The cooler weather continues unabated and that has all us locals smiling once again although we would sure like to see more snow…as in a few feet more! Still and all its been wonderful to feel the cold once more. With this recent streak of cooler temps – this morning was the first below zero temp I’ve recorded since December 27th’s -15.7 F and that makes 40 contiguous days across one of the two coldest months in Talkeetna – has come clear weather and heavy morning frost. I thought I’d seen ‘heavy’ frost in the lower 48 but once again Alaska has trumped my previous perceptions. We’ve seen eight straight days of clear weather and each day the frost has grown more and more mainly because daytime temps have remained in the teens with night-time lows slowly dropping from the single digits to around 0 F. As this occurs the frost builds across the days to form some amazing structures as evidenced by the following images:
Ice crystal formation on the railing of my back porch
A screw on my back porch railing pushed up by the repeated freeze/thaw cycles
A frost sheathed small tree in my back yard
The build up of frost can and does produce beauty equivalent to the aftermath of an ice storm but without all the resultant damage. It’s especially pretty in the sunlight. In the lower 48 the sun would normally melt off any frost but its been cold enough recently and the sun remains at a low enough angle that this hasn’t happened. Given we’re forecast to remain a bit cooler than normal across the next seven days there’s little doubt the frost will continue to grown with the passing days. Once more my new home both surprises me and amazes me with its unexpected beauty!
Anyone reading my previous blogs is aware I am a ‘weather weenie’ in that all things meteorological fascinate me and I love to watch the skies and develop an ability to guess the near term weather based upon current conditions. Having done this for many decades in the lower 48 I was actually pretty good at it; sure, as I moved to different areas I had to fine tune my ability but overall it’s served me well. At least until I moved to Alaska; now I can add learning to predict upcoming weather by watching the skies and immediate weather data as yet another area I have much unlearning to do. I’m okay with this concept because, after all, its dabbling in weather and I love that but it’s also fun to just stretch one’s self. I have a feeling I’ll be getting both in spades across the upcoming years; yes, it takes years to really develop and refine this ability because so much is based upon experience.
The past eleven days has shown me just how extreme Alaska weather can be in terms of data; interestingly enough, the actual weather has not always reflected the extreme data. On December 3rd at 03:20 AKST I recorded a barometric pressure of 1,042.872 Mb (30.796″ Hg); this is the highest barometric pressure I’ve ever experienced. The accompanying weather conditions were classic for extremely high pressure; crystal clear azure skies, no wind and cold temps. And now, just eleven days later on December 14th, I recorded a barometric pressure of 977.413 Mb (28.863″ Hg) at 00:10 which is the lowest I’ve yet experienced. In this case what I would’ve expected in terms of weather conditions was completely wrong. Given such low pressure one would normally expect howling winds and snow falling by the foot because the air temp was around 18 F. However, while I did record NNE winds to 16 mph on the evening of the 13th by 01:00 AKST on Saturday, December 14th the winds were calm and have remained so. We did pick up 3.1″ of snow overnight but that doesn’t even merit mention from NWS. As an aside I noticed that Wayne County in SE Michigan is under a Winter Storm Warning and expected to see a total of 2 to 4 inches of snow; NWS serves all fifty states and uses common terminology in their products like forecasts, advisories and warnings yet said common terminology is obviously ‘tweaked’ by location. Up here a snow event producing 5″ to 10″ of snow might get a Winter Weather Advisory while the same in SE Michigan would get at least that Winter Storm Warning and probably a Heavy Snow Warning as well. Regardless, if such low pressure occurred anywhere in the lower 48 one would expect high winds and copious precipitation.
To put these pressure values in some perspective I’ve taken some pertinent information from the http://www.noaa.gov website. “The accepted world record maximum “sea-level equivalent” pressure for stations below 750 meters was observed at Agata Lake (66 degrees 53 minutes N; 93 degrees 28 minutes E) in Siberia at 1200 GMT on 13 December 1968: that record is 1083.8 mb (32.00 inches) as noted on the site at http://wmo.asu.edu/world-highest-sea-level-air-pressure-below-700m. The station elevation is 263 meters; the temperature was -46 degrees C. Extraordinarily high surface pressures observed nearby at the same time corroborated the record measurement. Seven stations recorded pressures in excess of 1070 mb, indicating that the pressure at Agata was in keeping with the general situation over the area.” Here’s what that same site says regarding the minimum barometric pressure: “The lowest sea-level pressure ever recorded 870 millibars (or 25.69 inches of mercury) in the storm Typhoon Tip. It was recorded 300 miles west of the island of Guam in the Pacific Ocean at latitude 16 deg 44 min north, longitude 137 deg 46 min east, on Oct. 12, 1979. A hurricane hunter plane flying through the Category 5 storm’s eye of Wilma, on October 19th of 2005 found a minimum central pressure of 882 millibars, this would be an all-time record for an Atlantic storm surpassing the record set in 1988 by Gilbert which was 888 millibars (Mb). The purist in me demands I point out that water seems to enhance low pressure mainly because said pressures occur in hurricanes (or typhoons). So what’s the lowest barometric pressure ever recorded over land? “Here’s the lowest pressure ever recorded over land: 892 Mb (26.35 ” Hg); Craig’s Key, Florida, eye of the Labor Day Hurricane, 2 September 1935.”
Another way of getting perspective on the low pressures is to note that a ‘typical’ Category 2 hurricane would see pressures around 995 Mb while an ‘average’ Category 3 hurricane would see pressures around 960 Mb. Given this the low pressure we’re now experiencing is in the realm of a Category 2 storm and that’s pretty impressive given its occurring over land and in winter with the cold temps. I find it amazing that within less than two week’s time I’ve experienced both the highest pressure and the lowest pressure I’ve ever seen. This really speaks to the extraordinary extremes that seem to be the foundation of Alaskan weather. And I do love such impressive shifts in the local weather as it really does keep it interesting. Just another reason I find ‘The Final Frontier’ such an amazing place in which to reside!
Bottomed Out Aneroid Barometer; actual pressure was 28.84″ Hg