Tuesday, June 21, 2016

Wet Summer So Far

The scene is wet and breezy in Fairbanks today, as showers move quickly through the area on a brisk westerly flow.  This is the 14th day with measurable rainfall so far in June, which is the most since 1994; only 7 days have remained dry this month.  The month-to-date rainfall of 2.25" (not including today) is the 3rd highest on record, behind only 1955 and 1977.



The chart below shows that year-to-date precipitation is now about an inch above normal, which is a huge turn-around from the record dry conditions at the beginning of the year.  The difference is that we no longer have El Niño-related low pressure in the North Pacific, keeping dry southerly flow over Alaska; this month so far we have seen quite the reverse, with above-normal 500 mb heights south of the Alaska Peninsula and low pressure over the Beaufort Sea (see the map below).  Unsurprisingly Barrow is also seeing a wet summer so far, with a record 10 days of measurable precipitation and near-record 0.61" of total precipitation already this month.


Here is today's 3am AKST 500 mb analysis from Environment Canada; note the strong shortwave disturbance over the North Slope.




This year is now wetter to-date than any of the past 5 years in Fairbanks (see below), but the record summer rains of 2014 got under way at about this date, so it's highly unlikely that this year will remain ahead of that year for much longer.


With respect to temperatures, the excessive warmth of spring has been replaced by some modestly negative anomalies at times in recent weeks.  Only 16 days so far this year have reached 70°F, which is the lowest number since 2008; but this is also equal to the 1981-2010 normal, so the coolness could hardly be called unusual except in comparison to recent years.


14 comments:

  1. More rain often means fewer forest fires. Choose your inconvenience.

    Still it's a great place to live if the flocks of seasonal Snowbirds escaping the heat of the USA's SW states are any indication. I know a few and they are pleased to be here.

    Is there a relation between our current weather and the Lower 48's heat?

    Gary

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    1. Good question Gary. Wavelengths of the upper flow are shorter in summer, and anomalies are weaker, so the spatial scale of teleconnections is (I believe) smaller. I'm inclined to say yes, there is probably some connection, but it wouldn't be as strong as spatial correlations across western North America in winter.

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  2. It looks like the post-winter-El Nino cool summer is happening after all, as was recently discussed (http://ak-wx.blogspot.com/2016/05/possible-end-to-warmth.html). If this trend continues for a couple more weeks, could we make the prediction of a cold rest of the summer?

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    1. Not with any degree of confidence from a purely statistical standpoint. Looking at the correlation between June temps and July-August mean temps, there is only a slight connection on the cold side, i.e. a cold June is only weakly indicative of a cold June-July. On the other hand a very warm June is usually followed by a warm July-August.

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    2. Eric, through the 21st, Fairbanks is 2.4°F below normal for June. Annette Is. is 0.6°F below normal and McGrath is 0.1°F below normal. Every other major climate site is either above normal or way above normal for the month of June. Plus, all the mid- and long-range forecasts are strongly suggestive of above normal temps in July-August. It's premature to say that a cool summer is happening.

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    3. Thanks Richard and Brian.

      I was hoping that we would have a cool summer. Hot summers ~~ forest fires == bad. However, if Fairbanks is being anomalous (probably because of clouds) then I suppose that forest fires are inevitable. I'm still betting on La Nina cooling things down later this year, though.

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  3. Big thunder and lightning today in Interior Alaska. Will be interesting to count the strikes when it's all done in a day or two. We may smell smoke later.

    Gary

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    1. Indeed Gary, the radar shows intense storms - quite impressive. Looks like some spots are getting very substantial rainfall - hopefully no flash flooding.

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    2. Yes there's lots of rain that started SW>NW this AM. Have a look at the time series (those new to this select "Loop" per direction) of the various FAA webcams (http://avcams.faa.gov) for Alaska to see the development. Something like that should be retained for future review but don't know if they do.

      Gary

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    3. http://fire.ak.blm.gov > Maps > Lightning information for a map of the strikes.

      Gary

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  4. I'd be curious to see if wetter summers lead to cooler night time lows on clear nights following a hot day (80+?). I've noticed this difference in Juneau where it cools off quite well at night despite high daytime temps but that may have to do with the location of cold air drainage there as well. It's intuitive to think that in Fairbank's case moist ground would be cooler and also evaporation at night would cause a shallow surface inversion in the valleys for cooler nights the. It's dry counterpart. Thoughts?

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    1. Edit to last line: versus it's dry counterpart. Thoughts?

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    2. Interesting question Mike, the data will reveal the answer. My instinct says that higher humidity will help keep overnight temperatures higher compared to dry conditions - moist air "traps" more infrared radiation - but high-latitude behavior might be different. I'll plan to look into it.

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