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Winds aloft forecasts and seeing, an example

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#1 havasman

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Posted 07 May 2021 - 05:26 PM

https://www.aviation...er.gov/windtemp
That links to the NOAA Aviation Weather Center's winds/temp forecast page. Last night's forecast was interesting for it's depiction of a wide "laminar flow" across most of the central plains US. A broad swath from @ W Minnesota to E Idaho down through the central plains into N & NW Texas, Arkansas, Missouri and as far E as W Kentucky & Indiana showed a remarkably consistent directional flow from NNW to SSE curving gently back to ENE in the SE extents of the range. Speeds were generally from 60 knots to 100 knots. The extraordinary thing to me was that from 9000' to 56000' there were no counterflowing or cross layers anywhere in the whole range. Those make turbulence and that can effect seeing. Surface winds were negligible all night and really seemed to be about zero from midnight on.

So when I found Lyra getting high toward meridian I did not hesitate to put the 3.7 Ethos in the focuser for 464x at 0.7mm exit pupil and was rewarded with a tightly rendered colorful M57 with the varying thickness and uneven density of the ring's structure intact even in a 12.5" aperture.

Before sunset another club member had come by and I mentioned the forecast to him. He'd consulted the bar charts and allowed that they'd indicated either seeing or transparency were s'posed to be good but he couldn't remember which. Turned out both were.


Edited by havasman, 07 May 2021 - 05:27 PM.

  • payner, dave253 and Barlowbill like this

#2 payner

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Posted 07 May 2021 - 08:41 PM

I'm farther east in Kentucky than you mentioned, but it has been a remarkable cool, windy (10-15 mph) the last 7-10 days here. We typically do not have winds this high for any length of time. No freezes, but well below seasonal temps by 10-12 degrees F, with lots of wind.

 

Glad you got excellent sky conditions, Dick. Thanks for the post.

 

Randy




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