Summer Outlook Update: On the Warmer Side But With Wide-Ranging Rainfalls


Dedicated to Beloved Family Member: Mac: 9/14/98-6/26/16

In my initial Summer Outlook for Southeast Lower Michigan I discussed the changeable, roller coaster type of summer temperatures pattern expected; resulting in temperatures averaging a degree or two above or below normal, depending on the dominant trend. The overall pattern I expected has materialized with the warmer side seemingly winning out.

 From the original Outlook:

"Our best analogues this past winter, 1982-83 and 1997-98 contained normal summer temperatures averaging very close to 72; just a few tenths different from each other. Likewise; I look for the summer to continue to display the more roller-coaster type of temperature pattern (not unlike seen this spring and also dominated, the Spring of '83) with sometimes significantly above, below and everything in-between but ultimately resulting in the normal or typical summer. 
Summarizing: I look for temperatures to average 1 - 2 degrees of the summer norms across Southeast Lower Michigan."

Temperature Update:

Considering prevailing trends thus far this summer; instead of temperatures averaging one or two degrees above or below the norms, I now expect temperatures to average one to three degrees above the norms with warmer than average weather winning out. No other change in the pattern is expected with active, roller-coaster type of pattern earlier to continue to hold.

Along with the temperature pattern; it appears the stormier side discussed in previous analogues may be finally becoming more prevalent as the summer moves on and the pattern to the south drifts northward. However; to predict where these convective rains will rule is exceedingly challenging this summer especially since it appears in just short distances vast differences of rainfall have already occurred recently. While this is typical of summer rains anyway, there will likely be even more variable total rainfall because of the exceedingly dry conditions that prevailed in most areas up until this July.

From Original Outlook:

In conclusion: Look for rainfall to average normal to above across the southern half of Southeast Lower Michigan and normal to below across the northern half.

Rainfall Update 

Prevailing and expected pattern the rest of the summer dictates rainfall to contain wide ranging totals due to a drier June into early July. Even if more typical normal or even above normal rains occur; overall rainfall will generally range from below normal to around normal. This was the pattern I was looking for over the northern half of the region in the original Outlook. There may be even some pockets of above normal due to heavy dumping convective rains.

Again narrowing and tightening-up the original summer outlook some; look for the summer to average up to a couple of degrees warmer than normal with below to normal rainfall prevailing across most areas with pockets of above normal.

Enjoy the remainder of the summer!

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


Very Dry Weather Over Much of the Area Thus Far This Summer and Growing Season

Dedicated to Beloved Family Member: Mac: 9/14/98-6/26/16
                                   Dedicated to Beloved Family Member: Mac: 9/14/98-6/26/16  
The worst of the summer in Southeast Lower Michigan in many people's opinion of the season has been the dry weather; particularly if a one's a farmer, garden or owns a garden or landscape business. Thus far this summer /June/, we've generally had less than half the normal rainfall across the land. Of course, what makes matters worse is that May's average rainfall again, was also around a half or less of the normal. And, that is still not the extent of it; the rainfall since the start of this growing season /April/ has been in notably deficit with most areas receiving only 50 - 60% of the normal rain. See the chart below.

There is a chance of some rain overnight after midnight; so the June stats should remain the same as departures account for no rain through midnight.

                                   Growing Season 2016 Precipitation

How much the rainfall has been below normal can been seen on this departure growing season map below. Also note, the extreme dryness bulls-eye over southern Iowa and northern Missouri; while wet bulls-eye lies over northern Wisconsin and West Virginia with the recent flooding.

Adding to the dryness, June's warm temperatures have been normal to slightly above (about a degree or two).

That may be surprising since we've had some hot days in June. The main reason the average temperatures haven't been even warmer is that the dry weather allowed readings overnight to fall-off more appreciably. Humidity levels have been generally somewhat lower than normal for many summer nights.  Therefore, our daily diurnal temperature variances have been larger on average - a bit more typical of weather experienced in the Great Plains.

Because of a wet late winter and early spring /Mar/, the overall aridity of the region is still more surface based than deeply based. However; this offers no solace to plants and crops that normally have shallower roots than the deeply rooted ones. 

Drought Map and link for the Midwest and Michigan

Midwest and lower Ohio Valley

Highly variable rainfall was noted over the region’s Abnormally Dry (D0) and Moderate Drought (D1) areas. Relatively narrow swaths of moderate to heavy rain (1-4 inches, locally more) resulted in reductions of D0 and D1 coverage, most notably from Ohio into east-central Iowa. Conversely, D0 was increased over central and southern Michigan, where 60-day rainfall has totaled 50 to 70 percent of normal. Topsoil moisture in Michigan was rated 60 percent short to very short as of June 26 by USDA-NASS, a 13-point jump from last week and 57 percentage points higher than a year ago. While state-wide net gains were noted in soil moisture (percent short to very short decline week to week) from Missouri into Ohio, D1 was increased in southeastern Iowa and northeastern Missouri to reflect 60-day rainfall near or below half of normal. In the western-most Corn Belt, D1 was introduced in south-central Nebraska where 60-day rainfall was likewise less than 50 percent of normal.


Ok then; Why the dryness??

The pattern expected for the summer of roller-coaster temperatures resulting from conflicting air masses has been strong as forecasted but most storms and rainfall resulting from it has been along and south of the southern border of Michigan. Add to this; timing of frontal passages and a occasionally capped atmosphere (too warm aloft) which inhibited storm growth has resulted in the dryness of much of Southeast Lower Michigan.

Note the big difference in rainfall the past month along and just to the south of the region and further west (resulting in some sharp contrasting differences in short distances)!

Again; there is a chance of some rain overnight after midnight but then much of the holiday weekend looks dry. Latest models have a system moving where else, just south of Southeast Lower Michigan on July 4th. Any changes, I'll update our chances.

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




Strong Upper Air Patterns This June Continue to Battle It Out For Dominance!

Anyone watching the upper air patterns these past few months have noted the strong resilience of the cold upper low periodically settling down into eastern Canada. This has partly been resultant of a remarkable oscillating Arctic Oscillation pattern since spring. While this is a somewhat normal event, the strength and tenacity of the strong reoccurring upper low pattern is something to take note of, especially now that we are into summer. Anyone reading my blogs this past several months have seen my discussions on the effect this has had, and will have on Southeast Lower Michigan's weather. My latest Outlook discussed its likely effect this summer:

"I look for the summer to continue to display the more roller-coaster type of temperature pattern (not unlike seen this spring and also dominated, the Spring of '83) with sometimes significantly above, below and everything in-between but ultimately resulting in the normal or typical summer".

Note the active oscillations of late on the Arctic Oscillation:

While every season has its roller-coaster pattern of temperatures, I stated this summer is likely to be more exaggerated at times; due to a new upper low from Canada periodically battling the upper ridge over the south-central to southwest. And thus, this creates a see-saw type pattern over North America. Over the past few months, this has materialized and now, a more contrasting upper air height pattern is expected to form next week. This will result in a battle of air masses set for early in the week.

A strong early summer season upper high pressure area over the Southwest with upper heights pushing up to around 600 dekameters has and will continue to allow temperatures to rise well over the 100 degree mark in that region. The mountainous high pressure will help surface temperatures possibly challenge some all time record highs in that region. It will also influence our temperatures this weekend and Monday with high temperature readings in mid 80s to near 90. 

Meanwhile; the balance between the strong upper high pressure over the desert Southwest and cold upper low in eastern Canada /sub-546 dekameters/ is set to become unbalanced shortly. Meaning; the Canadian upper low is projected to aggressively kick the upper ridge back west and south. The strong upper low will surge southeast once again, toward southeast Canada and bring with it cool, modified Polar air for mid June. It should be noted however; next weekend the upper ridge is once again projected to build once again into the Plains and further northeast with time (the see-saw persists). Models are consistent with this change with varying amplifications and intensities and for simplicity sake, I will stick with the American Model /GFS/.

As it stands now for early next week:

The cooler air from Canada, modified by the summer sun, will plow into the Great Lakes next Monday to Tuesday time frame. Latest indications the cold front will make it all the way into the deep south. It is also during this time frame, the potential rises for severe weather across the Lakes as the cold front dives southeast later Monday into Tuesday. If the potential increases as it is still early, I will send out a FB Weatherhistorian chat.

Note the radical change below in the upper air pattern in just a few days projected by the GFS as the upper low dives southeast and dislodges the impressive ridge west and south!

Also note the cooler, refreshing air is progged to surge well south with reinforcing waves of cooler air pivoting southeast across the Lakes early-mid week. This should push high temperatures back down into the 60s and 70s into at least mid week.

Ironically; the summer solstice this year will also be on Monday June 20th at 624 PM when the expected cold front is slated to move through the Great lakes.

In addition; here's another interesting tidbit about this years solstice: 

This June 20, the Full Moon appears on the same night as the June Solstice! A Full Moon hasn’t occurred on the same day as the Solstice since 1948.

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




Summer 2016 Outlook: Ongoing Changeable Pattern And Analogues Makes Summer Prognostication Challenging

Looking Back At Spring - A Wild Ride!

No one has to be told what a changeable and variable spring we encountered across Southeast Lower Michigan. While temperatures averaged slightly above normal; getting there was certainly not a direct road. First half of March started out on the cold side only to warm up big-time later giving us a preview to mid-late spring's typical weather. By month's end; temperatures averaged around 6 1/2 degrees above normal! Meanwhile, rain and even snowfall despite the warmth was plentiful; a couple inches above normal as a whole. The first half of April did an about-face in the temperature department with a cold snap leading to temperatures averaging 5 to 7 degrees below normal (just the opposite of March). The rest of the month moderated some but still, April averaged a degree to three below normal depending on location. Precipitation amounts slacken off a bit in April with most areas seeing slightly below rainfall but normal to above snowfall due to the cold. May weather was all over the board; especially the second half with near record or record cold giving way to near record heat. As the heat increased, the rains decreased - not a good thing for the growing season nor the approach of June and Summer. A somewhat rare bird of sorts was seen in mid May with the cold bringing scattered pockets of snow and sleet (or graupel) on the 14th and/or 15th; setting snow records for occurrence on those particular dates. Latest snow observed around the region in May has been the 31st, fortunately this was not challenged this year. And speaking of a challenge...


A rapidly changing ENSO pattern is quite evident in not only current data but projected data for the summer into the fall. El Nino has just about died a quick death and we are entering Neutral conditions for the summer, see current SST's broken down weekly for May 2016 (Chart -1) and model projections below that (Chart -2). Neutral SST's indicate really no influence from the Pacific for the summer into the early fall, anyway. This only heightens the complexity for an Outlook since summer typically has a weaker upper wind pattern pattern to start with, then add to this, a Neutral ENSO pattern, little in the way of patterns

Recently; the present pattern still has some of the "El Nino lag" with the southern jet quite active across the southern Plains and less further east and north. Meanwhile; the influence of the semi-stationary Polar vortex over northern into eastern Canada has been absent over the Great lakes during the latter half of May (Chart - 3, May 500 MB). This has lead to very warm conditions /near record at times/ with no substantial rains. Some areas have seen next to nothing to speak of since mid May.

Chart - 1


Chart - 2

Chart - 3

Summer 2016 - Where Do We Go From Here?


With the spring pattern all over the place; investigating the true trend of our recently past weather is difficult. Therefore; are there any patterns seen in the analogues that may match up with the current local and hemispheric pattern? Analogues below indicate a relatively normal summer as far as temperatures (within a degree or so) but with above normal rainfall; certainly contrary to the recent pattern, but not unlike our earlier spring pattern - what to do?

First off as far as Temperatures:


Recent variability but trends toward normal to above normal gives us a little more weighting to at least normal temperatures (the most predominant in the analogues) and against the three below normal summers displayed. On the flip side; I must mention, no where did I come up with a hot summer talked about in some media venues. Hot summer meaning placing in the top 10 warmest summers. As a matter of fact with the possibility of a cooler June (or at least dominated in the trend displayed strongly by the analogues) an outlook for a normal summer is more suitable.

Our best analogues this past winter, 1982-83 and 1997-98 contained normal summer temperatures averaging very close to 72; just a few tenths different from each other. Likewise; I look for the summer to continue to display the more roller-coaster type of temperature pattern (not unlike seen this spring and also dominated, the Spring of '83) with sometimes significantly above, below and everything in-between but ultimately resulting in the normal or typical summer. 

Summarizing: I look for temperatures to average 1 - 2 degrees of the summer norms across Southeast Lower Michigan.


Recent rainfall trends in late May certainly contradict the dominant analogues for the summer with a preference for above normal rainfall. Out of the limited seven analogues, five were wetter than average (and inch or better above normal), one normal (within an inch of normal) and one below average (an inch or more below average).


There was quite a range of totals from as little as 5 inches way back in 1889 to just over 15 inches even further back in 1878. More recently however, over 12 and a half inches /12.60"/ was measured during our waning period of the last very strong El Nino in 1998.


Comparing the two best analogues of the winter at Detroit; 1982-83 and 1997-98; 1983 was a better analogue for temperature trend of the winter but was drier during the winter; then became wetter that spring and summer. The Winter into Spring of '98 was somewhat more uniform in precipitation amounts and pattern. Both analogue summers turned out wet (over far Southeast Lower Michigan around Metro Detroit). Ironically; both also contained above normal precipitation amounts  of 11 to 12 1/2 compared to a normal of just under 10 inches /9.89/.

However; researching further north in Southeast Lower Michigan gives a different account of rainfall distribution (though Flint and Saginaw analogues not shown for the summer, rainfall is below). Drier conditions prevailed further north from the Flint and Saginaw area into the Thumb region both in 1983 and 1998, particularly in the Summer of '83, when all areas in Southeast Lower Michigan saw a dry August. The one trend that continued was the variability of rainfall amounts and summer distribution. Analogues strongly suggest at drier and wetter regions over Southeast Michigan for the summer with the more likely the  drier areas, further north. 


In conclusion: Look for rainfall to average normal to above across the southern half of Southeast Lower Michigan and normal to below across the northern half.

Another interesting item noted was both summers were fairly busy with thunderstorms and logically as one might think; more occurred where the higher rainfall totals were over the southern areas, or south of I-69. Just as an example on how skewed summer rainfall amounts can be with convective rains; most of the 4.24" of rain of July's 5.72" total at Detroit in 1998 fell in one thunderstorm complex on 7th. Now, this doesn't necessarily mean it will happen exactly like that again this summer as far as rainfall amounts and distribution but an item to keep in mind.



1983    June                      July                     August

4.88 4.53 1.57


2.69 5.72 4.19


Monthly Rainfall Flint|Saginaw for Summer's of '83 and '98




    June          July        August

3.942.06 2.241.66 2.262.32




    June          July        August

1.251.81 1.131.30 2.62 1.51

Severe Weather


Later analogues that contain data; 1973, 1983 and 1998 all had their abundance of storms and occasional severe weather during the summer. Severe weather, thus far through the spring season has been almost absent; so any increase would be notable. Most storm activity occurred when we generally peak, mid June to mid July.  Another second peak was noted mid July thru August. 

What does our finest season model /CFV2/ project for the Summer?







Basically; it looks very similar to the researched and chosen analogues this time around. Temperatures near normal and precipitation normal to above. Even detecting a "shading" or possibility of higher rainfall across the southern portion of Southeast Lower Michigan.


Whittling it down further by month (JJA - click on the maps for better resolution).


Temp                                                                                Precip


Have a great summer and try to enjoy the weather when able because before you know it; winter will be just around the corner. Thus far, a La Nina Winter is expected at that; hmmm.

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



Winter of 2015-16: An Exceptionally Warm Winter That Strongly Correlated To Preferred Analogue Models

Winter of 2015-16 Over Southeast Lower Michigan


Strong Placement in Warmest Winters Ranking


The Winter of 2015-16 statistically went down as one of the warmest winters on record across Southeast Lower Michigan. The Winter of 2015-16 placed at the sixth warmest winter on record at Detroit; the second warmest winter at Flint and Saginaw. Reflecting on Chart -1 below; compare the EL NINO of 2015-16 to that of the other two preferred very strong El Nino winters in our analogue selection /1982-83 & 1997-98/. Even though the strongest and warmest El Nino's were preferred in the study; this past winter's El Nino was also expected to behave differently in its overall pattern as time wore on. The weakening influence of the El Nino along with a resilient strong Polar jet stream over northern and eastern Canada was expected to put a damper on the warm and historically, snowless winter. Mainly because of December's excessive warmth, the entire winter managed to place near the top warmest.

Strongest Placement for December's Warmth Across The Region

December's warmth secured a top billing for the warmest December ever...and at all three climate sites /Chart-2/! Never before had there been a December this warm over the entire region since record keeping commenced. This included both Detroit's and Flint's average temperature placing in the lower 40s. Above normal temperature departures ranged from between 11 to 12 degrees above normal at Detroit and Saginaw; to as high as 13.6 degrees above normal at Flint! The last time it was even "close" to this warm was back in December 2006 and that pales in comparison to December 2015 /see, chart-2 below/. The very strong El Nino analogue Winter of 1982-83 also made a very good showing with its December warmth in the warmest December chart with all three stations again, placing in the top 7 warmest Decembers. However; it's interesting to note that December of 1997, our other very strong El Nino analogue, never even placed in the top 20 warmest Decembers at any site.
Chart - 1

Comparing three strongest El Nino's /1982-83, 1997-98 & 2015-16/  and resulting winter temperature averages at Southeast Lower Michigan's climate stations.

Top 20 Coldest/Warmest Winters in Southeast Lower Michigan
RankDetroit Area*Flint Bishop**Saginaw Area***

Chart - 2
Top 20 Coldest/Warmest Decembers 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 17.8 1876 41.1 2015 16.1 1989 41.0 2015 16.2 1989 39.1 2015
2 18.0 1989 40.6 1881 16.6 2000 37.2 1982 17.2 2000 35.3 1923
3 19.2 2000 39.3 1889 17.4 1976 36.8 1923 18.8 1983 34.5 1982
4 20.8 1983 38.1 1877 17.8 1958 35.4 2006 18.9 1976 34.4 2006
5 21.5 1976 37.7 1923 20.1 1983 35.4 1965 19.0 1958 34.2 1931
6 21.8 1917 37.4 2006 20.5 1944 34.7 1931 19.1 1917 34.1 2012
7 21.9 1880 37.3 1982 20.8 1963 34.1 2001 19.5 1919 33.5 2001

Even with a very strong El Nino; Flint managed to capture the snowiest list this past winter, coming in at 15th snowiest /Chart-3 /. Areas north and northeast into the Thumb had even more snow in places (I explain why below in storm tracks).

Chart -3

Top 20 Snowiest/Snowless Seasons in Southeast Lower Michigan
RankDetroit Area*Flint Bishop**Saginaw Area***

Winter/Cold Season Temperature and Snowfall Comparisons and Results

Though the Winter of 2015-16 was warmer than what was projected by the analogues on average; the preferred and thoroughly discussed Winters of 1982-83 and 1997-98 were right in-line with this past winters. In addition; the overall pattern projected (fading El Nino influence, intermittently influenced by Polar jet and better snows than typically fall in a very strong El Nino) materialized where they were projected; north of metro Detroit over Southeast Lower Michigan. Normal to above normal snows were measured north of the Detroit Metro area into the Saginaw Valley and Thumb - NOT typical of a very strong El Nino but where intimated by the analogues.

The unseasonably warm December negated somewhat; my temperature departure number outlook for the entire winter. I wasn't warm enough for the winter on my above normal departures (up to four degrees above normal was stated) for all of Southeast Lower Michigan; as evidenced by the seven /6.9/ degrees above normal!  Had December been more in line with the warmer Decembers, the overall winter departure would have been much closer to my call. December's blow-out warmth was not expected though in my and the analogues defense; it was expected to be the warmest and largest above normal departure of the three winter months. Sticking with the above normal departure average on just the two preferred winters would have been much better in retrospect - my bad. The main reason I chose to be somewhat cooler than just the two analogue winters was; I expected the real warmth of the winter to run into trouble mid to late winter and thus, January and February not to average as warm as in 1983 and 1998 - which did happen. The mid and late winter was not as warm as its two warm analogue winters.

On a side note: in retrospect and commented on previously, this brings up the most common weakness seen in the analogues. While the sign (+, -, 0) of the departure may be a degree or more in the right direction (seen frequently), the magnitude remains probmatic at times and may be off a few degrees or more.

At the same time however: the way the winter's subsequent pattern unfolded was spot on with the analogue trend. Warmest weather relative to normal was expected to come early in the winter (predicted and materialized big-time in December). The bigger question was how the rest of the winter was to unfold after December? All research and subsequent analogues strongly suggested the entire winter would not behave as a typical very strong El Nino. In other words, previously dominant hemispheric patterns were expected to challenge "the new kid on the block" - El Nino.

From my Winter Outlook:

During the strong El Nino's of 1982-83 and 1997-98 the atmospheric characteristics and downwind affects really didn't peak until the winter period. Thus far, along the central and southern West Coast, the "wave-train" of storms has yet to materialize but if history is any indicator, next month should see things pick up some. Things have begun to change here in November though with some storms tracking further south into the West Coast, deepening on the lee side of the mountains and heading into the Great Lakes. However, this pattern is really not unusual for any late fall period so, nothing too El Nino-like.

At the same time; the Polar/Arctic jet has shown signs of expanding and phasing further south into the sub-tropical jet, typical for November. While the subtropical jet is becoming more active, so is the Polar/Arctic jet. This has created a combative, progressive rolling jet pattern across the country. I look for this pattern to continue into at least into early December as timing is always an issue this far out. While the Polar Vortex is expected to remain much of the time up in the Arctic; looking at my data and the past few winters, I look for it to be a player at times.


"I look for the winter pattern downwind to behave at times like a Hybrid or Modoki El Nino  rather than just the typical classic El Nino. Because of the other hemispheric patterns in place; I would expect more of a "roller-caster" type of temperatures pattern established especially going into the winter, as mentioned above and coming out; directly involving the El Nino, EPO and NAO.

In any event; look for a milder, less cold winter than the past couple with temperatures averaging around 2 to as much as 4 degrees above the established normals. 

Again, as it turned out even while predicting up to four degrees above normal which would have placed Southeast Lower Michigan in the Warmest Winter's listing as it were. What was warm enough for the winter were the preferred and strongest El Nino winters of 1982-82 and 1997-98. The Winter Temperatures chart below shows the average temperatures for winter months/season and departures. As you can see, the exceptionally warm December boosted the winter average temperature by several degrees and it alone was mainly the reason the winter turned out so warm. Both January and February were also warmer than typically felt but not to the extent of December.



While the snowfall was expected to be at least around normal across the northern two-thirds of the landscape, it too was exceeded mainly around the Flint region into the Thumb. As expected, Southeast Lower Michigan became the battle ground at times between the Polar Vortex to the north and the moisture brought in by El Nino from the west and south. The central part of Southeast Lower Michigan was often "ground zero" for these battles, as mentioned in my Winter Outlook. Also, the snowfall chances were higher later in the season and this materialized as late as mid May - one of the latest observed.

"However, all is not lost snowfall lovers! Two winters contained normal snowfall at Detroit, one normal and two above normal at Flint and finally; two normal and three above normal at Saginaw. Therefore, the most obvious pattern seen in these winters is that the further north one goes in Southeast Michigan, the better chance for more snow. The same can be said for general precipitation across the region. The Winters of 1991-92 and 1972-73 saw the best snows across the entire region with normal to above normal. The Winter of 1940-41 saw the next best "snow showing" the entire region but still well below at Detroit /26.8/ to near 50 at Saginaw /49.7/. The actual snow pattern for this winter will be watched for updates". 

Snowfall Chart

Preferred Storm Tracks Verification

This also showed up and verified well in the preferred storm tracks across Southeast Michigan and also along the East Coast (which also was busy at times). Note the track I posted for Southeast Lower Michigan with the El Nino influence and phasing occasionally with the cold from the Polar jet. The storm track was estimated to cut right across the region with more snow to the north - matching the forecast. This track placement was too, a direct result of analogue preference for snow patterns in Southeast Lower Michigan.

All analogue winters comparisons including data from this past winter


Here is the entire set of analogue winters with the Winter of 2015-16 added at the bottom of the years, along with updated Winter types. As with any other image here; click on it to see a larger/better resolution.

Reflecting back on El Nino's strength this past winter

The Winter of 2015-16 was widely anticipated to be unseasonably mild mainly due to the projections of an El Nino in record territory. The El Nino didn't disappoint in that regard; it maxed-out with the two previous strongest El Ninos of 1982-83 and 1997-98 - but was it the strongest? A very good computation and summation of that question can be found from NOAA; written this past February when El Nino was clearly beginning to wane. However, there isn't much said on the comparisons to 1982-83 with 1997-98 and 2015-16 being the top contenders.

So is this the strongest El Niño on record, or what?

This is definitely one of the strongest three going back to 1950.  It’s hard to say definitively what single El Niño is the strongest, because there are a lot of different ways to measure strength.

The Oceanic Niño Index, the three-month-average sea surface temperature departure from the long-term normal in one region of the Pacific Ocean, is the primary number we use to measure the ocean part of El Niño, and that value for November – January is 2.3°C, tied with the same period in 1997-98. There are other areas of the ocean that we watch, though, including the eastern Pacific (warmer in 1997/98) and the western Pacific (warmer in 2015/16).

Also, don’t forget the “SO” part of the El Niño/Southern Oscillation (ENSO), which is the all-important atmospheric response. All that extra heat in the tropical Pacific Ocean warms up the atmosphere above it, leading to more rising air, which changes the circulation all around the globe. By one measure (the EQSOI), the El Niño-related changes in the atmospheric circulation in 1997/98 and 2015/16 are tied; by another (the SOI), 1997/98 was stronger.

There are other areas of the ocean that we watch, though, including the eastern Pacific (warmer in 1997/98) and the western Pacific (warmer in 2015/16).

El Nino SSTs and Subsequent Hemispheric Wind Jet Placement

What is just as important if not more for our interests, is where (latitude/longitude) El Nino peaked as far as SST departures over the Pacific. Were they mainly over the far eastern Pacific nearer to South America or more toward the middle Pacific? Actually both happened this past winter and this is also discussed in NOAA's analogy. They don't mention timing during the winter which I feel is important for the overall evolution of the winter weather hemispheric pattern.

In my Winter Outlook issued back in November, this was a main concern to me and how it would affect our evolution of our mild strong El Nino winter.

Hemispheric Winds Compared for Each El Nino

Below are the maps for each of the three El Nino's jet (and max wind speeds in the red highlighted regions). Note where each El Nino's jet maxed out: this past cold season /Nov-Mar/ it was over the far west Pacific. It's interesting also to note the troughing aided by the second weaker wind max over the eastern US. This is where the Polar Jet and El Nino subtropical jet interacted and thus; gave us more interesting and stormy weather than typically seen in very strong El Ninos. This was particularly significant at the start of the cold season /Nov/ and then again later in the season /Feb-Mar/. Also, important was the very weak to almost absence of the troughing out west, typically this is stronger and aids in bringing very mild air the entire season. Basically, the El Nino induced sub-tropical jet was displaced further north and one of the main reasons southern California remained drier (see precipitation maps down further).

Cold Season of  2015-16

During the cold season/El Nino of 1982-83 the strongest upper level winds were mainly over the west and central Pacific. Note the more defined trough over the western U.S. with very little jet action over the eastern U.S. This was especially true during December of '82, which mimicked our December of '15 much better than December of '97 for unseasonable warmth (see December comparisons further down).

Cold Season of  1982-83

During El Nino of 1997-98, like 1982-83, the max winds were out over the west and central Pacific with notable troughing again in the western U.S. These two combined to bring flooding rains to California that winter. Meanwhile, the troughing from northeast Canada is just about absent over the east while a second subtropical jet established further south.

Cold Season of  1997-98

Cold Season Composite Temperature Comparisons

The map shows widespread warmth over the north-central and northeast; while mild conditions existed elsewhere. However; it is very important to remember the map over the north and east is skewed warmer than existed the entire winter because of mainly one month, December.


The cold season of 1982-83 below was much more typical of a strong El NIno with warm departures over the north and cooler departures over the south.


Again; the cold season of 1997-98 was more typical of a strong El NIno with warm departures over the north and cooler departures over the south.


December Comparisons

One can see the December temperature departure placement were more similar between the El Nino of '82 and '15 than El Nino of '97.

One of the most interesting examples of "very strong El Nino non-like precipitation" fell this past winter. First off; southern California was just about promised heavier rains, or at least more rain than normal - it never materialized with any needed regularity (note the drier the average conditions over that region). Heavier rains were deflected north and extended from northern California into Oregon and Washington State along with the main jet.

In addition further east; some places forecasted drier than normal were wetter, some MUCH wetter. This became even more pronounced and evident during the cold season /Non- Mar/. Also, note the subsequent verification maps from CPC below the precipitation maps. In addition; the temperature forecast/verification maps from CPC are displayed below the precipitation. Temperatures were much more in line with the forecast in the north but faltered somewhat in the south, where warmer than normal conditions also prevailed more than expected.


Polar Projection of the 500 Heights

Looking at the polar projection 500 MB heights for basically the climatological winter shows the very strong El Nino influence over the western/central Pacific; spreading out somewhat as she came inland on the West Coast with main jet deflected a bit north. In our neck of the woods; the bulge south of the Arctic/Polar jet shows up nicely as it intermittently nosed into the upper Midwest, Great Lakes into the Northeast.


Next Up - That All Important Summer Outlook Due Out Shortly - I'm shooting for the first weekend of June. 

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