Potential New Snow System To Affect Southeast Lower Michigan /Update/

              Written by: William R. Deedler, Weather Historian 12/2/2011 (Updated 12/4)

A strong positively tilted low pressure trough will push in the western part of the country over the weekend and slow the progression of a cold front sliding across the mid part of the country by early next week. The recent model trend from the 12/2&3 - NAM /12z and latest 00Z/ indicate the front will push just east of Southeast Michigan and then stall or slow to a crawl while extending southwest into eastern Oklahoma and western Arkansas.

Weak waves of low pressure along with a surplus of moisture will ignite a streak of snow and rain which will extend from Texas into the southern Great Lakes by early next week. Snow accumulations could be notable if the front stalls long enough as it gets hung up under the strong southwesterly jet. The latest 12/3 - GFS /00Z/ model also has the front slowing but the best moisture still hangs just to the south and east of Southeast Michigan. Stay Tuned.

This is a very recent development in this system as the models had for several days, pushed the entire boundary further east with little overrunning precipitation under the baroclinic zone. This system is a "sling-shot" type of system I talked about in my Outlook and were one of the more prevalent type of snow makers for Southeast Lower Michigan during my analogue winters.

From the Outlook

I mentioned the "sling-shot" pattern in my earlier discussion in regard to the jet stream. Plain and simple, by looking at the storm track map you can see how the Arctic/Polar jet prefers to take a dive southward (southeast or even southwest) to the lee of the southern Rocky Mountains in these analogue winters. This in turn, loads the storm "sling-shot "and shoots it east northeast toward the Great Lakes and then "somebody gets stung in the....";-).  Who gets stung remains to be seen as the pattern evolves.

Check out the 500MB and Surface and you can visualize these vort maxs pivoting around the Southwest Trough and being "shot" northeast toward the Lakes. It is still very early to run for the snow shovels and also (like stated in my most recent post), the models have some trouble with forecasting the jet that feeds these systems from the Pacific, so this is just a heads ups at this time!  
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**Update**

From above-

The latest 12/3 - GFS /00Z/ model also has the front slowing but the best moisture still hangs just to the south and east of Southeast Michigan. It is still very early to run for the snow shovels and also (like stated in my most recent post), the models have some trouble with forecasting the jet that feeds these systems from the Pacific, so this is just a heads ups. Stay Tuned.

**All recent models trends have now (12/4) shifted back to the earlier GFS/Euro trend consensus of keeping the axis of precipitation pushing slowly east as colder but drier air infiltrates Southeast Lower Michigan. While some light snow is still expected on the backside of this system, amounts will be light. The upper low spun up over the Southwest will also shift east with time and will be moving into the Ohio Valley later in the week but at this time, the system is slated to stay south of our region.**

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  Earlier  NAM 12/3-00Z Model Run Fri Night for Monday Night @ 72hrs

                           


Making weather fun while we all learn,
Bill Deedler -SEMI_WeatherHistorian

Are We In For One Troublesome Forecastable Winter?

Written by: William R. Deedler, Weather Historian 12/01/2011

In answer to the question of the headline: "Well, I really would hope not but analogue data indicating the interactions of the main jet streams involving strong wind maxs, does make one wonder".

Straight up: 

As we can see by the projected analogue winter jet streams, the problem readily shows up in the northern Pacific. Not only is this where a couple of jets are likely to phase/not phase this winter but also where observational data is scant. Much of the surface and aloft data is lost over the Pacific once it leaves Eurasia (including Japan) but thank our heavens above (no pun intended, well maybe a little) in the advancement of technology for satellite data (and upgrades). 

A big boom to forecasting came in the 1970s when satellite advancement really began to take off from its infancy in the 1960s. I recall at the WSFO at Detroit Metro Airport (at the time) what a ground breaking product this was and this was especially true for the local WSFO/WSO's in the Great Lakes what with: winter ice coverage and Lake Effect snows, synoptic rain and snow systems and severe weather. One could hardly wait at times for a recent picture to come out of the satellite machine (LOL) which currently is just another standard but important tool for forecasting!  Then, fairly quickly at the WSFO's, the micro-scale satellite interest expanded to a macro-scale interest over the US and points west, south and east with the Pacific Ocean, Gulf of Mexico and the Atlantic all having important watchable satellite data.

Back to the subject at hand:

As it is said, a picture is worth a thousand words and referring back to a few of the map pictures from my projected analogue jet stream and storm tracks in my Outlook, depicts nicely what we are up against.

The interaction of the Pacific and Polar/Arctic jets along with phasing location and timing; will have large repercussions on the downstream subsequent weather development this winter across the States. Of course, to a large extent, this happens most winters depending on the ENSO cycle, etc, etc as discussed in the Outlook. However, with the analogue data from this particular set of winters chosen, I feel tends to zero in on the perspective trouble spots and likely outcome. In addition, throw in at times the sub-tropical Pacific jet nosing in its beak for good measure and the complexity only grows. And to top it all off; the surface and aloft weather data you receive from many of these locations is very limited (if non-existent) and again, why satellite is such a valuable tool.

Analyzing the aloft data from the analogues, gives a valuable clue as to where the dominant storm tracks and subsequent forecast problems will likely arise. And, one eye on recent weather maps (surface and aloft) and the other on our analogue map projections reveals we are in the right place. 

Latest data from extended models is hinting at another dive of cold Pacific and Polar air over the western and central US next week; and possibly Arctic orientation air diving in the same location after that. Of course, this is too far out to get any sort of a grasp of its reality but December is beginning to show more of a mixed weather pattern as winter evolves (and the way analogues suggested).

December:

Along with write ups and updates on notable weather affecting Southeast Lower Michigan and the Great Lakes and posting my well received Christmases Past article;  I'll explore another troublesome area of forecasting...the ever elusive NAO/AO.

                                                                          Happy Holidays and may you have a

                                                                          prosperous and healthy New Year!

Making weather fun while we all learn  
Bill Deedler -SEMI_WeatherHistorian    

Outcome of Eastern Great Lakes Storm Difficult To Forecast

                        Written by: William R. Deedler, Weather Historian 11/29/2011

Well I will have to say, many of the assortment of weather forecast models had our present /11/28-30th/ significant upper and surface low pressure system over the Ohio Valley & eastern Great Lakes pegged well out in time. I started conversing with my fellow meteorologists and weather enthusiasts back on November 19th about this system and it's been a nightmare ever since for the models and forecasters alike.

It wasn't so much a question of something developing as time marched on as much as: what would impact the area (rain versus snow), exactly where it would develop and its timing. And, though things are coming together there are still significant questions on the system. The general public still has a very limited knowledge of what hassles a winter storm can be to forecast. Those common remarks such as: "they were forecasting 2.0" of snow and we got nothing" or "they were forecasting 2.0"-4.0" in my area and I got 6.0" follow many storms." 

First off, "they" includes a hell of a lot more weather forecasters than ever before. Gone are the days from when I started that the forecast was from one general source; the National Weather Service. I can't tell you the amount of times I've heard "they" said this or that and ALL forecasts were attributed to the NWS. The general public in this day and age receives many more opinions out there of what could (or will) happen in just the daily forecasts, let alone days or weeks out.

Secondly, just to give you an idea of the problems still facing the forecaster, the following was taken from an excellent area forecast discussion /AFD/ issued just this Tuesday morning /29th/ from the NWS at DTX on the system and changes still coming in. He gives his educated and expert opinion of what he personally (sometimes with the help of co-workers) interprets the latest models are trying to convey to him on this storm.

"THE MODEL TRENDS EARLY THIS MORNING ARE CLEAR...FASTER TIMING...AND MAIN LOW TRACK MUCH FARTHER EAST...IN BETWEEN LAKE ERIE/ONTARIO. THIS IS IMPORTANT...AS IT WILL ALLOW FOR A FASTER WIND SHIFT TO THE NORTH/NORTHWEST BETWEEN 00-03Z WEDNESDAY...RESULTING IN FASTER CHANGEOVER TO SNOW. THE TOUGH PART OF THE FORECAST IS THE DEFORMATION ZONE WILL LIKELY BE CONSTRICTING TONIGHT...AS THE NOTICEABLY DRIER AIR OVER THE DAKOTAS...MINNESOTA...AND WISCONSIN (SURFACE DEW PTS IN TEENS AND 20S) INFILTRATES THE CENTRAL GREAT LAKES. A VERY SHARP PRECIPITATION GRADIENT LOOKS TO EXIST WITH THE STRONG BUT STRETCHED MID LEVEL DEFORMATION...AND MIDLAND COUNTY LOOKS TO BE ON THE EDGE OF THIS GRADIENT (SEE 00Z CANADIAN MODEL). ON THE FLIP SIDE...THIS LOW LEVEL DRY AIR WILL HELP WITH WET BULBING EFFECTS...INCREASING CONFIDENCE WE WILL SEE SNOW...BUT DBZ IS VERY HIGH UP AND STILL DIFFICULT TO GAUGE HOW MUCH OF THE SNOWFALL WILL BE WASTED DUE TO THE WET GROUND. REGARDLESS...TEMPERATURES EVENTUALLY FALL TO FREEZING AND BELOW...ASSURING THE SNOW WILL BEGIN TO STICK. SKEWING THE FORECAST TOWARD THE COLDER AND CONSISTENT 00Z EUROPEAN...EXPECTATIONS ARE GENERALLY 3 TO 5 INCHES ALONG AND WEST OF U.S 23...WITH 1 TO 3 INCHES EAST. LOOKING AT MOSTLY AROUND 1 INCH TOWARD THE CANADIAN BORDER AND MONROE COUNTY...AS THE MARGINALLY MILDER MARINE LAYER HOLDS ON AND MORE IMPORTANT FOR THE CITY OF DETROIT AND MONROE COUNTY...IT LOOKS LIKE THE MID LEVEL DRY SLOT WILL IMPINGE ON THE AREA...LIMITING THE QPF. JUST ABOUT ALL THE SNOW SHOULD BE DONE BY 12Z WEDNESDAY.


Next: We'll look at why these systems whether days or hours out, can still be such a pain in the butt and could this present system be telegraphing the difficulties of things to come this winter?

Making weather fun while we all learn,
Bill Deedler -SEMI_WeatherHistorian

Analogue Years...Mild or Warm November>>>Mild Winter?

Written by: William R. Deedler, Weather Historian 11/17/2011

Interestingly when you are retired and not dealing with the daily grind and other stuff that comes up at the weather office, you actually get more of a chance to look at other weathermen's views on climate, the weather and in this case; their winter outlooks.

A very common gripe right now across the land is the relatively warm November and what does this foretell for the winter and their winter outlooks. I can't vouch for their outlooks but I can do a little more investigation on my own.  Therefore, I went back and took all my analogue years at Detroit and plugged in the above normal Novembers that preceded the winters. Now mind you, November is only a little better than half way over but is does look like the month will average above normal looking at the extended models so we'll go with that assumption.

I found only three Novembers in the 16 analogues that averaged above normal and they were: 1928@42.5, 1964@44.9  (BTW: I feel 1964-65 is a good analogue winter along with 1974-75) and 1999@45.2  (new Nov normal now is 41.6). Here are the composite maps for those above normal Novembers and subsequent winter months that followed from my analogues. Note: pay attention to the below/above normal numerical departures since they change as some months/seasons were more extreme (like Jan for example).

 As one can see just doing a quick scan,   a

  mild or warm November (in these analogues

  anyway) did not foretell a mild winter. What 

also is interesting is that the really cold air

  did not really make headway into  the             country and take up residence until              

sometimes as late as January when below    

normal temperatures ruled in the north

 (and what a change)! Decembers seemed to 
 be the transition month relative to normal.

                                                        

                                   

Some of you may be thinking: ok fine but with such a small sample of just three Novembers, how much does that really tell? I tend to agree, therefore I plugged in the normal to above normal Novembers and then, the sample jumped up to nearly half of my analogues (7 out of 16  but as you can tell, a cold November was still dominant). Anyhoo, when taking the normal to above normal Novembers in the analogue years, you get the following composites:

 

 

 

It's basically the same trend, Decembers were still somewhat mild but with a big change happening by mid to late December (or even as late as early January) which then persisted into February and even March with this bigger sample. I can recall some winters in these parts where the cold and snowy weather really didn't begin to around the holiday season with exact timing always a forecast issue. In my outlook I stated: the coldest weather relative to normal would be mid to/or late season and with this new data added, I'm sticking to it. 

It seems this ole' switcheroo or flip-flop temperature trend was quite common when the 
late autumn and even early winter season started out mild. I only had a few really mild 
winters in the whole sample (but then again I have learned, never say never it CAN happen). The past trend here, however, does point to a notable change as the season evolves and like anything else, time will tell and we shall see.

Making weather fun while we all learn,
Bill Deedler -SEMI_WeatherHistorian

Mother Nature Adds an Extraordinarily Gorgeous Northern Light Show To This Autumn's Color Season!

A spectacular northern lights show extended far south across the sky over the U.S. Monday evening, October 24th 2011. After Mom Nature did her usual beautiful leaf painting this autumn, she added a big bonus by painting the sky with vivid brilliant reds and greens with a teal shade. Just take a look at this picture (compliment of Lake Superior Photo) of the heavens on Monday night October 24th, 2011!

This shows the sun is active with solar activity and the number of solar flares is on the increase the past few years as we climb up the new solar cycle. I talk more about the controversy of solar cycles affecting the weather on the planet in the Winter Outlook.

In the meantime, see Northern Lights from the AP for more information on this event.

Record Low Pressure in Detroit for October Likely Established and Breaks a 118 Year Old Record !

On my blog yesterday I mentioned this current storm was projected to come close to the record low pressures for Detroit in October: At 3AM EDT this morning (10/20/11), Detroit's sea level pressure fell to 29.08" /985 MB/ which according to my records is the lowest pressure ever recorded for the month of October at Detroit! Just last October, a more powerful storm and very intense low pressure moved through the upper Midwest and set numerous record low pressures for that region. While the pressure was also low at Detroit, it did not eclipse the record low pressures for October when it fell to 29.24" on October 26th, 2010.

From yesterday's blog

"She's a beaut' of a storm and note its placement late Wed evening on the12z 10/19/11GFS with a projected central pressure of 988MB /29.22"/ in or near SE Mich. The record low pressure for Detroit in October was way back on 10/14/1893 in an intense low pressure of 985MB /29.09"/.  In more modern times, back in La Nina Fall (which ran from JJA 1970 – DJF 1971/72 & ONI of -1.3) on 10/16/1972, the pressure crated to 985MB /29.12"/ for the second lowest pressure at Detroit. Of course, remember these readings don't have to necessarily denote the central pressure of that particular storm since the center of the low pressure didn't have to pass right over Detroit. We will have to see how low the pressure actually gets at DTW.  Mother nature does seem to have a preference toward spinning up the deepest storms for October in Southeast Lower Michigan during mid month.;-)"

Peak Fall Color Nears in Southeast Lower Michigan Will Mother Nature Spoil the Show? Yes (and Update on the Latest Storm To Do It)

               Written by: William R. Deedler, Weather Historian SEMI - 10/12/2011       

/*Latest Update - 10/19/2011/

Fall leaf color is basically caused by lack of sunlight and to a lesser extent is influenced by the September and October weather. Drier than normal weather late in the summer into early fall will tend to accelerate the leaf changing process, causing the leaves to fall prematurely. Likewise, a wet September and October will tend to produce fewer vivid colors and the leaves may also fall earlier due to the rain, wind and storms. The prime weather conditions which are conducive to brilliant fall colors are warm, sun dominant days and cool, crisp nights but without frosts or freezes; such as high temperatures in the 60s and 70s with lows in the mid 30s to around 50 or similar to the our Indian Summer or Indian Summer-like weather (depending on location) experienced recently. 

 

These sharp, daily temperature swings and more importantly, the decrease in sunlight, play vital roles in the development of the leaf color. This combination of weather and lack of sunlight, creates a blocking effect on the sugars which are manufactured in the leaves and keeps them from reaching the root system. Eventually, these sugars convert to pigments that produce the vivid and brilliant colors seen on many trees in the fall. Evidently, the green chlorophyll in the leaves begins to fade during the shorter fall days with subsequently, less sunlight. Thus, the other color pigments already in the tree leaves are exposed come out and produce the fall color splendor. The yellow color seen in some leaves is created by the xanthophyll pigment, while the orange-red color is caused by the carotene pigment and the red-purple color can be attributed to the anthocyanin pigment. 

 

While color peak may vary season to season across Southeast Lower Michigan, generally the maximum leaf color occurs during the second and third week in October.  This appears to be close to schedule with the trees changing quickly now and most likely will peak about the third week of the month (or approx the 18-26th).  Unfortunately, it looks as though the beautiful gorgeous weather of the past ten days or so is on the wane, because of rain and waves of colder weather. For the next week or so, periods of wet weather along with progressively colder temperatures will spoil our peak autumn color season at least, somewhat. This next weekend will be nothing like last weekend with damper, breezy and colder weather to hold sway over Southeast Michigan. Best chance for rain will be late this week. Parts of the weekend may be salvageable for color viewing but the wind may screw that up too. 

After, early indications are that the models intimating another more powerful cold air mass to blow into Southeast Lower Michigan by mid-late week /18-21^st/ and this would follow the trends written in the Outlook. Preliminary indications a cold rain should move across the region sometime Tuesday into Wednesday with brisk wind conditions and unfortunately, this lousy weather will accelerate leaf drop. At their coldest, highs should be in the 40s to around 50 with lows in the 30s (some 20s are even possible if we clear out one night and winds decouple by the weekend). Normal highs at this time are in the upper 50s to lower 60s while lows fall into the lower to mid 40s.
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*Update 10/19 on predicted storm:

Deep storm with heavy rain and strong winds is on track to affect the entire region through Thursday (for current forecast, see: NWS Southeast Lower Michigan ).

She's a beaut' of a storm and note its placement late Wed evening on the12z 10/19/11GFS with a projected central pressure of 988MB /29.22"/ in or near SE Mich. The record low pressure for Detroit in October was way back on 10/14/1893 in an intense low pressure of 985MB /29.09"/.  In more modern times, back in La Nina Fall (which ran from JJA 1970 – DJF 1971/72 & ONI of -1.3) on 10/16/1972, the pressure crated to 985MB /29.12"/ for the second lowest pressure at Detroit. Of course, remember these readings don't have to necessarily denote the central pressure of that particular storm since the center of the low pressure didn't have to pass right over Detroit. We will have to see how low the pressure actually gets at DTW.  Mother nature does seem to have a preference toward spinning up the deepest storms for October in Southeast Lower Michigan during mid month.;-) 

Also just in Wed Aftn 10/19:
Latest GFS model guidance intimates we a not done with these cold October blasts nor storms. Another powerful cold jet core is being suggested on the GFS model diving out of northern Canada and into the Midwest/East next week (and this is not the first model run this has shown up for mid next week). If this happens,  it would open the door for more storminess and subsequent cold air. HOWEVER, the European model is much weaker and further west with this cold air plunge and trough. If this is right, warmer weather will push out ahead of the system with a ridge developing over the East.  So, the fun has just begun! Check back to see how this one plays out too, if this continues to be forecasted. --------------------------------------------------------------------------------------------------------------
After the gorgeous stretch of weather thru October (basically thru the 11th with temperatures averaging some 6-7 degrees above normal and virtually no rain) mid October offers quite a change and things will go downhill fast (at least for awhile). 

From the Autumn Outlook issued early September:
The thing that is worth noting were the sharp contrasting cold snaps that periodically erased the longer warm spells.  However, in spite of those sharp cold snaps throughout the fall, it also should be noted that October and in some years, early November had the best chance to contain some of the nicest weather. However, on the flipside, these sharp cold air masses tended to bring the risk of snow and the start of winter as a whole, earlier than on average. 

So, the moral of this fall’s story remains the same:

Enjoy the periodic nice weather & Indian Summers while you get the chance!

La Nina Continues to Strengthen...A Weak to Moderate La Nina for the Winter

La Nina conditions continue to build in the Pacific this Autumn 2011 along with an encompassing negative Pacific Decadal Oscillation. La Nina conditions of course refer to cooler than average sea surface temperatures /SST/ extending in a band from the coast of South America, westward across the central Pacific. A negative PDO /-PDO/ refers to cooler than average general Pacfiic weather temperatures west of the U.S. across the central and northern Pacific west of which, will only aid the La Nina. In April 2008, scientists at NASA’s Jet Propulsion Laboratory announced that while the La Niña was weakening, the Pacific Decadal Oscillation—a larger-scale, slower-cycling ocean pattern—had shifted to its cool phase (negative).

The ultimate maximum strength of this La Nina should be interesting as I've noticed a subtle shift in model projections toward a consensus to the lower end of the plot scale (with the mean or average in weak La Nina territory rather than Neutral). Where it finally lands, in part, will affect our weather patterns this winter in Southeast Lower Michigan and the Great Lakes. Of course, the important wild card, as always, will be the dominant phase of the North Atlantic Oscillation.


  
CPC gave an interesting narration recently on the current La Nina and some of the the individual model projections:

During September 2011, La Niña conditions strengthened as indicated by increasingly negative sea surface temperature (SST) anomalies across the eastern half of the equatorial Pacific Ocean.

Currently, La Niña is not as strong as it was in September 2010. Roughly one- half of the models predict La Niña to strengthen during the Northern Hemisphere fall and winter (Fig. 6). Of these models, the majority predict a weak La Niña (3-month average in the Nino-3.4 region less than -0.9°C). In addition, a weaker second La Niña winter has occurred in three of the five multi-year La Niñas in the historical SST record since 1950. However, the NCEP Climate Forecast System (CFS.v1) predicts a moderate-strength La Niña this winter (between –1.0°C to –1.4°C) and CFS.v2 predicts a strong La Niña (less than –1.5°C), which rivals last year’s peak strength. For CFS forecasts made at this time of year, the average error for December-February is roughly ±0.5°C, so there is uncertainty as to whether this amplitude will be achieved. Thus, at this time, a weak or moderate strength La Niña is most likely during the Northern Hemisphere winter. 

In any event, our new La Nina seems to be chugging along nicely so another moderate La Nina I think is as likely as a weak one (a "borderline" La Nina?;-) 

It will be very important to analyze the latest SST temperature plot and computer projections before I issue the Winter 20011-12 Outlook early November.