To understand the setup for this event, one has to look to the Hawaiian Islands where two streams of tropical moisture are being injected into the mid latitudes. In particular, there is a subtropical ridge centered just to the east of Hawaii that is pumping moisture directly from the tropics over the islands that is confluent with a potent river of subtropical moisture associated with a trough to the northwest of the Islands (click to enlarge).
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| 1600 UTC 16 Jan 2012 precipitable water (contours every 5 mm) and 925 mb wind vectors (click to enlarge). |
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| 1200 UTC 16 Jan 2012 precipitable water (contours every 5 mm) and 925 mb wind vectors forecast loop valid through 0000 UTC 21 Jan |
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| Source: NOAA/NWS/CPC |
Bottom Line: The atmosphere is locked and loaded. Buckle up for a wild ride.
Surface obs are showing southerly winds and dewpoints in the lower to mid 70s around Oahu and Kauai. Looks like a pretty warm AR type of event. I'm afraid some of the Oregon and California ski areas might get a good bit of rain, but ours are probably high enough in elevation to avoid that.
ReplyDeleteWe're going to see periods with high snow levels if the GFS verifies. The current forecast puts 700-mb temperature peaks at -3C at 1800 UTC Thursday, and 0C 0600 UTC Saturday. The latter would give us a freezing level near 10000 ft and a snow level near the base of Alta. Of course, these are the periods with the warmest temperatures over the next several days, but the ups-and-downs are going the be happening on the warm side of climatology.
ReplyDeleteDew points in the mid-70s are consistent with the tropical fetch related to that very low-latitude anticyclone. How important that circulation feature is to this event is unclear, but I suspect it's got to be helping some.
Some of the forecasted snowfalls are just incredible. Mt. Rainier is looking at potentially over 100 inches of snow in just three to four days.
ReplyDelete