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January 2015 obs/disco/short range


AlaskaETC

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I would think strong CAA westerly winds would mitigate the UHI somewhat, but I'm sure DCA will be the warm spot.  

 

Actually did a small study a few years ago of whether wind could mitigate the UHI for DC.  Didn't find anything conclusive, unfortunately. 

The wind does have an effect on DCA and it will tonight=it will achieve a more accurate reading. You will not find BWI, IAD and Andrews coming in 10-15 degrees lower than DCA as the wind will homogenize things. Were it a clear and calm night, with current near 100% snow cover, then DCA would manifest it's inexplicable ability to overcome all of the atmospheric and surface condtions and report a bogus 15* low when IAD, BWI, Andrews and even Annapolis would be ranging 0 to 8.

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The 4pm DCA ob was a bit better at 24°.  Still, NW flow with fresh snow and it is reading the same as Ocean City, while Andrews, BWI and IAD are all around 20.  Now I sound like Tenman.

You sound like someone who is realizing that what I have long been talking about is in fact of merit.

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DCA is regularly 2 to 3 degrees warmer than Capitol Hill or other locations on the Mall, which are arguably even more urbanized.

 

There's a buoy  on the Potomac River, right near DCA, that I like to compare it with:

 

http://www.wunderground.com/MAR/buoy/WASD2.html

 

Even that buoy is usually about 2 degrees colder than DCA in the winter.  Right now it reads 21, while DCA reads 24.

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DCA is regularly 2 to 3 degrees warmer than Capitol Hill or other locations on the Mall, which are arguably even more urbanized.

 

There's a buoy  on the Potomac River, right near DCA, that I like to compare it with:

 

http://www.wunderground.com/MAR/buoy/WASD2.html

 

Even that buoy is usually about 2 degrees colder than DCA in the winter.  Right now it reads 21, while DCA reads 24.

Compelling. And that buoy is surrounded by 35* water.

DCA works for the FAA.

DCA is very vague about where the recording site is. Is it on or near the tarmack. Or is it right outside their office on the roof.

This air mass that we have right now is Way Too Powerful, and windy, and snow covered to be overwhelmed by the mysterious urban heat island effect; kinda like trying to say that striking a match really warms the interior of a 20'x20' room.

There is not a primary interest in getting it right for NWS or weather purposes.

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DCA is regularly 2 to 3 degrees warmer than Capitol Hill or other locations on the Mall, which are arguably even more urbanized.

 

There's a buoy  on the Potomac River, right near DCA, that I like to compare it with:

 

http://www.wunderground.com/MAR/buoy/WASD2.html

 

Even that buoy is usually about 2 degrees colder than DCA in the winter.  Right now it reads 21, while DCA reads 24.

 

the buoy is 21 and DCA was 22 at 4:52....There are a bunch of 20-21's around currently...even a 23 and a 24 though they are outliers...DCA isn't really that inconsistent with what's around

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Compelling. And that buoy is surrounded by 35* water.

DCA works for the FAA.

DCA is very vague about where the recording site is. Is it on or near the tarmack. Or is it right outside their office on the roof.

This air mass that we have right now is Way Too Powerful, and windy, and snow covered to be overwhelmed by the mysterious urban heat island effect; kinda like trying to say that striking a match really warms the interior of a 20'x20' room.

There is not a primary interest in getting it right for NWS or weather purposes.

 

Snowcover is not really going to mitigate the effect of UHI.  Buildings and asphalt are still going to absorb and emit heat. A couple inches of snow on the grass doesn't change that.  There is really nothing that mysterious about UHI.  We largely know how it works and it is a scientific fact.  I am more interested in the siting issue.  While there are rules and regulations in place, and I believe the instruments are calibrated according to protocol, there are probably various options on where they can site it.  And there may be places to site it that are more consistent with surrounding obs.  I think the recording site is on the roof.  I don't know how that affects things, but I imagine there are better places to site it.  

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Snowcover is not really going to mitigate the effect of UHI.  Buildings and asphalt are still going to absorb and emit heat. A couple inches of snow on the grass doesn't change that.  There is really nothing that mysterious about UHI.  We largely know how it works and it is a scientific fact.  I am more interested in the siting issue.  While there are rules and regulations in place, and I believe the instruments are calibrated according to protocol, there are probably various options on where they can site it.  And there may be places to site it that are more consistent with surrounding obs.  I think the recording site is on the roof.  I don't know how that affects things, but I imagine there are better places to site it.  

When the land is covered by 2-3" of snow, and the parking lots, and the sidewalks, and the temp is 25 degrees for 24+ hours then there is NO emitting of heat for there is no heat to be emitted and no method to emit it because it is blanketed. DCA is east of some office buildings, we are not talking about gigantic manufacturing and industrial plants, located on a strip of land off of a tree lined parkway, and next to a river. It's not Times Square NYC. A couple of strips of highway being exposed, and some office buildings do not, repeat do not, emit enough radiant heat to influence a valid temperature recording mechanism. I could, and will e-mail to a party if requested, provide the telephone number to the station. Call them and ask why they measure so much higher than the surrounding. I think you will find how you are responded to as very interesting.  I think it is jsut a matter of working for the FAA and not really being interested in getting it accurate from a weather observation point of view

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When the land is covered by 2-3" of snow, and the parking lots, and the sidewalks, and the temp is 25 degrees for 24+ hours then there is NO emitting of heat for there is no heat to be emitted and no method to emit it because it is blanketed. DCA is east of some office buildings, we are not talking about gigantic manufacturing and industrial plants, located on a strip of land off of a tree lined parkway, and next to a river. It's not Times Square NYC. A couple of strips of highway being exposed, and some office buildings do not, repeat do not, emit enough radiant heat to influence a valid temperature recording mechanism. I could, and will e-mail to a party if requested, provide the telephone number to the station. Call them and ask why they measure so much higher than the surrounding. I think you will find how you are responded to as very interesting.  I think it is jsut a matter of working for the FAA and not really being interested in getting it accurate from a weather observation point of view

 

I don't disagree about possible siting choices. I'm pretty sure it is on the roof.  As far as UHI, I think you are just inventing reasons that fit your narrative.  You don't understand how UHI works...

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I don't disagree about possible siting choices. I'm pretty sure it is on the roof.  As far as UHI, I think you are just inventing reasons that fit your narrative.  You don't understand how UHI works...

UHI is very real at Times Square.  It's very nearly a myth and/or excuse for DCA.

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The DCA sensors are to the east of the runways towards the river. Well documented and pictures are available.

One of the questions that one would have a very hard time obtaining an answer to is the transmission of any such sensor readings to the office. I have been told by the MIC that they do manually go out and take obs. I have also been told that in extreme weather they are focused on the FAA aspects and are not, for example, going to send someone out to "determine if it is 17* or 21* in order to satisfy weather weenies"

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