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+--- Thread: Kona Low Alert (/showthread.php?tid=17899)
Kona Low Alert - Ino - 12-14-2016
This is an Alert as the weather pattern is very complicated and we’ll have severe wx nearby so heads-up.
Very cold air aloft will plunge South over the North Central Pacific late this week and weekend. A strong Kona Low will develop about 600 miles North of us;
https://en.wikipedia.org/wiki/Kona_storm
The coldest air will stay to our North/NW. The progression of the cold air can be monitored here;
http://tinyurl.com/gsrpmqn
The wx models have really struggled with where this Low will go. So confidence in the forecast is low.
The heaviest convection looks to stay to the East of us- where the warm and cold air will be mixing it up the most.
http://tinyurl.com/z4vqs8k
Look for SW winds to ramp up on Thurs./Fri. These winds will be counter to our prevailing wind direction and can bring wind damage at lower wind speeds than one might expect if the high winds were coming at us from our prevailing E/NE direction;
http://www.prh.noaa.gov/hnl/graphics/pfm/winds_big_HILO.png
Pressure gradients are not expected to be that high here but the situation bears monitoring- summits will be very windy;
http://www.stormsurfing.com/cgi/display_alt.cgi?a=hi_slp
A frontal passage will be possible here Fri./ Fri. night and Sat. There’s a chance that the front will stall out right over us.
Early next week as the Low weakens (cold air warms, modifies) it is predicted to move to the West of us and when this happens it could draw the heavy convection that was to our East back over the top of us as the trades return-Yeah!.
Best chances for Thunderstorms here will be Fri./ Sat. as cold air aloft reaches it’s coldest over us at that time. Freezing level (FL) could drop as low as 10.5k here. Haleakala on Maui might even get snow. Remarkably the FL just a few hundred miles N/NW could reach as low as 6k!!
Prepare and enjoy the show!
RE: Kona Low Alert - Kapoho Joe - 12-14-2016
Fantastic work Ino, mahalo!
RE: Kona Low Alert - TomK - 12-14-2016
We're expecting winds to approach 100mph at the MK summit this weekend with night-time temperatures near 20F. Can't wait to see what the windchill values turn out to be*.
*Not sure if windchill calculations work for winds that high. Ino?
RE: Kona Low Alert - Eric1600 - 12-15-2016
quote:
Originally posted by TomK
Not sure if windchill calculations work for winds that high. Ino?
The movement of the air increases the loss of heat by convection, so your face cools down faster (faces are specifically part of the model). The altitude doesn't really matter too much even though air density is less so convection is a little less.
Chill Factor: -8.7 F (@20F and 100mph wind)
Using: https://www.weather.gov/media/epz/wxcalc/windChill.pdf
For more detail http://journals.ametsoc.org/doi/pdf/10.1175/BAMS-86-10-1453
RE: Kona Low Alert - macuu222 - 12-15-2016
One of the few times when puna has beautiful weather and Kona has clouds and rain! [8D]
RE: Kona Low Alert - Ino - 12-15-2016
Mahalo for the links Eric1600
Here’s a wind chill calculator;
http://tinyurl.com/h29l9mn
I can’t find any resource to describe the effect air density has on wind chill. Might be time to develop a new wind chill chart. Last one was revised in 2001 and IMO air density would have to be a factor as the air thins so much as you go up and I would think that less density=less effect.
Check out the other calculators- like Love.
These conditions are going to bring a chance for lenticular clouds to form over or near the summits of both Mauna Loa and Mauna Kea, especially Fri. and Sat. evenings and nights.
Except for the vog part it's nice to see a weather role reversal. Go Puna!
RE: Kona Low Alert - Kiana - 12-15-2016
Mahalo Ino, as always love reading your posts. Weather is so interesting, and I appreciate all of the information you share. Better than the usual forecasts! Looking forward to the next one.
RE: Kona Low Alert - TomK - 12-15-2016
Apologies, I think my question turned out to be a little ambiguous! When I said high, I should have said strong, although now I'm curious if altitude and density will make a difference.
The reason for my question is that I recall reading something, somewhere, that the current windchill formula broke down for winds above a certain strength. However, I've not been able to find a reference, so may just be misremembering.
RE: Kona Low Alert - alaskyn66 - 12-17-2016
Tom.. having spent 20 years in Alaska, in Temps as low as -50F with winds bringing the wind chill down to -70.. it doesn't really matter after a certain point.wind chill at -70 will freeze your skin just as fast as -50. Humans can only withstand freezing air For so long.( minutes at those temps).. before skin starts freezing.
"It does make sense that the wind's impact and windchill effect would be reduced. Less air density = less mass = less force pressing on you and less less convection of heat.
Simplified, fewer atoms/air molecules ... less effect."
( regarding high altitude)
Windchill only has an effect if you have exposed skin..
RE: Kona Low Alert - HereOnThePrimalEdge - 12-17-2016
Windchill only has an effect if you have exposed skin..
I lived for many years in an old farmhouse on an exposed ridge top, heated with wood. When the wind was howling on winter nights, it definitely had an affect on the size of my woodpile. If I wanted to keep the pipes from freezing and keep myself warm It required burning substantially more split oak when the wind kicked up to 30 mph, than on a calm night. I'm sure you've noticed that in Alaska too, alaskyn66. Unless you were fortunate enough to have a thermostat hooked up to an automatic source of heat.
"One may pretend knowledge of philosophy more successfully than that of arithmetic." -Last Aphorisms (or how about, one may pretend knowledge with an opinion more successfully than with facts)