Watching The Hudson Bay Low, Potential For Major Arctic Blast

Well a few blogs ago I talked about the bitterly cold air locked up over northwest Canada and much of Alaska.

Some of the long-range forecast models show the Hudson Bay low pressure strengthening as we head into next week.

Now keep in mind the circulation around a low pressure is counter-clockwise.

So what this would do is as it strengthens, or grows in size, the circulation around the low pressure would pull down a pool of that bitterly cold air on the west side, putting locations along and east of the Rockies in the deep freeze.

The heart of the coldest air would slide into the upper midwest, where we usually see it. (i.e. the Dakotas, Minnesota, Iowa, etc.)

There have been so many comments left on the blog over the past few days. I love it! Keep the chat going.

One comment talked about the flooding rains in the southeast. Both Chattanooga and Huntsville set daily rainfall records on Tuesday.

Several rivers and streams are out of their banks in the Tennessee River Valley.

Flooding is also taking place in Washington and Oregon.

After weeks of heavy rain and snow, and storm after storm, the Pacific Northwest is simply waterlogged.

They are currently getting moisture via the Pineapple Express, which is visible on the satellite picture linked below.



See the fetch of moisture?

Because it flows from the tropics and the vicinity of Hawaii, meteorologists have nick named this pattern the "Pineapple Express".

Wintry weather can be found in the northeast, where once again, an ice storm has cut power to several thousand residents of that region.

Here in Colorado, along the Front Range and in the Denver metro area, we're holding onto our hats as a downslope windstorm impacts the region.

In Boulder County, the winds have blown power lines down and started some large wildland fires, placing thousands of homes in danger.

Here are some wind gusts clocked so far...

Mt. Audubon (Boulder County) -- 107 MPH

Berthoud Pass (Clear Creek County, near Winter Park) -- 101 MPH gust, sustained at 89 MPH

Northwest Boulder -- 87 MPH

Evergreen -- 85 MPH

Rocky Flats (between Golden, Boulder and Arvada) -- 81 MPH

South Ft. Collins -- 75 MPH

Aurora -- 47 MPH

Denver -- 41 MPH

Back to the blog comments, another comment someone left was asking me to talk about the National Weather Service forecast discussions.

If you have never read one, they often use alot of acronyms, weather jargon and are written with incomplete sentences.

A forecast discussion is simply the forecaster(s) at your local weather office, documenting his/her mental forecast process, much like you might document minutes from a meeting at work.

It usually has 3 parts -- the now, the short-term (meaning days 2-3) and the long-term (days 4-7).

They come out twice a day (one in the morning, approx. 4 am local time) and again in the afternoon (approx. 4 pm local time).

If there is breaking or rapidly changing weather, the office may issue updates at any time.

I guess the best thing for me to do, as far as teaching you how to read one, is to have you send me examples and let me "decode" them for others.

The following is a clip from the forecast discussion out of the Quad Cities (Iowa/Illinois) National Weather Service offices.

TUESDAY AND WEDNESDAY...LOWERED TEMPERATURES BY 5 TO 10 DEGREES AS
ARCTIC AIR CRASHES IN WITH 850 MB TEMPS OF -15 TO -25C WITH FURTHER
LOWERING OF TEMPS BY 5 OR MORE DEGREES SUGGESTED. KEPT DRY ATTM BUT
COPIOUS FLURRIES AND LIGHT SNOW POSSIBLE WITH NW WINDS OF 20 TO 35+
MPH SUGGESTED FOR A VERY COLD PERIOD OF ARCTIC WEATHER.

Translation : Tuesday and Wednesday -- the forecaster is saying he has lowered the forecasted temperatures by 5 to 10 degrees and computer models show arctic air invades the region. The 850 millibar temperatures (5,000 feet above sea level) are forecasted to be in the -15 to -25°C range, possibly even 5 or more degrees lower. He or she is keeping the forecast dry at this time (ATTM= at this time) but copious flurries and even light snow is possible with northwest winds of 20-35 MPH, which combnined with the forecasted cold would make for a very cold period of arctic weather.


Here is another paragraph from the discussion:

DAYS 8-14...OMEGA BLOCK UPPER AIR PATTERN TO CONTINUE WITH GENERALLY
BELOW TO WELL BELOW NORMAL TEMPERATURES.

Translation: In days 8-14, computer models suggest we will be under an omega block pattern in the lower 48 states. I have an example of that below. This is a weather pattern where a deep trough of low pressure in the middle is surrounded by two ridges of high pressure, one on each side. The high pressures act as a block, and this pattern can temporarily clog up the upper air flow around the globe.

What that means is those under the ridges get a prolonged period of mild, usually quiet weather, and those under the trough get a long, unsettled period of weather.

It is called the Omega Block because the pattern looks like the symbol for the greek letter Omega.

So if this block pattern sets up, those under the trough of low pressure will be in the deep freeze for several days potentially.




RISK OF DECENT STRENGTH ALBERTA CLIPPER SNOW EVENT CIRCA 15-16 JANUARY. THEN...POSSIBLY EVEN COLDER ARCTIC AIR INVASION WITH POTENTIAL FOR COLDEST AIR OF THIS WINTER TO BE CLARIFIED NEXT COUPLE OF DAYS.

Translation: the forecaster goes on to say he or she feels if all this comes together like models show, the upper midwest is in for a really tough time with bitter cold and snow. The approximate timing for all this is January 15-16.

I said in my blog a few days ago I felt this could all take place between January 18-25, so it now looks like it may be just a little earlier, but could last into that time frame.

So hopefully that gets you started on translating forecast discussions. If you come across specific things you have a question about, such as ATTM -- which means at this time -- let me know and I will do my best to help.

This has turned into a pretty long blog so I will close for now. See what your feedback does to me?

It get's my brain crankin' and I just can't stop writing!