Overall Gorgeous September Introduces October on a Fall-Like Note - With a Hurricane To Boot Out East

No one can deny this September was not only but very pleasant - so much so; its been surely one of the, if not THE BEST, weather month of the year! With temperatures well above normal, all sites placed in the top three warmest Septembers! Along with numerous back to back sunny days (particularity the second half) this has made September - terrific! Temperatures in September averaged in the upper 60s to near 70; some 5 - 7 degrees above normal! While dry conditions prevailed over the Metro Detroit -Ann Arbor- Port Huron areas; normal to locally wet conditions prevailed across the Flint - Saginaw and Thumb Region (maps don't include 9/30 but little if any change noted).

Recent model runs have been intimating some notable changes from our tranquil and warm September for at least the first third of October with cooler (actually, closer to normal) and sometimes, stormy conditions. With the influx of Autumn hemispheric patterns; more and more variable model solutions have become the norm this past few weeks, the up-coming week not withstanding. Latest model runs all bring a huge dome of cool fall air down across Southeast Canada with ridging into the Lakes and New England. The strength of the high is fairly impressive on the GFS for the opening of October pushing 1045 MB /30.86in/ over the weekend! Strong highs coming down out of the Polar region were the rule the past few falls and winters; this is something to watch for the upcoming El Nino winter and just one more piece of the complex puzzle.

Of course, the big news for points mainly SE-E-NE will be what Hurricane Joaquin will ultimately do this coming weekend into early next week. As with winter storms, models have been all over the place for intensity and movement. As of the 12z /8am/ run Wednesday; most major models now bring him inland toward North Carolina/Virginia late in the weekend. One major exception is the European model which now shifts him off to sea, away from the East Coast (see maps below). Even the Hurricane model /WFR/, brings him inland and all about the same timing strangely enough; over night Saturday into Sunday morning then along the Coast. I should mention; the Canadian /GEM/ model also brings Joaquin into North Carolina but later Saturday afternoon. With these solutions; no doubt is it surely something to give the Hurricane Center headaches. For a continued watch on their projections of Hurricane/Tropical Storm Joaquin - check here.

 

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

Autumn 2015 Outlook for Southeast Lower Michigan: How Will a Strong El Nino Affect Our Fall?

Mom Nature gave the region a good send off for summer weather with a warm to hot week to close off the summer right into the Labor Day weekend period. A summer that was very mixed overall as far as temperatures and weather  (for a summer review, see my previous post on Reflections Back on the Summer of 2015).

Probably the most persistent climatological item the media has been trumping-up lately is our strong El Nino that is, by all accounts, projected to even grow stronger during the fall months. This presently strong El Nino could very well rival the two most recent very strong El Nino's; 1997 and back further, 1982. Thus far, there are some striking similarities between the 1997 El Nino, including the overall, Pacific water temperatures and this season's El Nino. Widespread, above normal water temperatures dominated in 1997 over the Pacific and now again, in 2015.

Therefore; does it mean the upcoming fall and winter will be similar to that of 1997's - if only it were that easy. There are many other variables to research to get a most likely scenario for both the fall and winter, therefore let's deal with the fall first.

AUTUMN 2015 OUTLOOK

TEMPERATURES

I look for temperatures to average a degree or two below normal this autumn.

Analogues (below) and history tells us while September's temperatures have started off above normal and may very well, average above for the month; that is not the main trend of the entire El Nino fall. Generally, El Nino fall temperatures are normal to below with chances of below normal temperatures increasing as the fall unfolds (see analogue discussion). One of our best analogues as far as El Nino strength and above normal Pacific water temperatures is 1997. That autumn averaged over two degrees below normal (in line with the analogues) but there are other just as important variables such as the NAO, EPO and PNA that dictated the below average temperatures along with El Nino. Recent upper air trends across Canada suggest an aggressive upper low and resulting jet stream with time.



RAINFALL

All data suggests rainfall to average normal to below normal rainfall with only one out ten falls wet.  Analogues were quite variable as far as rainfall trends and amounts but with a slightly drier overall trend. Generally drier than average conditions develop into the winter of El Nino years.


EL NINO

Below are the August water temperature anomalies across the Pacific. A one can see there are a lot of above normal water temperatures in both the central and southern Pacific. Note the two distinct above normal water temperature bands extending west from North America and South America ( El Nino). El Nino is highlighted in the white rectangle with specific descriptions, below. I find many people still don't have an understanding of what "El Nino" constitutes and where it is over the Pacific.

Description of above map :
Sea-surface temperature anomalies (degrees Celsius) in the Pacific Ocean on Aug. 13, 2015. The area highlighted by the white rectangle shows the warmer-than-average waters of the equatorial Pacific Ocean. Significant warm anomalies also were present in the eastern Pacific Ocean west of California and Mexico's Baja peninsula, while cool anomalies were seen in parts of the equatorial western Pacific Ocean.   

Areas of interest in ENSO

Anomaly Departures

Latest computer projections for the present El Nino strength and timing

All computer trajectories increase El Nino's strength this fall, before decreasing (and some rather dramatically) El Nino's strength by late winter into spring. On a side note; the timing and actual decrease later this winter may set up some interesting and plausible scenarios for our late winter-springtime time period.

AUTUMN 2015 ANALOGUES

Cooler than Normal Autumn?

The most notable take from this set of data reflects a cooler than average fall. In addition, the chances for below normal temperatures increase as the fall wears on. Why the ten Septembers were mixed and averaged a degree below normal, there were still four where the temperature averaged normal to above which could very well happen again this fall. October's tended to average normal to below with just two above normal out of ten. Moving into November; shows the weather held mainly cooler than normal with seven below normal, two normal and just one warmer than average and that was only a degree and a half.

Frost/Freeze Data

Scanning records from all nine of these falls showed two distinct periods where a killing frost or freeze took hold of the region. Using the mid 30s for the threshold at Detroit proper, most other areas would likely dip into at least the lower 30s and experience a killing frost/freeze. The most common period came mid to late October, or about the normal time. However, there was a notable subset of frost/freeze dates occurred earlier as early as mid to late September!

Rainfall 

All data suggests rainfall to average normal to below normal rainfall with only one out ten falls wet. Analogues were quite variable as far as rainfall trends and amounts. Generally drier than average conditions develop into the winter of El Nino years.

Snow Data

Five out of the nine years /1876 is N/A/ had near to below normal snowfall through November during the autumn. However, there was a quite notable exception of the remaining four:  9.8" in 1925;  9.1" in 1940;  7.1" in 1972 and 4.7" in 1997 / This is too much of a trend to ignore and tells me with the dominance of colder than average Novembers; there is the risk of a significant snow in November IF the storm track and cooler than average temperatures align as in the past, something to watch for. Normal snowfall at Detroit is just 1.5" at Detroit/, with a inch or two more further north into Flint and Saginaw.


Important Dates This Fall

Autumn begins: Wednesday morn - September 23, 4:21 A.M.EDT
Harvest moon:  Sunday eve-night - September 27, 2015. And it’s not just any Harvest Moon. It’s also a supermoon that’s staging a Blood Moon eclipse.
Halloween:        Saturday  - October 31st 2015
Thanksgiving:   Thursday - November 26th, 2015

More on the rare super/blood moon 

 The last time a super moon and blood moon occurred at the same time dates as far back as 1982 — and the next isn’t expected to occur until 2033.  Interesting it occured the fall of our strong El Nino and analogue year. 

Enjoy the fall colors if we get the chance!

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

Reflections Back on the Summer of 2015

Cant believe summer's already hit the road? However; with last week's cool temperatures and this weeks hot - think again. As far as meteorological fall it begins on Sep 1st, though the calendar may differ about three weeks. It's nice to review this past summer to see how we stacked up against a typical summer in Southeast Lower Michigan along with how my Summer Outlook and analogues fared.

Summer Review

Temperatures across the area actually averaged very close normal for the summer with readings swinging above normal to below and back again. The summer might have "felt" somewhat cooler than normal because we lacked any really hot weather spells during the period. In June through August time-frame; we felt only a few more than half our normal 90 degree days at both Detroit and Flint with just six /average is 8-12/. Of course, this is changing this first week of September where already some more 90s have been recorded. Inhabitants around the Saginaw region really got short-changed if you like hot weather with just two days where the thermometer hit or exceeded  90 degrees, the entire three month period. There were plenty of 80s (several upper 80s) however, which made up for the lack of really hot weather. While there were muggy days and nights, they came in just occasional periods which also made the summer more tolerable.

Generally; the summer started on the wet side with a gradual lessening to the rainfall periods and drier conditions mid summer; only to be replaced with normal to above rains again late summer.  Therefore; all regions saw adequate rainfall with normal to above normal totals in the summer. While severe weather popped up during the season, thus far it's been below average with only a few notable events.

Let's check out the analogues for Detroit that I chose for the summer; against the actual readings and averages.

Detroit's summer analogues performed exceedingly well and actually accounted for the very slight below normal departure mainly due to the inflated heat island norms. The average temperature of 71.1 degrees fell right on the average temperature projected by analogues /71.1/, not an easy feat to do. Rainfall totals also came remarkably close to the average projected /9.92"/ with 10.24" actually falling, or just a third of an inch /.32"/ higher.

Analogues for Flint and Saginaw were not figured for the summer but temperatures for the entire region were discussed and forecasted. From the Summer Outlook;

Temperatures :

Overall; I look for temperatures to average around normal but with notable swings as the upper low and troughing in eastern Canada via for dominance against upper ridging, aided and at times, even suppressed by El Nino affected winds across the south. This is a difficult forecast as we dealing with two distinctive upper wind patterns, not always present in such fashion in the summer. The outcome is not only going to be affected by conflicting air masses but also with the timing and the extent of dominance by each air mass. 

Also, the chances of long hot spells are less than average and subsequently; average to below average /8-12/ so too are the amount of 90 degree days.  Overall, while a typical /six normal/ summer dominated as far as temperatures.

That being said; In the end, I look for  temperatures averaging between +1.5 degrees and -1.5 degrees of the summer norms across Southeast Lower Michigan...a bit wider range than typical.

Rainfall:

I look for rainfall to be quite variable as mixed data presents conflicting results and where and how much may also be exasperated more than what is typical for many summers. Taking all data (past and present) into account; rainfall is expected to be above normal over the southern sections of Southeast Lower Michigan and normal to possible even below across the Saginaw Valley and Thumb Region. As with temperatures, timing of the wettest and driest periods will be quite variable - not unlike the spring.

 

Resulting temperatures for all of Southeast Lower Michigan averaged a 1/2 degree /+0.5/ above normal when both Flint and Saginaw were factored in to Detroit's data. Not surprising Flint and Saginaw data averaged above normal given the cooler norms when compared to Detroit. Still, this was well within the projected temperature forecast  (-1 1/2 to +1 1/2) and actually fulfilled the above normal range average projected at both Flint and Saginaw.

Rainfall, on the other hand was higher across the Saginaw Valley than what was expected with Saginaw receiving nearly a foot /11.96"/ and just over three inches /3.09"/ above normal! This was primary due to a wet August as convective boundaries fired off and stalled a bit further north as the summer advanced. In fact; just four days accounted for nearly five inches of the August's total at Saginaw! Thunderstorms containing heavy rain fell on the 2nd /1.55"/, 10th /1.11"/, 14th /1.31"/ and 23rd /0.99"/ which made up 4.96" of the 5.50" that fell /or 90%/. All locations had normal to above normal rainfall which was projected, save the Saginaw Valley.


See the temperature and precipitation table below for the entire region:

All data is preliminary
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Next up; what will this El Nino Autumn bring to Southeast Lower Michigan.

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