Monday, November 17, 2014

Warm Water Equals Cold Air

Take a look at the sea surface temperature anomalies off the coast of Alaksa.  3°-4° above normal.  WOW!  Even off the coast of Siberia the water temperature is running 3°-6° above normal.

Why care about that?  The warmer water helps to keep large storms fueled as they move across the northern Pacific which in turn can cause an upper-level blocking pattern.  When the blocking pattern takes hold, cold air from northern Canada and the Arctic rush down the east side of the Rocky Mountains and through the central Plains helping keep the lower 48 in the freezer.

If you like reading about some of the tidbits mentioned above, be sure to follow me on Twitter (@johndissauer).  I tweet out a lot of stats, weather tidbits and thoughts on the forecast.

Friday, November 7, 2014

Arctic Chill

Tis' the season.  Cold air is building over the Arctic and it appears much of the lower 48 will tap in to it next week.

As of 5pm EST, the temperature in Alert, Canada is -23° with a wind chill in the -30°s.  The reason I mention the temperature in far northern Canada... That's where the source of cold air lies.

Long range computer models continue to advertise the cold air will filter in to the United States next week behind a strong arctic cold front.  A 1040-1044mb high is projected to fill in behind the front.  This allow cold air from northern Canada to slide down through the country.

Here's a look at Tuesday morning's temperature projection and upper-level winds from this morning's run of the European Computer Model.
12z ECMWF Temperature Projection
(Click on image to see larger version.)
Yeah, the purple colors are representative of cooooold air.  The cold air begins to infiltrate the United States late Sunday night.  It will sink south and southeast over the following days.

There are signs that the cold air will be around for a long period of time.  Temperatures could remain below freezing in many locations of the United States for six to nine days.

Here is a look at surface temperature projections from both the European forecast agency's computer model and NOAA's long range Global Forecast model.
12z ECMWF Temperature Projection - Shown in Celsius.
(Click image to see larger version.)
12z GFS Temperature Projection - Shown in Celsius
(Click image to see larger version.)
There are similar temperature plots for St. Louis and Indianapolis.  Temperatures around and below freezing, especially at the end of next week and in to the following weekend.
Plot of temperature projections for Indianapolis from various computer models.
(Click image to see larger version.)
Plot of temperature projections for St. Louis from various computer models.
(Click image to see larger version.)
With the cold air the question about snow begins to increase.  At this time, not major snow storms appear to be in the cards over the next week.  That isn't to say some snow couldn't fall.  I think there will be a couple of chances for snow in Colorado Springs/Denver and central Indiana.  That is something that will become more visible as we get closer to the middle/end of next week.

In the mean time, use the weekend to find your winter coats, gloves, hats and long underwear.  As always, you can follow me on Twitter (@johndissauer) to get the latest on next week's cold air intrusion.

Friday, May 16, 2014

Loooooong Range Outlook: May 17-June 15

Latest run of the experimental loooooooong range computer model is in.  I've had a chance to look at the data and make a few observations of what could come between May 17 and June 15.

One thing to remember, you should take all of the thoughts with a MAJOR grain of salt. This is only an experiemental computer model and not reality. You should not get too hung up on details just yet. Things can and likely will change.

Enough with the disclaimer, on to the observations:
  • Warm weather in southern United States May 21-23.
  • Upper-level low develops in western United States May 20.
  • Well above normal temperatures in the northern Plains and south-central Canada May 22-25.
  • Warm-up in southwest United States in through the northern Rockies (Idaho, western Montana) May 27-30.
  • Warm-up in Colorado through the central/northern Plains May 30-June 1.
  • East coast storm develops May 30-June 1.
  • Warm-up in Iowa, Missouri, Kansas, Illinois and Oklahoma June 1-2.
  • Warm-up in Indiana, Ohio, Kentucky, West Virginia, Virginia and North Carolina June 1-3.
  • Pacific storm develops and impacts the northwest United States June 2-5.
  • Warm-up in southern United States/central Plains/Missouri June 10-11.
  • Warm-up in desert southwest (California, Arizona, Utah, New Mexico) June 12-15.

Keep in mind, the model is just that. A computer model. The farther out the model looks, the higher the possible error rate. The key to look at this kind of data is not to look at specifics but instead trends and long wave patterns.

Friday, May 9, 2014

Winter Storm for Mother's Day

Still need to get mom a gift for Mother's Day?  Well, Mother Nature may be able to help you get something useful.  If you're in eastern Colorado you could get her a shovel.  She may need it Sunday and Monday.

An area of low pressure is moving through the Gulf of Alaska off the northwest coast of the United States.  (See the satellite loop below taken Friday morning.)

Computer models project the low/energy will move southeast in to the Rocky Mountains Saturday.  Once in the mountains, a surface low is expected to develop over southeast Colorado Saturday afternoon.  As the low moves east, cold air will begin to filter in from the north/northwest.

Almost all of the data suggests moisture will begin to fall in the central mountains of Colorado Saturday.  The moisture is expected to move east and southeast over eastern Colorado Sunday afternoon.  Both medium-range computer models, the GFS and European forecast agency's model, suggest that moisture will remain in place over eastern Colorado through mid-day Monday.

Overall, the computer models are very bullish with the amount of moisture falling from this system.  Here is a look at a 27-computer model average of how much moisture will fall for locations in southeast Colorado through 6pm Monday MT.
  • Colorado Springs: 0.70"
  • Monument Hill: 1.03"
  • La Junta: 0.48"
  • Lamar: 0.37"
  • Pueblo: 0.61"
Initially, moisture will likely fall as rain but in some locations it will change over to snow.  Places that get snow, could got a lot of snow.  Here is a look at the 27-computer model average of moisture that computer models project will fall as all snow through 6pm Monday MT.
  • Colorado Springs: 0.52"
  • Monument Hill: 0.76"
  • La Junta: 0.08"
  • Lamar: 0.01"
  • Pueblo: 0.13"
As you can see, data is suggesting higher amounts across El Paso County and north.  This also likely suggests higher snow amounts in the higher elevations west of I-25 (Teller/Fremont counties).

Keep in mind this is still a couple days away from happening.  Computer models will get a better handle on the storm, the amount of moisture and the timing once it gets better sampling over the land.
Winter Storm Watch (in blue) Saturday night
through Monday morning.
In the meantime, the National Weather Service in Pueblo has issued a Winter Storm Watch for areas west of I-25 Saturday night through Monday morning.  I'll be in throughout the weekend and will have further updates on KOAA-TV, on Twitter, and time permitting, my blog.

Thursday, May 8, 2014

Looooong Ranger: May 10 - June 4

Looking over the latest run of the experimental loooooong range European forecast model.  Nothing too significant for the Midwest or Colorado.  There's a possibility of severe storms in May.  Here are a few observations...
  • Upper-level low develops in northern Plains May 12.
    • Cooler temps in Colorado.
    • Severe weather in central/southern Plains May 12.
    • Severe weather to Missouri, Arkansas and Illinois May 13.
  • Upper-level storm moves from Great Lakes to southeast United States May 16.
  • Cool and wet in Carolinas through May 23.
  • Warm-up in Colorado May 17-22.
  • Pacific storm develops off west coast May 21.  Moves onshore May 24.
  • Warm-up central United States May 24-28.
  • Warm-up in southeast United States May 26-30.
  • Warm-up Colorado/New Mexico June 1-4.
Keep in mind, the model is just that.  A computer model.  The farther out the model looks, the higher the error rate.  The key to looking at this kind of data is to not look at specifics but instead trends and long wave patterns.


Thursday, May 1, 2014

2014 Deaths from Tornadoes

Statistics are starting to come in from the deadly outbreak of severe weather this past week.

Through April 29 preliminary statistics from the Storm Prediction Center shows there have been 31 deaths from tornadoes in 2014.  All of the deaths occurred April 25-28.

The National Weather Service and Storm Prediction Center work to identify the location the deaths happened so as to get a better look at what may have occurred..  Homes, mobile homes, outdoors, permanent building/structure, vehicle and unknown.

Twenty-four of the 31 death locations have not been categorized yet.

Of the known death locations from tornadoes this year here is how the numbers break down.  57% of deaths have occurred in mobile homes.  28% of deaths have occurred in vehicles.  14% of deaths have occurred in homes.

A look at historical numbers for the previous 12 years shows:
  • 36% of tornado related deaths occurred in mobile homes.
  • 34% of tornado related deaths occurred in homes.
  • 11% of tornado related deaths occurred in permanent buildings/structures.
  • 8% of tornado related deaths occurred in vehicles.
  • 2% of tornado related deaths occurred outdoors.
On the surface it appears the threat in mobile home and homes is nearly identical.  However, that isn't quite the same.  According to the United States Census Bureau, there were 304.09-millions people living in the United States and 6.6% of the population were living in mobile homes.  That works out to around 20-million people.  Obviously, there are many more people living in non-mobile home domiciles.  Looking at it from this perspective would suggest there is a higher threat living in a mobile home versus non-mobile home location.

Thursday, April 3, 2014

Severe Weather Today & Tonight

The threat exists for severe weather in parts of the Midwest today through tonight.  The brunt of this post is going to be for southeast Missouri, southern Illinois and western Kentucky.

The Storm Prediction Center has already issued a Tornado Watch for parts of southeast Missouri, southern Illinois and western Kentucky.  The watch is in effect until 7pm CT Thursday.


Looking over morning computer model data, it appears there will be a decent amount of divergence in the atmospheric column over southeast Missouri, western Kentucky, northwest Tennessee and northeast Arkansas, especially in extreme northeast Arkansas and the Missouri bootheel.  What this basically means is that there will be a lifting mechanism in the atmosphere.  Lifting air allows for thunderstorm development, amongst other things.

Data also suggests instability will be in place over the area through late tonight (10pm-12am).

As of 1pm CT, there is ample "fuel" in the air over southeast Missouri, southern Illinois and western Kentucky.  The area is located in the "warm sector" of the storm.  Dew points have already climbed in to the 60°s.  The moisture, indicated by dew point temperature, acts as the gasoline for the storms.

All we need now is a trigger.  Oh wait, there is a trigger.  An area of low pressure is currently located over eastern Kansas and western Missouri.  This will move to the east and bring a cold front through the area overnight.

So here is my thinking as of now...

There could be two rounds of storms in southeast Missouri, southern Illinois and western Kentucky.

First round is this afternoon where scattered thunderstorms will be possible.  These storms will have the potential to drop large hail, tornadoes and gusty wind.

Second round comes through later tonight as a squall line develops over southwestern Missouri and western Arkansas.  The storms contained within the line will have the potential to produce damaging winds, hail and a couple of tornadoes.

Right now, I think the biggest threat for tornadoes will come during the first round this afternoon through early evening.  Any discreet cells that develop will need to be watched closely.  I'm not saying there couldn't be a tornado later tonight, but I think the better chance will be with the first round.

I used to play a little game where I would pick my target location for storm chasing.  If I were chasing today, my initial target would be Piggot, Arkansas.  Keep in mind, part of choosing a location is for the ability to re-position myself if things change.  Strategically, Piggot would be my spot.

FREAK-OUT-METER:

  • Southern Illinois: 6
  • Western Kentucky: 6
  • Southeast Missouri: 6
  • Missouri Bootheel: 7
Be sure to have a way of receiving severe weather alerts this afternoon/tonight.  If you have a NOAA weather radio, be sure the batteries work and the unit is turned on.

Do NOT rely on warnings from Facebook.  I've discussed this before, but due to Facebook algorithms only 3%-7% of status updates are available for viewing in news feeds.

Twitter is an ok option.  Be sure to follow me at @johndissauer where I send out watch and warning information along with other bits of information on a more real-time basis.

Friday, March 28, 2014

Around the Corner; Looking Long Range in to April

Have some extra time and looking at the experimental looooooooong range computer model projection from the European forecast agency.  I don't see any horrific cold snaps coming to the Midwest or Colorado anytime over the next month.  That isn't to say there won't be days below normal, as I think there likely will, but noting long-standing.

Here are a few observations from the data that goes out to April 27.
  • Pacific storm arrives to west coast April 1.
    • Cooler air arrives April 3.
    • Impacts Great Lakes April 4.
  • Upper-low develops over NW United States April 8.
    • Transitions to upper-Plains April 9-10.
    • Sends storms to Midwest April 11.
  • Warming up in Colorado April 14.
  • Warm-up in St. Louis and Indianapolis April 15.
  • Warm-up in Colorado and central Plains April 17.
  • Warm-up in Missouri, Illinois, Indiana, Kentucky, Arkansas, Tennessee April 18-19.
  • Upper-level ridge develops over western United States April 19-22.
    • Pacific storm arrives April 24 breaking down ridge.
  • Ridge re-develops over western United States April 27 until ?? (This is the outer edge of the computer model's projection.)
  • Cool and active weather in Midwest/Great Lakes/Northeast United States April 27 until ?? (This is the outer edge of the computer model's projection.)
Keep in mind, the model is just that.  A computer model.  The farther out the model looks, the higher the error rate.  The key to looking at this kind of data is to not look at specifics but instead trends and long wave patterns.

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