Summer of '17 - Rather Quiet and Dull with a few Notable Exceptions and a Look into Autumn

Summertime Temperatures

The Summer of 2017 will go down on average as a typical summer are far as temperature averages with all of Southeast Lower Michigan averaging close to a degree /+0.9/ above normal. In spite of the average temperatures being slightly above normal; the contradictory thing was the lack of 90 degree days during the summer months (which we have made up some in late September). Detroit recorded only 4 days with 90 or above, Flint registered 3 days of 90 or better and Saginaw just 2 - nearly all of the 90s were recorded in June which normally has the least of the summer months.

September's Outstanding Heatwave Changes Things:

As discussed last week in my blog; the upcoming heatwave had the potential to set some record highs and it did, and more.... 

 

Additional 90+ degree temperature highs were recorded recently in late September along with many being record highs. As of Sep 26th, Detroit has received 3 more days of 90 or better, Flint - 6 and Saginaw - 6. Therefore for this warm season; Detroit has now had 7 days of 90 of better, Flint has had 9 and Saginaw 8 days. Generally; 8-12 days of 90 or better are felt in SE Michigan during the year; the most generally being at Detroit. 

Detroit attained three record highs with the final one of 93 on Sep 26th being the hottest of the records and hottest temperature ever recorded so late in the season. Note: on Oct 7th, 1963 Detroit reached 92 which had been the hottest so late in the season but given it's later in the season (though one degree cooler), to this climate guy - it still has just as much clout! Flint chalked-up an incredible six days of records, the last also being Sep 26th. Besides establishing six record highs, the 94 degrees reached on the 23rd set a record for the highest temperature ever recorded so late in the season. Up at Saginaw; they too had a six day string of record highs and the hottest day on the 24th of 94 also was the hottest so late in the season!

Summer Rains (Feast or Famine)

Rainfall for the entire Summer was quite variable from below normal to much above across the region and is best displayed on the rainfall maps (below). One notable exception to the rather inactive summer pattern occurred in late June over the far northern areas of Southeast Lower Michigan, Persistent, flooding rains fell on June 22nd - 23rd with 4.00" to 8.00" measured from heavy thunderstorms from the Mt Pleasant area, east across Bay City into Midland. Extensive flooding occurred; resulting in pushing-up the Tittibawassee and Chippewa Rivers to record levels. By the end of June; Saginaw reported nearly eleven inches /10.76"/ of rain for the month which established a new heaviest rainfall record for the month of June - and the second heaviest rainfall ever recorded for any month. The record wettest month /16.16"/ occurred during the widespread flooding of mid- Michigan in September 1986. I wrote an in-depth article on the major flood event here.

On the flip side; while flooding rains fell over the extreme north early in the summer; a gradual rain deficit grew over the central and southern areas. As shown in rain statistics at the climate stations in Southeast Lower Michigan below, both Detroit and Flint ended the summer with a deficit in rainfall (see table). The majority of this below normal rainfall occurred from the southern Metro Detroit area, west southwest across Ann Arbor into the Jackson region.

     Percent of Normal Rainfall for the Summer of 2017

When rains did fall over the entire region; frequently they were heavy convective rains with long periods between them of little, if any rain. Perhaps no place did this show up more than the drier areas shown where only 50 to 100% of normal rain fell.  Meanwhile; sufficient to surplus rains of 100 to 150% of the normal occurred over the far northern areas.

Years ago /1997/; I did a local study for the metro Detroit area researching; the likelihood of dry spells during the summer. As a resident of metro Detroit since birth; one of many things I noticed about our local climate was the frequent occurrences of dry spells in the summer.

Basically I found out the following: 

"FIRST...THERE MUST BE SOME GENERAL DEFINITION OF A "DRY SPELL" 
INCLUDING RAINFALL AND DURATION. HERE...CLIMATIC STATISTICS OF THE AREA 
SHOULD BE THE GUIDE. THEREFORE...A DRY SPELL IN SUMMER DURING THE PAST 
30 YEARS COULD BE DEFINED AS...LIGHT AMOUNTS OF RAIN (.50 OR LESS) 
FALLING ON ONLY A FEW OF DAYS IN A PERIOD OF GENERALLY 2 TO 4 WEEKS. 
THIS IS OPPOSED TO THE MORE SEVERE "DROUGHT" WHICH IS MORE PRONOUNCED 
IN BOTH RAINFALL DEFICIENCY AND DURATION.

IN THE PAST 30 YEARS USING THIS DEFINITION...NEARLY 9 OUT OF 10 TIMES 
(OR 87% OF THE TIME) SOUTHEAST LOWER MICHIGAN EXPERIENCED A NOTABLE
DRY SPELL SOMETIME DURING THE SUMMER MONTHS. THUS...IT IS UNUSUAL NOT 
TO HAVE A DRY SPELL IN THE SUMMER".  

As you can see; this is very common and again materialized this summer. The most notable extended from portions of metro Detroit; west southwest across Ann Arbor into the Jackson region. This region had two notable dry spells using Detroit Metro Arpt /DTW/ stats and the map displayed. Not only is the dry spell important but when it occurs; especially for gardeners and farmers.  Both dry spells occurred at the arguably the worst times for plant/water interests. Between May 30th to June 22nd (over three week period); less than half inch /.45"/ fell at DTW. Of course, amounts in the area displayed can be more or less but historically, DTW represents the region. I don't have to tell gardeners nor farmers of the importance of adequate rains needed for newly planted seeds, plants and crops. In addition; this coincides with sun riding high in the sky (near or at the solstice). The second dry spell befell the same area from July 16th through August 10th when sufficient rains are certainly needed for proper growth and maturity. During this nearly 4 week period only about a third of an inch /.36"/ of rain fell. This also is generally the warmest time of of the summer. Even at Flint which was closer to normal rains; a distinctive dry period extended from May 25th through June 16th when only a half inch /.49"/ fell. It would be remiss of me if I didn't mention the normal or average rains during each of the summer months are generally around 3.00 - 3.50" for a summer total 9.00-10.00".

The mid July to early August dry spell which took place this summer was found to be the second most common in the study. The most common dry period fell from mid August to early September. Thus far, this September continues to dry trend overall with all areas already having a deficit of two to three inches! A reversal of fortunes, so to speak, has occurred with now the far northern areas the driest this month.

Summer Temperatures and Rainfall Statistics

DTW - DETROIT  v	FNT - FLINT v	MBS - SAGINAW v
Temp Ave: 72.4/+0.7	Temp Ave: 68.7/+0.9	Temp Ave: 69.6/+1.1
Pcpn Tot:  8.37/-1.52	Pcpn Tot:  9.26/-0.31	Pcpn Tot:14.52/+5.65
SE MICHIGAN    >	AVE TEMP: 70.2/ +0.9

SUMMER TEMPERATURE MAPS

 SUMMER RAINFALL MAPS

 MONTHLY TEMPERATURE AND RAINFALL DEPARTURES

JUNE

JULY

   

                                                              

AUGUST

SEVERE WEATHER: LIMITED

While most people will be glad to see this; severe weather buffs already know - severe weather occurrences thus far in 2017 have been pretty limited or scant. Yes, to put it bluntly it's been rather boring. Up through the third week in September; only 50 severe weather warnings have been issued by the NWS DTX in White Lake for all of Southeast Lower Michigan. This is the second lowest thus far this year using the improved Doppler 88-D radar since 1995.. Interestingly; just last year was the lowest since 1995 with only 42 warnings issued (note; this is not events). In addition; only one tornado has occurred in Southeast Michigan thus far this year when a weak, small /EF-0/ tornado formed on August 17th near Kingston in Tuscola County

So why has it been an uneventful year; especially when you note that other areas around us have higher amounts of warning and events? The main reason was timing of potential severe weather which limited instability. Most potential for severe weather was squashed because the pre-frontal storms either had weakened in the overnight hours to our west - or most new storm development just started to juice up for severe weather either over SE Michigan or east of us.

Summer Outlook Performance?

So, looking back to the opening of summer; How did the Summer Outlook perform? Really pretty good on both temperatures & rainfall expectations and pattern recognition.

From the Outlook -

TEMPERATURES

I look for overall normal temperatures during the summer with any "heat waves or warm periods" to be routinely tempered by cooler air pushing south out of Canada. I'm looking for an occasional -NAO to help deliver the cooler weather as discussed in Hemispheric Patterns below and in the Analogue section. On specific temperature departures; I expect temperatures to average from +1.5 to -1.5 of normal.

Average for Southeast Lower Michigan: 70.2
Departure: +0.9

RAINFALL

Latest model and atmospheric trends agree with Summer Analogues for generally below normal rainfall this summer as heaviest rains generally fall west and southeast/east of the region.  Of course; there will be pockets of heavier rains with convective activity but overall, below normal rains are expected.

 

More than half the region saw less than 100% of their average summer rainfall (see stats and maps). There were indeed pockets of heavier rain over the northern areas as mentioned above. 

 

DTW - DETROIT  v	FNT - FLINT v	MBS - SAGINAW v
Temp Ave: 72.4/+0.7	Temp Ave: 68.7/+0.9	Temp Ave: 69.6/+1.1
Pcpn Tot:  8.37/-1.52	Pcpn Tot:  9.26/-0.31	Pcpn Tot:14.52/+5.65
SE MICHIGAN    >	AVE TEMP: 70.2/ +0.9

 

Autumn 2017 Signs and Remainder Outlook:

September's temperature weather pattern thus far; I feel fairly confident it is good example for the entire upcoming weak La Nina autumn. The month's first week started out well below normal an the coldest September up to that point since 1935 - impressive. But; just as impressive is the warmth since then and ultimately, the heat she turned on late in the third and beginning of the fourth week. As the present final week unfolds; it promises to have some of both as mentioned in my previous blog on the current "heat wave." Temperatures starting off well above normal will fall to near normal then below as the week closes - or sort of a summary of September's weather. The other most notable item this month has been the dry weather. As stated; all reporting stations average two to three inches below normal as of the 26th for September.

The Autumn jet pattern has become more active across the country as September's jet evolved into amplified ridges and troughs taking center stage. Abnormally cool weather across the Great Lakes shifted to record heat! Looking out to analogue Neutral-weak La Ninas suggest more of the same. Neutral to weak La Nina falls generally contain normal to above normal average temperatures on the whole but with moderate to strong fluctuations in temperatures...both warm and cold. This is not an atypical pattern with the majority our falls but these changes generally are more exaggerated with the expected pattern since there usually is less effect from the Pacific (as opposed to El Nino). Therefore, meridional jet air masses can "do their thing" without much hindrance from a Pacific zonal jet to diffuse their effects. (The term "meridional is used in meteorology such as "meridional wind flow" (a.k.a. meridian) or "in the north–south direction" as opposed to zonal or west to east flow.

Therefore, for the remainder of Autumn... 

Temperatures should average normal to above but with more significant swings.

Precipitation patterns continues to intimate dry and wet periods but with a sided preference for normal to below normal precipitation continuing to hold sway.       

Killing frost and freezes which normally arrive by mid-late October should be on time due to the amplified jet.  First sight of snow (trace) usually comes around Halloween into early November - with measurable later in November. I don't see any reason to deviate from that at this time.       

Notable Dates:

Halloween -      Tuesday   10/31/17
Thanksgiving - Thursday 11/24/17 
Christmas -       Monday   12/25/17
New Years -      Monday   01/01/18                  

Winter Begins:  Thursday 12/21/17 @ 11:28 EST

 

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

Summer Refuses to Budge; A Look at the opening of Autumn

In the past few weeks; some were looking forward for the autumn weather to arrive later this week via the calendar /Friday - September 22, 4:02 P.M. EDT/. I guess someone should let mom nature in on the change, since the weather has been and will continue to be nothing like our typical early autumn days. High temperatures are expected to rise well into the 80s to around 90 through the weekend and, at least into the early part of next week; well above the 70ish norms. High temperatures may flirt with/or may even challenge some record highs over the period but a few are tough nuts to crack.

This warm weather pattern is due to a strong summer-like ridge of high pressure blocking any cooler fall-like air masses from surging southeast into the Great Lakes and eastern half of the country.

By mid-week; a stronger jet core is progged to evolve into the trough as another upper low drops into the trough in the vicinity of North Dakota (above). As the system advances east, this is slated to push into the Lakes Region (below). Of course, this is days away but a notable change from this week.
 

Enjoy the several days of summer-like weather as indications are for more typical fall-like weather near the close of the month. However, this won't be the last of the above normal or warm weather as extended patterns indicate variable fluctuations in the prevailing jet stream early October.

Next we'll take that look back at the rather mediocre summer - in a few ways.

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



 

The Ongoing Active Tropical 2017 Season Begs the Question: Hurricanes in Michigan??? Along with...Hurroncane!

 Hurricanes in Michigan??? Along with...Hurroncane!

Originally written September 1999 & Updated September 2004/2012/2013 and with more the latest reanalysis information - 2016. And in 2017; all tropical remnants listed in Table-1 have links to the paths of the storms along with attending narratives back nearly a century to 1923!

Monday, September 25th is the 76th anniversary of one of the most unusual and intense wind storms ever to hit Southeast Lower Michigan. Well over seven decades ago on September 25th, 1941; the remnants of a tropical storm hit the region. This storm was not that usual being in that the remnants of tropical systems do occasionally make it up to the Great Lakes region. But, the coming together of all the meteorological components made for this Astonishing Storm of September 25th, 1941

At first glance, when one reads that headline, one might say, "What? Hurricanes here in the Great Lakes?? No way!" Of course you'd be right, no actual hurricane has ever been observed in Michigan under the true definition of a hurricane. The definition of a hurricane, according to the Glossary of Weather and Climate edited by Ira W. Geer, is as follows: "A severe tropical cyclone with maximum 1-minute sustained surface wind speed greater than 64 knots (74 mph) in the North Atlantic Ocean, Caribbean Sea, Gulf of Mexico and the Eastern North Pacific off the west coast of Mexico to the International Dateline. West of the Dateline they are known as typhoons." Furthermore, the definition of a tropical cyclone is as follows: "A generic term for a non-frontal synoptic-scale cyclone originating over the tropical or subtropical waters with organized convection and a definite cyclonic surface wind circulation." Clearly, neither definition applies in the Great Lakes area, although remnants of hurricanes that have become extra-tropical (loses its tropical characteristics) occasionally do make their way into the Great Lakes region.

Scanning a century's (since 1917) worth of hurricane track data suggests that remnants of a hurricane or tropical storm make their way into the Great Lakes region on an average of nearly twice a decade, especially the southern Great Lakes area (see Table-1). Also, in the majority of instances, by the time they visited this region they diminished to an area of rain with maybe some squally winds with many of the rainfalls/winds on the tail-end of their "lives".. There have been a few instances, along the way, however, that do bear mentioning, and ONE STORM in particular that screams for attention!

TABLE - 1

REMNANTS OF HURRICANES/TROPICAL STORMS THAT HAVE AFFECTED THE GREAT LAKES AND SOUTHEAST LOWER MICHIGAN (SINCE 1921)
DATE (Storm's life cycle)		DETROIT RAINFALL/DATES (Inches)	MAXIMUM WIND (mph)
	10/16-19 1923	.55 - 10/18	SE - 22
	7/22-8/2 1926	1.11 - 8/1	E - 25
	8/27-9/3 1932	2.95 - 9/3-4	NE - 21
	9/10-22 1938 $	.23 - 9/21-22	SW - 20
	9/16-25 1941	Trace - 9/25	SW - 52 *
	9/1-6 1948	.82 - 9/6-8	N - 25
	9/27-10/6 1949	1.30 - 10/6-7	SW - 21
Connie -	8/1-8/14 1955	.69 - 8/13-14	W - 20
TD ** -	6/22-6/28 1960	.31 - 6/28	SW - 23
Carla -	9/3-9/15 1961	.13 - 6/14	W - 29
Candy -	6/22-26 1968	2.55 - 6/24-26	NE - 30
Hugo -	9/10-24 1989	Trace - 9/22-23	NW - 38
Opal -	9/27-10/6 1995	1.41 - 10/5-6	N - 38
Fran -	8/23-9/8 1996	.99 - 9/7	NW - 25
Isabel -	9/6-9/19 2003	0.25 - 9/18-19 #	W - 33
Ike - 9/1-9/15 2008                                 3.78 - 9/13-14                                           N - 43 * denotes officially at Detroit City Airport, but gusts were clocked up to 75 mph across the Metro      Detroit area. ** TD - Tropical Storm # Up to 2.50" reported along the St. Clair River

$ 1938 New England Hurricane: Fast forward speed reached 70 mph on September 20th, making it the fastest-moving Atlantic tropical cyclone on record.

>>Note; Hurricane Sandy's path /2012/ did not pass over/near Southeast Lower Michigan<<

First off, under the "mention" category in 1932 (well before hurricanes were named), a hurricane that developed in the Caribbean on August 27th, tracked northwest into the Gulf of Mexico, then generally north, across Alabama, eastern Arkansas, southeast Missouri, into southern Illinois and then from there, headed northeast across Indiana into Southeast Lower Michigan. The storm approached Southeast Lower Michigan late on September 3rd. A light to moderate northeast wind proceeded the storm on the 2nd and 3rd averaging around 11 mph with gusts into the lower 20s, hardly anything noteworthy wind-wise. The storm did however, pass right over Detroit, causing the barometric pressure to fall from around 30.20 inches early on the 2nd to around 29.60 late on the 3rd. Rain began to fall lightly but steadily early in the morning on the 3rd, but from mid afternoon into the evening, moderate to heavy rain fell and by midnight, over two and a half (2.55) inches was dumped on the Detroit area. Close to an additional half inch or so of rain was added to that on the 4th for a total of nearly three inches.

Another mentionable was odd from the start because of its timing; occurring very early in the season during late June of 1968 (only one other June system was found since 1921 to have affected the Great Lakes: the weak remnants of a tropical storm that moved from the Gulf of Mexico to near Chicago, June 22-28th, 1960). On June 22, 1968, Tropical Storm Candy formed off the coast of eastern Mexico and then headed north into southeast Texas, just north of Corpus Christi. She then weakened, headed north-northeast through eastern Texas and Oklahoma, central Missouri and Illinois, then she pivoted on a more easterly track across northern Indiana into extreme northwest Ohio, over Toledo. Candy began to influence Southeast Lower Michigan's weather on the morning of the 25th. A nearly steady rain, interspersed with a few thunderstorms, continued through the day and evening, depositing nearly two and a quarter (2.17) inches. More scattered, lighter showers fell on the 26th, adding another .38 to give a grand total of 2.55. Through it all, an east to northeast wind blew averaging 10 to 14 mph with gusts into the 20 to 30 mph range.

During the busy mid 1990s; a fairly impressive tropical system wound its way north out of the Gulf of Mexico, through Alabama, Tennessee, Kentucky and into Northern Ohio. She was known as Hurricane Opal and had a 10-day life span from September 27th to October 6th, 1995. On the evening of Oct 5th at 8pm, the remnants of Opal were located over the eastern Great Lakes. What was left of the "eye", or center of the storm, was well indicated on the NWS Doppler radar in White Lake (DTX). The radar showed the "eye" over Sandusky, Ohio moving north out over western Lake Erie. Light to moderate rain, with isolated areas of heavy rain, extended from Southeast Lower Michigan east across Southwest Ontario and Northeast Ohio. Spotty light rain first made an appearance in Southeast Lower Michigan earlier in the day, during the forenoon hours. During the afternoon, steadier rainfall developed with the heaviest rain (.54) falling between 5pm and 7pm. The rain ended just after midnight with a total of 1.41 inches falling from the storm. With the approach of the storm on the 5th, a generally north wind picked up and averaged over 15 mph with gusts up into the 30s (peak wind gust was 38 mph)

One of the more recent Hurricane remnants to affect Southeast Lower Michigan was Isabel, which moved quickly through the Eastern Great Lakes on September 18-19th, 2003. Rainfall from the system was quite variable ranging from just a trace over far western areas of Southeast Michigan, to as much as 2 1/2 inches at local spots along the St. Clair River. In 2008, remnants of Hurricane Ike September 13-14th brought very heavy rains to the region along with strong winds and a brief EF2 over western Wayne County on the 13th. The EF2 tornado struck Plymouth Township and damaged an apartment complex, flipped over cars and knocked out power to several hundred residents.

The Astonishing Storm of September 25th, 1941

Earlier, I mentioned "one storm that screams for attention", but maybe "howls" would be more appropriate. Before researching this project, I expected to find the above case scenarios, but not the following...

 Recently /2013 changes/ the Hurricane Research Division /HRD/ did a reanalysis of the hurricane and its associated track and wind speeds. *Note the asterisks in the following storm account are adjusted for those changes. (Thanks to Hoosier, moderator of American Weather for the heads up on the reanalysis)
   
* The storm made landfall in Texas as a category 3

* After moving onshore and through its entire remaining path, the storm was upgraded by maintaining tropical force winds as she evolved from a tropical storm to extra-tropical.. Also note the shifted, slightly westward track depicted over upper Ohio Valley and Lower Great Lakes in Indiana and Michigan.

Comparing the two tracks;

Original

  Reanalyzed

A tropical storm (#2 on original analysis map & #17-under 19-21, unseen on reanalyzed) formed in mid September over the Gulf of Mexico on September 17th, 1941. As it formed it meandered over the Gulf, making a loop in its track, well south of New Orleans. By this time it was a hurricane, intensifying briefly to a category #3 storm (111-130 mph wind) offshore as it took aim on eastern Texas. The hurricane made landfall late on the 23rd near Freeport, Texas with an estimated wind of a category #3* (111-130 mph), extremely high tides of nearly 11 feet and a barometer reading of 28.31 inches (959 MB). Further to the northeast, a ship just offshore of Texas City recorded a lowest pressure of 28.66 inches and winds of 83 mph. Other wind gusts were estimated near 100 mph at several locations near the hurricane's center along the Texas Gulf Coast. The hurricane quickly weakened to a category #1 (74-95 mph) as it made landfall and by the time the storm pushed on north to Houston, wind gusts had already dropped to 75 mph. Four lives were lost from the storm in Texas and property damage was estimated at $6.5 million (1941 dollars).

The storm continued to roar on its northward path through Texas and by 7 am on the 24th, it was located near the city of Tyler, over extreme northeast Texas. From this point on, the storm's last 36 hours or so really grabs ones interest for peculiarity as it tracked through the Mississippi Valley and on into the Great Lakes. From 7AM on the 24th to 7am the 25th, the storm shot northeast from Tyler to near Battle Creek, Michigan, covering close to 1000 miles in 24 hours! Thus, the forward movement of the remnants of the hurricane averaged 40 to 45 mph as it approached Southern Lower Michigan. As the storm tracked into the Great Lakes, it merged with a fairly strong cold front that pushed across the upper Midwest into the Lakes. The combination of the strong push of cool fall air, strong upper level dynamics and the remnants of the hurricane created quite a storm (not unlike the more common intense late fall cyclones that are seen in the Great Lakes). In addition, the track and speed of our "hurricane" brings to mind that of the "Panhandle Low" type of low pressure system in the winter (more information). While the speed of the system was fairly quick, it's not uncommon for hurricanes to accelerate northeast as they become extra-tropical and get "picked up" by the mid-latitude upper winds or jet stream. Yet, what was really unusual and noteworthy was the surface wind that accompanied the storm as it moved through the Great Lakes. By the time hurricanes make it this far north, they usually have blown themselves out, at least to the extent that surface winds are only gusting to, at best, 30 or 40 mph. Note the following, taken from the Detroit weather records on September 25th, 1941:

Windstorm: An intense tropical cyclone moving up from the Gulf thru eastern Texas (causing great damage in Texas), along the Missip. Valley and thence Newd across Ill & Mich, passing W & NW of Detroit with gale force winds and gusts to 65 mph from 10:18 AM - 2:30 PM & gusts to 75 mph 12:30 PM - 2:00 PM (see envelope back of book for newspaper clippings).

Most of the above noted news clippings show widespread wind damage to trees and power lines that would be commonplace in severe thunderstorms or a derecho. A derecho is a widespread windstorm consisting of a complex of thunderstorms that develop into a long-lived squall line. But there also were some unusual or freakish happenings (as the Detroit Free Press deemed them) as well. The following is taken September 26th, 1941, the day after, from the Detroit Free Press about the storm:

"River goes dry"

There were many freakish effects of the wind, including baring of the Detroit River "middle grounds" off Belle Isle when water was backed into Lake St. Clair. The southwest gale literally blew the water out of The Detroit River, reducing its level by three feet, and leaving hundreds of pleasure craft high and dry on the muddy bottom. Several yachts broke their mooring or were heeled over at the Detroit Yacht Club. Another odd effect was the noticeable swaying of Downtown skyscrapers as the full force of the gale struck. Office employees who left tall downtown skyscrapers, were later reassured by engineers.

The Free Press goes on to say that "shortly after noon, the wind blew steadily at 56 miles an hour, but a times gusts reached hurricane velocity of 75 miles an hour." Dozens of people were injured by falling glass from windows blown out or debris tossed by the wind. One woman was literally blown into a fire hydrant, suffering a possible skull fracture. Other reports of scattered damage to homes and businesses across the region were mentioned in the article. In addition, the fierce wind churned up giant waves on the Lakes, including Lake Huron into the St. Clair River where two barges were blown ashore from of the shipping channel, even after dropping their heaviest anchors. In Southeast Lower Michigan, Storm Warnings were posted on Lakes Huron, Erie and St Clair at 10:30, the morning of the 25th. Downed telephone lines caused a disruption of service and communication across the Great Lakes and elsewhere. The "dying" hurricane left a trail of damage from Texas clear up into the Great Lakes and Canada. The wind of the storm was equated to an intense fall low pressure system that hit the area on November 29th, 1919 in which the wind blew 67 mph in Detroit and to the "Black Friday" storm in November of 1913.

The fact that the remnants of the hurricane, after weakening and becoming extra-tropical, traveled over a thousand miles, while sustaining an impressive amount of wind itself was very noteworthy. This, and the important addition of a relatively strong polar front traveling southeast at the same time across the Midwest, made for quite the enhancement and gave the additional punch and life to the storm's "tropical" characteristics. The surface map for the morning of the 25th is available (first and second map, below) and  depict quite nicely our extra-tropical storm racing northeast. This, combined with a rather potent cold front pushing southeast out of the Midwest, wrapped-up into the storm of tropical origins! This type of strong interaction is more likely observed on the East Coast. I inverted and then, enlarged the shading so the data could be seen better (click on all maps).

Being it was 1941, no upper air data/maps are available from the original time but a reanalysis of the day shows some interesting items (click on all maps). Note the strong (for the time of year) 500H /18kft/ trough digging into the upper Midwest. The 500H anomaly map below that map, depicts this nicely - the potency, depth and generally out of character of the trough for late September- very well. The last two maps are the Meridional (north/south) average wind at 500H and 850H /5kft/. Note the max-cores (depicted in meters/sec) over the eastern Lakes that is shown and the large upper trough over the Midwest at these levels in the 24 hour average (remembering that this is a reanalysis for the entire 24hour period - and thus, the average).

 

As the storm moved into Southern Lower Michigan, its center tracked northeast across Battle Creek, Lansing, Saginaw and then out over Lake Huron and into Ontario. Judging by the lowest pressure readings at Detroit (29.25 inches) and Flint (29.17 inches), where the wind gusted to 69 mph, its central pressure was estimated to around 29.10 inches (about 985 MB). Quite impressive for the remnants of a "dying" hurricane in the Great Lakes in September. In fact, this is the second lowest pressure reading ever recorded in Detroit during the month of September (the first being 29.21 inches on Sep 29th, 1966, during the passage of an intense early fall low pressure system).

One can only make a random guess as to the chances of another hurricane-force wind storm, from remnants of an actual hurricane, hitting the Great Lakes again. Since it was the only one of its kind in the record books at Detroit since records began in 1870, it may take several 100 years before another similar storm affects the region!

Hurroncane

One final, extremely interesting "hurricane" that affected the Great Lakes must be mentioned to make this article complete. While this storm was not from remnants of a tropical system, its development over Lake Huron had many uncanny likenesses to tropical systems...

The first likeness was its timing, forming over the Great Lakes right at the height of the typical hurricane season, September 11-15th, 1996. What started as a typical core-cold 500 MB low pressure system evolved into a warm-core system as it settled over the relatively warm waters of the Great Lakes, in particular, Lake Huron. The low pressure system actually had moved past Lake Huron but then retrograded, or was "drawn back", to the relatively warm waters of Lake Huron. (Similar to the tropics, the Great Lakes usually reach their warmest water temperatures late August into mid September.) The storm then deepened and intensified at the lower levels of the atmosphere compared to aloft, typical of a warm-core low. It is believed that the warm waters of Lake Huron and associated low level instability over the lake were, to a large extent, the major contributing factors in this storm's evolution. The storm went on to form a broad cyclonic circulation, including the "spiral bands and eye", typically seen in hurricanes! At one point, the cyclone produced tropical storm force winds (39 - 73 mph) and some of the spiral bands even had rainfall exceeding 10 cm (better than four inches), causing some flooding.

On satellite, the storm looked very much like the classic hurricane picture:

This "Hurroncane" reached its maximum intensity during the day on September 14th, when a central pressure of 29.34 inches (993 MB) was recorded in the late morning by a Lake Huron buoy that fortunately was positioned, at one point, in the "eye". By 2 PM, that "eye" measured close to 20 miles across and had a ring of tall convective clouds surrounding it, strongly resembling that of an "eye wall". The convective showers encircled the "eye" well out over 300 miles. As the "eye" moved to the southwest (retrograded), over the aforementioned buoy, the surface wind backed from west at close to 35 mph to the southeast, and then diminished to near 10 mph. After, the "eye" continued to track to the southwest, away from the buoy, and the surface wind backed further to the northeast, and briefly attained tropical storm force. A similar scenario but with varying wind speeds, would also be expected at the ocean's surface if a tropical system retrograded from northeast to the southwest overhead. In addition, the air temperature rose from 13°C (55°F) in the spiral shower bands, to near 18°C (64°F), which was also the lake temperature, in the clearing above the "eye". The storm weakened overnight as the surface lake temperature dropped 5°C (9°F) back into the mid 50s due to up-welling and mixing. The lower water temperature helped greatly in weakening the storm as a result of the lower latent heat supply.

For additional information on hurricanes, check in with the National Hurricane Center.

Background on "Hurroncane" was provided by a paper entitled "Hurricane Huron" by Mr. Todd Miner of Pennsylvania State University along with Dr. Peter Sousounis, Mr. James Wallman and Dr. Greg Mann of the University of Michigan.

- Next up; Looking back at the Summer of  '17 along with trends of the Fall.

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