Saturday Summary

Trough will dig a little dipper into the east producing 1 below normal day on monday and a rainy sunday as the cold front pushes through. Overall we will not see that much cooling form this trough but just near normal departures from today to wednesday. A very strong ridge is centered over the eastern rockies and the plain states which is producing 35 C+ degree heat throughout texas, oklahoma, arkansas, colorado, kansas,arizona,misouri and louisiana. As you can see the heat is over a large area. By tuesday 40 C degree heat will extend all the way from texas north to wyoming! This ridge will then midgrate eastwwards for a short period of time(before a cold fornt moves through ushering in cool air) producing a quick 2 day heat surge into southern and eastern ontario next thursday and friday. Saturday will still be hot for places like montreal and quebec city but not western areas in ontario. The GTA has the potential to reach 30 on thursday and then possibly 33 on friday. I think what is developing now is what we are going to see as we go forward this summer. The southern plains are have been drying out lately allowing for very warm temperatures(a warm source region) where the ridge axis is centered and anyone under the ridge. I believe the ridge will stay fairly strong quite often although not as strong as the recent one. The ridge will produce heat for the northern plains and mid sections of the u.s and will tend to migrate eats or west at times (but not frequently). In my summer forecast I made it clear that prolonged heat would not be a problem this summer although the potential is there for a few above normal days before a cool down. The reason the Euro has so much heat under this ridge is because it brings debby under the ridge and not off to the east and near the florida coast. Hurrricanes are meant to move the transfer the heat from the tropics to the polar regions and therefore it pushes a lot of heat (possibly record breaking) out in front of it under the strong ridge developing in the southern plains. The GFS is less aggressive on the heat because of where it moves the storm. The track of this storms will be very key to seeing if we can get are 2 days of heat. If the GFS is right it won't be as hot, if the euro is right then we may see a near repeat performance of this week although only 2 days long in southern and possibly eastern ontario. After this time period it appears as though more frequent troughs and more average temperatures will rule ontario and the east while the ridge weakens. By july the 10th-15th we are going to have to deal with the most prolonged heatwave of the season(which i have been mentioning now for weeks) possibly lasting 7-10 days. Before I though it would come earlier but the MJO has slowed down slightly pushing the timing back. This years MJO phase shares many similarities wiht 2006 as well as enso phase and the overall pattern. This is what it looked like from july 13th 2006 to july 22nd. This may be what it will look like during july this year with a lot of heat surging up into the great lakes,ohio valley,midwest,ontario, northern plains and even the east coast.

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Follow up on previous post about next winter

Following up on my previous post and wanting to dig deeper...

If a spike in the cold PDO to warm creates very cold winters in the east then why aren't all el nino's in a warm PDO severe winters. Why is it that the spike in the cold PDO causes cold winters but a regular warm PDO with an el nino causes generally warm winters?

Looking at all el nino's in a warm PDO we can see warmer temperatures across north america and cooler temperatures across the arctic:

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500mb Heights:

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Surface Pressure:

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All el ninos in a cold PDO with a warm spike:
Heights at 500mb:

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Surface Pressures:

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I threw in 1959 which had a PDO spike as well and a very cold winter. This is just another good example of how the theory works,even in the case of an el nino following an el nino.

To sum this up, what is occurring is that because the PDO is permanently warm the pressures are lowering even more over the pacific as well as the heights. The atmosphere always wants to balance itself out so if this occurs then there will need to be more of a compensation over north america. What happened in many of these years was that there was a compensation in pressures over northwestern canada but because more of a balance was needed this also translated in a rise in heights over eastern and central america which caused warmer winters. A good example is 1982-3 which shows this pattern.You can see the warming of the arctic but the eastern U.S and canada as well because of the need to balance.

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If a brief warming of the PDO is created then there is less of a lowering of pressures in the pacific (because of the weaker strength and shorter duration of the warm PDO) and less of a compensation of rising pressures across north america. This causes the arctic and greenland to warm without causing warming across the eastern U.S and instead it lowers the pressures across the east.

400mb Theory For Next Winter

I have been doing some research with how 400mb temperature trends in november correlated with very warm and very cold winters. What I found was that very warm winters have novembers with very warm temperatures across the arctic and antarctic. Cold winters have very COLD temperatures across the arctic and warm antarctic temperatures at 400mb. This was a surprising setup considering the fact that a warm arctic and greenland usually translate to a colder north america in fall and winter but this was not the case and in fact the opposite. Lower heights across greenland and the arctic are what translate into cold winters. Fascinating! 

400mb heights in novembers proceeding very cold winters across the u.s:

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400mb heights in novembers proceeding very warm winters across the u.s:

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This is what my preferred analogs looked like at 400mb in novembers proceeding there winters. For this analog set I chose weak to moderate el nino years following double or triple ninas that are east based with a spike in the PDO to positive. You will notice that the arctic temperatures are on the cold side and the antarctic on the warm side(meaning a good setup for a cold winter):

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Severe Thunderstorms Hitting SW Ontario, Heading for the GTA

Latest Radar picture showing severe storms heading straight of the city of Toronto. A severe thunderstorm watch is in effect. Some lighting and thunder have already been recorded in the city as well as damaging winds!

Severe Thunderstorm threat tonight

Storms will start firing up along and in front of the cold front. Pop up severe storms in front of the line will begin to effect our area and areas to the east of us first at around 7:00 PM. The main line will probably pass through at around 9:00 or 10:00. According to the last few runs of the HRRR (10z and 9z are showing this) a cell will move right into the toronto/hamilton area. At this point it is very hard to pinpoint the exact location of this cell but this is something we should watch out for. The last few runs have been more confident with this and are showing stronger storms affecting us! We should await the next few runs to see if this teen continues and the idea of this cell stays.

10z HRRR at hour 10:

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CAPE at hour 10 appears to show a huge spike along the lake towards 2500j/kg. The question is if this will actually occur or is just exaggerated by the model. If it does that would aid in the development of severe storms. The montreal area is surrounded by high CAPE values.

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VIL levels(hour 10) show the possibility of some small hail with these cells although i don't think this will be the main threat.

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Heavy downpours, very strong winds, frequent lightning and thunder will be the main threat with these cells. An isolated tornado cannot be rules out somewhere along the line but this will be unknown until the storms form. There is plenty of lift in the atmosphere shown by the LI at hour 10:

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Storm relative helicity is showing some rotation in some of the cells including the one i mentioned which has higher values within it if you look closely around the toronto area. Values are between 100 and 150(probably not big deal). Hour 9:

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I will be closely monitoring this to see if this line packs a punch or fizzles like we've seen many times before!

Why T-storms fizzle as they cross Lake Huron

Today was just another example of the frustration we face in southern ontario when michigan gets blasted with strong storms which appear as though they are going to nail us too and then at the last second they rapidly weaken. I have done some research on this, because it has really interested me(the fact that T-storms fizzle quickly when passing the eastern shores of lake huron). My theory is that when these storms are crossing the lake that has a colder water temperature then the air temperature above it(the air in which these cells fire up in (warm air masses)). This will cool the surface air and create a capping inversion by cooling any air parcels that may begin to rise or are in the process of rising. This will leave cooler air parcels relative to the surrounding air, especially as you go up into the atmosphere and this cuts off convection and thunderstorms development even if conditions may be favourable.This will also weaken any storms that have previously developed. Unless we are in the middle of the summer months and in a situation very supportive for thunderstorms (a widespread outbreak we usually see in august with tornadoes) when a line of storms crosses lake huron they tend to weaken otherwise. A better source region for a line of storms would be from the south of lake huron or from the lake erie area SSW of us in southern ontario. Lake erie is not as wide as lake huron and does not have nearly the same effect on T-stomrs. Any comments or questions feel free to let me know!!

Revised Summer Outlook for the U.S

The area that I forecasted below normal for the summer looks pretty good so far with michigan above normal and the ohio valley all the away south and east to florida below normal as well as PA and the mid atlantic. Going foreword i believe that the southeast will stay below normal and the great lakes and mid atlantic will as well. Michigan may end up warmer then previously thought but its a wild card definitely! Will enough trough's position themselves west enough and frequently enough to effect that region. The northern pains should stay above normal with the tendency of the ridge to shift westwards instead of eastwards which will give much needed improvement to the cold west right now. The core of the warm will set up in the rockies like it is right now with wild fire danger. West texas is much warmer then east texas which is vulnerable to gulf moisture and tropical storms/hurricanes. An east coast hit will contribute to the cool ideas i have along the eats coast. to sum it up august is cooler then july in the lakes. July will probably end up near normal there but august below leading to the -1 to -2 departure I put up.

Revised forecast:

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This is what I believe the mean pattern is going to look like for july with that trough showing up in the east as the SOI's start falling.



The july cooling will really start occurring after a 7-10 day heat wave I believe is coming after the 4th of july. July will average close to normal in the east with an area of slightly above normal in the great lakes and an area of below normal in the southeast/mid atlantic. August i believe will be the coldest month as the SOI values continue to cars and the el nino takes hold. Mean trough will be positioned in the east with cooler then normal and wetter conditions in the great lakes and northeast. Warm core backs into the central part of the country and getting into the west at times. This is what the mean 500mb pattern should look like for august.

Some Blocking Theology For You

These are the main factors that i look at to see if blocking will develop next winter

1) Mid and upper level temperatures. Very cold mid and upper level temperatures like we saw last winter will force the bundling of the jet northwards(a stronger polar vortex) toward the poles and force the positive AO that we saw last winter! This is also why alaska and greenland experienced a very cold winter. This contributed to record amounts of sea ice in the bering sea. The reason for last winters very positive AO and NAO was the very cold mid and upper level temperatures that were present before and during the winter time. We need the mid and upper level temperatures to warm up towards next winter or at least level off if we want to see the cold penetrating north america.  Most people just said its the positive AO that caused the warm winter or its the jet stream position that caused the warm winter but it is what made that occur that actually caused the warm winter pattern. 
Look at the huge drop in temperatures from 2010(tan) to 2012 (green)
At 600mb:


And at 400mb:


This caused the 500mb pattern to look like this last winter. When stratospheric warming finally occurred last winter the cold air bundled itself over the larger continents (which it naturally does in this type of pattern where the PDO has recently switched phases). When you turn down a thermostat in your house the air in the room cools before the surface does and it is the same with regards to the atmosphere where the PDO is the thermostat of the earth. When you cool the PDO then you are lowering the energy budget of the earth and start rapidly cooling the mid and upper levels of the atmosphere. It takes a while before the surface can begin to cool as well. So as long as we are in this pattern and the upper levels stay cold then the cold air will always bundle towards the poles. If forced to come down due to a stratospheric warming ETC then it will bundle over europe and asia and cause blocking there and not in north america.

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This is what europe looked like at 500mb with blocking across the north and cold air funnelling in for good reason.

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2) If blocking is found in the southern hemisphere during summer:
we can see big swings right now in the AAO from very negative to very positive and perhaps in the tank again. I did a blog post on the CFS forecast of this summer in the southern hemisphere and how that has effected us in north america int he past.

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3) If we see a pronounced atlantic tripole (warm, cold, warm SST's)
We can see that in the year of 2009-10 contributing to the strong persistent blocking that showed up.

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Also in the winter of 1952-3 we can see the warm, cold then warm pattern setting up. This winter had consistent blocking for most of the fall, winter and spring.

1952 10 -0.28
1952 11 -1.32
1952 12 -0.49
1953 1 -0.12
1953 2 -1.00
1953 3 -0.45
1953 4 -1.96

SST's

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There are more examples...

4) Solar activity 
We know that years with low solar had strong blocking showing up. This year we are heading to wards our maximum although it is not very high when compared to other years. I don't feel as though there is a strong signal in the effect that solar activity has on this winter.

5) Volcanic acitvity 
Years where arctic volcanoes erupted had very strong persistent blocking such as 2009-10. This also contributes to a big drop in global temperatures the following years. Due to the volcanos that recently arrested we may see some strong cooling showing up this winter or the following winters due to this.
In the year of 1912-13 we saw mount novarupta erupt and this produce major cooling 3,4 and 5 years later.


In the winter of 2009-10 we saw Mt. Redoubt in Alaska, Sarychev in Russia and Eyjafjallajökull in Iceland. If we do the math we can see that as history is shown to repeat itself we will see a lot of cold showing up in north america in the winters of 2012-13, 2013-14 and 2014-15.


6) A negative QBO

Digging deeper into the winter pattern

Taking a look at why we need a spike to warm in the PDO in order to get a cold and snowy winter in the east.

If we look at 1951-2 and 1972-3 we can see lower heights in the west due to the cold PDO that hangs on and this causes higher heights in the east and warm winters.

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This contributed to warm surface temperatures, drier and less snowy conditions in the east and central part of the country. The west, meanwhile stays cold in this type of pattern.

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Looking at the pressure pattern in those years we can see lower then normal pressures where the el nino develops while we also see higher then normal pressures where the pool of warm water is found in a cold PDO. This is surrounded by lower pressures where the horse shoe of cold water develops. Because of this we see the compensation of lower then normal pressures in the arctic and across greenland (which is what caused the low amounts of blocking in those years) and higher then normal pressures across eastern canada. This type of pattern does not support strong highs coming down from north west canada which would bring very strong cold air masses to the east. This is quite the opposite and it makes it very hard for that to occur. Also, we see a drier pattern in the eastern U.S because we are not seeing lower then normal pressures developing in the area.

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If we look at 4 years that were in a cold PDO overall and were el ninos after double or triple la ninas we can see the higher heights over the west(caused but the warm PDO which would favour more ridging in the west as opposed to the constant troughiness and cold weather we are seeing there now) and we are seeing a strong trough in the east. This produces a very cold temperature pattern in the East. We can also see the higher then normal heights across the arctic and greenland which allows blocking to develop and this brings cold air masses down into the eastern part of the country and allows strong snow storms to develop.

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If we also look at the pressure pattern in those winters we can see lower then normal pressures where the el nino develops as well as where the pocket of cold water develops due to the cold PDO. We see a ring of higher pressures around it. This creates a compensating rise in pressures across northwestern canada as well as the arctic and in tern we see lowering of pressures in the eastern part of the country. This is an exact OPPOSITE pattern of the other two years I showed you caused by the difference in the PDO! This is the perfect recipe to bringing strong highs down from northwestern canada. This, combined with a strong sub tropical jet that the moderate el nino produces allows for more storms to meet up with very cold air masses. In one of my blog posts I mentioned the fact that the spike warm in the PDO is the key to producing blocking for north america across Greenland. The reason that the blocking develops is due to the rise in pressures around Greenland (created by the compensation needed in the pressure pattern because of the Warm PDO that developed) and this also allows for the lowering of pressures in the east. These relationships I am showing you are going to be the keys to unlocking what occurs next winter and why.

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This type of el nino pattern along with a spike in the PDO to just slightly warm(it doesn't need to be very warm) translated to some of the most severe winters ever for the eastern part of the country! This story is not told by the temperature departure map at the surface but we all know how brutal these winters were both snow and cold wise!

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The CFS and the CFSv2 are showing this weakening in the PDO occurring but I believe as we go on in time it will even become more bullish on this idea. The modelling right now isn't really picking up on the specifics of what might happen in this pattern but they will come around as the SST's for next winter become more certain. I believe that I have a really good handle on the pattern that is going to develop next winter whether a warm PDO develops or not and I hope you guys enjoyed my post! Feel free to comment!