WeatherHistorian-SeMI: 09/01/2013

9/18/13

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

Originally written September 1999 & Updated September 2004/2012/2013 (see updated reanalysis information).

This week is the anniversary of one of the most unusual and intense wind storms ever to hit Southeast Lower Michigan. It was over seven decades /72-yrs/ ago on September 25th, 1941 when the remnants of a tropical storm hit the region. This storm by far, was not the usual remnants of tropical origins that occasionally make it up to the Great Lakes region but one of extraordinary circumstances for it truly was the 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 over 80 years (since 1921) 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 twice a decade, especially the southern Great Lakes area (see Table-1). Also, in the majority of instances, by the time they visit this region they have diminished to an area of rain with maybe some squally winds. 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 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
	7/20-8/2 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

>>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.

A more recent storm (and last under the mentionable category) was fairly impressive as it 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 the area 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 brought very heavy rains to the region along with strong winds and a brief F2 over western Wayne County.

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 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 hurricane, after weakening and becoming extratropical, traveled over a thousand miles and still was able to maintain that much wind is extraordinary in itself. 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 lake temperature dropped 5°C (9°F). 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, Dr. Greg Mann and Mr. James Wallman of the University of Michigan.

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

9/9/13

JUST WHAT IS INDIAN SUMMER AND DID INDIANS REALLY HAVE ANYTHING TO DO WITH IT?

Written by: William R. Deedler, Weather Historian
(originally written in the Autumn of 1996)

An early American writer described Indian Summer well when he wrote, "The air is perfectly quiescent and all is stillness, as if Nature, after her exertions during the Summer, were now at rest." This passage belongs to the writer John Bradbury and was written nearly an "eternity" ago, back in 1817. But this passage is as relevant today as it was way back then. The term "Indian Summer" dates back to the 18th century in the United States. It can be defined as "any spell of warm, quiet, hazy weather that may occur in October or even early November." Basically, autumn is a transition season as the thunderstorms and severe weather of the summer give way to a tamer, calmer weather period before the turbulence of the winter commences.

The term "Indian Summer" is generally associated with a period of considerably above normal temperatures, accompanied by dry and hazy conditions ushered in on a south or southwesterly breeze. Several references make note of the fact that a true Indian Summer can not occur until there has been a killing frost/freeze. Since frost and freezing temperatures generally work their way south through the fall, this would give credence to the possibility of several Indian Summers occurring in a fall, especially across the northern areas where frost/freezes usually come early.

While almost exclusively thought of as an autumnal event, I was surprised to read that Indian Summers have been given credit for warm spells as late as December and January (but then, just where does that leave the "January Thaw" phenomenon?). Another topic of debate about Indian Summer has been "location, location". Evidently, some writers have made reference to it as native only to New England, while others have stated it happens over most of the United States, even along the Pacific coast. Probably the most common or accepted view on location for an Indian Summer would be from the Mid-Atlantic states north into New England, and then west across the Ohio Valley, Great Lakes, Midwest and Great Plains States. In other words, locations that generally have a winter on the horizon! But then, what about the king of winter weather in the United States, Alaska? Do they have an "Indian Summer", or something similar? Some places in Alaska are lucky to have a "summer", let alone an Indian Summer! One would certainly have to throw out the notion of it usually happening in October or November, when, winter generally has already taken an aggressive foothold on much of the state. What about other locations that come to mind, The Rocky Mountain States and parts of Canada, particularity in the east and south? Note: If anyone reading this has any information on Indian Summers in those areas questioned, or just thoughts on Indian Summers drop me a note or comment. (Editors note: Over the years while at the NWS, I received several fascinating notes from all over the world on how common and widespread "Indian Summers" were with each having it's own specific local or regional definition).

A typical weather map that reflects Indian Summer weather involves a large area of high pressure along or just off the East Coast. Occasionally, it will be this same high pressure that produced the frost/freeze conditions only a few nights before, as it moved out of Canada across the Plains, Midwest and Great Lakes and then finally, to the East Coast. Much warmer temperatures, from the deep South and Southwest, are then pulled north on southerly breezes resulting from the clockwise rotation of wind around the high pressure. It is characteristic for these conditions to last for at least a few days to well over a week and there may be several cases before winter sets in. Such a mild spell is usually broken when a strong low pressure system and attending cold front pushes across the region. This dramatic change results from a sharp shift in the upper winds or "jet stream" from the south or southwest to northwest or north. Of course, there can be some modifications to the above weather map scenario, but for simplicity and common occurrence sake, this is the general weather map.

Now we come to the origin of the term itself, "Indian Summer". Over the years, there has been a considerable amount of interest given to this topic in literature. Probably one of the most intensive studies occurred way back around the turn of the century. A paper by Albert Matthews, written in 1902, made an exhaustive study of the historical usage of the term. Evidently, the credit for the first usage of the term was mistakenly given to a man by the name of Major Ebenezer Denny, who used it in his "Journal", dated October 13th, 1794. The journal was kept at a town called Le Boeuf, which was near the present day city of Erie, Pennsylvania. Matthews however, uncovered an earlier usage of the term in 1778 by a frenchman called St. John de Crevecoeur. It appeared in a letter Crevecoeur wrote dated "German-flats, 17 Janvier, 1778." The following is a translation of a portion of the letter:

"Sometimes the rain is followed by an interval of calm and warmth which is called the Indian Summer; its characteristics are a tranquil atmosphere and general smokiness. Up to this epoch the approaches of winter are doubtful; it arrives about the middle of November, although snows and brief freezes often occur long before that date."

Since the writer says, "it is called the Indian Summer", obviously one could argue that term would have had to been used before him and became popular, but by whom, an earlier explorer or possibly an Indian tribe?

Now, after looking at all of this, the question you might ask yourself is, "Does the term 'Indian Summer' really have anything to do with Indians?" Again, there is host of possibilities, read on...

One explanation of the term "Indian Summer" might be that the early native Indians chose that time of year as their hunting season. This seems reasonable seeing the fall months are still considered the main hunting season for several animals. Also, the mild and hazy weather encourages the animals out, and the haziness of the air gives the hunter the advantage to sneak up on its prey without being detected. Taking this idea one step further, Indians at that time were known to have set fires to prairie grass, underbrush and woods to accentuate the hazy, smokey conditions. But Albert Matthews pointed out that the Indians also did this at other times of the year. Other possibilities include; the Indians made use of the dry, hazy weather to attack the whites before the hard winter set in; that this was the season of the Indian harvest; or, that the predominant southwest winds that accompanied the Indian Summer period were regarded by the Indians as a favor or "blessing" from a "god" in the desert Southwest. Another idea, of a more prejudicial origin, was that possibly the earliest English immigrants equated Indian Summer to "fools" Summer, given the reliability of the resulting weather. Finally, another hypothesis, not at all in the American Indian "camp" of theories, was put forward by an author by the name of H. E. Ware, who noted that ships at that time traversing the Indian Ocean loaded up their cargo the most during the "Indian Summer", or fair weather season. Several ships actually had an "I.S." on their hull at the load level thought safe during the Indian Summer.

In any event, there are several theories or possibilities of the explanation and origin of the term "Indian Summer", yet no one theory has actually been proven. Given the fact it has been centuries since the term first appeared, it will probably rest with its originators. All in all, even with the variety of opinions on this weather (or seasonal) phenomenon, the most popular belief of Indian Summer is as follows...It is an abnormally warm and dry weather period, varying in length, that comes in the autumn time of the year, usually in October or November, and only after the first killing frost/freeze. There may be several occurrences of Indian Summer in a fall season or none at all.

Since Indian Summers are fairly common, it would be interesting to find out if there is any correlation between the years that had no Indian Summer (in a particular area) and the type of winter weather that followed. Oh well, possibly another time and another article but enjoy the Indian Summer while its around, because one thing is for certain, it never lasts!

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

Autumn 2013 Outlook For Southeast Lower Michigan

"Basically, autumn is a transition season as the thunderstorms and severe weather of the summer give way to a tamer, calmer weather period before the turbulence of the winter commences." I wrote that sentence back in 1996 when doing research on Indian Summers which was one of my most popular articles. Look for the *article at the bottom of this Outlook.

Autumn 2013 Outlook

Temperatures

Indications are temperatures this fall will be quite variable (even more than usual see Upper Wind Discussion below) but in the end, temperatures should average near normal to below (or -1.5 to +0.5 degrees of normal). The data in our neutral analogue falls remains quite mixed and looking at that, along with the upper wind projections, suggest end results will average near normal to below.

Precipitation

Precipitation over the area is projected to average around normal to above in keeping with our recent trend.

The ENSO pattern over the Pacific Ocean is expected to hold in the Neutral state through the fall. Since the ENSO state will hold Neutral, this leaves very little to go on for the fall period in regards to influencing patterns for the Great Lakes from the Pacific and not unlike our recent summer.

Upper Wind Discussion

Upper air general projections indicate normal ridging oscillating with a deepening troughing pattern early to mid fall. By mid to late fall more troughing will extend from mid and eastern Canada into the upper Midwest and Great Lakes. While this is in agreement with the normal or average season change; early indications are upper wind patterns including the Polar jet over the Arctic extending into Canada will become more aggressive than average and dip south. In addition, our Neutral Autumn analogues also suggest more below normal temperatures as the fall unfolds.

Latest model guidance intimates an average to slightly above average overall. This data lies more heavily on very recent trends.

On to the Analogues

Our most recent Autumn Analogue to this fall occurred in 2008 when neutral conditions persisted from the summer. While the summer of 2009 was also basically Neutral ENSO, the following autumn evolved into an El Nino...not expected this year. Looking at the data from the Autumn of 2008 gives us the following;

AUTUMN 2008 TEMPERATURES/DEPARTURES

LOCATION SEPTEMBER OCTOBER NOVEMBER FALL


DETROIT	66.3 / +2.4	50.6 / -1.3	39.0 / -1.7	52.0 / -0.2
FLINT	62.7 / +2.0	49.2 / -1.5	37.3 / -0.8	49.7 /+0.4
SAGINAW	62.1 / +2.1	47.7 / -1.5	37.8 / -0.2	49.2 / -0.2

AUTUMN 2008 PRECIPITATION/DEPARTURES

LOCATION SEPTEMBER OCTOBER NOVEMBER FALL

DETROIT	5.99/+2.72	1.15/- 1.08	3.31/+ 0.65	10.45/+2.29/20^{th wettest}
FLINT	8.64/+4.88	1.26/-1.08	2.10/-0.55	12.00/+3.25/6^{th wettest}
SAGINAW	4.55/+0.60	2.26/- 0.23	1.47/-1.18	8.28/-0.81

Looking at our earlier Neutral analogue fall statistical package (below) and comparing it to our most recent Neutral fall 2008 data (above) holds us in good stead and thus, continues to be useful. Data from all analogues was extremely mixed and basically, there are as many of warmer falls as cooler with some normal falls tossed in for good measure. In addition, the same can be said about the precipitation side of things with some dry falls, wets falls and near normal falls. This “equal-parts” variability is somewhat unusual and one of the most mixed season data set seen.

NEUTRAL ANALOGUE AUTUMNS

(Normals 1971-2000)

In this smorgasbord of weather are there even any subtle trends? Not really other than there were notable wet and dry falls, similar to preceding summers. Keeping one eye on our recent rainfall trends and the other on the 2008 period, I'm inclined to keep rainfall projections at least around normal if not above.

How about monthly trends? Temperatures in September and October were mixed with little in the way of prevalent trends. Novembers did show a bit more consensus toward a cooler than normal, but even that wasn’t a strong trend. Overall, the composite charts for the fall do indicate temperatures averaging a degree or so below normal for Southeast Lower Michigan while precipitation averages around normal.

Frost and Freeze Trends:

Our guidance indicates temperatures are quite variable and most years our frosts and freezes were on schedule. Checking back on the years in our study reveals some common frost/freeze statistics. Using our stats from Detroit, (and estimates of frost when most areas saw overnight lows fall in the lower to mid 30s for the first time). Our analogue falls show the risk of frost and/or freeze the last week of September into the first week of October. This is right in there with the average frost dates. The more widespread freezes occurred by the third week of October.

Indian Summer this Fall?

Perusing our analogue autumns, the likelihood of a period or two of Indian Summer weather this fall looks promising. Note, most temperature patterns in October and November varied considerably in the analogue years, this is generally a prerequisite for Indian Summer falls. You want a progressive amplified upper wind pattern during the fall to deliver large cold high pressure systems. While these highs can bring sharp cold snaps (and attending solid frost/freezes, necessary for Indian Summers), after they move east, impressive strong warm-ups, sometimes lasting as long as a weeks bring Indian Summer weather…let’s hope.

Notable Autumnal Dates

Harvest Moon: Thursday - Sep 19th, 2013 (Traditionally, this designation goes to

the full moon that occurs closest to the Autumnal (fall) Equinox. The Harvest Moon

usually comes in September, but about every three or four years it will fall in early

October - closest full moon to the beginning of fall).

Autumn Officially Begins: Sunday - September 22nd, 2013 at 444PM EDT

Average First Freeze Date: October 21st (Detroit area), October 11^th (Flint and

Saginaw area)

Halloween: Thursday, October 31st, 2013

Thanksgiving: Thursday, November 28, 2013 (latest possible)

Have a nice fall and look for my Winter 2013-14 Outlook early in November

*Indian Summer
http://weatherhistorian.blogspot.com/2013/09/just-what-is-indian-summer-and-did.html

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

9/3/13

Summer of 2013: Projections of a More Comfortable Summer Come to Pass Along with Quite Variable Rainfall Amounts!

Overview

Certainly one of the more comfortable summers than in recent years was enjoyed across Southeast Lower Michigan in 2013. Projected temperatures in my Summer Outlook of around normal readings came to fruition along with why we would see a less hot and humid summer (see upper air pattern discussion). Careful, that above average temperature for the summer is misleading.

*Summer 2013	Average Temperature (Departure from Normal)	Normal
Immediate Detroit Area	71.9 / +1.1*	70.8*
Flint	70.5 / +1.1*	69.4*
Saginaw	69.7 / +0.7*	69.0*

* SE Mich Ave 70.7/+1.0 69.7

* Data from NWS DTX - Summer Normals are computed based on each site's period of record, which is different than the 1981-2010 period used to compute individual monthly statistics

Comparing this summer's temperature averages to the past several shows one of the main reasons this summer felt cooler!

Top 20 Coldest/Warmest Summers 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

66.5

1915

74.8

2005

65.4

1992

74.2

1933

64.8

1915

73.0

1933

67.0

1992

74.5

1995

66.1

2009

74.0

1934

65.1

1992

73.0

1931

67.3

1927

74.5

1955

66.2

1958

72.7

1936

65.5

1982

72.5

1955

67.5

1875

74.4

2010/11

66.3

1960

72.6

1939

65.8

1945

72.3

1995

67.6

1903

74.2

1988

66.5

1969

72.6

1931

65.9

1950

72.1

1930

67.8

1985

74.0

1933

66.6

2004

72.6

1921

65.9

1924

72.1

1921

67.9

1912

73.8

1949

66.7

1985

72.3

2010

66.1

1985

72.0

2010

67.9

1907

73.7

1921

66.8

1972

72.3

1949

66.4

2009

72.0

1988

68.1

1982

73.6

1952

66.8

1967

72.2

1955

66.4

2004

72.0

1937

68.2

1972

73.5

1991

66.9

1962

72.0

1935

66.4

1979

71.9

1936

68.3

1979

73.5

1959

66.9

1927

71.9

1938

66.5

1977

71.7

1998

68.3

1902

73.5

2002

67.0

1982

71.8

1988/11

66.6

1951

71.5

1934

36th warmest 71.9 2013 25th warmest 70.5 2013 36th warmest 69.7 2013

Perhaps no month displayed the temperature difference between this past summer and several previous summers than July. Note the marked contrast in temperatures and rankings this past July when compared to the past several Julys.

July 2013               Actual    Normal    Departure

 Detroit                       74.0         73.6          +0.4

 Flint                           73.0         70.5          +2.5

Saginaw                     71.7         71.0          +0.7

Rank & Average Temperature Records for July

Detroit

Rank	Average Temp.	Year
1	79.3	2011
2	79.0	1955, 2012, 1921
5	77.9	1916
6	77.7	1931

38TH 74.0 2013

Flint

Rank	Average Temp.	Year
1	78.0	1921
2	77.7	1935
3	76.8	2011
4	76.7	1934
5	76.5	1955
6	76.1	2012

22ND 73.0 2013

Saginaw

Rank	Average Temp.	Year
1	77.5	1921
2	76.8	1916
3	76.4	2012
4	76.1	2011, 1935

36TH 71.7 2013

Digging Deeper into the Summer Temperatures

Ok, so all these statistics show why this summer was considerably cooler and more comfortable when compared to the past several. While it's a given the average temperatures for the cities/summer were still a bit above normal, one must deep a bit deeper to really get the full picture. Where all temperature statistics really above normal over the region? And if not, what statistic wasn't above?

Looking across ALL of Southeast Lower Michigan paints a bit of a more complete picture. Note, average highs this summer actually averaged below normal. So it wasn't the highs that were above normal...and another reason it felt cooler this summer. During the day (where summer is typically measured by the public) on average, it was actually cooler than normal. It was the average low temperatures that came in above average for the summer. Enough above normal to push the summer averages just above normal statistical threshold when computed.

Even with the heat island influencing Detroit Metropolitan Airport temperatures, check out each monthly average high temperature compared to normal at Detroit. Every month failed to make its normal high. The average high for the summer comes out to be 80.6, nearly a full degree below normal. And, what does this say about areas away from the city?

Location                June    July August        Summer
Detroit Ave High      78.5               82.5              80.9              80.6
Normal                    79.3               83.4              81.4              81.4
Departure            -.8                -.9                -.5               -.8

Another way people judge the summer is how many 90 degree days occurred? Normally Southeast Lower Michigan "feels" about 8-12 ninety degree days (depending on location). Here's another reason why it felt cooler than the statistics might want you to believe. Detroit had only five 90 degree days less than half its 100 year normal of 12. In addition, those 90s occurred all in one week in July when it was hot and humid. There were no 90 degree days in June nor August...highly unusual, especially August. Flint fared better with twice as many 90s /10/ than Detroit...which looks a bit strange at first glance but then add Saginaw's number of 90s to the mix /8/ and maybe not. (Just for the record, I do believe Flint's ASOS temperature runs about a degree or so hot when compared to surrounding sites). There is another reason Flint and to a lesser extent Saginaw chalked up more 90s than Detroit...moisture in the ground due to wide variances in rainfall between the cities. Simply put; Detroit had heavy amounts of rainfall this summer (see rainfall) whereas Flint just crept up to near normal while Saginaw was substantially below normal. Wet grounds tend to hold temperatures in the summer down a bit...not to mention the increased cloud cover due to more rain.

Number of 90s This Summer
City            M J    J    A
Detroit    0 0 5      0
Flint       1       2     6      1
Saginaw    1       1     5      1

*Hot Spell - Detroit                          *Cool Spell - Detroit

July Hi Lo Av Dep Aug Hi Lo Av Dep

  15     93    75    84    10                            12     74    65    70     -3

  16     90    77    84    10                            13     69    55    62    -10

  17     94    75    85    11                            14     72    51    62    -10

  18     94    75    85    11                            15     75    51    63     -9

  19     95    73    84    10                            16     79    56    68     -4

*There were other hot & cool spells during the summer but these two were two of the most notable.

Summer Rainfall Tallies

Summer 2013 /Rainfall/ /Norm/ /Depart/ /Summer 2012/

Detroit                       16.13           9.89          +6.24         3rd wettest summer

Flint                             8.83           9.57           -0.73

Saginaw                      6.53           8.94           -2.34          27th driest

The vast majority of the region saw suitable amounts of sunshine along with generous to abundant amounts

of rainfall during the summer. I say the vast majority since there were still some notable pockets of below

normal rain creating a minority of drier regions. All in all, good weather for gardens and vegetation was had

across the majority of the region with limited areas having rainfall deficiencies, those being mainly in portions

of the Saginaw Valley into parts of the Thumb (see second map; departure map). Ok then, how about too

much rain?

If anything; the occasional circumstance brought too much rain from thunderstorms with heavy to torrential rains which led to briefly saturated grounds. Heavy rains across extreme Southeast Lower Michigan brought predominately wet conditions to the far corner of the state. There was quite a difference in rainfall across Southeast Lower Michigan this summer! Totals (first map) ranged from only four to six inches over portions of the Thumb (mainly Bay and Tuscola Counties) to as much as 15 to 20 inches over parts of Monroe County. Note the departures above normal (second map below; based on radar rainfalls) of up to a foot, mainly over Monroe County. Heavy rains led to Detroit's third wettest summer on record. This summer was a classic example of where rainfall projections of below to above normal are most suitable (see Outlook performance)

SUMMER RAINFALL AMOUNTS - Radar Estimated

The last few heavy rainfall events were near the close of the summer with heavy rains on August 27-28th and again on the 30-31st. See maps below;

June Rainfall & Departure Map

June rainfall is one of the most important monthly rainfall for vegetation; note the wide variance this past June!

Upper Air Patterns of the Summer

The upper air pattern of the summer consisted of strong summer sub-tropical ridge that dominated over the Southern Plains and Desert Southwest which occasionally built east into the Upper Mississippi Valley and Great Lakes Region. This ridge oscillated as far east as the East Coast at times connecting with the summertime Bermuda High. Just as as important the ridge was the other main feature of the summer; a strong, below normal height upper low pressure system that dominated over northeast and eastern Canada. This upper low occasionally retrograded or redeveloped over south-central Canada. It was the interaction of these two patterns that created our comfortable summer.

In my Summer Outlook it was these two features I spoke about and why I thought this summer would turn out cooler than the past several. From the outlook;

Hemispheric Patterns

As the summer ridge builds into the center part of the country, I look for it to oscillate over the Great Lakes and the East, routinely bringing warm to hot weather to the region. However; it should be duly noted that the distinct upper air pattern that has been a key player since mid winter into spring, albeit naturally weakening with time and becoming less frequent, shows no signs of leaving during the summer. I'm speaking of the occasional blocking across the northern latitudes in which I expect to play a distinctive role this summer. By occasionally phasing with weaker mid continental impulses, troughing will dive into the Great Lakes and points east and thus, intermittently deliver enough cooler spells of weather to balance out somewhat the heat and humidity we do get, for a more normal and comfortable summer than the past several.

Based on the above upper wind pattern and analogue discussions below, my temperature forecast read as follows.

Temperatures
Recent hemispheric patterns and analogue summers (discussion below) suggest to me a more comfortable summer than the past several. In fact, temperatures should average closer to normal or average between 1.0 degrees below normal to 1.5 degree above.

Analogue Performance

Again from my outlook after researching other analogue summer;

Analogue Trends Seen

Temperatures

The Neutral analogue summers are really quite mixed on the temperature front this time which is hardly surprising given the hemispheric and SST environment. Even though Detroit’s summer data favors normal to below normal temperatures, one must closely compare this data to Flint and Saginaw. The reason being, the normals at Detroit were increased in the past few data sets (1971-2000 & also 1981-2010) due to mainly the effect of the local heat island that now encompasses the Detroit Metro Airport; whereas Flint and Saginaw saw little change in their normals. This would logically then, skew Detroit’s departure temperature data down somewhat. In any event; analogues suggest normal temperatures will prevail.

Rainfall and Severe Weather

Dominant trends past (previous analogues) and recent (past few months) suggest variability in rainfall trends. April was wet while May was dry relative to normal or average rainfall. While the majority of analogue summers lean toward the dry side; a minority were especially wet! We've already seen this wider range variability recently and it looks like it will continue. When speaking of summer's total rainfall; I look for a range of below normal to above normal given the present and past trends

Rainfall averaged decidedly below normal in the analogue set with about 75% below normal...a strong trend. However; the remaining years were very wet and while a minority of years, it still is an important subset of wet years! This suggests to me that the pattern portrayed in my hemispheric discussion could lead to a stalling of the frontal conflict and storminess and thus, runs the risk of repeating in the same general region. While analogues state drier summers prevailed; we still run the distinct risk of a stormier summer including training echoes if the pattern happens to stall in our neck of the woods. In conjunction with this kind of scenario; there is more likelihood of a wider range of rainfall amounts from below normal to above over Southeast Lower Michigan.

In Summary

The resultant Summer 2013 statistics reflect well my forecast for the summer including the projected upper air pattern and consensus of analogue data. Temperatures across Southeast Lower Michigan were kept in check which led to a more typical summer than recent summers due to the aforementioned upper air projections. Not to be outdone; projected rainfalls across Southeast Lower Michigan of below normal to above normal also materialized, mainly as a result of the forecasted macro-scale pattern, down-scaled for Southeast Lower Michigan.

Overall one could say it was a normal summer but with some hidden abnormalities (temperatures) and not so hidden (third wettest summer on record at Detroit and possibly worse points south).

Next Up; What's the Autumn Look Like??

Fall Color Time

Fall leaf color is basically caused by lack of sunlight and to a lesser extent is influenced by the late summer weather. However; drier than normal weather for the entire summer into early fall tends to accelerate the leaf changing process, causing the leaves to fall prematurely. Likewise, a wet late summer into September and October will tend to produce fewer vivid colors and the leaves may also fall earlier due to the rain, wind and storms.

The prime weather conditions which are conducive for brilliant fall colors are warm, sun dominant days and cool, crisp nights but without frosts or freezes; such as high temperatures in the 60s and 70s with lows in the upper 30s to lower 50s. These sharp, daily temperature swings and more importantly, the decrease in sunlight, play vital roles in the development of the leaf color. This combination of weather and lack of sunlight, creates a blocking effect on the sugars which are manufactured in the leaves and keeps them from reaching the root system. Eventually, these sugars convert to pigments that produce the vivid and brilliant colors seen on many trees in the fall. Evidently, the green chlorophyll in the leaves begins to fade during the shorter fall days with subsequently, less sunlight. Thus, the other color pigments already in the tree leaves are exposed, come out and produce the fall color splendor. The yellow color seen in some leaves is created by the xanthophyll pigment, while the orange-red color is caused by the carotene pigment and the red-purple color can be attributed to the anthocyanin pigment.

While color peak may vary season to season across Southeast Lower Michigan, generally the maximum leaf color occurs during the second and third week in October.

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