11/3/18

Aggressive Cold Snaps into Mid Month Likely to Bring Some Snow

Long term models are coming together for some significant waves of cold air to surge out of the Arctic region, through Canada into the Midwest, Great Lakes and East over the next 10 days. A few periods of short moderation can also be expected between the cold blasts. A few of these cold air masses will be impressive even for early November standards.

A strong low pressure is slated to form along the axis of Polar-Arctic air as it plows south and southeast into the country. Intense energy aloft will also accompany the upper air dynamics as it makes headway into the country by Election Day.

Selected maps for the upcoming week, approximate timing and results:













The frigid air will arrive and be accompanied by waves of rain, cold and then likelihood of snow showers. There is even the possibility of a bit of measurable snow over Southeast Lower Michigan late in the week into the following week with this weeks system and a few clippers. Further out in la la land; look for some moderation toward Thanksgiving.

Will an infrequent type El Nino possible this winter be accompanied by non-typical El Nino weather? 

Watch for my innovative Winter Outlook developed the past few decades by Thanksgiving's Weekend. I know it's a bit later this year but latest El Nino and hemispheric pattern changes along with up to date latest guidance seem to be working well into my new researched analogues.


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

 

9/23/18

A Change in the Wind; Appropriately on Autumn's Arrival Signals Bigger Changes in the Offing

Autumn arrived last evening /Saturday Sep 22nd at 954PM/ and the strong cold front that surged through Southeast Lower Michigan later Friday; brought fall-like air to remind us of the abrupt change in season. Temperatures well above average into 80s and Lower 90s this past week helped make September thus far, about six degrees above normal. Well; things are changing as successive waves of colder air, reflected by a radical change in the jet stream are forecast to take hold in the next few weeks.

They say "a picture is worth a thousand words" and the following snaps state it well. Note the aggressive shift in the jet stream, the belt of winds at the 500MB level (18kt) and up pushing further south and east with time starting by mid week. Colder, polar air that is entrained in the systems will eventually make it down to the surface with time accompanied by intervals of warmer air, classic of the change of season.



Tue 9/25


 Wed 9/26


Fri 9/28


As you can see in the maps, the northern jet becomes very active this upcoming few weeks; phasing with the Pacific jet at times and progressing east across the country.

Further out in "la la land" the GFS model continues the aggressive jet stream lock with a "full-lat" trough over North America. Of course; I must state that especially further out in time, of course these prognostics maps can be more questionable. It's been my experience that it's the trend or change of trend in the patterns that is most helpful. Many times the trend does develop but is slower to evolve and variances in the upper air pattern form. I'm sure variances in this pattern change will be projected in the next several runs.



Sat 9/29

Sun 9/30

Mon 9/30


Closer to the ground at 850MB /5kt/ we can see the colder air making its advance through the northern tier of the country. The trend shows this is the time more widespread frost/freezes (not scattered lighter frosts) MAY occur by early October, which is earlier than average in parts of Southeast Lower Michigan. A killing freeze generally doesn't occur across all of Southeast Michigan this early but needs to be watched. It will be outstanding even if the trend of the model predictions come to pass. Temperatures are projected to fall into the 30s over much of the region early October.

Mon 10/1


Wed 10/2



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










9/10/18

Another Feast or Famine Summer Unfolds in an Atmosphere of Heat

While severe weather was at bay the majority of the summer; there is still plenty of other things to mention about the Summer of 2018. Again, it was warm with hot spells like so many other summers this new millennium. Feast or famine in the title not only refers to periodicity of the rain but also the resulting amounts. If this summer felt familiar it should, the Summer of 2016 was very similar with it's pattern of heat and erratic rainfall though it was warmer, still.

There is a stark contrast in the summer temperatures again between Detroit; and both Flint and Saginaw and especially White Lake in the northern suburbs (see Statistics Table, below). Detroit's average temperature of 74.4 made it the 6th warmest summer on record in the warmest summer lists. However; this was more as a result of the heat island frequently affecting overnight low temperatures and somewhat less due to the highs. Detroit Metro Airport /DTW/ average highs came in at 83.4 degrees while the normal or average high for the summer is 81.4 degrees therefore; the average high was two degrees above normal. Looking at the average low departure speaks more of the heat island. The normal average low for the summer is an even 62 degrees. The average low for the Summer of  '18 was 65.2 or 3.2 degrees above normal.

Heat Island Micro-Climate

What's even more significant about Detroit's normals is that the temperatures at the Detroit Metro Airport have been contaminated by the sprawling heat island affect since the 1980s. Case in point; the average summer temperature in Detroit in the 1980s (using 1951-80 norms) was just 70.0 degrees as compared to 71.7 now; or +1.7 warmer. The norms at Flint /FNT/ rose just 0.4 of a degree from 68.2 to 68.6 in the same time period. I don't have the exact change at Saginaw /MBS/ but I know when we did an in-house study at DTX years back, it showed little change. I worked at the NWS/DTW from the 1970s thru mid 1990s and witnessed the change in the airport's micro - climate and it's gradual temperature rise. My co-worker at the time, Dennis Dixon did an in-house study on the local heat island beginning in the 1980s at DTW.  Later, the new runways with the McNamara development in 2002, has  likely only added to the problem.  New normals for our present period (1991-2020) should be processed in the early 2020's. One guess as to what they'll show with temperature norms?

Summer's, What It's All About...
 
                                                                                Chart - 1

Perhaps no place is the heat island at Detroit Metro Airport become more apparent than in the temperature records - take for example the warmest summer records. Detroit's average temperature of 74.4 degrees and placed 6th for warmest summer on record. In comparison, Saginaw just managed to squeak out 16th warmest summer and Flint never even placed! In fact, Flint's average at 70.5 was a full degree /1.1/ below the 20th warmest spot for Flint.

                                                                            Chart - 2


Looking back at 21 summer temperature averages at the NWS at White Lake /DTX/ shows that this past summer was in at 6th place (a small sample, indeed with just 21 summers). What stands out the most is the fact that all the rest of warm summers beat out this summer's average by a degree or better.


DTX   Summer ave temp   Year
    1-             70.5               2005
    2-             70.3               2010
    3-             69.5               2011
    4-             69.2               2012
    5-             68.6               2016
 < 6-            66.9               2018

*Updated to add from the NWS Summer Temperature/Rainfall Averages
Slide12.PNG


Feasts or Famine Summer Rains 
The isolated to scattered heavier rains that appeared over the southern areas of Southeast Lower Michigan (including DTW) early in the summer moved north over the northern half of the region in August.  Heavy rains at both Flint and Saginaw more than made up for what had been a dry summer at both locations June and July. In contrast; many southern areas including DTW saw deficits of rain in August. The driest parts of this summer came latter part of June and the first half of July. Rainfall at Detroit Metro while being around normal at that time; did not represent much of the region as evidenced by these rainfall in percent of the mean, maps. The worst of the dry spell came the first part of July; especially across the southern areas of South-central and Southeast Lower Michigan.


                          1                                                           2


The lack of rain during these periods can really be appreciated by looking at Map 2. Most areas saw less that less 1/4" of rain in July through mid month and that time period actually could be extended to June 23rd - July 13th. More general rains and thunderstorms appeared later in the summer. The areas in and around both Flint and Saginaw received 7-8"+ of rain in August. Flint measured 7.69" while Saginaw had 8.02". Both stations posted the 4th wettest August since records began. The surplus of rain; mainly due to convective training rains, shows up well over northern parts of Southeast Lower Michigan in this August departure rainfall map.



*Updated to add from the NWS Summer Temperature/Rainfall Averages







Summer Analogue Performance 

I already surmised the analogues were too cool and is why I went a numerical value of up to 1.5 degrees above normal for the summer.  The average temperature departure across the Southeast Lower Michigan came in at +1.8    (see SE Mich temperature departure in Chart-1) As noted above, what can play havoc with these outlooks can be the heat island at Detroit Metro Arpt.

The best analogue years were 2006 and 2012. Analogue 2006 was a warm and somewhat wet summer like some parts of the region; whereas 2012 was even warmer than 2006 but drier - again like some other parts of the region. Looking further back into the spring; shows 2012 was a warmer spring than this past spring. In fact, Spring of 2012 was the warmest spring on record at all three stations. That year of 2012 recorded 30 annual 90 degree days at Detroit. Thus far this year; Detroit has recorded 25 through Sep 10 2018 and it's still possible to record a few more. So, as you can see both summers, 2006 and 2012 are good candidates for analogues.

Another recent summer, 2016 was not a strong hemispheric analogue as far as ENSO timing but is a good analogue for weather and patterns. That summer the SST's were changing from a El Nino pattern to Neutral; whereas this year's SST's pattern is the reverse; going from a Neutral pattern to El Nino. However; given the SST's were still similar during both summers; the Neutral Summer of 2016 was also another very warm summer and fairly wet across the Upper Midwest and Ohio Valley.

 

SUMMER 2018 ANALOGUES 












DETROITJUNJULAUGSUM AVESUMMERS90 DEG DAYS 

TEMPS
189470.773.969.471.01       N/A
189968.771.572.270.826
191169.573.670.771.3314
191866.671.174.870.8415
195167.872.769.570.017
197670.672.770.771.3521
198562.871.369.267.823
200069.470.370.870.231*
200169.573.574.172.3614
200669.376.172.972.8110
200967.868.971.269.344
201272.379.073.074.8230*
Ave68.872.971.571.1AVE11
Norm69.473.672.071.7NORM       8-12
Dep-0.6-0.7-0.5-0.6















DETROITJUNJULAUGSUM TOTSUMMERSTSTM DAYS

PCPN

18942.632.620.165.411NA/NA
18991.822.950.625.392NA/NA
19111.480.791.313.583NA/5_9/7_6
19183.300.741.295.334NA/5_7/6_8
19513.134.102.9910.22129/7_8
19763.261.471.686.41529/4_7/5
19851.623.964.8810.46237/7_9
20004.905.404.6314.93139/6_7/8
20013.401.162.877.43633/4_5_8/6
20063.954.382.0510.38329/7_9
20095.272.562.7610.59421/5_5
20121.313.672.257.23734/7_8
Ave3.002.822.298.11

Norm3.523.373.009.89TSTMLEGEND
p-0.52-0.55-0.71-1.78First #Annual Total





Second/ThirdHiest





#'sMonth_Total
ColorTempsDegreesRainInches

Legend:Below1.0>Below1.00>NANot Avail

Normal0.0-1.0Normal0.00-1.00


Above1.0>Above1.00>


_________________________________________________________________

Autumn Analogues  - More of the Same or not?

A weak El Nino is expected to continue to evolve during the fall. Weak El Nino's tend to affect our Autumn weather negligibly, especially if at the forefront of a developing El Nino. A moderate to strong El Nino tends to bring wet, cool falls to the region and luckily it doesn't appear she's is or will advanced that much.

As just discussed above; 2006 and 2012 were our best analogues and while the Summer of 2016 is a good analogue for the Neutral summer; the pattern went off into a La Nina that fall, not El Nino.

Check out the following Autumns of 2006/2012

Temperatures




Precipitation



By the looks of the temperature patterns in 2006/2012; the El Nino's were already affecting the country by Autumn with cooler than average weather extending from the Great Lakes south into the Ohio Valley and Southeast. Precipitation was generally typical for the falls in the Lakes but above in the Ohio Valley.


Autumn 2018

As we progressed into fall a notable cooling engulfed the area - as though Mom Nature read the calendar season change. Extended model guidance basically brings back the more normal to above temperature pattern recently experienced.  The best performing analogues for the summer, especially in regard to temperatures; conflicts with the fall warmer models below.

Comparing the analogue data with the computer data results in both temperature and precipitation conflicts


Check out the Outlook for the Fall by model standards...

Temperatures






One doesn't have to be a climate guru or meteorologist to see the various models keep our normal to above normal temperature regime continuing with the American model the most aggressive for warmth.

Rainfall





There is a discrepancy between the models as far as precipitation for the fall also with the American CFSv2 and British model leaning toward a wetter, mild fall; while the European and France model leans more toward normal precipitation, possibly a bit below. Again, the American model is the most aggressive in chances for the wetter scenario. These wetter solutions would intimate that El Nino begins to exude its influence sooner.

Temperatures & Precipitation For the Autumn

Given the conflicting recent and analogue patterns along with model forecast; 

I look for an average fall with regard to temperatures with normal to above precipitation.

Look for that all important Winter Outlook in early November!

Upcoming Autumn/Early Winter Dates:

Autumn arrives on Saturday Eve, Sep 22nd at 954PM.
Halloween is on Wednesday, October 31st
Thanksgiving is the earliest possible this year: Thursday, Nov 22nd.

Winter arrives on: Friday, Dec 21st at 522PM EST
Christmas is Tuesday; Dec 25th 2018


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