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A New Discovery?  The Chehalis River Fog Jet

A New Discovery? The Chehalis River Fog Jet

The high-resolution satellite tv for pc imagery yesterday morning revealed a transient, however fascinating characteristic:  a slender present of fog emanating out of the western portion of the Chehalis River valley.   This fog present then handed over Aberdeen and Hoquiam earlier than pushing out into the Pacific Ocean.

Here is the NOAA/NWS GOES satellite tv for pc picture round Eight AM Sunday that exhibits this superb characteristic.  You can see the fog accumulating within the Chehalis River valley after which jetting out to the west.  Just superb how this present was in a position to keep integrity for tens of miles.  About roughly ten miles offshore it misplaced its construction, with the cool, moist air producing a blob of low clouds.


If you look carefully, a weaker fog jet was produced on the exit of the Columbia River.    
Just as a reminder, right here is the Google terrain map for the area.  The Chehalis River Valley is effectively outlined with comparatively steep aspect slopes.  Cool air can drain from aspect valleys into the principle Chehalis channel, leading to cool air within the valley.   And if the air is moist sufficient, the air is cooled to the dew level, producing fog.
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Surface observations Sunday morning similtaneously the satellite tv for pc picture exhibits easterly (from the east) move at Hoquiam and temperature of 36F…and even cooler down within the valley in the direction of Montesano.   Cool, dense air escaping the valley was aided by a regional strain gradient with larger strain inland and decrease strain in the direction of the coast.

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The observations at Hoquiam Airport illustrate the climate circumstances throughout the passage of the “fog jet”.  The time is in UTC (identical as Greenwich Mean Time) with 1405 being 7:05 PDT.  The fog was solely over them for about an hour, with easterly winds of 7-Eight knots and temperatures within the mid-30s.

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High decision climate prediction fashions received a bit of this characteristic.  Here is the anticipated wind fields for 7AM from the UW 4/Three km runs (the grid factors are 4/Three km aside).  You can see the easterly move and a comparatively slender jet of robust winds.

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And the forecast for 9 AM, exhibiting floor winds and temperature (shading), signifies chilly air within the Chehalis River Valley and the plume of cool air transferring out into the Pacific.

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The a lot coarser NOAA/NWS HRRR mannequin (3-km grid) had a distinction resolution.  Here is the forecast visibility for a similar time.   A really weak plume of low visibility is popping out of the Chehalis River valley, however there’s a distinct plume and an offshore fog space related to the Columbia River valley.  The NOAA mannequin would not have the decision to correctly simulate the slender Chehalis River valley.

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Anyway, this characteristic is maybe a one on the meteorological Richter scale, however fascinating however, and take a look at of my occupation’s excessive decision fashions.

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