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

 

 

May's Weather, Model Data and Analogues Suggest a Mixed Summer

Many times I've noticed through the years how Mother Nature will tip her hat as to the weather likely for the next season late in the current season and I feel with this May is one of those cases. That, along with computer generated outlooks and previous and newer El Nino analogues suggest this is the case for the summer.

In my last blog, I stated strongly contrasting air masses would rule the second half of May...cold...warm with more storms and rain as a result. The second half of May certainly lived up to that projection with several warm days rudely interrupted by notable cold snaps. Impressive cold snaps that actually brought temperatures down into the 30s along with scattered frosts as late as the 23rd. Take a look at these low temperatures for the morning of the 23rd across Southeast Lower Michigan.

However, in spite of the of the cold interjections, May still managed to average several degrees above normal and that was primarily a result of a very warm first half of the month. Temperatures the first couple of weeks averaged at one point as much as 10 degrees above normal before settling back to about half of that. Analogue projections had called for a changeable spring with colder than average weather early, moderating to normal and above normal by the time May rolled around along with overall, drier than average predominate conditions. March's temperatures averaged below normal across the region along with drier than normal conditions, where as warmer winds commenced in April bringing temperature averages up a couple degrees above normal weather but with continued drier than average rainfall. By the end of April, most areas were two inches or more below normal for rainfall.

May's weather was a mixed bag as far weather with again warm and cool air masses interchanging but with a decided preference to warmer. Not surprising, along with the conflicting air masses was the pick up in wet weather. After two months of relatively dry weather; May's rainfall averaged near normal to above normal (especially at the end of the month and over the south) with rather frequent periods of showers and strong thunderstorms. Actually the month's rainfall was generally below normal across much of Southeast Lower Michigan until the last two days when very heavy rains from a stalled front and attending low pressure wiped out most deficits for the month. Interestingly, while the heavier rains wiped out the deficit for May and led to a normal to above normal rainfall statistic across the south (Ann Arbor through metro Detroit) for May and the spring; areas to the north remained below normal for the spring. This is one of those cases across the south where the trend of the spring was actually dry, yet the rainfall amounts were normal to above but mainly due to just two days, the 30th and 31st of May.

Note the heavy rainfall map across Southeast Lower Michigan From 8am 5/30/15 - 8am
5/31/15 and this does not include the rainfall after 8am on Sunday, the 31st. 

 


This is a summary of the past - now what about the future?

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. Interestingly, this oscillating 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.

 

Look for my entire, detailed Outlook coming this week.

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

 

Change in Upper Air Pattern Mid-May Liable to Bring More Contrasting Temperatures and...

I my blog regarding May's weather outlook I stated; I expected a warmer than normal May and thus far, Southeast Lower Michigan is averaging 8 - 10 degrees above normal thru the 13th. In addition, on 5/2 when I wrote the blog I stated:

"Why there is still the risk of a frost or freeze, none looks likely in the next week to 10 days anyway and there's less than a 30% chance through the month with the above normal temperatures. I'll keep the blog updated if the risk does arise if colder air masses make their way out of Canada".

I stated that because even though I expected a warm May overall, sharply contrasting air masses have been the rule this spring and I expected May to be no exception. After days in the 80s (including record territory), sharply colder air from Canada has aggressively plowed back across the region, driving temperatures down some 30-35 degrees recently! While temperature swings of 30-40 degrees in the month of May happen, it's not as commonplace as its spring month counterparts of March and April across Southeast Lower Michigan.

Our upper air pattern has reverted back to "ridge-trough pattern" of April as opposed to primarily ridge the first two weeks of May. The projected pattern discussed on the 2nd served well the first two weeks of the month (or as stated  "next week to 10 days") with above to much above temperatures. In addition, I stated I would update if the need arises after that period and the need has come....

Remainder of May Outlook
After a cold start and risk of scattered frost across the region overnight into Thursday morning as a rather strong high pressure dominates, look for temperatures to start a moderate climb once again through the 60s and into the 70s and breaking into the 80s over the weekend. In addition, the risk of showers and thunderstorms will be on the increase as the warmer air rudely surges back into the region. With this contrasting pattern in the works the next few week, severe weather potential also rises.

Looking ahead, I expected this oscillating pattern to be more the rule than the exception through  much of the remainder of the month. While temperatures will average above normal for the month, enough cold air will also be able to make it down occasionally to bring the possibility of a frost and/or freeze.

The old adage of planting after Memorial Day (and it comes the earliest possible this year) still seems the best advice - especially in the more frost/freeze prone areas of Southeast Lower Michigan!

 

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

Analogues and Guidance Indicate a Warmer and Somewhat Drier May In Store for Southeast Lower Michigan

Thus far, the current spring pattern has evolved as indicated by both analogues and recent guidance. A colder than normal March evolved into a near normal to above in April as temperature patterns projected and in actuality; transitioned from below normal to above. The timing of the pattern change has been somewhat ahead of the timing of both spring analogues and models by about a week or two week. But, I'm not complaining after last winter and early spring with spring development, now in full force.

TEMPERATURES
Spring analogues for May called for a near normal May temperature-wise while latest guidance indicates above normal temperatures. With out timing of pattern changes seemingly ahead of past analogues, above normal temperatures are the best forecast. Typically May's average high temperatures start out in the mid 60s and warm to the mid 70s by the close. Overnight lows begin the month in the mid 40s and rise to the mid 50s by the close. Why there is still the risk of a frost or freeze, none looks likely in the next week to 10 days anyway and there's less than a 30% chance through the month with the above normal temperatures. I'll keep the blog updated if the risk does arise if colder air masses make their way out of Canada.

RAINFALL
Drier than normal or average spring conditions were projected by both the analogues and models, and continue to be upheld by latest precipitation guidance for May. Local analogues projected Spring rainfall would average at least an inch or two below normal across all of Southeast Lower Michigan. Thus far this spring through the end of April, precipitation has averaged around two inches below normal. Latest model projections continue the drier than average pattern with below normal rainfall. Note the CFSv2 is calling for a notable bull-eye of below normal rainfall to our south, over the Ohio Valley. Interesting since this is the area that has been most active with precipitation the past several seasons on average. May is generally one of our wetter months with around three inches of rain usually falling - therefore this dry pattern established bares watching for the growing season.

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

Record Breaking Late Season Snowstorm of April 23rd-25th 2005, The Incredible Snowstorm of May 9th 1923 and Lastly, The Unbelievable Late Snow of May 21-22, 1883

You  might be grumbling about today's snow flurries but just cast you mind back ten years ago!  While our weather this spring has been less than desirable, it has been worse; on tomorrow's date in history and later. Take a look at my write-ups on just three of these memorable snows.

Record Breaking Late Season Snowstorm of April 23rd-25th 2005

With such an exceptionally variable and stormy winter it was actually fitting that the Winter of 2004-05 went out with a bang and not a whimper. If the persistent cold and snow during March wasn't enough to extend an already lengthy winter, Mother Nature really gave the inhabitants of Southeast Lower Michigan a sucker punch late in April.

A very nice stretch of sunny, dry (actually too dry) weather commenced late March into the first three weeks of April. This beautiful early spring weather reached a climax on the 19th when record highs were attained at all three climate stations (DTW/FNT/MBS). Ironically, not only did all three cities have record highs but it also was with the same temperature, 83 degrees. After the 19th, however, the weather was all downhill, accelerating big-time by the weekend. A series of cold fronts pushed south across the Michigan from the 20th to the 23rd, dropping temperatures some 40-50 degrees by the weekend /23-24th/!

An intense low pressure developed along an arctic cold front over the Upper Ohio Valley Saturday into Sunday and actually backed westward into the Eastern Lower Great Lakes (over Southwest Ontario - central pressure about 29.25" /986 MB/). This storm brought the worse late April weather seen in these parts in several decades. Snowfalls from the storm ranged wildly from a trace to as much as 16.5" with the heaviest falling across the highland areas from central Oakland County northeast into the Thumb Region (around Bad Axe). This very late snowstorm was the "icing on the cake" so to speak on what already had been a very snowy season. More information is available on April snows and total snowfall amounts from this storm. Incredibly, the May 9th, 1923 snowstorm which contained similar snow depths is over two weeks later!

The phasing of upper level jet steams, resulting in intensifying low pressure systems over Lower or Eastern Great Lakes have been responsible for some of our worst snowstorms; as evidenced by the above and following...

   Snowstorm of May 9th, 1923 

Not since records have been kept in Southeast Lower Michigan      
(Detroit as far back as 1870), has the snowstorm of May 9th
in 1923 been equaled in season lateness and magnitude.

A strong cold front, of Arctic origin, pushed across Southeast
Michigan on the afternoon of the 8th, creating scattered thunder-
storms. The strength of the front was quite evident in Detroit.
The temperature plummeted from a near normal reading of 62
degrees at 100 pm to a winter like one of 34 degrees by 600 pm.
Behind the front, the stage was set for some startling weather    
developments for the month of May...even in Southeast Lower
Michigan. Rain mixed with snow fell across the area during the
evening of the 8th. Detroit received an estimated inch of snow
which melted on the ground before ending by midnight.

On the morning of the 9th, a low pressure area developed along
the front in northwest Ohio and moved over Lake Erie during the
afternoon. The developing low pulled warmer, moist air north from
the Ohio Valley and mixed with the unseasonably cold air mass
over Southeast Lower Michigan. As a result, a heavy, wet snow
began falling during the forenoon hours and continued through the
afternoon. Arguably, one of the most astonishing things (and
there were several) about the mid-spring snowstorm was that the
bulk of the snow fell during the time of day which is normally
considered "the heat of the day" or "afternoon heating" when
normal highs of the day are attained. The afternoon temperatures
never budged from the lower 30s (31-33) and was accompanied by
a stiff northwest wind, averaging 15 to 25 mph. Keep in mind,
the normal or average high for May 9th is 67...some 35 degrees
warmer! 

The snow ended by the evening in Detroit and at 800 pm, six
inches was reported on the ground. The story was even more
fantastic as one traveled west and north of Detroit across
Southeast Lower Michigan. Generally, six to nine inches fell 
west to the Ann Arbor area, northwest through Howell, north
across Pontiac and northeast up to Port Huron. Even more
incredible, snow depths of around a foot were reported at Flint
and Lansing north into the Saginaw Valley. Widespread damage was
reported to trees, power lines (many had a two inch circumference
of snow hanging on them) and telephone poles, especially in the
Saginaw Valley. Even so, economic damage was surprisingly small,
especially to spring vegetation. Evidently, the earlier spring
weather had been abnormally cold and this led to a late green up.
Substantial damage from the cold to vegetation and crops was
actually averted due to the insulation affect of the heavy, wet 
snow. Many May snow records (amounts and lateness in the season)
were shattered and stand firm to this day over Southeast Lower
Michigan.

By the next morning (10th), much of the snow had melted and by
the evening, it was just a memory. The official high in Detroit
on the 9th was 39, but that occurred just after midnight, before
the storm. The low was 31, which occurred in the afternoon during
the storm, giving a mean of 35 for the day and 21 degrees below
the normal of 56. Other May record snowfalls in Detroit pale in
comparison. In 1912, 1.5 inches fell on May 13th for the second
highest amount and the latest snow actually occurred the last day
of the month, May 31st, 1910 with a trace.

So, the next time you think it's too cold for this late in spring
or we can't possibly have a measurable snowfall in May across
Southeast Lower Michigan, you might want to THINK about it again
(or maybe not).

Unbelievable Snow of May 21-22, 1883  

Since this was so long ago; it was questioned at one time if it really occurred and 

if the snow amounts were legit or not. While at NWS, DTX, I was very curious

myself and dug back into the archaic records of nearly 132 years ago now,

to investigate the authenticity of such occurrence. Not only was there snowfall 

recorded between 7PM EST May 21-7AM EST May 22, 1883 but it was impressive

amounts being so very late in the spring!

Snow began to accumulate during the evening hours of the 21st, leaving a snowfall

of 2.3" by midnight (snowfall, not snow depth). The snow continued from midnight 

until the early morning hours of the 22nd, leaving an additional 2.7" snowfall 

recorded by 7AM the next morning. Therefore, there was a total of 5.0" of snowfall 

during that 12 hour period - the entire event. However; I don't ever recall seeing

a 5" snow depth on the ground the morning of the 22nd, as part of the snow melted

as it fell. Record lows of 32 degrees were reported both days, the evening of the

21st and early morning of the 22nd, mainly during the snowfall. In addition, a record

low maximum of just 41 degrees was recorded on the 22nd! Normal highs for that late 

in May are lower 70s while lows in the lower 50s! Therefore; the temperature average

for May 22nd, 1883 was 37 degrees or 25 degrees below normal /62/, extraordinary for any 

winter month - let alone late May! 

The Monthly Weather Review quotes Detroit as having snow on the 21st-22nd though

the amounts were not listed. I was able to pull up the daily morning weather maps

from May 21, 1883 and May 22, 1883; See for yourself, this storm along with its

development again bring up the Ohio Valley/Eastern Lakes Low development that 

matures over the East and Northeast part of the country. This type of pattern is

reminiscent of many of our major snowstorms, including the rare late season ones

discussed here.

                           SURFACE MAP OF 5/21/1883 - 7AM

                SURFACE MAP OF 5/21/1883 /Cropped and analyzed-WRD/

The central pressure of the low had deepened close to 29.30"/992 MB /lowest 

pressure analyzed 29.34 IN outside of the center/ moving into West Virginia

the morning of the 21st. The sub 40 degree temperature isotherm is entered in a 

blue dashed line.

                             SURFACE MAP OF 5/22/1883 - 7AM

The central pressure of the low remained close to 29.40"/995 MB /lowest pressure 

analyzed 29.47 IN outside of the center/ in the Washington DC area the morning

of the 22nd. The sub 40 degree temperature isotherm is entered in a blue dashed

line. 

Of course, the 500 MB upper air map was non existent for the date but can be 

extrapolated and it must have been a mighty cold upper low to support that kind

of storm and snowfall so far south, a little better than a week before June. 

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

A Cool Week is In-Store for Southeast Lower Michigan - Hold Off Planting Vulnerable Plants This Earth Day Week

After a relative slow slow start to April warmth; the past couple of weeks have more than made up for the cool start to spring thus far. With March averaging 2 - 3 degrees below normal, the growing season was put on hold into early April. However since April 9th, temperatures have averaged consistently above or well above normal these past 10 days or so. So much so, that the average temperature thus far April is now averaging in the upper 40s to lower 50s - or about 4 degrees ABOVE normal. The last time freezing temperatures were seen and felt was early in April on the 6th at Detroit /32/, and the 11tth at Saginaw /32/ and 12th at Flint /also 32/. In fact, sometimes it has been safe to start planting hardier crops mid to late April. Cool weather crops such as peas, broccoli, cabbage, etc etc can be usually put in at least by late April.

Therefore; is it safe to plant?

I would definitely hold off planting anything frost/freeze sensitive that will germinate the next week to 10 days. A pronounced cool spell through this upcoming week anyway, will definitely take a bite out if that above normal average temperature accumulated this month. A return upper wind flow, back cross Polar will take  hold this week. This pattern is much like the bitter cold, cross Polar flow seen recently in mid to late winter. Of course, the air has moderated some since then and will continue as the solar angle increases with the spring but will still carry a punch. Frost, freezes and possibly even a period or two of snow flurries are all in our near term weather scenario. The outcome will depend on the actual coldness of the air mass over the region and whether or not cloud, cover dissipates overnight allowing for good radiational cooling along with local temperature affects.

 
As noted in my map above, Earth Day is this Wednesday. It is what it says, a day to reflect on our mother planet and to appreciate our life giving environment. Earth Day began in the early 1970s as we became more and more concerned about our pollution of environment and the longer term affects.

Earth Day Flag

Next up - Record Breaking Late Spring Snowstorms & What's May looking like?

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

-Update 4/9/15: Stormy April Beginning To Come To Fruition: Severe Weather Potential 4/9-10

Quick Update This Evening Into Friday - 4/9/15

Very little change from yesterday's blog with timing issues and low level stability major deterrents for an organized outbreak of severe weather. If anything; all things considered now, any organized severe weather looks doubtful with the strongest weather /winds/ coming in isolated strong storm/severe, ahead of and along the cold front overnight and toward morning. Widespread strong winds are expected after cold frontal passage near sunrise (as stated yesterday, see next paragraph below). Winds on Friday look to rev-up to between 25 - 40 MPH with gusts possible 40 - 50.


-4/8/15
Review
Overall with the data I've looked at as of the 18Z GFS Wed 4/8 run, I see the best (or worst if you prefer) of the strong weather, mainly west, southwest and south of Southeast Lower Michigan. This mainly because of late timing issues and somewhat out of alignment severe weather parameters.

Thunderstorms look likely, some elevated and some strong to possibly a few severe with gusty damaging winds, mainly from late afternoon into the over night hours with the evolving squall line. However, the strongest of winds could very well be behind the line of storms, the early part of Friday.

 Any notable changes, look for updates.
______________________________________________________________________________
It was just last week when I called for a stormier April and now we have out first potential severe weather event, Thursday into early the morning hours of Friday. It's been relatively calm too long and mainly due to the the overhang of cold, Polar air over the region. This brought the colder than average March but with the change of the month, came a change in the over weather and temperatures pattern and - the springtime conflict of air masses. With the strengthening heating of the atmosphere comes the usual air mass battle and resultant storms and severe weather.

It's been relatively calm across the country this spring as the cool, stabilizing residual Polar air masses continued to slide down across Canada into the eastern half of the country while this has brought a slow start to spring across much of the Great Lakes and Northeast, it also has kept severe weather basically at bay. In addition the near freezing waters of the northern Great Lakes basically, 30s to lower 40s over the southern Great Lakes have a remarkable effect of local and downwind areas. Today is an excellent example of the contrasting low level air masses across a rather small region of the country. The combination of a cold polar high pressure in southeast Canada and its attending northeast wind across the icy Great Lakes, show the strength of air masses in this classic early spring weather pattern. Meanwhile, much warmer (some places close to 40 degrees) bubbles up from the south and southwest as warm spring-like winds push rudely northeast into this cold, stable dome of air. Below, look at the contrasting temperatures of both air masses over the Great Lakes and Northern Ohio Valley.

Water Temperatures remain in the 30s to lower 40s over the Eastern Great Lakes.
(Click on ALL maps for larger depiction and clarity)

 Great Lakes Surface Map as of 5PM 4/8/15

 

Outstanding, all that's needed to mix up these opposing foe's is some sort of catalyst to come along and surge one air mass into the other. Cue surface/instability maps for Thu into Fri>>>>

During Thursday:
The warm front pushes north through the lower Great Lakes by early evening along with ushering in more unstable air and decent helecity (which aids in the development of tornadoes). Storm Relative Helicity (third map) along a warm front is generally where it is best available because of the clockwise turn of the air from the colder air mass to the north and east to the warmer air mass south and southwest. Therefore, east to southeast winds gradually turn to south and southwest in the lowest layers of the atmosphere. The Storm Relative Helicity Index map relates those numbers, the higher the number the more likely of tornadic storms using the scale below (third map). One very important caveat to remember however, is that strong instability (CAPE/LI/Bulk Shear among other parameters) is also needed. Many times, one of these parameters may blow the roof off (no pun intended) but with the absence of another, severe weather fails to materialize.

 

GFS 18Z SKEWt

beta.wxcaster.com/cgi-bin/parse_skewt_trace_all.cgi?model=GFS&STATIONID=DTW

DATA TABLE

    Helicity Amount of Rotation

> 100 Some storm rotation

>  250 Enough rotation to support supercell thunderstorms

    and some tornadoes

>  400 Enough rotation to support dangerous tornadic thunderstorms

5PM 4/8/15 - Helecity

 8PM 4/8/15 - Helecity

 

GFS 03z SKEWt

Note that while helicty remains potent, the atmosphere begins to stabilize as nightfall overtakes the region, particularity so early in the heating season. April severe weather events can be one of the most extreme events because of strong, almost winter-like dynamics (wind fields/energy) feeding the low pressure storm system. And, when strong winter-like dynamics meet up with spring or even summer-like air masses all hell can break loose.

11pm Thu - Helecity

 

I introduce the bulk shear here at 2AM Fri as it maximizes out out west of the main storm action. Not quite best aligned and over the line of storms for best strong storm wind action at the surface.

The bulk shear here at 7AM Fri pushes through Southeast Lower Michigan just on the heels of the line of convection. Strong winds indicated aloft behind the line of storms will blast down to the surface behind the front bringing strong, gusty surface winds!

Review
Overall with the data I've looked at as of the 18Z GFS Wed 4/8 run, I see the best (or worst if you prefer) of the strong weather, mainly west, southwest and south of Southeast Lower Michigan. This mainly because of late timing issues and somewhat out of alignment severe weather parameters.

Thunderstorms look likely, some elevated and some strong to possibly a few severe with gusty damaging winds, mainly from late afternoon into the over night hours with the evolving squall line. However, the strongest of winds could very well be behind the line of storms, the early part of Friday.

Any notable changes, look for updates.

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

SPC Severe Weather Outlook Issued Wednesday afternoon

 

 SPC AC 081730

   DAY 2 CONVECTIVE OUTLOOK 

   NWS STORM PREDICTION CENTER NORMAN OK

   1230 PM CDT WED APR 08 2015

   VALID 091200Z - 101200Z

...THERE IS AN ENH RISK OF SVR TSTMS THURSDAY AFTERNOON AND EVENING ACROSS PARTS OF SOUTHERN GREAT LAKES REGION AND LOWER OHIO VALLEY...SOUTHWARD THROUGH THE OZARK PLATEAU AND ARKLATEX REGION...

...THERE IS A SLGT RISK OF SVR TSTMS SURROUNDING THE ENH RISK

AREA...ACROSS THE GREAT LAKES REGION AND OHIO      VALLEY...SOUTHWARD  INTO THE SOUTHEASTERN PLAINS...

...THERE IS A MRGL RISK OF SVR TSTMS AS FAR SOUTHEAST AS THE EDWARDS  PLATEAU AND ADJACENT PORTIONS OF THE RIO GRANDE VALLEY...

   ...SUMMARY...

 SEVERE THUNDERSTORMS ARE LIKELY THURSDAY INTO THURSDAY NIGHT ACROSS  SOUTHERN PORTIONS OF THE GREAT LAKES REGION...AND MUCH OF THE MIDDLE  MISSISSIPPI AND OHIO VALLEYS INTO THE SOUTHEASTERN PLAINS.  THIS WILL INCLUDE THE RISK FOR DAMAGING WIND GUSTS AND LARGE HAIL.  A  COUPLE OF STRONG TORNADOES ARE POSSIBLE.

   ...SYNOPSIS...

A SIGNIFICANT IMPULSE...WITHIN THE SOUTHERN BRANCH OF SPLIT

WESTERLIES EMERGING FROM THE MID-LATITUDE PACIFIC...IS FORECAST TO CONTINUE AN EAST NORTHEASTWARD ACCELERATION OUT OF THE GREAT BASIN DURING THIS PERIOD.  THIS FEATURE IS EXPECTED TO REACH THE CENTRAL  HIGH PLAINS BY 12Z THURSDAY...AND THE UPPER MIDWEST BY THURSDAY NIGHT...WHERE/WHEN MODELS SUGGEST THAT IT MAY INCREASINGLY PHASE WITH A SIGNIFICANT NORTHERN STREAM IMPULSE.  AS THIS OCCURS...MORE SUBSTANTIVE DEEPENING OF AN ASSOCIATED SURFACE CYCLONE...EMERGING FROM THE CENTRAL PLAINS...IS EXPECTED TO PROCEED ACROSS AND EAST  NORTHEAST OF THE GREAT LAKES REGION.

ALTHOUGH SUBSTANTIVE DEEPENING OF THE LOW IS NOT CURRENTLY FORECAST  AS IT TRACKS FROM THE MID MISSOURI VALLEY TOWARD LAKE MICHIGAN DURING THE DAY THURSDAY...IT STILL IS EXPECTED TO BE AT LEAST MODERATELY STRONG WITH LOWEST PRESSURES AT OR BELOW 1000 MB.  A TRAILING SURFACE COLD FRONT APPEARS LIKELY TO ADVANCE SOUTHWARD THROUGH THE MIDDLE MISSISSIPPI VALLEY AND PORTIONS OF THE OZARK PLATEAU AND SOUTHEASTERN PLAINS...WHERE IT WILL GRADUALLY OVERTAKE A WELL-DEFINED DRYLINE.  A WARM FRONT EAST OF THE LOW APPEARS LIKELY TO ADVANCE NORTHWARD THROUGH THE GREAT LAKES REGION...WHILE COLD AIR REMAINS DAMMED TO THE EAST OF MUCH OF THE NORTHERN AND CENTRAL APPALACHIANS.

AIDED BY THE PRESENCE OF MOIST AND POTENTIALLY UNSTABLE AIR IN THE WARM SECTOR OF THE CYCLONE...LARGE-SCALE FORCING FOR UPWARD VERTICAL MOTION SHOULD BE SUFFICIENT TO SUPPORT WIDESPREAD THUNDERSTORM  ACTIVITY...FROM THE MISSISSIPPI VALLEY AND SOUTHEASTERN PLAINS INTO THE APPALACHIANS...PERHAPS PORTIONS OF THE PIEDMONT TO THE EAST OF THE SOUTHERN APPALACHIANS.  IN THE PRESENCE OF MODERATELY STRONG...40-50 KT DEEP LAYER MEAN FLOW AND DEEP LAYER SHEAR...ANUMBER OF THESE STORMS MAY BECOME SEVERE.  MUCH OF THIS ACTIVITY  SEEMS LIKELY TO BE FOCUSED ON THE AFOREMENTIONED SURFACE BOUNDARIES...PARTICULARLY ALONG THE SOUTHEASTWARD SURGING

FRONT/DRYLINE ACROSS THE OHIO VALLEY INTO SOUTHEASTERN PLAINS BY  THURSDAY EVENING.

   ...GREAT LAKES/OHIO VALLEY INTO SOUTHEASTERN PLAINS...

MODELOUTPUT IS SUGGESTIVE THAT DEEPER/RICHER BOUNDARY LAYER  MOISTENING MAY BE CONFINED TO A RELATIVELY NARROW CORRIDOR IN  ADVANCE OF THE COLD FRONT.  AND CONSIDERABLE CONVECTIVE ACTIVITY MAY  BE ONGOING IN THE WARM SECTOR ACROSS PARTS OF THE MIDDLE MISSISSIPPI   AND OHIO VALLEYS AT THE OUTSET OF THE PERIOD.  BY 12Z THURSDAY...IT ALSO APPEARS THAT THERE MAY BE CONSIDERABLE STABILIZATION OF THE  BROAD AREA OF STEEP MID-LEVEL LAPSE RATES NOW PRESENT ACROSS THE  PLAINS INTO THE VICINITY OF THE APPALACHIANS.  THESE FACTORS...AMONG

OTHERS...MAY BE LIMITING FACTORS TO A POTENTIALLY MORE SUBSTANTIVE   SEVERE WEATHER RISK FOR THIS PERIOD.

  STILL...GIVEN THE LARGE-SCALE FORCING AND STRENGTH OF DEEP LAYER   FLOW/SHEAR...INCLUDING A RATHER BROAD AREA OF 40-50 KT SOUTH   SOUTHWESTERLY 850 MB FLOW DURING THE DAY...THE ENVIRONMENT WILL BE  CONDUCIVE TO ORGANIZED CONVECTIVE DEVELOPMENT...INCLUDING SUPERCELLS.  AND POCKETS OF STRONGER DESTABILIZATION COULD YIELD  SCATTERED AREAS WITH POTENTIAL FOR INTENSE SUPERCELLS CAPABLE OF   PRODUCING A STRONG TORNADO OR TWO...IN ADDITION TO VERY LARGE HAIL.

IT IS POSSIBLE THAT ONE OF THESE AREAS COULD DEVELOP NEAR THE WARM   FRONT...IN THE VICINITY OF THE SURFACE LOW...ACROSS PARTS OF   NORTHERN ILLINOIS...INCLUDING THE CHICAGO METRO AREA...

DURING THE MIDDAY AND AFTERNOON HOURS.  ANOTHER COULD DEVELOP NEAR  THE COLD FRONT/DRY LINE INTERSECTION...ACROSS PARTS OF THE OZARK  PLATEAU AND ARKLATEX REGION DURING THE LATE AFTERNOON AND EVENING.    HOWEVER...TOO MUCH UNCERTAINTY CURRENTLY EXISTS CONCERNING COVERAGE  AND AREA TO SUPPORT 10 PERCENT SIGNIFICANT SEVERE WEATHER  PROBABILITIES AT THE PRESENT TIME.   OTHERWISE...DAMAGING CONVECTIVE SURFACE GUSTS MAY EVENTUALLY BECOME  THE MOST PROMINENT SEVERE WEATHER THREAT WITH AN EVOLVING SQUALL  LINE ALONG/AHEAD OF THE COLD FRONT BY THURSDAY EVENING.

   ..KERR.. 04/08/2015