Author Topic: Bad METAR SLP data from KORL  (Read 668 times)

0 Members and 1 Guest are viewing this topic.

Offline galfert

  • Forecaster
  • *****
  • Posts: 867
Bad METAR SLP data from KORL
« on: July 30, 2018, 11:22:26 AM »
I noticed that ASOS Orlando Executive Airport KORL has consistently bad Sea Level Pressure (SLP). So essentially bad QFF data. (SLP is another name for QFF). Their SLP is consistently higher than Altimeter Pressure (QNH).

QNH (Altimeter) is calculated with ISA temp of 59 F.
SLP is calculated with the mean average temperature of the past 12 hours.

Since the mean average temperature of the past 12 hours has been consistenly greater than 59 F then SLP (QFF) should never be greater than Altimeter Pressure (QNH).

KORL consistently shows SLP as greater than QNH and that is impossible for being at an elevation greater than sea level and the mean temp being > than 59 F.

For the record KORL Altimeter pressure QNH seems perfectly accurate in comparing to two other nearby airports KSFB and KMCO. So I don't believe that the equipment is bad or not calibrated correctly. Rather I feel that they are doing something wrong to calculate Sea Level Pressure QFF.

Sometimes KORL does report QNH = SLP. Which would only be okay if the mean average temp was 59 F. And it is summer in Florida and so QNH = SLP is wrong too. As we are way over 59 F as an average temperature.

So I started by contacting the NWS office in Melbourne FL because they are in charge of the equipment. The lady was very nice on the phone. She listened and said that they regularly check the station at KORL and she would let the technicians know of my report. She did say though that if nothing is wrong with the equipment it could be a fault of the observer person at the airport that is maybe doing something wrong to come up with SLP that is the problem. Or maybe their software is wrong in some way. So she told me to contact the airport.

Okay so I now call Air Traffic Control at KORL phone # (407) 281-9463. The person that answered the phone (didn't get their name) was short with me. They put me on hold just as I mentioned that I wanted to report that I felt there was a problem with their METAR information and I hadn't gotten to the details yet..(so like 15 seconds and they interrupt and tell me to hold). They come back on the phone and they ask me whom I am and what what is my title and if I'm from the FAA or what department of the government I'm from. I tell the person that I'm just a weather observer hobbyist. Right there they cut me short and say thank you we'll look at the METAR data. I then quickly said, "WAIT you haven't heard from me yet what is wrong." The person then says, "Okay what is the problem." But they sound like they really aren't interested and just want to get rid of me. I quickly told them that their Altimeter Pressure is correct but that their Sea Level Pressure calculations must be wrong because Sea Level Pressure can't be greater than Altimeter Pressure when mean temperature is above 59 F. They responded okay thank you and hung up. Sheeez! Yeah they are going to do something about it surely.

Some of my thoughts into the problem of what could be occurring... I noticed that SLP is frequently missing from METAR data. It is there sometimes and not others. So maybe the SLP calculation is using some zeros (0) for the previous mean average temperature and that could alter the SLP to then basically be using a number that is less than 59 F and then SLP could come out to be greater than Altimeter Pressure QNH. Or maybe there is a bug in the software they are using. Or maybe there is a negative sign in the formula that shouldn't be there for calculating SLP. Or maybe someone at KORL just doesn't know what they are doing as they publish METAR because I understand that METAR information has to be verified by a human and not automated. When METAR is automated there is a note as part of the METAR data that it was not verified by human and that happens sometimes if weather changes quickly and METAR information goes out at a different interval than the hourly one at 53 minutes past the hour.

So anyone have any thoughts? Has anyone here ever attempted to fix bad METAR reporting from ASOS location? If yes how did you go about it?


« Last Edit: August 04, 2018, 08:52:46 AM by galfert »
WS-2902A | ObserverIP | WeatherBridge (Meteobridge)
WU: KFLWINTE111  |  PWSweather: KFLWINTE111
CWOP: FW3708  |  AWEKAS: 14814
Tele-Pole flag pole is here (not installed yet)

Offline galfert

  • Forecaster
  • *****
  • Posts: 867
Re: Bad METAR SLP data from KORL
« Reply #1 on: July 31, 2018, 02:19:57 PM »
Update:

Well it didn't sit well with me how I was treated and dismissed by Air Traffic Control of KORL. So today I called the ATC Manager. First I reported the issue. She was very nice on the phone. She asked follow up questions to really understand the issue. She assured me that she would have someone look at this and she asked for my name and number in case they had further questions. I gave her my info and she thanked me for bringing this to her attention. Well it went so well that I decided to tell her about the not so professional treatment I got the day before by one of her ATC people. She apologized and assured me that I should not have been dismissed and treated so unprofessionally and that she would also look into that matter.

WS-2902A | ObserverIP | WeatherBridge (Meteobridge)
WU: KFLWINTE111  |  PWSweather: KFLWINTE111
CWOP: FW3708  |  AWEKAS: 14814
Tele-Pole flag pole is here (not installed yet)

Offline galfert

  • Forecaster
  • *****
  • Posts: 867
Re: Bad METAR SLP data from KORL
« Reply #2 on: September 04, 2018, 01:22:22 PM »
UPDATE: Over the past month I finally got in contact with a NOAA meteorologist. Well there was a lot of back and forth between me and the NOAA meteorologist that worked with me on this issue over the past month. Long story short is that over the course of a month technicians went out twice to check things out. They came back empty handed each time. I think their focus was on calibration vs. configuration of software that uses the readings and the scope of this issue may be outside of their training. The Meteorologist agreed with me in my findings. But the issue is not critical because the error we are talking about is about .2 to .4 millibars. So nobody is going to do anything more for this.

Here is the final say in the matter and the last communication I received from NOAA and I've come to accept that this is it. But at least I feel good that I was able to track down a responsible person, that understood me, and was able to get this expert to agree with me in my findings. At least now I know that I'm not the only one that knows and who knows maybe someday someone will look at this system and then fix it and then someone will say, "oh yeah, that issue came to light a while ago and we weren't able to fix it."

Final Email from NOAA Meteorologist:
Quote
I'd like to provide one final follow-up to your most recent email.

As a meteorologist, I definitely get what you are staying (and have been saying) and personally, I agree with you.

That said, our electronic technicians work based on preventative maintenance tolerance values (i.e. within an acceptable calibration range) as you've surmised. For NWS/FAA purposes, the critical pressure value is the altimeter reading (as that is the pressure variable that pilots utilize), not SLP or Station Pressure.  Since the SLP falls within their PM tolerances, they consider the error which you've pointed out, as "noise" (i.e. too small of an offset to make a difference for any NWS/FAA SLP uses). As long as the value falls within tolerance, they unfortunately do not see the need to investigate further - as other maintenance/equipment issues take precedence.

While I would prefer the SLP bias that you've identified to be investigated and corrected, it is unlikely that the technicians will pursue this item further, for the reasons described above. In fact, I even sought the advice of  the technical specialist for observing equipment at our Regional HQ following your initial and second emails, and he concurred with our local electronic technicians.

I'm sorry I couldn't assist to resolve the issue that you raised.

Sincerely,
[Name withheld]

I thanked the NOAA Meteorologist for giving me the time of day and working so hard with me understanding and dealing with this issue. I learned a lot in this process. I also got to see some screenshots of the airport weather and METAR software. How nice it was to finally deal with an intelligent individual that took responsibility.


« Last Edit: September 04, 2018, 01:36:49 PM by galfert »
WS-2902A | ObserverIP | WeatherBridge (Meteobridge)
WU: KFLWINTE111  |  PWSweather: KFLWINTE111
CWOP: FW3708  |  AWEKAS: 14814
Tele-Pole flag pole is here (not installed yet)

 

anything