

[Mike the Strike]

On Apr 23, 9:10*am, Frank Whiteley > wrote:
> On Apr 23, 9:30*am, Bruno > wrote:
>
> > I am looking out the window of my office in Salt Lake City, Utah right
> > now to rain falling. *Tomorrow is expected to be in the mid to upper
> > 60's and sunny with fairly low humidity. *Might be a decent soaring
> > day. *How long does it take the ground to dry up enough after rain for
> > thermal soaring conditions to get good again? *I am sure the answer
> > might be different when the temps are in the 60's and 70's compared to
> > 80's and 90's summer time. *What have you all experienced?
>
> > Thanks,
> > Bruno - B4
>
> Just stay out of the valleys.
>
> During the Open Class Nationals in the UK in '93 or '94, it was
> raining and gray as the pilots' meeting started at 10am. *All assumed
> it would be a rest day, but were astonished when CD Ken Sparkes called
> a grid time of 12:30pm. *He'd been consulting with Tom Bradbury who
> was forecasting for the 15m Nats up country. *Tom said there was a gap
> coming, and it would be soarable in the gap. *We had Meteosat images
> and a contact out west who confirmed when the gap had arrived there,
> and indeed it was soarable in the gap. *The gap slowed and arrived
> about 30 minutes late. *The field launched and started, heading into
> the gap, dog-legged south to the second TP, back to TP3, and home
> again to Enstone as the gap closed. *It was raining again as they were
> putting the gliders away. *IIRC 37 of the 45 competitors finished the
> task. *A few didn't start and one or two landed out. *One of the UK's
> top senior pilots complimented Ken saying 'gutsiest call I've ever
> seen'. *He was very proud to have called a contest day when no one
> else would have dared.
>
> Frank Whiteley

On one of my first cross-country flights from Magalies Gliding Club
(quite a few years ago), I ran into a light rain shower, tried to run
under it and ended up on the ground as it killed all lift. As I
waited for my retrieve crew, a thermal moved across the field, not
half an hour after I had landed, and soon the sky filled up with
lovely cumulus from horizon to horizon.

The answer depends on how much rain, how dry the soil, how soon the
sun and how unstable the air! Half-an-hour may be enough.

Mike

Mike

[AK]

On Apr 23, 11:30*am, Bruno > wrote:
> I am looking out the window of my office in Salt Lake City, Utah right
> now to rain falling. *Tomorrow is expected to be in the mid to upper
> 60's and sunny with fairly low humidity. *Might be a decent soaring
> day. *How long does it take the ground to dry up enough after rain for
> thermal soaring conditions to get good again? *I am sure the answer
> might be different when the temps are in the 60's and 70's compared to
> 80's and 90's summer time. *What have you all experienced?
>
> Thanks,
> Bruno - B4

It seems it is always too late!

[Bruno[_2_]]

On Apr 23, 3:38*pm, AK > wrote:
> On Apr 23, 11:30*am, Bruno > wrote:
>
> > I am looking out the window of my office in Salt Lake City, Utah right
> > now to rain falling. *Tomorrow is expected to be in the mid to upper
> > 60's and sunny with fairly low humidity. *Might be a decent soaring
> > day. *How long does it take the ground to dry up enough after rain for
> > thermal soaring conditions to get good again? *I am sure the answer
> > might be different when the temps are in the 60's and 70's compared to
> > 80's and 90's summer time. *What have you all experienced?
>
> > Thanks,
> > Bruno - B4
>
> It seems it is always too late!

All very good things to thank about. Thanks for the replies.

Soar safe!
Bruno - B4

[Andy[_10_]]

On Apr 23, 1:20*pm, Mike the Strike > wrote:
> On Apr 23, 9:10*am, Frank Whiteley > wrote:
>
>
>
>
>
> > On Apr 23, 9:30*am, Bruno > wrote:
>
> > > I am looking out the window of my office in Salt Lake City, Utah right
> > > now to rain falling. *Tomorrow is expected to be in the mid to upper
> > > 60's and sunny with fairly low humidity. *Might be a decent soaring
> > > day. *How long does it take the ground to dry up enough after rain for
> > > thermal soaring conditions to get good again? *I am sure the answer
> > > might be different when the temps are in the 60's and 70's compared to
> > > 80's and 90's summer time. *What have you all experienced?
>
> > > Thanks,
> > > Bruno - B4
>
> > Just stay out of the valleys.
>
> > During the Open Class Nationals in the UK in '93 or '94, it was
> > raining and gray as the pilots' meeting started at 10am. *All assumed
> > it would be a rest day, but were astonished when CD Ken Sparkes called
> > a grid time of 12:30pm. *He'd been consulting with Tom Bradbury who
> > was forecasting for the 15m Nats up country. *Tom said there was a gap
> > coming, and it would be soarable in the gap. *We had Meteosat images
> > and a contact out west who confirmed when the gap had arrived there,
> > and indeed it was soarable in the gap. *The gap slowed and arrived
> > about 30 minutes late. *The field launched and started, heading into
> > the gap, dog-legged south to the second TP, back to TP3, and home
> > again to Enstone as the gap closed. *It was raining again as they were
> > putting the gliders away. *IIRC 37 of the 45 competitors finished the
> > task. *A few didn't start and one or two landed out. *One of the UK's
> > top senior pilots complimented Ken saying 'gutsiest call I've ever
> > seen'. *He was very proud to have called a contest day when no one
> > else would have dared.
>
> > Frank Whiteley
>
> On one of my first cross-country flights from Magalies Gliding Club
> (quite a few years ago), I ran into a light rain shower, tried to run
> under it and ended up on the ground as it killed all lift. *As I
> waited for my retrieve crew, a thermal moved across the field, not
> half an hour after I had landed, and soon the sky filled up with
> lovely cumulus from horizon to horizon.
>
> The answer depends on how much rain, how dry the soil, how soon the
> sun and how unstable the air! *Half-an-hour may be enough.
>
> Mike
>
> Mike

I'm with Mike - it depends. I've seen thermals within an hour or so
after a light shower on an otherwise hot, sunny and dry day in
mountainous terrain. I also recall a day at the standard nationals in
Kansas where a lot of rain one day left soaked soil and standing water
that killed thermals in some areas for a day or more.

9B