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  1. #1
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    Default weird temp spike

    I'm looking at the graph from yesterday (6/28) and there was a weird temp spike from 6-9AM, then a sharp drop. Is that real or an artifact? Some breeze up from the valley?

    Dan

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    Here is a view of the graph for reference

    Brad (a 6288 club member)
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    They have been installing new equipment, maybe that had something to do with it?
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    Looks real to me. They probably broke out of the clouds or the sun was hitting the shack. The sharp rise corresponds with sunrise. Then the temp fell back to the dewpoint as the summit clouded over.

    Whatever happened the graph looks realistic. I'm not sure I'd use the word "sharp" either. The temp rise took place over 4+ hours.
    Bill
    Next up: Vermont City Marathon: May, 2011
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    A couple of weather alerts just came thru - heavy rain across NH - 1/2 inch hail - high winds up to 35 mph. Talking about 1 1/2 inches of rain in 30 minutes.

    I hope no one is out hiking this morning!
    Brad (a 6288 club member)
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    Quote Originally Posted by Brad View Post
    A couple of weather alerts just came thru - heavy rain across NH - 1/2 inch hail - high winds up to 35 mph. Talking about 1 1/2 inches of rain in 30 minutes.

    I hope no one is out hiking this morning!
    According to the radar it is coming your way. Probably in less than an hour.
    Steve
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    The weird spike is not from instrument tampering, time of day, or sunlight vs. clouds vs. fog. This looks like a classic frontal passage (FROPA in METAR code). Since I was bored today, I did a little investigating like I used to do when doing consulting meteorology for court cases. First take the site closest to the incident which in this case was the summit of Mount Washington, which worked out great since there is a station there. Grab 48 hours worth of data and focus the search down to 24 hours with the window of interest inside of it. Then grab three triangulated stations around the site. In this case: Berlin, NH (North), Whitefield, NH (Northwest), and Fryeburg, ME (Southeast). All stations in the same time frame showed a warm up and cool down of about 10 degrees during the morning hours peaking at roughly 11 am EDT to noon and then declining for the rest of the day until beginning to warm once again. Looking at weather maps from this day and today and from personal observation living at the base of the mountain, I can say that this spike was from a quasi-stationary front from the north on the 28th. Warmer air rode ahead of the front with colder northern air moving down after the front. Things then warmed again on the 29th as a result of a warm front that passed this morning. And it should be noted that although our digital thermometer we use for the auto-road display (the display with the graph in question) showed a max temperature of about 62.5F, the actual high for the time period was 59.18F according to our observers sending out the METAR’s. There are reasons behind this but for another time. Hope this helps. And “Bill O” said it best; it isn’t really sharp when spread over 4-6 hours warming and about 2 hours of cooling. To see a sharp decline, check the graph after a severe thunderstorm.
    Ryan Knapp
    Staff Meteorologist/Night Observer, KMWN (Mt Washington Obs., NH)

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    Cool - so to speak.
    Brad (a 6288 club member)
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    http://public.fotki.com/MWO/saved/2012/ MWO image & video archive site 2006-2012

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    Thanks Ryan...
    Last edited by Bretton Woods Brat; 06-30-2008 at 10:16 AM.
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