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The great July heat wave of 2013


Ian

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Glad you posted that, JT. I noticed the PWS near my house had a DP of 79... I had to do a double take

 

 

79 is still on the upper range of the possibilities for a true reading but more likely it's near 73-76. There are really two main factors that can go into bogus dew point readings. A is that dew point is really the hardest measurement of the basic weather variables to make a accurate instrument for. B is that the weather station site greatly effects dew point on a day like this because of evapotranspiration, and if the station is too close to vegetation that that can throw the dew point off. My guess is that for most stations it's a bit of a and a bit of b.

 

74-75 max and probably lower..

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79 is still on the upper range of the possibilities for a true reading but more likely it's near 73-76. There are really two main factors that can go into bogus dew point readings. A is that dew point is really the hardest measurement of the basic weather variables to make a accurate instrument for. B is that the weather station site greatly effects dew point on a day like this because of evapotranspiration, and if the station is too close to vegetation that that can throw the dew point off. My guess is that for most stations it's a bit of a and a bit of b.

 

Lucky for me and my station, roof's don't evapotranspirate and the fan on the radiation shield helps mitigate the "A" effect.

 

Thanks for the explanation!

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Everyone freaks out over a warm day. I shutter to think what happens down here when it really hits the fan.

I think mid 100s are kind of the highest temps we would ever see around here i.e. 105 or 106. I don't think temps above that would be possible here, especially above 110.

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74-75 max and probably lower..

So the 77 dew at KMTN is incorrect because of reason A or B?

I thought the dews were genuinely higher because of the proximity of the bay.

Now I'm confuzzled... Please unconfuzzle me. :)

Droid Bionic 4G LTE

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So the 77 dew at KMTN is incorrect because of reason A or B?

I thought the dews were genuinely higher because of the proximity of the bay.

Now I'm confuzzled... Please unconfuzzle me. :)

Droid Bionic 4G LTE

 

That is the exception. The air over the bay definitely does have higher dew points (79-84) with water temps now in the lower 80's with 100% humidity at nights and not much lower during the day. What we were talking about before was more inland areas. The original post I made touched on this fact when an easterly river breeze jumped my dew points and thus my heat indices.

See the CIBIBS bay buoy site for bay weather info, though I find it rather silly that they give air Temp/RH/Pressure but not DP.

 

edit: The dew point at Thomas Point lighthouse (10 mi SE of Annapolis) is 85°F

post-741-0-64083000-1373923055_thumb.png

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