| AVSIM Utility Review ThinMetar for Fly! |
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ThinMetar is the Cadillac of the current available weather utilities. FLY! by itself does a decent job of using the needed METAR data but ThinMetar overcomes the limitations of FLY! by giving the user options. Lots of options! It takes the base model and upgrades it to the luxury edition with lots of dealer installed upgrades.
Before we get into all the details of ThinMetar I think it would be appropriate to discuss METAR data in general. In addition the U.S. National Weather Service has an excellent website on this subject which you can access here.
METAR for Aviation Routine Weather Report are observations that are compiled hourly for dissemination to the aviation community. As this data integrates with FLY! the most important thing to understand is that these are observations. An observation differs from a forecast in that it is the current weather condition at the time that the observation was taken, while forecasts are the anticipated conditions based on the available information. These observations are taken primarily at airports with control towers, or Flight Service Stations. METAR reports can be prepared either automatically, using equipment located at the station, manually by an FAA specialist, or combination of the two. In addition, the weather report may be prepared in one of several different service levels, depending on the size of the facility. Large Hub airports will have more elements of information than smaller GA airports. Finally, data on ceiling heights other than the lowest layer may not be available unless the observation is taken manually. This is especially true when ceilings are reported as broken. When the ceiling report comes in as overcast you will almost never have a report of a layer above. Why? Because the overcast layer obscures any observation by the specialist or the automatic equipment of layers above. My favorite flying is in between layers. But don't expect this when you over-fly an area of overcast below. FLY!'s default overcast layer is rather thin, about 2000 feet thick. In real flying a overcast layer—especially one with thunderstorms, hail, or heavy snow—is often 10,000 feet thick, with some peaks that may reach 50,000 feet.
What does this mean to the simmer? Try to choose airports in ThinMetar that are major hub airports, because they generally have the most complete METAR data. I also recommend using the observation of the previous hour as this will be the most complete data available. Depending on the time that the data is downloaded from the NOAA site you may only have a handful of available observations. This will seriously reduce your ability to experience the current weather. Unless conditions are changing very rapidly, you probably won't notice any difference between the current and previous hour. Here is a sample of METAR fields: KEWR 250251Z 04009KT 7SM SCT140 BKN200 M01/M04 A3002 RMK AO2
PRESFR SLP163 T10111039 56009
ThinMetar Options
This takes us to the proper utilization of the ThinMetar options. The use of these options are going to depend on exactly what the user wants out of the METAR data. Do you want an accurate portrayal of the weather, or the most interesting weather available within the current area. David Sandberg goes to great length in explaining the various options in the Readme file. I will try to sum these up and edit them a little based on my experience.
Station Spacing: This gives you the minimum distance between stations. For this I prefer to keep this at 0. Since ThinMetar does an excellent job of reducing the METAR file, a few extra stations doesn't matter. In fact, it seems to smooth out some of sudden changes in sky condition.
Buffer Space in mile around flight path: Keep this at the default 120 miles is more than enough unless your just joyriding.
Station Selection Order: This determines what the basis of station selection. I prefer the location only. The weather will be more accurate, and I find transition is smoother.
Exclusion Method: I used the default Flight Path, and didn't even attempt the bounding rectangle.
Remove few/scattered layers below rain clouds: If you're trying to capture intense precipitation leave this checked. If you want low IFR leave unchecked.
Convert all thunderstorm reports to create lighting: Best left checked, as thunder almost always means lighting.
Combine body elements unto a single line: No reason to turn this off.
Remove remarks that look like temp/dewpoint: This should have little if any affect on your program, and it may correct the problem that some people had with the PMDG B757, where engines were shutting down when using imported METAR data.
Convert Cloud Heights to MSL (rather than AGL): This should be left on, evidently David Sandberg has discovered that FLY! assumes all cloud heights to be an MSL altitude. METAR Cloud Height are in fact AGL.
Disable prompts for file overwrite and file complete: I like to leave this off, that way I'm sure that the file generated correctly.
Running ThinMetar
Running ThinMetar is a snap. You must first download a METAR file from a site. The user double clicks the exe file and then chooses the METAR source file name. (Hint: Here I like to use AutoMetar for the import since it's automatic then use the previous metar.txt file as your source file because the data is much more complete.) The most common site is the NOAA site. Choose a file to for the ThinMetar utility to export to, I recommend using the default ThinMetar.txt. Next modify the options to your liking, then choose two or more ICAO Codes for airports along your flight path. Now click the generate button. The metar file is thinned according to your settings and writes to the export file.
Now you can start FLY!. Remember you must still import the newly generated ThinMetar file into your environment settings. Upon starting the FLY! flight planner, you must go to the environment settings page and left click the "Import METAR" button. Next a window will pop up. Click the Add file button on the bottom and choose the default ThinMetar.txt file assuming this is the one ThinMetar generated to. Click OK. The Importer will start and the horizontal barber pole will tell you when it is complete. Now you can click the red "Fly" button or make other adjustments to your flight plan. However, except for the distant clouds back drop, don't change any of the Environment settings! Ken Wood has uploaded, to the Avsim site, an excellent and brief tutorial on using the METAR function within FLY!. You can download his tutorial here .
Test Flight
For a test flight of ThinMetar we will use the January 24th storm that blanketed the southeast with unprecedented snow accumulations.
We will file our flight from Newark to Raleigh-Durham. As in the AutoMetar review we will provide some basic weather data from the Government sites and compare it to the Weather that ThinMetar generates.
On this flight we should encounter broken clouds at high altitude. Somewhere in the vicinity of Washington D.C. cloud coverage will continue to close-in as in the Weather Depiction Chart above-left. Crossing into Virginia and North Carolina, a solid overcast should be encountered. Unfortunately for the reasons I mentioned earlier, the overcast layer will cause layers above to be obscured from view. Although the radar summary chart above right shows cloud peaks in excess of 25,000 feet. The METAR import will show blue skies above the obscuring layer as clear. This of course is a limitation of using solely METAR data for weather import. Below us snow should be falling at moderate to heavy intensity. The images below are from our flight. The weather was true to the government data, albeit with FLY!'s limitations. What I especially appreciate is that the tweaked data helped to improve the weather transition. Thinning the METAR file also seems to improve the framerates during the transitions.
Conclusions
Once again we have come across a must-have FLY! utility. In fact David Sandberg's ThinMetar could just as well been called RobustMETAR! No other weather utility goes to such length to right the limitations of the FLY! code. Yet, still leaving the options up to the user on how to address his/her specific simulation needs. There is rumor about that Sandberg is at it again, in a few weeks we should be seeing something new from his workshop. We look forward to tinkering with his newest creation. Until then you can download ThinMetar from the Avsim Library by clicking here.
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