Severe Weather Outbreak of June 22-23, 2015

The severe weather event we were up against was well televised by our meteorological models and, at least in my point of view, could have been worse given the projected instability, shear in many lower levels of the atmosphere and over all strong dynamics and winds aloft. I mentioned July 2nd, 1997 and July 7, 1991 as one of the previous severe weather events it reminded me of when forecast by the guidance. One major difference was timing as with both previous July events; the cold front moved through at or near peak heating. Another factor was the disruption and stabilizing factor, at least somewhat, of the warm front and attending storms that pushed through mid-late afternoon. These storms developed on the old storm outflow boundary set up the night before, generated over the upper Midwest. The cloud and rain debris was also responsible for a mainly cloudy day (another limiting factor) on Monday even before the afternoon storms.

All in all, it was a memorable event with four tornadoes and numerous severe thunderstorms spawned Monday into the early morning hours of Tuesday. One tornado touched down just east of Birch Run /EF2/, another in the vicinity of Decker/Deckerville /EF1/, a third just north to northeast of Manchester /EF1/ and a fourth, just southwest of Emmet /EF0/. A fifth tornado hit Portland /EF1/ over Southwest Michigan earlier on Monday afternoon.

See report from the NWS-DTX

Mesonet Storm Report

Update 6/22/15 930p - Conflicting Air Masses of "Dynamite" Potential Set for Monday Into Early Tuesday Morning

Update 930 P

Round -2 The Cold Front Action

Fasten you seat belts; it's gonna be a bumpy night!!!

http://www.spc.noaa.gov/products/watch/ww0338.html

 URGENT - IMMEDIATE BROADCAST REQUESTED
   TORNADO WATCH NUMBER 338
   NWS STORM PREDICTION CENTER NORMAN OK
   915 PM EDT MON JUN 22 2015

   THE NWS STORM PREDICTION CENTER HAS ISSUED A

   * TORNADO WATCH FOR PORTIONS OF 
     NORTHEAST ILLINOIS
     NORTHERN INDIANA
     SOUTHERN LOWER MICHIGAN
     NORTHWEST OHIO
     LAKE ERIE
     LAKE HURON

   * EFFECTIVE THIS MONDAY NIGHT AND TUESDAY MORNING FROM 915 PM
     UNTIL 300 AM EDT.

   * PRIMARY THREATS INCLUDE...
     A COUPLE TORNADOES POSSIBLE
     SCATTERED DAMAGING WINDS AND ISOLATED SIGNIFICANT GUSTS TO 75
       MPH POSSIBLE
     SCATTERED LARGE HAIL AND ISOLATED VERY LARGE HAIL EVENTS TO 2
       INCHES IN DIAMETER POSSIBLE

   SUMMARY...THUNDERSTORMS ARE LIKELY TO INCREASE IN COVERAGE AND
   INTENSITY THIS EVENING AS A STRONG UPPER JET AND COLD FRONT APPROACH
   THE REGION FROM THE WEST. A WARM AND VERY MOIST AIRMASS ACROSS THE
   WATCH AREA WILL FUEL ROBUST STORM UPDRAFTS AMIDST INTENSIFYING
   DEEP-LAYER WIND FIELDS. THIS SHOULD SUPPORT BOTH SUPERCELL AND
   FAST-MOVING LINE SEGMENTS WITH DAMAGING WINDS...LARGE HAIL...AND
   POSSIBLY A COUPLE TORNADOES.

   THE TORNADO WATCH AREA IS APPROXIMATELY ALONG AND 70 STATUTE
   MILES NORTH AND SOUTH OF A LINE FROM 35 MILES NORTH OF MOUNT
   CLEMENS MICHIGAN TO 45 MILES NORTH OF CHAMPAIGN ILLINOIS.  FOR A
   COMPLETE DEPICTION OF THE WATCH SEE THE ASSOCIATED WATCH OUTLINE
   UPDATE (WOUS64 KWNS WOU8).

   PRECAUTIONARY/PREPAREDNESS ACTIONS...

   REMEMBER...A TORNADO WATCH MEANS CONDITIONS ARE FAVORABLE FOR
   TORNADOES AND SEVERE THUNDERSTORMS IN AND CLOSE TO THE WATCH
   AREA. PERSONS IN THESE AREAS SHOULD BE ON THE LOOKOUT FOR
   THREATENING WEATHER CONDITIONS AND LISTEN FOR LATER STATEMENTS
   AND POSSIBLE WARNINGS.

   &&

   OTHER WATCH INFORMATION...CONTINUE...WW 335...WW 336...WW 337...

   AVIATION...TORNADOES AND A FEW SEVERE THUNDERSTORMS WITH HAIL
   SURFACE AND ALOFT TO 2 INCHES. EXTREME TURBULENCE AND SURFACE
   WIND GUSTS TO 65 KNOTS. A FEW CUMULONIMBI WITH MAXIMUM TOPS TO
   500. MEAN STORM MOTION VECTOR 27035.

Update- 145P
Round -1 Warm Front Action

As discussed yesterday, as the warm front approaches this afternoon and early evening, the old meso-complex of storms ignited overnight ahead of the front will continue to advance into Southeast Lower Michigan. The air mass ahead of the complex is moderately to strongly unstable along with upper wind Bulk Shear in the neighborhood of 50 knots. This has weakened from earlier readings of 75 knots and is depicted by a general weakening of the storm complex as of early afternoon. Non-the-less as the old storm complex/outflow moves into more favorable conditions it's identity should be maintained enough and thus the issuance of Severe Thunderstorm Watch. #333

Reasons for the watch from SPC:

...GREAT LAKES/MIDWEST REGION...
   A LARGE -- BUT GRADUALLY WEAKENING -- MCC CONTINUES MOVING ACROSS
   THE GREAT LAKES/MIDWEST ATTM...CENTERED OVER SRN WI/NRN IL AND LK
   MI.  STORMS HAVE INTENSIFIED OVER THE PAST HALF HOUR IN THE SRN LK
   MI/SWRN LOWER MI AREA INVOF A SHARPENING WARM FRONT...AND EXPECT
   POTENTIAL FOR STORM REDEVELOPMENT ACROSS THIS AREA -- AND SWD INTO
   ADJACENT NRN IL/NRN INDIANA -- AHEAD OF THE MAIN MESOSCALE LOW
   ASSOCIATED WITH THE MCC.  ALONG WITH RISK FOR STRONG/DAMAGING WINDS
   AND HAIL...A COUPLE OF TORNADOES WILL ALSO BE POSSIBLE -- GIVEN
   PRESENCE OF THE AFORMENTIONED WARM FRONT AND STRENGTHENING FLOW
   ALOFT WITH TIME.

No change in blog through tonight!
_______________________________________________________________________________
6/21/15

In my Summer Outlook; I stressed the likelihood of impressive jet stream conflicts along with their attending surface air masses outcomes with wetter, stormier conditions for most of the region at least part of the summer depending on air jet stream/air mass dominance. It's been notably active to our south and west all season.

"Summer as a rule can be one of the more difficult seasons to forecast for because of the lighter, variable upper wind jet dominance. This summer that general trend may not apply as much as two dominant upper wind patterns via for center stage; a relatively strong polar jet that has had no trouble visiting the Great Lakes throughout the spring along with the sub-tropical/tropical jet aided by an ever increasing El Nino. 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." 

Both the GFS and  NAM Models have been strongly suggesting we have the above to contend with - in spades- Monday into early Tuesday morning while the European has been somewhat weaker with the overall system. Latest 12Z guidance of the Euro now intensifies the low center to 988MB by the time it reaches Ontario Tuesday morning.

Thus far; this severe weather season has been intermittent and on the slow side as Southeast Michigan has remained much of the time in the more stable air masses, aided at times by the cold to cool Lakes and easterly fetch as systems approach from the southwest.The dynamics, upper and lower strong wind jets along with the instability, deep layer shear and CAPE/LI's projected this time are further north over Wisconsin and Lower Michigan and are quite strong. In fact, this time around the worst (or best depending on your point of view) severe weather dynamics look to be coming together just to our west and northwest Monday night and Tuesday morning, then advecting into our region during the very early morning hours of Tuesday. One caveat to limit severe weather after warm frontal passage and before the cold front approaches in the overnight hours will be the warmer air pulled north aloft into the strong system to our northwest and thus, this will provide a temporary cap against the development of severe weather. At this time, it looks as though the dynamics of the system along with cooler air aloft (both advected in and slight overnight cooling aloft) with aid in eroding any cap that does form by the time the cold front approaches Tuesday morning. All severe weather risks are here, including strong damaging winds and tornadic cells and may be realized for at least some. At this time, we have two general periods of severe weather potential - warm frontal and cold frontal.

Warm Front Risk

Never trust a warm front! I learned that early on back in the some of the stormy 70's summers and a even more notable case was the Frankenmuth tornado and flash flooding. Ironically,  the Frankenmuth Tornado occurred on this date; June 21st, back in 1996. I remember it well as I was working along with two other METS and the newly installed Doppler Radar was still in its infancy having been installed in the early 1990s. While leery of the warm front draped over Southeast Lower Michigan, most eyes were watching the cold front and severe weather possibility over Wisconsin with a watch box issued for that region. As the atmosphere cooled aloft, thunderstorms and very heavy flash flooding rains popped like popcorn in the proximately of the warm front. Helicity values and instability were notable along the warm front and thus, helped spawn the infamous tornado.

Therefore; this is definitely something that has to be watched with this aforementioned system with both the warm front and cold front as helicity/EHI values are extremely high promoting tornado risk! The biggest negative is while all this "dynamite" exists, will it become lit or realized? It could become negated if part or all of Southeast Lower Michigan becomes too warm aloft which inhibits thunderstorm growth. At this time, with the warmer air rushing in aloft and best dynamics northwest, the risk of severe weather with the warm front will be marginalized (become capped) but can not be ruled out and bears watching until the warm front clears the area!

GFS Maps:

 SPC's Take

Jun 21, 2015 1730 UTC Day 2 Convective Outlook

Updated: Sun Jun 21 17:32:26 UTC 2015 (Print Version |  | )

Probabilistic to Categorical Outlook Conversion Table

Categorical Probabilistic  Population  Cities  CWAs  Interstates  Counties  ARTCC  FEMA Regions Categorical Day2 0600Z Outlook Day 2 Risk Area (sq. mi.) Area Pop. Some Larger Population Centers in Risk Area ENHANCED 129,731 27,151,847 Chicago, IL...Detroit, MI...Milwaukee, WI...Toledo, OH...Madison, WI... SLIGHT 143,283 14,682,662 Cleveland, OH...Minneapolis, MN...Buffalo, NY...St. Paul, MN...Fort Wayne, IN... MARGINAL 190,594 20,003,960 Indianapolis, IN...Columbus, OH...Kansas City, MO...Pittsburgh, PA...Rochester, NY...

Forecast Discussion

SPC AC 211732 DAY 2 CONVECTIVE OUTLOOK NWS STORM PREDICTION CENTER NORMAN OK 1232 PM CDT SUN JUN 21 2015 VALID 221200Z - 231200Z ...THERE IS AN ENH RISK OF SVR TSTMS GREAT LAKES AND UPPER MS VALLEY... ...THERE IS A SLGT RISK OF SVR TSTMS FROM THE UPPER MIDWEST TO LOWER GREAT LAKES... ...THERE IS A MRGL RISK OF SVR TSTMS ACROSS PARTS OF THE N-CNTRL/NE STATES... ...SUMMARY... SCATTERED SEVERE STORMS ARE LIKELY ACROSS PARTS OF THE UPPER MISSISSIPPI VALLEY AND GREAT LAKES REGIONS...SOME OF WHICH SHOULD BE INTENSE...MAINLY FROM MIDDAY THROUGH THE EVENING ON MONDAY. ...UPPER MS VALLEY/GREAT LAKES... STRONGLY CONSIDERED AN UPGRADE TO MODERATE RISK WITH POTENTIAL FOR CLUSTERS OF INTENSE SEVERE STORMS WITH ALL SIGNIFICANT SEVERE HAZARDS POSSIBLE. BUT WILL DEFER GIVEN ENOUGH UNCERTAINTY WITH REGARD TO EVOLUTION OF LATE D1 CONVECTION WITH ITS SUBSEQUENT EFFECT ON THE DEGREE OF DOWNSTREAM DIURNAL DESTABILIZATION...ALONG WITH TIMING OF THE PAIR OF MID-LEVEL SHORTWAVE IMPULSES WITH RESPECT TO PEAK HEATING. GUIDANCE IS CONSISTENT IN DEPICTING STRENGTHENING LOW/MID-TROPOSPHERIC FLOW IN RESPONSE TO A CONVECTIVELY-GENERATED MCV FROM LATE D1/EARLY D2 AND APPROACH OF AN UPSTREAM SHORTWAVE TROUGH CURRENTLY OVER THE SRN CANADIAN ROCKIES. THESE FEATURES WOULD ENHANCE LOW-LEVEL WAA OF THE RICHLY BUOYANT AIR MASS CURRENTLY PRESENT OVER THE LOWER MO VALLEY. AVAILABLE CAMS VARY MARKEDLY WITH THE DAYTIME EVOLUTION OF AN MCS EXPECTED TO BE ONGOING ACROSS PARTS OF SRN MN/NRN IA. IT SEEMS PLAUSIBLE THAT THIS ACTIVITY SHOULD PERSIST THROUGH THE DAY WITH AN ORGANIZED SEVERE RISK ON THE EDGE OF A ROBUST PLAINS EML. THIS TYPE OF SCENARIO MAY RESULT IN LEAD CONVECTION OUTPACING THE MORE FAVORABLE THERMODYNAMIC ENVIRONMENT CHARACTERIZED BY RATHER STEEP MID-LEVEL LAPSE RATES AND VERY LARGE BUOYANCY. AT LEAST SCATTERED UPSTREAM TSTM DEVELOPMENT SHOULD OCCUR BY LATE AFTERNOON ALONG THE COLD FRONT FROM CNTRL/ERN WI SW TO THE IA/IL BORDER AREA AS CONVERGENCE ALONG THE FRONT AND DIABATIC HEATING OVERCOME INHIBITION DUE TO THE INITIALLY STOUT EML. SUPERCELLS ARE EXPECTED IN INITIAL STAGES OF DEVELOPMENT...WITH SOME OF THIS CONVECTION GROWING UPSCALE DURING THE EVENING. WITH LOW-LEVEL FLOW BECOMING INCREASINGLY VEERED IN THE WAKE OF THE LEAD MID-LEVEL IMPULSE...MAIN HAZARDS WITH SW EXTENT SHOULD BE VERY LARGE HAIL TRANSITIONING TO PREDOMINATELY SEVERE WIND. WHERE 850 MB WINDS CAN REMAIN QUITE STRONG WITH ENLARGED LOW-LEVEL HODOGRAPHS /MOST LIKELY IN ERN WI TO LOWER MI/...A RISK FOR STRONG TORNADOES AND/OR SIGNIFICANT SEVERE WIND GUSTS MAY DEVELOP. ..GRAMS.. 06/21/2015

Part Two: The Cold Front

The second villain in the piece (and possibly the worst) will be the strong cold front as it sails east-southeast at 45 to 50 mph through lower Michigan during the overnight hours of Monday into early Tuesday. As the storms approach, the intense wind max moving through the region at all upper levels will help push any storm development and line eastward of upwards of 50-60 mph aiding some very turbulent storm downdrafts creating scattered high wind damage. The risk of tornadic cells will gradually decrease with time as wind directions at all levels align with straight line high winds remaining the main risk.

This entire system reminds me of a few of our stronger squall lines including bow echoes and derechos; May 31st, 1998 (which is also an analogue), also July 7th 1991 and July 2nd 1997 because of the tornado threat. I'm sure there are others, too numerous to mention. Again the dynamite appears to be there and whether of not the extreme weather conditions materialize will be an up to the minute realization. Models are predicting one of the stronger severe weather events in recent times as the dynamically driven system runs rudely into explosively unstable air mass. I wouldn't be surprised in SPC upgrades some of the area to a moderate risk if these parameters continue in successive model outputs. Keep tuned to NWS web page/NWR and other weather mediate outlets during the day Monday into Tuesday morning!

I will update any notable changes as usual through the period.

GFS Maps:

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

Update 6/12 - Severe Weather Potential Now Decreasing Today

Update 6/12...

The combination of a suppressed surface wave, residual precipitation from an old outflow boundary and cool easterly winds off the Great Lakes are all making it difficult for the projected surface wave and subsequent instability to advance northeast into southern lower Michigan.

As of early afternoon Friday, the low pressure and associated instability and conflict of air masses is remaining south of the Michigan border. At this time, it looks as though just the southeast corner of  the region has the best chance of any severe weather. I'm mainly referring to Lenawee and Monroe counties (as has been the case all week) and possibly pushing as far north as the Ann Arbor and Metro Detroit areas. Therefore the risk of severe thunderstorms should pretty much hold over the Southeast corner...generally around I-94 and south.

The next risk of severe weather at this time looks to possibly be Sunday.

-------------------------------------------------------------------------------------------------------
Original 6/10 -
 
I have yet to write about any severe weather potential this season as there really hasn't been too much to get excited about except for some scattered or isolated events; with the most widespread being the flooding rains of May 30-31st.

I'm seeing an increasing potential for severe weather across the region, especially the southern two thirds of Southeast Lower Michigan possibly beginning overnight Thursday but more likely Friday. Actually the evolution of the event has roots in my Summer Outlook and the two main jets I discussed that would affect the summer's weather. One of course, is the Polar Jet diving through Canada into the northern tier of the country and the other; the potent sub-tropical jet enhanced by warmer than normal water temperatures out over the Pacific.

I depicted the Summer 2015 Weather and it's main influences in the following maps;

Focusing on the interactions of these two jets in the Summer Outlook and then again; in the severe potential for Friday gives a clearer picture and parallels. Note the cropped version of the above expected Summer upper wind pattern and then, the following discussion for the severe weather potential.

Late Thursday Into Friday

The past couple of days; our forecast models have been intimating a frontal postion would become hung-up across the northern Ohio Valley or Southern Great Lakes area. Where, exactly that happened would dictate the best risk of severe weather. This has been happening to our southwest and south this late spring into early summer and thus; it's been busy and wet down there. Moisture from the Pacific and at times Gulf; ran into the predominantly cooler winds coming in from Canada that dove south and east through the southern Plains and Ohio Valley.

 

However as the summer advances, we are getting into the time of year that is normally our busiest thunderstorm and severe weather season, June into July or more specifically mid June to mid July. And, as though cue'd by the summer upper wind pattern discussed, this change into more typical summer weather for the Great Lakes seems to be upon us now.

 

Particulars& Maps

Fri morn

           

                             Phasing Upper winds and subsequent Bulk Shear available

By late afternoon Friday; 

Many things come together for a severe weather event; good instability and shear as the low and colliding frontal positions move across Southeast Lower Michigan. CAPE approaching 2500-3000, Li's -7 to -9 and even helicity in the 150 range. Precipitable water bursts through two inches to our west, so torrential rains are also included as these storms march northeast around 40-45 mph - but there's one caveat; it's all model driven. And, it's the NAM model which tends to be a bit "hot" sometimes. Therefore, we'll watch later model runs to see if the severe weather looks as promising as it does Wednesday eve.

 

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

 

 

 

 

Summer 2015; Variable Data Suggests Mixed Weather for the Summer

Summer as a rule can be one of the more difficult seasons to forecast for because of the lighter, variable upper wind jet dominance. This summer that general trend may not apply as much as two dominant upper wind patterns via for center stage; a relatively strong polar jet that has had no trouble visiting the Great Lakes throughout the spring along with the sub-tropical/tropical jet aided by an ever increasing El Nino.

Depending on the jet and wavelength; the El Nino aided jet stream can create a more zonal flow across the country than is typical in the summer and at times; even amplify ridging over the center of eastern part of the country as upper lows push into the West. There are actually three broad areas of warmer than normal Pacific water temperatures evident at this time (see map of sea of surface temperature anomalies in May below). The first is over the northeast Pacific extending from the Gulf of Alaska to off the Pacific Northwest. The second lies from the central Pacific extending from off the California Coast to Mexico and of course, the third El Nino itself, which is over the equator region. The second warmer region over the central Pacific was more extensive early last winter and acted as a "pseudo El Nino" and thus, was a major reason for our warmer than average December when temperatures averaged 3 1/2 to 51/2 degrees above normal..

And while your glancing at the map, note the colder than average temperatures remaining south of Greenland (off the map) that extend into northeast Canada. This is primary due to the strong Polar/Arctic jet over eastern Canada into the northern Atlantic. Also note the pockets of warmer than average SST's over the Northeast and over the Gulf.

As mentioned, the El Nino is expected to continue to strengthen into the fall as depicted below by various dynamic and statistical models. At this time last year, the models were predicting a distinct El Nino for the Winter of 2014-15 which did not materialize as the ENSO remained Neutral-borderline El Nino. This time around, the models are more aggressive with the development of El Nino and its subsequent strength. Note the SST's warming on average to between +1.5 and +2.0C

Some models are projecting a strong El Nino this fall and early winter, something not seen since 1997-98. A moderate El Nino appeared also in 2002-03 then again in 2009-10 and interestingly, both moderate El Nino winters were snowy with normal to below normal temperatures - sound familiar? Therefore; while an El Nino is projected this winter, its above normal SST's and subsequent intensity will be very important. While a strong El Nino nearly always points to a mild winter, a weak to moderate does not! But, I'm getting ahead of myself...more on the Summer of 2015!

 Year     DJF   JFM   FMA  MAM  AMJ  MJJ    JJA    JAS   ASO   SON  OND  NDJ

1997	-0.5	-0.4	-0.1	0.2	0.7	1.2	1.5	1.8	2.1	2.3	2.4	2.3
1998	2.2	1.8	1.4	0.9	0.4	-0.2	-0.7	-1.0	-1.2	-1.3	-1.4	-1.5
1999	-1.5	-1.3	-1.0	-0.9	-0.9	-1.0	-1.0	-1.1	-1.1	-1.3	-1.5	-1.7
2000	-1.7	-1.5	-1.2	-0.9	-0.8	-0.7	-0.6	-0.5	-0.6	-0.6	-0.8	-0.8
2001	-0.7	-0.6	-0.5	-0.4	-0.2	-0.1	0.0	0.0	-0.1	-0.2	-0.3	-0.3
2002	-0.2	0.0	0.1	0.3	0.5	0.7	0.8	0.8	0.9	1.2	1.3	1.3
2003	1.1	0.8	0.4	0.0	-0.2	-0.1	0.2	0.4	0.4	0.4	0.4	0.3
2004	0.3	0.2	0.1	0.1	0.2	0.3	0.5	0.7	0.8	0.7	0.7	0.7
2005	0.6	0.4	0.3	0.3	0.3	0.3	0.2	0.1	0.0	-0.2	-0.5	-0.8
2006	-0.9	-0.7	-0.5	-0.3	0.0	0.1	0.2	0.3	0.5	0.8	1.0	1.0
2007	0.7	0.3	-0.1	-0.2	-0.3	-0.3	-0.4	-0.6	-0.8	-1.1	-1.2	-1.4
2008	-1.5	-1.5	-1.2	-0.9	-0.7	-0.5	-0.3	-0.2	-0.1	-0.2	-0.5	-0.7
2009	-0.8	-0.7	-0.5	-0.2	0.2	0.4	0.5	0.6	0.8	1.1	1.4	1.6
2010	1.6	1.3	1.0	0.6	0.1	-0.4	-0.9	-1.2	-1.4	-1.5	-1.5	-1.5
2011	-1.4	-1.2	-0.9	-0.6	-0.3	-0.2	-0.2	-0.4	-0.6	-0.8	-1.0	-1.0
2012	-0.9	-0.6	-0.5	-0.3	-0.2	0.0	0.1	0.4	0.5	0.6	0.2	-0.3
2013	-0.6	-0.6	-0.4	-0.2	-0.2	-0.3	-0.3	-0.3	-0.3	-0.2	-0.3	-0.4
2014	-0.6	-0.6	-0.5	-0.1	0.1	0.1	0.0	0.0	0.2	0.5	0.7	0.7
2015	0.6	0.5	0.6

Summer 2015 Outlook for Southeast Lower Michigan

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. 

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. Analogues favor the cooler side of normal which seems reasonable considering upper wind patterns over Canada and El Nino trends. Interestingly, this temperature range may very well sum up the summer on a week or two and/or a monthly basis. 

 

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.

 

                                 Analogues for Summer 2015

The majority of these analogues were chosen due to a strengthening El Nino in play during the summer whether it turned out later either a moderate or strong winter event. That obviously wasn't going to affect the previous summer's outcome. That being said, many were chosen where the previous few seasons were either neutral or weak El Nino, as in the present case. Others were not chosen even though the summer was in a ongoing El Nino, if the previous season or two were in a La Nina Phase or the timing was off and thus, were more subjective.

 

 

As stated in the opening, the analogue summers were extremely variable but with definite trends within with four cooler than normal, six normal and two warmer with a generally a comfortable summer projected. Not surprising, the average temperature while in the normal range, leaned a bit toward below normal - makes perfect sense with twice as many cooler than warmer summers. This is not surprising as El Nino Summers lean toward the cooler side of average. 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, less could be said about rainfall.

 

Rainfall was the most variable in not only seasonal amounts but areal coverage; in other words it was far less common to get close to uniform amounts. This is similar to 2013 where heavy amounts were seen over the south and lighter, below normal amounts were observed in the Saginaw Valley and Thumb. Speaking of 2013, I've noticed similarities to that summer in just this past May with the upper jet associated with mainly the Canadian upper low and to a lesser extent, the subtropical jet coming into the Southwest and South. The Summer of '13 was a Neutral Summer and thus, little affects from ENSO.

 

Summer 2013 

Stats for the Summer of '13

 

*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

Though temperatures averaged above normal the Summer of '13 it wasn't because of the highs.

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

Summer 2015

Glancing at the upper wind projection for the Summer of 2013 show similarities to this summer and differences. The difference noted for this summer 2015 projection is the better subtropical jet projected and thus, a more variable upper ridge strength. This is a result of building and flattening ridging in response to short waves riding in and through the region from the west. This is depicted on both maps with the first a computer generated 500 Heights and my interpretation of active areas of surface patterns. The second map, my interpretation of summer dominant and placement of air masses.

 

Summer 2015 500H along with surface patterns

 

Summer commences June 21 at 12:38 P.M. EDT calendar-wise; while meteorologically it began June 1st and runs through August 31st.

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