Strong Dominant Hot Ridge and Occasional Deep Upper Low in Eastern Canada Responsible for Very Warm and Dry Pattern Thus far This Summer /Updated 90 stretch - DTX/

The Summer of 2012 has started just like the past few summers with plenty of heat with above normal warmth across Southeast Lower Michigan. Now with the last day of June recorded in the record books; June of 2012 will go down as the 9th warmest June on record placing a smidgen ahead of 1994's 72.2 (originally 9th place) with an average of 72.3. This places it right smack dab between 1994 and 1991.

Interestingly; neither Flint nor Saginaw placed in the top ten warmest Junes. In fact, Flint did not even place in the top 20 warmest Junes; while Saginaw placed down at 17th. Flint's June average temperature was 69.2 degrees, while Saginaw's average was 69.8 replacing 1987.

Top 20 Coldest/Warmest Junes 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	62.8	1985	74.6	1933	60.1	1969	75.0	1933	60.6	1982	73.9	1933
2	62.8	1903	74.1	2005	60.9	1958	74.9	1934	61.0	1926	73.5	1919
3	63.1	1915	74.0	1919	61.5	1980	72.1	1949	61.5	1915	72.3	1971
4	63.4	1928	73.3	1949	62.5	1985	71.7	1925	61.8	1958	72.3	1934
5	63.4	1926	73.2	1934	62.5	1972	71.5	1921	61.9	1917	71.7	2005
6	63.4	1916	72.8	1943	62.9	1982	71.3	1943	62.1	1980	70.6	1931
7	63.6	1927	72.7	1952	63.1	1977	71.2	2005	62.1	1916	70.5	1976
8	63.7	1980	72.4	1991	63.3	1960	70.3	1952	62.3	1945	70.4	1949
9	63.7	1889	72.2	1994	63.4	1928	70.3	1987	62.7	1977	70.3	1967
10	63.8	1878	71.6	1995	63.6	1945	70.3	1939	62.8	1985	70.2	1932
11	63.9	1958	71.6	1890	63.8	1927	69.8	1931	62.8	1928	70.0	1995
12	63.9	1902	71.5	1944	64.2	1992	69.8	1923	63.2	1947	69.9	2007
13	64.1	1917	71.4	1921	64.5	1947	69.7	1991	63.2	1902	69.9	1923
14	64.2	1982	71.3	2007	64.6	2003	69.6	1954	63.3	1903	69.9	1930
15	64.2	1972	71.3	1954	64.7	1961	69.6	1932	63.5	1969	69.9	1921
16	64.4	1881	71.3	1987	64.9	1986	69.5	1971	63.7	1972	69.9	1911
17	64.6	1935	71.3	1923	64.9	2009	69.5	1944	63.8	1927	69.8	1987
18	64.6	1897	71.2	1895	64.9	1974	69.4	1941	64.2	1978	69.7	1999
19	64.7	1969	70.9	1953	65.1	1978	69.4	1930	64.2	1940	69.7	1901
20	64.8	1907	70.8	2002	65.1	1948	69.3	1976	64.2	1924	69.6	1943
* Detroit Area temperature records date back to January 1874. ** Flint Bishop temperature records date back to January 1921. *** Saginaw Area temperature records date back to January 1900.

 
Why the discrepancy between Detroit, Flint and Saginaw? Again, mainly because of the heat island effect at Detroit Metro Airport. And, not just the overnight lows on the hottest of days but also on the coolest of nights! The reason both Flint and Saginaw placed so much lower in the top 20 hottest Junes (or not at all) was the decidedly, refreshing cool blasts that occasionally occurred during the month. This was due to our friendly cool upper low pressure centered over eastern Canada that plopped its caboose far enough south over the Great Lakes and Northeast, to break the hot spells. Of course, these cooler infiltrations happened at Detroit too but on several occasions; that cooler air was introduced across the region on a north to northeast wind. This is not conducive to the coolest of nights at Metro with the wind flow across the urban and suburban areas into Metro Airport.

With all the heat lately, it is easy to forget the strong cool blasts Southeast Lower Michigan did see in June. As a comparison; Flint's temperatures fell into the 40s for overnight lows ten times during the month and two of those were 42 degrees, ten degrees from freezing! Saginaw saw overnight lows fall into the 40s five times with the lowest; a double 46. Detroit had a lone 49 degree low for the month but still, there were numerous 50s. Take away the heat island effect; and I doubt Detroit would have placed much above the mid teens in the top 20 warmest Junes, like Saginaw. Unfortunately, this micro-climate does affect temperatures (mainly overnight lows) at Detroit and several other major cities...polluting long term records (but don't get me started ;-)).

Last year's hot Summer of 2011; tied with 2010 in Detroit at 74.4 for fourth hottest summer! We also did end up with 23 days where the temperature rose to 90 degrees or better. Thus far we are moving right along on the 90 degree track again with already 11 days of 90 degrees or better at Detroit; average is about 12-14. Even though Flint did not place in the top 20 warmest Junes; there still were 7 days with 90 degrees or better in June and one 100 (8 for the season). This is the best example of the contrasting temperatures during the month! Here Flint has had 7 days of 90 degree or better, including the 100...yet failed to even place in the top 20 warmest Junes! Want more proof? Get a load of Flint's June temperature extremes...100 degrees and two 42 degrees!

Why so hot; yet "so cool" with average temperatures just  2 1/2 degrees above normal? DRY! That's right, the upper wind pattern thus far this summer has been conducive to bring the blistering heat out of the Great Plains and Midwest, east into the Great Lakes. While to a lesser extent, the upper flow over Canada has occasional been impressive enough to break through the hot ridge and back it off further west and  thus keeping the worst of the heat; west and southwest of us until really just this past several days. While this has helped in the temperature department somewhat; it had added to the dry conditions. When these cooler air masses have surged out of Canada, they flow across the relatively, cool and dry continental regions of Canada. This, combined with the prevalence of the strong hot ridge west and over us; has lead to a relatively scant moisture supply being the usual Gulf summer moisture has been cut back some. 

Since the hot ridge has been so dominant over the country; increasingly dry soil conditions are exacerbating the heat and thus, exacerbate the dry conditions. Simply put; they feed on one another!  That's why it's been so easy to pop into the 90s...just look at your yard...it's becoming semi-arid out there in many places! This comes, of course,  at the worse time possible in the growing season. Many areas are at least two to nearly four inches below normal in this years growing season! A season that still has at least two solid months left yet. I feel this dry weather phenomena is just as important as any heat (and there at least so far, we've had some relief).

Check out the latest Drought and Dry Index Map>>>

 This map below, shows the growing season (90 day) precipitation (or really lack of), percent of normal departure.

And this map below, shows the expansion for the below normal rainfall for June (30 day percent of normal).
Note the worsening dry conditions as relayed by the percent of normal rainfall (or really, lack of).

Next up...
With the dominance of the hot ridge of high pressure thus far, I will be updating my Summer Outlook for the region by boosting temperature departures a bit higher anyways than I originally indicated. On the precipitation side of things; drier conditions looked like they'd be most likely from I-69 south; across two-thirds of the region. Preliminary indications here are; I will likely encompass the whole region but want to look at some indicators.

So then; will strong hot upper ridge continue to be the dominant player in our weather or will it begin to be squashed more often by the Canadian Low? And what of severe weather? Thus far, most of the action has been around us, especially south...will this continue?

Look for my mid-summer update within a week or two!

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

 

Competing Amplified Upper Air Pattern Coming To Fruition

Back in the Summer Outlook I displayed and discussed the two main weather patterns that seemed to me the most likely to "compete" during the summer months. Actually; I felt mother nature tipped her hand at the most likely weather pattern for the summer back in the spring and discussed that in the Outlook.

Overall; the strong ridge is expected to continue to be a dominant player and will oscillate from the center part of the country to the east; bringing the periods of heat. Normal to below trends will be brought about by the dubious North Atlantic Oscillation /NAO/ cycling lower into neutral to possible negative phases (more below) which would aid in emphasizing the upper low and troughing over central and eastern Canada.

This pattern has been well represented during the past several weeks with the cool and hot periods seen this June. Latest model trends continue to advertise this amplified competition... let's take a look at it on this hot day.

Present 500 MB: Tue 2PM 6/19

Present 850 MB: Tue 2PM 6/19
 

 Projected 500 MB Mon 10 AM 6/25


Note the complete flip-flop of the upper air jet pattern across North America! Not only the flip-flop change but the amplification is quite extraordinary one week from July!

Projected 850 MB Mon 10 AM 6/25

Likewise the cool surge of 850 MB temperatures (note the core of +3C over much of central and northern Michigan).

Another model for comparison to this anomalous pattern is the ECMWF and believe me it's no tamer. Just look the projected amplification of the 500 MB pattern, a strong ridge extends well into the Arctic circle while at the same time; the cold upper 500 MB vortex is displaced well south for late June over the eastern Great lakes. This is very reminiscent of some patterns seen earlier this spring!

 Projected 500 MB TUE 8 AM 6/26

What is even more fascinating is that the GFS strongly suggested this pattern way back on the 12th of June. Fascinating IF the actual upper air pattern resembles this anomalous projection that was about two weeks out!

Of course this is PROJECTED by both models and isn't actually observed data but with both models projecting such a strong amplified pattern...it bears watching.

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

SUMMER 2012 OUTLOOK FOR SOUTHEAST LOWER MICHIGAN: Neutral Pattern Leaves Our Summer Weather At the Mercy of Two Key Players - And One Overall; Dubious One

Summer 2012 Outlook For Southeast Lower Michigan

By: Bill Deedler; Southeast Lower Michigan Weather Historian

                                                      May 31st, 2012

Temperatures:

Overall, I look for summer temperatures to average cooler than last summer with closer to normal temperatures to slightly above normal /-1.0 to +2.0 degrees/. Local analogue data for this summer generally shows a variable summer temperature pattern as would be expected with negligible Pacific effects. More importantly for this summer are recent upper wind developments and projections for these upper wind patterns. Several models (see below) suggest the ridging over the High Plains eastward into the Mississippi Valley; will periodically expand east across the Great Lakes and East bringing heat into the region. In spite of the strong upper ridge however; will be the occasional influence of the upper level low and trough that made itself known this spring over eastern Canada when it still was able to penetrate; albeit infrequently, well south into the Great Lakes and Ohio Valley eastward to the East Coast.

Overall; the strong ridge is expected to continue to be a dominant player and will oscillate from the center part of the country to the east; bringing the periods of heat. Normal to below trends will be brought about by the dubious North Atlantic Oscillation /NAO/ cycling lower into neutral to possible negative phases (more below) which would aid in emphasizing the upper low and troughing over central and eastern Canada. Look for the number of 90 degree days this summer to closer to the normal /8 -14/.

Rainfall:

Overall rainfall this summer is challenging due to this past spring’s variable pattern. Recent patterns have been drier than normal conditions across the Ann Arbor into metro Detroit area. Wetter than average weather from the center part of Southeast Lower Michigan (around Flint into Port Huron) with about normal rainfall across the Saginaw Valley and Thumb Region. As I look into the summer; I feel this basic pattern will continue with normal to above rainfall from the I-69 corridor north; but normal to below south. Storm trends and severe weather are discussed under summer analogues.

Broad Scale Discussion

Last summer, generally Weak La Nina to Neutral conditions prevailed over the eastern Pacific through the summer. Then; another La Nina, albeit weaker than the Winter of 2010-11, formed again this past winter (2011-12). Recently, water temperatures  moderated this spring to again, near normal or neutral conditions  (Fig-1a).

                                                    Fig-1a

As one can see with Fig-1b/1c (location of Nino 3.4 and the projected sea surface temperatures /SST/ for the summer), the majority of model members are projecting a continuation of the recent warming (or moderation) of the sea surface temperatures /SSTs/ in area Nino 3.4. Latest mid-May guidance continues neutral conditions thru the summer with possibly a weak EL Nino commencing as early as late summer or early fall.
                                                                       

                                                     Fig 1b

           

                                       

                                           Fig 1c

Looking above at each specific dynamic model above shows they generally are in the same camp with the gradual warming expected to continue into summer and by late /JAS/, project just a hint of above normal readings. Under these conditions little, if any, significant downwind affects are slated for the Great Lakes. While there are some affects seen across the U.S. during stronger La Ninas (as with El Ninos), they are generally negligible when it comes to weak La Ninas, El Ninos or Neutral conditions, especially during the summer months.

Warm trend seen the past year or four seasons: Will that trend remain our friend?

Without a doubt; the most obvious and strongest trend seen by far in our (including much of the nation’s) weather has been the domination of warm, above normal temperatures relating much of the time directly to that dubious NAO/AO remaining in a positive phase (NAO+/AO+)!  The unprecedented string of nearly continuous positive NAO/AO; especially the last three seasons of Autumn 2011, Winter 2011-12 and Spring 2012 has been astounding!

While this persistence has been almost unreal; will it continue especially since it’s gotten “so long in the tooth”? It is difficult to go against such a strong trend but sooner or later all “good” things come to an end. The very recent pattern change seen first very weakly early April, then again in early May and now; much more pronouncedly in late May into early June may be an early sign of a change (or at least back to some sort of “normalcy trend’). Then again; a recent change does not a long term pattern make. At this time it would be prudent to watch for more repeated break-downs in the NAO/AO to more neutral to negative territory. Therefore; I have chose to incorporate this recent trend in my forecast, somewhat.

    

Selected  Projected Model Data for the Summer of 2012

The following temperature /C/ projections are from various named models for the summer.

             

            

All models show the general build up of heat (ridge) from Texas northward with a few suggesting a bit more north-northwestward. This summer pattern is almost a given; the big question is where exactly will the ridge and the eastern Canadian trough place.  With some models hinting at the ridging placing in a “north by northwest” position this would be important since it would allow more periodic digging of the Canadian trough and subsequent cool downs for at least the Great Lakes. It also could imply some retrograding of the main eastern Canadian Low at times which could bring more extensive cool downs, depending on its strength. And; while on that upper wind wind scenario, check out below what I feel gives the best representations of the 500 MB pattern projected for this summer.

              

                                             500 MB  Projection A  - NSIPP____  _______

          

                                             500 MB  Projection B  - ECHAM____  _______

I like both of these projections upper wind projections because:

A) The NSIPP-1 model because of it’s general placement of the 500 MB long wave  summer ridge (from Texas northward into the Dakotas but with expected occasional eastward building) and long wave trough extending from the Eastern Lakes into New England.  Mom Nature, I feel has already shown her hand this late spring for our summer pattern. The notable ridge that has been in place and dominant and to a somewhat less extent; the Canadian upper low and trough - both key players.

B) The ECHAM4 model because of its somewhat flatter pattern with weak short waves (impulses) topping the ridge instigating storm action.

I researched both upper air patterns from past analogue summers (below) and they seem most realistic and in conjunction; will serve up our summer weather.

    2012 Analogue Summers  

                                     (Click on Analogue chart to enlarge)


Note: The number 2 on some years denotes the Neutral conditions came after a second La Nina. The general cycle was: La Nina-Neutral-La Nina-Neutral. Also; the 1971-2000 norms were used reflective of less contamination of the heat island affect (DTW). They are closer to the century average used in composite maps norms of 1895-2000 and recently used in previous La Nina to Neutral analogue patterns.

Analogue Summer Trends

Looking at the trends seen in the analogues suggest the summer temperatures will be mixed with the dominant trend more difficult to peg. While the upper warm ridge has been dominant this spring; the recent appearances of a negative NAO along with the evolution of the trough in Canada hints at this more mixed pattern seen in the analogues for the summer. 

While most years were drier than normal, when it was wet, it was wet! When looking at just the statistics (of which I’m really not a fan of since they generally don’t tell the whole story), the odds this summer’s rainfall will come in an inch or more below normal are about 70%. In the past, when chances were that high in the analogue years, it was usually the way to go. What is troubling this time is when the rainfall came in above normal, it was well above normal! This says to me there is a decent potential of some extended battling of air masses and thus, some stalling of fronts (not to mention a higher risk of a forecast bust). The upper air pattern seen late spring could easily evolve into one of these patterns as the summer heats up and the trough in Canada holds somewhat tough, somewhere a confluent zone will likely set up along with heighten severe weather risks. At the same time, a dry or drier spell this summer looks just as likely and there‐in‐lies the problem. In this type of dilemma; the existing pattern of the location of previous rainfall pattern seems suitable.

Analogue Composite Maps Discussion:

Analogue composite maps below reflect nicely the overall pattern suggested by the computer models for the summer. A Broad ridge extending from Texas northward (first NSIPP 500 MB map) but also hint at the flatter ridge with short waves rotating through the mean ridge (ECHAM). Of course; these maps reflect what happened and are only another piece of guidance. I feel they represent the overall pattern expected this summer. Take note; the average temperatures in the fine scale (ie: areas of green or light blue) are less than a degree below normal.

A few notes on the following composites:

1) Its best to look at the trend of the temperatures or precipitation for entire season. In other words, warm or cool periods don’t always come neatly wrapped up in one month, many times a trend is seen overlapping from one month into another The whole season may indeed start out above or below normal but toward the middle or end, temperature departures average the opposite. 

2) The actual numerical departure value above or below for an analogue season projection is not as important as the sign(+/-) ahead of it.

                          
                             

                                     ANALOGUE SUMMERS 2012 MAPS

                               (based on the 1895-2000 average)

Taking into account written above about analogue precipitation trends (very wet versus dry); they are less helpful since they represent the average of all the years.

                    

            

              Since this average temperature departure is derived from the 1895-2000

average temperature (as opposed to the 30 year norm), it would be nice

to know what the summer average (s) are in Southeast Lower Michigan

for that century plus period.

Actually two temperature averages are displayed for Southeast Lower Michigan.

Area-1 paints much of Southeast Lower Michigan (roughly from the Flint and

Port Huron areas south to the Ohio border), while Area-2 encompasses the

Saginaw Valley and Thumb Region. Note history tells us that the Saginaw Valley

and Thumb Region summers are a few degrees cooler on average than the

remainder of Southeast Lower Michigan.

Area-1 displays a summer average of about 70.5

Area-2 displays a summer average of about 68.5

Since it is expected that Neutral conditions will prevail during the summer, it might be worthy of a look at past effects over the country when Neutral conditions existed. The top maps denote above normal, the middle below and the bottom, normal. This agrees with our local data of the dominance Note, the Climate Prediction Center /CPC/ explains these two categories (high frequency and trend adjustment) this way:

There have been significant trends in precipitation and surface air temperature

at many locations in recent decades, so it is worthwhile to examine the influence

of trends on ENSO composites.  For this purpose, two basic types of composites

are examined:

• High-frequency (denoted HF) composites
• Trend adjusted (denoted TA) composites

     

If conditions warrant, an updated Summer Outlook will be sent.

Have a good summer, enjoy any time off and may good weather be

your traveling companion.

SUMMER BEGINS: JUNE 20th at 709 PM EDT

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