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June 2014 Obs and Disco


wxmeddler

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Getting back to the DCA thing, this morning at 5:52am Andrews was 60/59 or 99% and all other stations 95%+ yet DCA 68/63 or 84% and that is even less pronounced difference than often occurs. What sort of drying mechanism is in place there? Is the UHI in effect like a giant smoker lid, like on a grill, that somehow thwarts the cooling and evaporationsal forces of tons and tons of atmosphere???

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Getting back to the DCA thing, this morning at 5:52am Andrews was 60/59 or 99% and all other stations 95%+ yet DCA 68/63 or 84% and that is even less pronounced difference than often occurs. What sort of drying mechanism is in place there? Is the UHI in effect like a giant smoker lid, like on a grill, that somehow thwarts the cooling and evaporationsal forces of tons and tons of atmosphere???

 

this is a great example of the misuse of RH vs other measures of atmospheric water vapor -- you're looking for some "drying mechanism" when in fact given the obs you cite here, DCA is the station with the greatest amount of actual water vapor -- and this "smoking gun" you think you found actually disproves your hypothesis of an "issue" with the obs at DC.

 

Let's assume for a second that the background synoptic scale moisture field over the DC metro region is the same at all obs locations -- let's just say it equates to a surface dewpoint of 59 -- this would lead to a RH value of 99% at andrews and a RH value of 73% at DCA (assuming a surface temperature of 68, as cited above). Now the difference in surface temperatures between DCA and Andrews is easily explained by UHI as been shown to you countless times -- so given that you know UHI plays a role at the DCA ob site, could you explain why you'd expect RH to be constant across the region? And if so, where does this added water vapor needed to get DCA up to 68/67 come from (to be consistent with the RH at Andrews) -- nighttime available energy for evaporation is negligible compared to daytime...

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Furthermore if you look at mixing ratio which is grams of water vapor per kilogram of air, the mixing ratio at DCA is 12.2 g/kg and at Andrews it is 10.6 g/kg. So how is some " drying mechanism" responsible for the difference in temperature?

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I'm probably wrong. Ensembles haven't been very good at higher latitudes lately. Take away that ull and we can sweat missiles and drink evening air.

On a persistence note, we have yet to establish any anomalous lasting warm pattern all year. They come and go when they do set up. On a climo note, were moving into primetime for a shot at triple digits. On a personal note, I despise Bermuda highs like 33 and rain.

Bob Chill > StudentOfClimo

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Bob Chill > StudentOfClimo

nah, plenty of time to flip to a brainmelting roasterama

Right now GEFS and Euro Ens are in really good agreement for the next couple of weeks on the overall evolution for north america. I don't pay as close attention to height patterns in the summer as I do in the winter so I'm not sure if it's an unusual config for early July but it looks a bit unusual to me. Elongated ridging in the southern 3rd with the center focused in the middle of the country. This leaves our area in what appears to be a long duration w-nw upper level flow. Mid level flow looks favorable as well at times.

If the setup verifies, we can expect normal to slightly above on temps but dews would likely be pleasant more often than not.

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Mentions on twitter of a hot July 4th

Yeah, I've seen a few of them like Tony Pann.  Not sure what he's seeing.  As Bob has mentioned, it doesn't look like a cool pattern, but not an uber-torch either.  

 

Last night's 0z runs have us in W-NW flow with a little bit of troughing

post-51-0-90318000-1403628469_thumb.gif

 

Today's 6z GEFS mean looks fairly similar

gefs-mnsprd_namer_252_500_vort_ht.gif

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Yeah, I've seen a few of them like Tony Pann. Not sure what he's seeing. As Bob has mentioned, it doesn't look like a cool pattern, but not an uber-torch either.

Last night's 0z runs have us in W-NW flow with a little bit of troughing

I'm not seeing signs of extended m-u 90's anywhere but low 90's are really easy in July. I'm not sure what everyone considers "hot". 92-93 in full sun is plenty hot even with dews in the l-m 60's. If July 4th is in the low 90's it will be remembered as a hot day because most everyone spends a good portion of the day outside. 92 is only a couple degrees above normal though.

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I'm not seeing signs of extended m-u 90's anywhere but low 90's are really easy in July. I'm not sure what everyone considers "hot". 92-93 in full sun is plenty hot even with dews in the l-m 60's. If July 4th is in the low 90's it will be remembered as a hot day because most everyone spends a good portion of the day outside. 92 is only a couple degrees above normal though.

 

I can live with 90 under dry/low dew point conditions. Anything above 85 with humidity is disgusting for me.

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Ensembles have been trending towards more ridging early next week in front of the trough/ull tracking through southern canada / n plains. We might score some 90's in the sun-wed time frame.

Overall the look is pretty boring for the next couple weeks. Signal for a low humidity 4th is still holding on. Pretty far out of course.

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