Great Stretch of Early Fall Weather Through Much of The Remainder of September!

Frequently I post about bad or inclement weather that's up and coming; but at times, I'll also post about nice or great weather in the offing...this is one of those times.

Over the next week to 10 days, a large blocking pattern in the atmosphere will evolve over the eastern half of the country; diverting most storm or rain systems well west and north of Southeast Lower Michigan. This will be our first Indian Summer-like pattern since much of the region has as of yet, experienced a killing frost or freeze. It's actually still a bit too early for a killing frost/freeze to encompass the region, even though most areas have fallen into the 30s at least once. This is why I use the term Indian Summer-like, since the overall pattern expected to evolve the next week is clearly reminiscent of what typically happens during an Indian Summer pattern - but with most areas lacking the forerunner killing frost/freeze. True, there is the brief cool down now in progress over the area that will last into early this week, but I don't look for any colder weather than what has been already realized. As the Autumn progresses, a killing frost/freeze will of course be realized over all of Southeast Lower Michigan but even then, it's usually a bit more of a gradual process. For more on what is a true Indian Summer, see my quoted article written early in my Weather Historian career with the NWS back in 1996.

As stated above; the upper air pattern projected by many atmospheric models display quite massive high pressure block developing over the eastern half of the country. This block with time, phases into the Bermuda High out over the Atlantic later in the week. The building surface and upper high pressure ridge is then expected to hold at least through the last weekend of September. There is some risk of rain but not until possibly early the following week (at the close of the month). As you can see on the prognostic maps;  the Polar Jet will also be pushed well north into Canada during the upcoming week as the general ridging grows and overtakes the eastern half of the country and western Atlantic.

The warmest of the weather should arrive later in the week into the weekend; possibly extending as far as early the next week. Many of the days from mid week on, will see high temperatures push back up into the 70s. As the weekend gets underway, readings will likely flirt with the 80 degree mark.

Something tells me the cider mills will be doing a brisk business - along with maybe even some beaches for a late season swim? Try to enjoy September's nice side for a change!

Teachers & Interest Groups: Maybe you were thinking you'd like a guest speaker on weather topics for your students or members this fall? In my free time, I would be open to scheduling a talk. Send me your name, school or group, location and topic(s) you wish to discuss via the comment section of this post/blog.  Talk subjects, times and fees are negotiable. Must provide visual aid equipment. 

Contact me here in comment section or at:

wxhstrn7414@gmail.com

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

*Update 9/1014 - Powerful Dynamic System Wednesday May Bring Round Two of Severe Weather in Less Than a Week

*Update 9/10

The GFS/Euro models continue to portray a weaker system than the NAM in regards to the severe risk on Wednesday and Wednesday evening. While lower and upper winds remain strong with the system, the marginal instability is being enforced by warmer air in the mid levels along with added tropical moisture. Strong to severe limit winds remain the primary focus with any convection that does manage to take hold with the marginal instability. As stated below yesterday, I continue to feel the NAM is on the strong side of actual outcome with this system. Still, if more instability is realized and is able to entrain into the system, then severe weather will be more likely.

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Original post - 9/9/14
A deepening low pressure system similar to last Friday will churn over the upper Mississippi Valley, Midwest and Great Lakes this Wednesday into Thursday. While the last storm center on Friday 9/5 had much better instability to work with, this one appears it will have better or stronger dynamics and wind fields, quickly turning clockwise winds at low heights (helicity) and powerful bulk shear force winds to compensate for weaker instability. Both bulk shear winds /Surface - 18,000 ft/ and heights as low as 925 MB /2500ft/ and 850 MB /5000ft/ are forecast to have winds estimated 50 - 70 knots. With that kind of wind just aloft, it won't take much to bring it down to the surface even with lesser instability this time.

This projected storm, better suited for late October or November with its projected depth (on NAM guidance which may be a bit strong), will take aim on the region Wednesday into Wednesday Night. Not unlike the last storm, the main threat will be damaging winds but in addition, there will be some risk of isolated tornadoes because of the spin in the lower atmosphere.

Maps are for Wednesday afternoon:

By Wednesday evening (below); the center of the low is slated to move into northern Michigan and while doing so, it will bring the most unstable air north into lower Michigan and thus, continuing the threat of severe weather into the first part of the night as the cold front swings across Lower Michigan into Southeast Lower Michigan.

Keep abreast of weather forecasts and potential of severe Outlooks, watches and warnings with this system especially if development continues to unfold as projected. The plotted model is that of the NAM which has been the stronger model with this system.

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

Autumn 2014 Outlook for Southeast Lower Michigan: A Tumultuous Fall?

It seems we just got started with summer and here it is, fall again. And, with the cool July this past summer, it even feels more that way this fall. 

Temperatures  

I look for temperatures to average around normal...or within two degrees of the normal. In my research, the normal range (or one standard mean deviation) for an average fall is in fact, about two degrees. At Detroit the 137 year mean now is 52.2... while the 30 year normal is a bit higher at 52.8. (see more, below).

Precipitation

The busy pattern of the summer looks like it will continue into the fall with normal to above normal rainfalls (see more below).

 

Fall is cited for its wild swings in temperatures and this fall certainly should be no different as impressive upper lows in Canada dive south and southeast into the U.S. The aggressiveness of this overall, now common-place pattern shows little change in the last year. Both upper air and analogues also do suggest typical to strong cold outbreaks along with some contrasting upper ridging to bring classic Indian Summer weather. Generally with stronger El Ninos, the risk of not having common Indian summers rises as the jet remains stronger across the south and less ridging/blocking is likely.

 

 Pacific Water's in Transition

The ENSO state continues to "ebb and flow" toward an El Nino state. The problem is just how much of an El Nino state will be recognized? Earlier this year; many dynamic and statistical models were gun-ho on at least a moderate El Nino but have since backed-off on this more aggressive state. This will definitely have an effect on the upcoming autumn and especially winter. Weak El Nino's can bring - or aid - in a variety of scenarios for the upcoming seasons.

Here is the CFS projections for the upcoming El Nino and its when and where positions into th winter. Notice the projections move from a general Pacific basin El Nino to an east base. This too, if accurate, would have repercussions on our winter.

                                                                        

 

 

 

 

 

 

 

 

 

 

 

                                                                     CFS Projected Temperatures

Pacific ENSO Sea Surface Temperature Projections

Latest run of the assortment of models project the following;

The most likely scenario realistically is a range (tan shading) between 0.6 and 1.1 which would place it as a weak El Nino. Therefore, the upcoming fall and winter while influenced somewhat by the El Nino state, will not be ruled by it. Of course, this opens the door to a whole realm of possibilities as to the outcome of the upcoming winter, but first lets take a look at one season at a time, autumn.

Upper/Surface Patterns 

Oscillations of upper and related surface patterns with a preference toward troughing and cooler than normal weather should be balanced out somewhat, leaving us with an average or normal fall with notable sharply contrasting patterns. That being said; it will be prudent to keep a watch on evolving phases of the NAO and AO...and once again and just as important, like the last several seasons; the EPO. While there is no projection of the EPO that I'm aware of; there is for the NAO/AO. 

 

The latest experimental projections of these oscillations are below, from Kyle MacRitchie, a Ph.D. candidate in Atmospheric Science at the University at Albany

 

Projections for North Atlantic Oscillation /NAO/  (above) this fall are fairly tame with of course in time, wider variations in ensemble projected data from October on into the opening of December.


Investigating the encompassed Arctic Oscillation /AO/ (below) proves to be more interesting. More negatively biased data output rules in the Arctic Oscillation during the autumn months. In addition; more wider swings in the ensemble package.

 Autumn 2014 Analogues

Temperatures

Autumn analogues continue the same trends seen in the summer analogues with the majority /5/ of the seasons containing normal temperatures; with two below normal and two above. The problem is the averages are the mean of the extremes, in some years! Look for some notable contrasts during the falls. October is highlighted with above normal temperatures but we know how monthly trends have been working recently. The actual temperature trends have been reliable but not timing. All I can gather from this is that warmer than normal temperatures are likely, likely creating some Indian Summer weather mid fall.

Preciptation 

Rainfall is very similar to summers analogues with a wild variety of outcomes with a tilt toward normal to below. I feel this is a bit too low given the trend we are in and likelihood of busy frontal activity. I look for normal to above rainfall across the region.

While the chances of a frost/freeze occurring near or before the average dates were good, the dates when the first snow flakes (trace) flew were more variable. October historically sees at least a trace of snow by the end of the month.

Get out and enjoy the good fall weather!

 

Important Dates

Autumn arrives: Mon  - Sep 22nd @ 10:29PM

Harvest Moon; Mon - Tue Sep 8-9th

Hunter's Moon: Wed - Oct 8th

Halloween:  Fri - Oct 31st

Thanksgiving Thu - Nov 27th

 

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

 ________________________________________________________________________________________

 

Teachers & Interest Groups: Maybe you were thinking you'd like a guest speaker on weather topics for your students or members this fall? In my free time, I would be open to scheduling a talk. Send me your name, school or group, location and topic(s) you wish to discuss via the comment section of this post/blog.  Talk subjects, times and fees are negotiable. Must provide visual aid equipment.

 

Links:

2014 temperature extremes: U.S. runs hot and cold

Farmers almanac's signs of a hard winter?

Summer of 2014; Was it Really So Cool? You Might Be Surprised! And, Was it Wet? No Surprise Here!

Overall summer across Southeast lower Michigan averaged right on normal across Southeast Lower Michigan when you average the three main climate sites.  What?

Yes, that's right! The one degree /-1.1/ below normal at Detroit is purely a function of the warmer 30 year normals for Detroit (as compared to Flint and Saginaw who actually averaged normal to slightly above - see stats below) The warmer normals at Detroit are mainly due to the expansion of Detroit's heat island out into the suburbs including Detroit Metro Arpt. In addition (and more proof of the heat island affect); the 70.6 degree average at the Detroit landed squarely on the 100 year normal for Detroit before the artificial heating /70.6/.

Want more proof that backs up the heat island affect at Detroit; look at the normal temperatures and this summer's averages at both Flint and Saginaw (below) whose sites have negligible heat island affects. Flint actually averaged about a degree /+0.9/ above normal, why Saginaw averaged almost right on normal /+0.2/. In fact at Flint, both June and August averaged close to 2 1/2 degrees above normal! Therefore, none of the climate sites in Southeast Lower Michigan landed anywhere near the top 20 coolest for the summer.

Reasons it felt even cooler:

Oh there were cooler statistics; the notable less than normal 90s across the entire region!
Detroit felt only three 90 degree or better temperatures. One each month, with the highest at 94 on 7/22/14. Flint only felt one 90 degree day on 6/17/14 during the summer season while Saginaw also felt a 90, on 6/28/14. These recorded 90s are far below the normal or average across Southeast Lower Michigan where 8-12 are routinely seen in a year (it is still possible yet to catch one or two in September).

Another big reason (if not the biggest) was the notably cooler than normal July. All three stations rallied on below normal statistics there! As far as my opinion, if temperatures are gonna be below normal...JULY is the welcome month!

Top 20 Coldest/Warmest Julys in Southeast Lower Michigan
Rank	Detroit Area*				Flint Bishop**				Saginaw Area***
	Coldest		Warmest		Coldest		Warmest		Coldest		Warmest
	Temp	Year	Temp	Year	Temp	Year	Temp	Year	Temp	Year	Temp	Year
1	67.1	1891	79.3	2011	65.6	2009	78.0	1921	66.0	2009	77.5	1921
2	68.8	1992	79.0	1955	66.9	1992	77.7	1935	66.2	1992	76.8	1916
3	68.9	2009	79.0	2012	67.3	1967	76.8	2011	67.1	1924	76.4	2012
4	68.9	1967	79.0	1921	67.3	1962	76.7	1934	67.2	1920	76.2	1935
5	69.6	1971	77.9	1916	67.4	1971	76.5	1955	67.3	1945	76.1	2011
6	69.6	1875	77.7	1931	67.4	1960	76.1	2012	67.5	1962	76.0	1931
7	69.7	1920	77.1	1988	67.5	2000	76.1	1931	67.5	1956	75.9	1955
8	69.9	2014	76.8	1999	67.6	1996	75.9	1936	67.8	1950	75.9	1936
9	69.9	1924	76.8	1901	68.3	2014	75.8	1933	67.9	2000	75.8	1988
10	69.9	1884	76.6	2010	68.3	1950	75.5	1987	68.2	1965	75.5	1934
11	70.2	2000	76.5	2002	68.4	2004	75.2	1988	68.4	2014	75.3	1933
12	70.3	1882	76.5	1952	68.4	1965	74.9	2002	68.4	1985	74.3	2010

Still another reason it felt cooler; it's been hotter in recent years and thus, comparatively it  "felt" cooler. And finally to a lesser extent it felt cooler; it rained a lot - more than average at all three sites.

Analogues/Outlook?

My analogues and outlook temperatures and projected averages performed well and right from the get go when I dismissed the projection's of a notably cool summer...

Temperatures :

Overall; a comfortable summer is on tap as I look for temperatures to average around normal to slightly below for the summer. That being said I don't anticipate a notably cool summer. I look for temperatures to average between +1.0 degree and -2.0 degrees of the summer norms across Southeast Lower Michigan (see a more thorough discussion under Analogues). Many others are calling for a cooler than normal summer across the Great Lakes; including Southeast Lower Michigan.

 

Since late fall of 2013, we have had a couple of years which take full marks for past prediction of the past few seasons; 1880-81 and 1981-82. And, maybe not surprising; 1881 contained a normal summer while 1982 had a cool summer (like our two prevalent trends seen). Another year; 1899 joins these analogue ranks as a decent performer during the winter and a good parallel this spring. All three analogues projected a cool spring with the temperature pattern we've seen this spring with time; below normal - normal - above normal. These analogue springs averaged below normal because of a very cold beginning to the season but will a gradual trend change from below to normal to above (Mar; Apr, May). The Summer of 1899 turned out to have a normal summer, therefore we have two normal summers and one below for the recent better performing analogues.

 

While the summer temperature and averages performed well; the pattern unfolded slower than prevailing analogues...just like the spring. May's above normal warmth held through much of June while June's expected coolness showed up by July. The sine-wave pattern returned to normal and above in August. While overall temperatures pattern trends and numbers/averages for the summer are realized, the timing remained somewhat elusive. And as stated before, temperature patterns most of the time don't come neatly wrapped in monthly intervals in the real meteorological world, therefore this signal is least important.

 

Wet and Wetter!

It was the 19th wettest summer at Detroit with 12.75"; 17th wettest at Flint with 12.04" and Saginaw just missed 20th spot with 10.52 (20th 10.63").

Of course the big news of the summer around metro Detroit was the big flash flooding event on August 11th with 4.57" of rain officially at Detroit. Other totals were higher and lower for a complete write up see here. The rainfall total at Detroit in August was 6.32", which made it the 9th wettest! Had that on day of flooding rains not occurred, August would have been drier than normal with just 1.75" falling the remainder of the month.

That 4.57" of rain in a calendar day was also quite noteworthy! After researching my records from Detroit, I noted that amount was the second highest amount of rain ever to fall on a calendar day in Detroit!  "Previous record was back in 1926 with nearly the same... 4.51" on August 17th, 1926. However this is NOT the record of all time for a date...that record also occurred in the 1920s...occurring back on July 31, 1924 with 4.74". 

You might remember last summer around metro Detroit was also a wet one; actually wetter than this one with its rainfall total; a whopping 16.13" of rain fell making it the third wettest summer of all time records in Detroit. However; Flint and Saginaw were decidedly drier and not placing in the top 20 wettest list.

Analogues/Outlook?

Rainfall:

I look for rainfall to be quite variable as mixed data presents conflicting results but this is not unlike many summers. Taking all data (past and present) into account; rainfall is expected to be around normal over the southern sections of Southeast Lower Michigan and normal to below across the Saginaw Valley and Thumb Region.

Rainfall projections for the summer, are really a mixed bag, as it frequently is in the summer with four normal rainfalls, four below and two above with the average skewed on the drier side. A notable trend from many of the summer analogues are wetter conditions early and/or mid summer with drier weather later summer.

No doubt about it, my call for normal rains south and normal to below north was too dry. While lesser rains did fall in the far northern sections of the region, most areas still received above normal rain. This was primarily do to just a day or couple days of torrential rains. In addition; the jet stream remained active across southern Canada and the Mid West as expected see Stormy Weather, below.



Stormy Weather?

All in all, severe weather seemed rather normal to maybe somewhat above for severe thunderstorm activity/warnings but well below for tornadoes with just two confirmed this summer. Don't quote me on these statistics since they aren't out.

Analogues/Outlook ?

Stormy Weather?

As mentioned above; the data to me depicts a notable confrontation zone and I believe we have just recently entered it as of late May. Typically, the busiest times for severe weather in these parts is June into July; with mid June to mid July prime-pickens. I've included the severe weather stats for Southeast Lower Michigan since 1980. Looking above at our analogue summers since then are 1982, 1991, 1997 and 2002 and all but 1982 contained normal to above normal (or busy) severe seasons. That's not surprising given the jet stream that's been dominant in Canada this year. Were this upper jet continued to be aggressive, notable wind events, squall lines and possibly a derecho event or two across the country would be the risk. 

This confrontation zone held well  (too well) through the summer as the upper low/northwest jet stream remained active all summer and thus, the parade of cold fronts, warm fronts and resulting heavier rains. 

Epilogue;  

Overall when considering both temperatures and precipitation, two analogue years held us in good stead for the summer; 1957 and 1968. Both were wet with temperatures averaging close to this summers (see analogue chart)

Next Up...The Autumn Outlook. 

Note; this summer data is preliminary and has not been released by the NWS
as of 900pm Monday, Sep 1st 2014.



Making weather fun while we all learn,

Bill Deedler -SEMI_WeatherHistorian