Davis Vantage Pro questions

1. Is anyone chasing with one of these mounted external ? - (meaning the integrated sensor suite with rain collector)
I feel I could get better temp readings / humidity readings RATHER THAN HAVING IT IN MY chase vehicle. By the way I have a mounting spot for it that would keep it safe, on the roof.

2. How high should my anemometer be from my roof top? And do I have to be driving north to get the correct direction? Is there something that I can do to get correct direction indications while mobile in all directions?

3. Should I ground this vehicle (chain or strap method) since I have this an other antennas on top?
Any thoughts on this would be appreciated.

bill
 
Bill,

For your anemometer, its best to have it a foot or two off the roof, and maybe extended up and out in front of your windshield. Doing this, the airflow over your windshield and roof doesnt affect the reading of your anemometer. I dont think that Davis makes a serial compass (allows you to get a correct North reading at all times), you may want to call and ask them though, couldn't hurt. Hope that could help a bit.
 
2. How high should my anemometer be from my roof top? And do I have to be driving north to get the correct direction? Is there something that I can do to get correct direction indications while mobile in all directions?

bill

I think Greg Stumpf told me the research they did on the mesonets for the vehicles the NSSL was using. the ideal height was 3 feet? Maybe he can jump in and correct me if I remember that wrong.
 
We have ours on a pole that can be raised up to 12 ft. The other sensors are mounted on the roof. You can see a pic of the pole mount at www.wxtech.com
 
The Anemometer should be positioned about 46 inches or so above the roof of the vehicle. This will get the sensor out of the the artificial low created by a vehicles slip stream (see Bernoulli Effect).

Remember, even while stationary the wind traveling over the vehicle will still create the effect. I believe the NSSL Mobile Mesonets figured 1 meter for theirs during IHOP and Vortex. I know we discussed this at length last fall, so you might try a search on "bernoulli" and see what that comes up with.

My sensor sits on a mast at the rear of my truck. It's normal travel position is about 18 inches above the camper shell. The mast will extend another 2 feet above that for a total of 42 inches above the vehicle top (this was by accident and not design!) Davis doesn't make the auto correcting compass that integrates with the different weather stations that I know of (at least I haven't seen it on their web site).

John
 
To get wind measurements while in motion will require a good anemometer with a vane with good resolution. Also you will need a gps. Import all the data into a computer and correct for the motion of the vehicle.
 
well thanks for the input about the wind - what about grounding the vehicle - waste of time? or isnt electruction much of an issue?
thanks
bill
 
well thanks for the input about the wind - what about grounding the vehicle - waste of time? or isnt electruction much of an issue?
thanks
bill

I have never grounded one. If you think about it, lightning just traveled through several miles of air (one of the best insulators there is), I don't think anything you do in the last few inches (or feet) is going to make much of a difference in the path it choses to take.

I have seen cars in the past that were struck and the lightning found ground by exiting the wheel through the tire (blowing it out of course).
 
I have to agree with David on this one. What are you going to do while your moving? Drag the chain behind you? Your chances of getting struck are rather small to begin with, but getting close to a Thunderstorm increases those odds. Getting out of the vehicle increases the odds even more, grounded or not. I would figure that grabbing a piece of metal to ground your vehicle is going to increase the odds even more.

Excercise due safety! Listen to your instincts here. If your brain is telling NOT to get out of the vehicle, DON'T! Yhere are several people on this board that have had near misses and are still around to tell about it. I've had lightning close enough to shut down and blow out all the electronics in the truck. I wasn't hurt.

John
 
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