Deconstructing Goliath; Bonus January Outlook

One of the benefits of being a hobby/amateur forecaster is that I really have no "skin" in the game.  While I really do want to give you good insight and accurate forecasts, my career doesn't depend on doing so.  So, unlike the pros, I'm happy to admit when I made a miscalculation in the spirit of learning and doing better next time.

While I realize I'm grading my own homework here, I thought it might be fun to deconstruct yesterday's storm against my own forecast.

What I Got Wrong:

1. The biggest thing I got wrong was the high temperature, and that impacted other parts of the forecast.  I predicted a high of 33, thinking that the warm air wrapping around the low would drive up the temperature as the system approached in the late afternoon.  Instead, I recorded a high of 28 in New Glarus -- also the official high at the Madison airport.
2. Because of the colder temperatures, we saw more snow accumulation than I expected.  I predicted 2-4".  Madison's official snowfall was 5.9", and here in New Glarus, I measured 4.5".  Still within the meteorological margin of error, I suppose, but I was low nonetheless.

Here's what the early snow totals look like around the region (click to enlarge).

What I Got Right:

1. First and foremost, I was ahead of this storm by 6 days.  While it's risky to start talking about a December 28th storm on December 22nd (as I did on Facebook), I felt that with the holidays and folks traveling, the reward outweighed the risk.
2. I got the "pre-slopitation" right.  Here in New Glarus (and nearly all other locations I was tracking), we had sleet, freezing rain and snow.  In fact, the sleet was steady for almost a 5-hour period between 2pm and 7pm, when precipitation changed back to snow.
3. The wind forecast was also correct.  The highest speed I recorded was 34 MPH, but other reports were as high as 60 MPH (which I accurately predicted would occur in the far southeast corner of the state).  
4. I mostly got the timing right.  I said the storm would start mid-morning.  Here in New Glarus, it started at 8am.
5. Finally, and this might actually be the most important thing, I said in a Saturday Facebook post that driving would be a really bad idea on Monday.  Safety is important to me in winter forecasts.  As you probably heard, emergency services responded to hundreds of crashes, rollovers and slide-offs in southern Wisconsin alone.

With that, let's look ahead to what January may have in store.

All models are currently showing a southern jet stream through at least the third week of the month.  This allows colder Canadian air to infiltrate the Midwest, setting us up for seasonably cold temperatures.  I don't see any polar vortices on the horizon; in fact, there's a chance we could get through January without even seeing subzero temperatures.  I don't know if that's ever happened before in January, but I'm looking into it with the State Climatology Office.  I'll keep you posted.

At the same time, major storm systems for the first couple weeks of January seem like they'll be relegated to both the east and west coasts (a trademark of El Nino winters), with very little action here in the Midwest.  The GFS model is showing a weaker disturbance next Thursday, January 7th, so I'll keep on eye on that.  Otherwise, there's not much out there.  Of course, that can change.

Finally, I want to say "thanks" to those of you who are genuinely interested in Rippeology.  Obviously, I enjoy it, but it is a bit of work.  Since Saturday, the blog has had over 250 visitors, which is pretty cool.  I appreciate your interest!

As always, let me know if I can answer any questions for you, either here or on Facebook.

~Scott

The Ice Man Cometh

In my November 13th winter preview post, I predicted, among other things, "more ice events" than usual this winter.  That should start to materialize tomorrow in Southern Wisconsin.

In fact, with temperatures hovering between 29 and 35, depending on your location, we could see the full gamut of winter pre-slopitation Monday and Monday night, including freezing rain, rain, sleet and snow.  Oh, and a shit-ton of wind.

Officially, the National Weather Service has posted a Winter Storm Watch for all 72 Wisconsin counties.  But the nature of the storm will be very different from north to south.

Here's the scoop:

The same intense low pressure creating extreme blizzard conditions right now in parts of New Mexico and Texas will push northeastward toward central Illinois overnight tonight.  Normally, this kind of "panhandle hook" track (explained here) would put much of Wisconsin in a heavy snow area.  But with El Nino's influence, this low will be so strong that it will wrap warmer air all the way over to the northwest side of the low.  With that warm air aloft, precipitation then starts as rain, and ends up falling to the surface either as sleet or ice, depending on the surface temperature.

Here's how the National Weather Service sees the map shaping up for 6am Monday (and remember, you can click on any image to enlarge):

That orange color represents freezing rain.  You'll see the low positioned in extreme southwestern Missouri.  What happens after that depends completely on where the low goes from there.  A track toward Rockford or Chicago keeps us in relatively "warm" space, meaning that rain and sleet are more likely.  A track toward Detroit puts us in a colder position, meaning more snow and freezing rain.

The GFS weather model, which forecasters rely on to predict the position of pressure systems, seems to split the difference between those tracks -- maybe just east of Chicago, but just west of Detroit.  These two images show the 12-hour advance of the low...

 

In all winter storms, pinpointing the track of the low is the key to accurate forecasting.  But in this storm, low track is even more important, because temperatures will hover right around the freezing mark.  That means that two areas only 10 or 20 miles apart, with only a 1-2 degree temperature difference, could see completely different types of precipitation at the same time.  

In fact, the only thing really certain about this storm is wind.  As the low gets closer during the day tomorrow, look for east/northeast winds to gust as high as 35-45 MPH.  This wind forecast shows lower Lake Michigan taking the brunt of the strongest winds:

Wind and ice, as all Wisconsinites know, is a terrible combination if you want to drive somewhere.  And an extra word of caution about that driving thing -- you may step out of your house and office, and driving conditions will seem fine.  But 5 miles down the road could be a completely different story.  If you are on Twitter, and you absolutely have to drive Monday or Monday night, keep your Twitter feed on Madison Traffic, 511 Wisconsin and Ready Wisconsin for timely updates on weather, traffic and crashes. 

If ice accumulates to more than a tenth of an inch -- which is likely in parts of South-Central and Southwestern Wisconsin, power outages and downed trees are also a distinct possibility.  So today is the day to get prepared for that eventuality.  Ice of a quarter inch or more is considered an extreme ice storm, and that can't be ruled out in some locations.

Mateo Earth models show New Glarus right in the sleet/ice (yellow) band for a lengthy period of time.  Here's 1:00pm Monday and 1:00am Tuesday:

Okay, I'm sure that's a lot more than you wanted to know about freezing rain.  What about the snow?

We can be pretty sure that snow amounts will be lowest in the far Southeastern part of the state, and highest in the Northwest.  Some locations won't see any snow at all.  In the New Glarus and Madison areas, I think we see 2-4 inches as the low passes to the east on Monday night.  That's not much, unless there's a layer of ice and sleet underneath it.  

So here's my official New Glarus forecast, subject to change as I watch the low progress today:

Monday:  Sleet and freezing rain starting mid-morning, changing to all rain for a brief time in the early afternoon, and changing back to sleet and freezing rain around sunset.  Total sleet and ice accumulation about 0.15 inches.  High 33.  Strong east wind of 15-25 MPH becoming northeast late in the day, with gusts up to 40 MPH.

Monday night:  Sleet turning to snow in the evening, accumulating 2-4 inches before diminishing late.  Winds remaining strong and gusty from the northeast, creating blowing and drifting snow.  Low 29.  

If you're traveling to the north or northwest Monday or Tuesday, look for snow totals as high as 8-14 inches toward the Eau Claire area.  

FYI, there is another chance of light snow on Wednesday, as a weaker system approaches from the west.  Late this week, we'll see our coldest temperatures of the season, with highs only getting into the teens in most places.

I'll take your questions both here and on Facebook!  And remember, you heard about this storm on Rippeology before anyone else was talking about it.  First post was last Tuesday morning on Facebook.  Just sayin'. 

Amaze Your Friends During Tonight's Storm

Wanna really geek out (like me) on tonight's snowstorm?  Here are 3 ways to amaze your friends with your meteorological savvy:

1. Pay attention to wind direction.  For most of the day and evening, the wind will be coming from the west.  When it starts to switch counter-clockwise -- first to the southeast, then to the east, then to the northeast -- you'll know that the heaviest band of snow is imminent.  That's because the heaviest bands of snow always fall to the northwest of the center of the low pressure system.  So, if the low is centered just south of Chicago, for instance, the counter-clockwise wind will put us in a northeastern wind, and to the northwest of the low -- the perfect recipe for a heavy snow band in south-central Wisconsin.
2. Strike up a conversation about "water content."  Fun fact: in a typical Wisconsin snowstorm, ten inches of snow would equate to one inch of rain -- meaning the water content in the snow is only about 10%.  When snowstorms come from the south, bringing gulf moisture with them, water content can be more like 30-40%.  This particular storm, however, will have even less water content than the average storm, because it has very little oceanic moisture to draw from.  The snow develops not because of moisture, but because of strong energy and lift in the upper atmosphere.  
3. Talk climatology.  And deer hunting.  Here are some fun facts: A) the average November snowfall in our area is about 2.5 inches; B) if we get 9 inches of snow, that will amount to 20% of the 45 inches we usually get in an average winter; C) the first regulated Wisconsin deer hunt was in 1851; D) last year on the eve of gun season, a warm front came through on Friday night, resulting in fog advisories on Saturday morning.  Near my house, at least, this didn't stop people from shooting at things they thought might be deer.

Any other fun stuff you want to know?

Storm Track, Intensity Now More Certain

Did your iPhone beep at 4:15 this morning?  That's because southern Wisconsin is now under a Winter Storm Warning.

Now just 12 hours in advance of the season's first major snowfall, the track and intensity of the storm appears even more certain.  Many models show the storm as more intense, and not quite as compact, as what was previously thought.

Snow should start right around dinner time tonight.  I'll be watching it from Kristi's Restaurant in New Glarus.  It'll get heavy at times overnight and start to taper late tomorrow morning -- except for those of you in far southeastern Wisconsin, where some lake enhanced snow will linger until late afternoon Saturday.

I'm going to stand by yesterday's predictions, knowing that I might be a little low when all is said and done.  It's quite possible that New Glarus could be more in the 8-9" range, rather than the 6-7" I predicted yesterday.

Here are some of the vital maps.  Click any image to enlarge.

First, the watch/warning area.  Areas in pink represent a Winter Storm Warning.  This is a wider north-to-south area than what was originally expected.

Here's The Weather Channel's current snowfall forecast, putting extreme southern Wisconsin in an 8-12" area.  They've named this storm "Bella."  I hate this practice of naming winter storms.

Here's the local WISC-TV snowfall map.

Here's the text of the Winter Storm Warning.

And finally, here is my list of the vital preparations you should take today:

• Get gas and oil for your snowblower; test start your snowblower
• Stock up on booze
• Find some sucker to take your Badger football tickets tomorrow
• Watch this video from my favorite amateur weather forecaster

Let me know if you have any questions or additional preparation tips!

Friday Night Snow in Southern Wisconsin

Deer hunters must be absolutely giddy about this.  When gun season opens Saturday morning, they'll be greeted by a fresh blanket of snow with which to track deer and keep their Busch Light cold.  

We're still a good 36 hours away from it, but there's some agreement in some computer models about southern Wisconsin's first snow event of the season.

There is significantly less agreement among forecasters about how much snow we'll get.  Forecasts still range from completely non-committal, to "light accumulations" to AccuWeather's aggressive 6-10" forecast.  Here's that map:

Officially, the National Weather Service has issued a Winter Storm Watch from 6pm Friday to 3pm Saturday.  That watch calls for snow ranging from 4 to 7 inches in extreme southern Wisconsin (Madison and Milwaukee included) and Northern Illinois.

Here's what's pretty certain:

• Low pressure will approach from the west late Friday
• It'll be a pretty fast-moving system
• Temperatures will support mainly snow, as a cold pocket sets up today and tonight
• It'll drop the heaviest snow in a narrow, elongated band
• Temperatures Saturday night will be the coldest of the season (mid-teens with single digit wind chills)

What's less certain:

• Exact track of the low, although most models show the Wisconsin/Illinois border as a primary focal point
• System strength (how low the pressure gets)
• The potential for brief lake-effect snow midday Saturday along Lake Michigan (from Sheboygan to Kenosha)

Storm track is always a key ingredient in predicting how much snow will fall in any one place, but in this case, the track is particularly important.  That's because the storm is very compact.  A nudge to the north or south changes snow totals dramatically.  If it does nudge, I think it nudges south.  Here's how Mateo Earth sees it at 4:00am Saturday morning...

Here are my early projections for snow fall, starting 6pm Friday and ending Noon Saturday:

Wisconsin Dells:  1-2"
Madison:  5"
New Glarus:  6-7"
Milwaukee:  7" (possibly more at the lakeshore)

Updates to come, especially if the track fluctuates!

Rippeology Winter Preview for Southern Wisconsin

Rippeology is back for the winter season.  Try to contain your excitement.

The Cliff's Notes version of this post:

• Milder temperatures
• Fewer snow events (but not necessarily less snow than normal)
• More ice events
• A brown Christmas
• An active February

All of those predictions, if they materialize, can be blamed on what is now the second strongest El Nino on record.  Only the El Nino event of 1997 was more intense.  The current El Nino may still surpass it, but I doubt it. 

El Nino is basically a warming of surface water temperatures in the eastern and central Pacific near the equator.  This phenomenon results in some pretty solid weather trends for North America.  Among those is a drier and warmer winter in the Midwestern section of the United States.

At first glance, those "warmer and drier" deviations may seem small.  Generally, El Nino would mean our average temperatures during the December/January/February "meteorological winter" might be 2-4 degrees above normal...and snowfall might come in 3-5 inches under seasonal averages.  But in 1997-98, El Nino produced a greater disparity for southern Wisconsin -- with temperatures averaging 7-8 degrees above normal, and snowfall averaging as much as 10 inches below normal.   

Here's a great summary of the '97-'98 El Nino from the National Weather Service out of Milwaukee.

The "nuance" of El Nino (for us, anyway) is that for warmer temperatures to occur, you need a greater frequency of south/southwesterly wind patterns.  And a few degrees can make a huge difference.

In the Madison area, the lowest average temperature in winter is 27 degrees.  That occurs in mid-January.  Add a few degrees to that average, and you're nearer the freezing mark.  Add a southerly wind flow, and you have the perfect recipe for ice storms, as warmer air overrides colder temps at the surface -- hence my prediction of more icing events above.

That more frequent southerly flow also diminishes, in theory, anyway, the frequency of Alberta Clipper snowstorms -- those fast-moving lows from the northwest that dump moderate amounts of drier, fluffier snow.  Hence my prediction of fewer snow events.

But if you start at the source of El Nino...add a south/southwesterly wind flow...mix it with intense low pressure in the New Mexico/Texas area, you increase the chances of the snowstorms that dump the most snow on southern Wisconsin -- panhandle hooks.  If you want to learn more about this specific storm track, read my post from this exact date last year.  So, while we may have fewer snowstorms, those that we do get may dump a lot of snow.  Hence the prediction that our average snowfall -- usually around 4 feet for the season -- may still materialize. 

So what about the February prediction?  Every El Nino computer model, and there are dozens, predicts a moderating of water temperatures as we go through the next 6 months or so...to the point where water temperatures return to near-normal by next May.  That moderation will make its greatest swing around February and March, which could lead to a more active weather pattern that feels more like a typical Wisconsin winter.  If Vegas had betting odds on this sort of thing, I'd put money down that February will be our most active weather month here in Wisconsin.  Thankfully, I'll be in Key West for the first half of it.

In the short term, look for higher than average temperatures and more rain events through December.  If it snows before Christmas, and it probably will, chances are good that temps warm enough to melt it.  Hence the brown Christmas.

That's my story, and I'm sticking to it.  Leave any questions in the comments.

Weekend Storm Fizzles; Monday Night Storm Strengthens

For the meteorologically impatient, like my friend John Urban, my 6pm Monday to Noon Tuesday snowfall forecast is divided into two predictions:

Madison airport: 3.8 inches (up slightly from the 3.4 I projected Friday)
Platteville: 5.6 inches 

I'm including Platteville here because it appears to be in the heaviest band of snow for this Monday night Alberta Clipper.

A quick look back at the weekend storm: we fell far short of the precipitation projection (I had 3.1 inches; the Madison total that will be released later today will probably be between 1.0 and 1.5).  I'm pleased that other elements of my forecast -- the two rounds of precipitation, the temperatures, the wind -- were spot on.

On Thursday, I mentioned 4 components of a winter storm that I watch for:

Storm Track: very favorable
Storm Intensity: moderately favorable
Surface Temperature: very favorable
Speed of Track: somewhat favorable

"Storm Intensity" ended up being the downfall of last night's forecast.  The low didn't deepen nearly as much as projected (pressure is 29.80 as of this moment), which means it didn't have the strength to produce significant snow on the back (northwest) side of it.  Thus is the peril of winter forecasting for southern Wisconsin.

On Friday, I predicted a second storm for Monday night, and that storm still appears likely.  The National Weather Service has issued a Winter Storm Watch for far southwestern Wisconsin (Iowa, Lafayette, Green and Rock Counties).  The Watch runs 6pm Monday to Noon Tuesday.

The bulk of the snow will fall in the overnight hours Monday into Tuesday.  A few maps:

The MeteoEarth projection, just after midnight Monday night (click to enlarge)

NOAA probability of 4"+ of snow in the 24-hour period ending Noon Tuesday.

NWS precipitation model for 3am Tuesday.

In the last 24 hours, models have ticked the center of the storm further south and west, which is why I place Platteville roughly in the heaviest snow band.

As I mentioned Friday, the weather story behind this storm will be temperatures.  An arctic blast means that after sunset tonight, our temperatures will range from -15 to +10 through Thursday.  Tuesday and Wednesday will feel especially cold because of wind, as wind chills dip to -25 to -40.

Because of the Monday night snow and Tuesday morning wind/cold, don't be surprised if schools either delay or close on Tuesday.  The morning commute on Tuesday won't be fun, as wind whips the new snow.

Temperatures will be close to normal again by Sunday, with only slight chances of snow during the day Thursday and late Saturday.

I'll update the Monday night snow total if conditions change.

Weekend Forecast (Plus Bonus Monday/Tuesday Preview)

Since I didn't already have enough weather models to geek out on...

I'm using a new forecasting and imaging tool that I think you're going to like.  It's called MeteoEarth, and it allows me to show you time-stamped snapshots of what our weather might look like at any given point in time.  But before we get to the pretty new pictures, here's a quick glance at the next 4 days:

Saturday:  Wintry mix early, then a break in precipitation, then evening and overnight snow.

Sunday:  Gusty winds, cold, snow showers ending, blowing snow throughout the day, some clearing at night.

Monday:  Very cold with snow developing late evening and overnight.

Tuesday:  Snow ending by Noon, continued cold.

So that's two separate storm systems -- one coming from the southwest Saturday into Sunday, and another coming from Canada on Monday night.

I have to say this first about the weekend storm: it strikes me as nearly irresponsible that the National Weather service office out of Sullivan, WI has not issued any weather advisories for the southeastern half of the state.  They still might, but with the mix of precipitation in the forecast and the real potential for travel hazards, they should have done it by now.  Just sayin.'

OK, let's get to the detail...

The weekend storm is setting up just as I described it yesterday, with two exceptions:  1) precipitation Saturday into Sunday will fall in two rounds, not one, and; 2)  the first round of precipitation may include sleet and/or freezing rain.

That first round starts tomorrow morning as the low brings warm and moist air up from the south.  That warm air aloft will override the cooler air at the surface, causing rain to form in the upper atmosphere.  But with temperatures still below freezing at the surface, that precipitation will fall as either sleet or freezing rain.  Expect this first round of precipitation to essentially last from 6:00am to Noon Saturday.  This snapshot from MeteoEarth shows the leading edge of precipitation coming from the south before sunrise tomorrow morning.  (Remember you can click on any image to enlarge.  Also note future time stamps in the upper right of the MeteoEarth images).

After that first batch of precipitation goes through, we'll get into a brief dry zone.  Skies will remain cloudy and temperatures will fluctuate within only 2 degrees of freezing -- about 30-34 degrees.  As the low passes to our east late tomorrow evening, snow will wrap in behind it, giving us a 6-9 hour period of light to moderate snowfall Saturday night into Sunday morning.

Here's the overnight image for early Sunday morning:

My snowfall prediction, 6pm Saturday to Noon Sunday:  3.1 inches.  Totals will be higher to the northeast (Fox Valley area) and lower to the west/northwest (La Crosse area).

So far, I'm only seeing one projection that thinks there could be a heavier band of snow in southern Wisconsin.

That orange band over southern Wisconsin is showing an 80% probability of 4 inches or more by Noon Sunday.  The same model suggests a 40% probability of 6 inches or more in that same period.  As I mentioned yesterday, these types of storms often contain narrow bands of heavier snow, but they're nearly impossible to pinpoint geographically.  So, I'm generally discounting the model above.

Behind that system comes the first of 3 shots of cold air that we'll experience in the next 5-7 days.  This image from MeteoEarth shows strong north winds on Sunday, as indicated by the closeness of the isobars (or equal lines of barometric pressure):

That cold air gets reinforced again Monday, then again Tuesday night.  Look for highs only in the single digits Monday and Tuesday, and perhaps barely reaching zero on Wednesday.

In between those arctic blasts will come a second snowstorm on Monday night.  This "Alberta Clipper" will produce a prolonged period of light snow from about midnight Monday to Noon Tuesday.  Other forecasters have snow starting earlier in the late afternoon or evening Monday, but I can't find a single computer model to support that.

Here's what overnight Monday looks like, according to MeteoEarth.

My snowfall prediction, midnight Monday to Noon Tuesday: 3.4 inches.  This time, look for slightly higher totals toward La Crosse, and slightly lower totals toward Green Bay.

Long-range models look dry (but bitterly cold) for the rest of next week, with the next potential snowstorm late next weekend.  I'll watch that for those of you planning on going to Lambeau next Sunday for the Packers playoff game.

As always, if and when things change, I'll let you know!

Yup, It's Going to Snow

Happy New Year from Rippeology!

Here's hoping you had a chance to enjoy to the 24th warmest and 4th driest December on record in Madison.  Both temperature and precipitation trends are about to turn in the opposite direction.

Southern Wisconsin will see its first winter storm of the new year this weekend, and a pretty strong cold blast will follow in its wake.  Here's how I'm sizing up the 4 most important factors in winter storm development, specifically for our area:

Storm Track: very favorable
Storm Intensity: moderately favorable
Surface Temperature: very favorable
Speed of Track: somewhat favorable

So, the two things that prevent this storm from being a real whopper are A) intensity, or barometric pressure of the low; and B) the speed with which the storm will come and go.

Nonetheless, a low pressure system is taking shape right now in west Texas.  It's a somewhat disorganized storm at the moment, and will take another 36-48 hours to really wind up.  When it does, it'll head northeast toward Chicago.  If you need a refresher on Texas Panhandle Hooks, see this post from mid-December.

Based on current path, I think this means 3-5" of snow for southern Wisconsin, starting around 6pm Saturday and finishing up around Noon Sunday.  As is always the case with panhandle hooks, narrow bands of heavier snow can pad the totals in localized areas.

Here's the probability map of 4" or more of snow, ending Sunday afternoon.

So, far southern Wisconsin is in that 50/50 area of 4" or more.  If you're in far southeastern Wisconsin, you may actually see some mixed precipitation at the storm's outset, but locations near Lake Michigan may also get some lake effect snow as the low pulls northeast into Canada and winds switch to the northeast.

This model shows the anticipated position of the low over northern Illinois overnight Saturday.  Models have been gradually ticking the low farther west over the last few days.

This model supports that track, meaning that for the most part, there's far less disagreement about storm track than most storms we've seen this year.

It's possible that the National Weather Service out of Sullivan may issue a Winter Storm Watch for our area.  If they're going to do that, it would likely be issued with this afternoon's 3:35pm forecast, or tomorrow morning's 3:35am forecast.  Issuing the watch is a strong indicator of computer model consistency, and therefore, forecast confidence.

So there you have it.  On a side note, I'll be tracking my own forecast accuracy throughout 2015.  For winter storms, I'll post a specific snow amount (to a tenth of an inch) 24 hours before the storm starts.  My goal is to be within 1.5 inches on these projections (based on official Madison airport totals).  You'll see running accuracy results in the right sidebar of the blog throughout the year. 

Also for 2015: more video forecasts from Rippeology!

Watch for the final snow prediction here and on Facebook, to be posted Friday afternoon.