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| crossing into/out of MVFR/IFR | ||
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Moderators: Tracy Fowler
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| ACU1 |
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 Registered Member #85 Joined: Sun Jul 26 2009, 04:19AMPosts: 21 | The only augmentation data the FAA is looking for in this project is operationally significant augmentation (freezing precipitation, ice pellets, and thunderstorms). These impact airport and aircraft operations. Weather elements such as clouds above 12,000 feet, variable sky condition, snow depth, etc. do not. | ||
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| weatheri |
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 Registered Member #3 Joined: Mon Jul 07 2008, 09:31AMPosts: 35 | Greetings, There are significant visibility values at the crossing point MVFR to VFR that greatly affect some airports. A prevailing visibility of 4SM vs 5SM is huge at some airports with dual runways. You can start using the second runway at 5SM as long as the ceiling is 020 or greater. However, since you never cross out of the MVFR category because of ceiling, these observations are not counted in this gathering of data. There are several other values with significance impacting operations at individual airports. These blanket studies cannot possibly account for all of them. At our location around 85% of all observations require augmentation or back up. I further broke that down by category, VFR, MVFR, IFR and LIFR; these numbers nobody wants. The ASOS already this month has had some type of outage 37 times for 85+ hours requiring some type of observer interface. I'm not talking about all those port errors, SIO errors, SY 9999 errors but real down time affecting operations. However, most of the outage time was between observations, so again not counted. The CWO had to go through all the gyrations of reporting the outage to AOMC and notifying the ATCT Sup which fields were being backed up; again not counted if back up by observation time. There are a lot of intangibles missed in every study, it's just the nature of the beast. Since I have no idea why the information is being gathered, I cannot offer any input or even comment if it is the right information. I can speculate until the cows come home but I might be way off or right on target. Looking at what is being gathered confuses me but that's just me, and it's coming from an uninformed position. Regards, weatheri | ||
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| hlsto2 |
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 Registered Member #2 Joined: Sat Jul 05 2008, 05:36AMPosts: 324 | I would argue that snow depth DOES impact aircraft operations. And the SNINCR group is a very useful tool in showing just how quicly the snow is accumulating. Without it, airport personnel would only get a snow depth report every 6 hours. Unless they wanted to try and determine it themselves. But, that would not be official. Remembering a few years back at ORD? the jet that slid off the runway in a snow storm. You can bet NTSB was extremely interested in the CWO's snowfall data. | ||
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| TCU_2U2 |
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| Registered Member #17 Joined: Tue Jul 15 2008, 07:20PMPosts: 123 | To take the snow depth data one step further ... I always felt that since you had observers at the site, why not introduce an "hourly snowfall / depth" group. Since we are required to get a reading each hour (to satisfy the SNINCR group for one) ... this data would also go a long way in "offical documentation" of snowfall to the nearest 1/10th of an inch per hour. As hlsto2 mentions ... NTSB and others doing investigations, etc ... this extra data could be very useful. Also for the daily / hourly operations of any airport during a snow event ... and for weather forecasters .. and other end users. Would free up the phone calls, thats for sure, while at the same time documenting for "offical use". [ Edited Sat Feb 20 2010, 06:05PM ] | ||
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| Tracy Fowler |
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  Registered Member #1 Joined: Mon Jun 30 2008, 05:10PMPosts: 43 | Our site is not required to take snow depth measurements, because in the past it was proven that our observation area cannot produce accurate depth measurements..... the only observation point we have is a flat roof of the terminal next to the old tower, winds raise havoc with the depth. | ||
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| hlsto2 |
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| Registered Member #2 Joined: Sat Jul 05 2008, 05:36AMPosts: 324 | And of course "snow measurements should not be taken from rooftops...paved areas...and the like". Taken from 7900 and the NWS training guide. At COS our snow measuring site was a large flat grassy area across from our parking lot. Bit of a walk since our obs point was in the old tower 60...feet up...all stairs...no elevator. There was a large roof area one story below us..protected by a 2' wall on all sides. We of course used the grassy area for measurements. I made a snowboard out of a 4x8 piece of plywood painted white that we left out all winter. The postage stamp snowboards the NWS issues are virtually worthless unless there is no wind. I did comparisons between the rooftop and the grassy area and of course the rooftop would always measure less. You could observe the snow beginning to accumulate in the grass before the rooftop...due to heat escaping from the roof. | ||
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| Tracy Fowler |
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| Registered Member #1 Joined: Mon Jun 30 2008, 05:10PMPosts: 43 | ours is the reverse, it would accumulate on the roof first in no wind conditions, not in the grass in the center of the field. but add in wind and all bets are off | ||
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