Southeast Alaska’s Dry Spot

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No, the rain gauges are not malfunctioning, (although that has happened before at some weather stations). It has been very dry in the north end of the Inside Passage. There is a natural dry pocket in this rainforest to the point of really stretching the term rainforest. This year the first part of summer has been drier than usual over the region meaning the driest areas are getting pretty dusty. There have been drier years, but not many.

Here’s the precipitation data for the past three months in map form, then more completely in table form–arranged top-bottom in case you need some help in identifying what towns the numbers on the map belong to. Look at the large variation in a bit over a hundred mile radius, with the dry bulls eye over Skagway:

nrthrn-SE-AK-precip-map

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The “years” column is the number of years of data that went into the average and extremes.

What’s behind the dry spell/dry spot?

Check out this recent surface map, a very recurring pattern this summer. The large high over the North Pacific is a semi-permanent summer feature and is in fact officially called the North Pacific High. Strong highs like this are effective at keeping frontal systems from impacting Southeast with any strength or regularity. That front slicing down through the interior and Cook Inlet brought about a quarter of an inch of rain to Anchorage and other areas, but fell apart (as most have) while trying to rake across the top of the high, and the panhandle got almost no rain.sfcmap18

However, for coastal stations, highs do not mean all is dry and sunny, for they push the ample oceanic low clouds (commonly called the marine layer) onshore, bringing not only clouds, but a mix of fog and drizzle and a smattering of light rain as the moisture gets wrung out of the marine air by our abrupt coastal mountains. But rainfall will stay below average with this kind of pattern. Bet why are the northern inner channels so much drier? They are protected from the both the low marine layer and the orographic (mountain induced) precipitation by the first several ridges of the coastal mountains. In a sense Skagway and Haines are not very coastal, but a little more like the interior. Everything is in shades in the weather business.

What’s next?

Will the dry weather continue? Climatology indicates that things must start getting wetter fairly soon. Even in super-dry 2009 the rains came in August and September, playing a strong catch-up game in the area. Such is the flip-floppy nature of the weather in much of Alaska.

The computer models are not showing a major shift for the next week anyway. There is some weakening of the pattern and there will probably be a little more moisture than we’ve seen, but probably very little in the protected areas discussed above. Our gardens could use a lot more than I think we’re likely to get over the next week. The real weather is the continuing strong lows moving into the Bering Sea, an example of which is pictured in the surface chart above. The west coast is getting way more storms than they probably want. The longer range maps from the Climate Prediction Center are not wanting to deviate from climatology (in other words they’re not sticking their neck out for above or below normal precipitation), except for continued wetter than normal for the next two weeks for the southwest part of the state.

The big issue for Haines is the upcoming Southeast Alaska State Fair coming up in two weeks. Despite Murphy’s laws on rain, its too early to say whether the fair will be warm and sunny, cool and rainy or somewhere in between.

 

 

 

I’d love to hear any comments or questions on this article, or any weather topic. Click on “comments” below, and let me know whether your hoping for rain or sun where you live.

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