Major Lake Effect Snow Outbreak

The NAM 4km WRF looks interesting with a WNW/NW flow dominating. 
Hour 22:

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Hour 31:

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Hour 54:

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A line from bluewater through goderich, kincardine and up to owen sound will see decent snow from this outbreak. Winds will begin in a WNW to ESE direction after the passage of the cold front but they will shift to more of a NW/NNW direction as we head into late thursday night/friday morning. I think squalls off of GB are weaker then huron but squalls on thursday will target areas from midland southeast to orillia. This band will stay north of barrie for the most part but is right on the edge of the city with lighter accumulations expected in barrie/wasaga. As the winds shift the band should move through the city but for a short span of time thursday evening. On Thursday night the band should settle on the SW end of the bay allowing owen sound, meaford and collingwood to get in on some snow. Down wind of lake huron the walkerton and mount forest areas will be effected first with the WNW flow to start.  These bands will shift around a lot thursday as they move from north to south. Heaviest accumulations will set up from goderich to kincardine and NE to wingham thursday night into friday as a strengthening band settles here for several hours. I think a band of 20-30cm+ will set up across this area with white out conditions likely. This band may strengthen enough to get into the stratford, st mary's and huron east areas but it should stay mainly north of london. I think the GTA may see a few cm's from this outbreak but nothing major.

With that being said here are my accumulation forecasts across the province:
Orillia: 10-20cm
Midland: 10-20cm
Barrie: 3-10cm
Wasaga: 3-10cm
Toronto/ Hamilton:1-5cm
Owen Sound: 10-20cm
Kincardine: 15-25cm
Goderich: 15-25cm
Huron East: 15-25cm
Stratford: 5-12cm
Hanover: 5-12cm
Walkerton: 5-12cm
Colligwood: 5-12cm
Meaford: 8-15cm 

MJO, Indicies Dictate Upcoming Pattern

It looks like we will see a cold shot for the first 5 days of feb with a train of clippers moving through. The MJO will head into a weak phase 1 after this which should bring some moderation into the east. Further down the road the pattern has the potential to be interesting with a more active STJ and transient pattern as the MJO progresses quickly through several phases. This means that we will see a more progressive and changeable weather pattern which will make it difficult to build a large snow cover in february. The mean storm track will shift around in the february 6-10th time period as well. Positioning of the blocking will be key. If we can see it set up stronger and further NW then we can see troughiness in the east. I am still not convinced just yet that this will occur with the very positive GWO, changeable MJO and weakening SSW event.

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I think the NAO will stay neutral to positive allowing for a further inland storm track and neutral to slightly positive PNA. The PNA will be key. If it trends positive after the initial cold shot(feb 1-5) then the storm track will shift to the east coast with the trough over the great lakes. This would set up a cold and dry pattern in the lakes but if the PNA trends neutral the mean trough shifts west allowing for more lakes cutters/apps runners if the STJ can get involved. The MJO supports the latter as the trough pulls back into the plains from the 6th of february onwards and i agree with this. The big question remains where you set up in relation to the BZ and each individual storm track to see if we can cash in on snow similar to late december fro many. The MJO will re-amplify in phases 2 and 3 which should open up a window for cold and storminess from the 10th-17th of february. 
MJO phase 8 in feb lines up with the first cold shot to start off feb. In phase 1 notice the trough pulling back west:

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Phase 2 and 3 brings the cold back in but in a progressive manor as the MJO moves quickly and a lack of blocking sets up. After the 25th of february the MJO will go unfavourable and SSW effects will wear off which should allow for a warming trend and a spring preview.

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February Looks Cold With Analog Year Support

The upcoming period of weather from february first to the 20th looks very interesting. The cold will come first and looks like it will lock in until the 9th-12th of february. Blocking should set up towards the end of the period which will allow the arctic air mass to linger across eastern canada. I expect the lowest departures to be across the western great lakes, northern ontario, eastern ontario, new england and quebec. Although air masses will be cold across southern ontario, the northeast and ohio valley  some modification will take place with the warm lakes. Dryness will dominate overall with some clipper activity and LES from the northern branch reinforcing the snowpack in ontario and the upper midwest/ohio valley. After this period the MJO will begin to move into phases that favor a wetter pattern and further NW storm track, which can bring some action to eastern canada, midwest and new england in the snow department. After the 20th of february the MJO will begin to propagate into phases that favor a ridge in the eastern half of north america and this lines up with my thinking. The pattern will snap fast this year by the last few days of february or beginning of march. Now remember, although departures can be warmer then normal storminess can still be a key player for the end of feb and beginning of march. I have put emphasis on march in my spring outlook as being warmer then normal but this march will not compare to last year in terms of departures.

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In terms of analog years i have been looking closely at some years and found 2003-2004 as a good match. This year had a neutral ENSO, warm PDO and AMO. Its not so much the SST's that had a perfect match but the MJO was very similar with the same type of movement but one month earlier. These high amplitude waves are common in la nada years and we are about to see this unfold. Keep your eye on the red line which shows the january MJO wave in 2004 looking very similar to our current wave.

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This is what january looked like as a whole:

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Long Range Outlook

KW propagating eastwards between 140 and 160 east. Notice the rebounding of water temperatures along the thermocline between 120E and the date line. This water may move towards the surface causing some further warming in the western nino regions but not all that much right now. Nino regions 1, 2 and 3 continue to stay colder then normal. We can see the corresponding WWB along with the MJO wave as pressures build towards darwin and SOI drops continue through next week. The STJ is beginning to gain strength and will becomes enhanced for the first week of february.

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MJO wave looks to propagate into phase 8 and then into 1 and 2. After the relaxation in the pattern for the beginning of next week we should see a return to a deep trough centred in the great lakes/upper midwest( a little further west then our current one). A tongue of cold will extend from the prairies into eastern quebec and ottawa, montreal and toronto will feel the arctic blast yet again. Snowier conditions are likely from february 3-11 as the MJO is favourable and the STJ gets enhanced as BZ migrates northwards. Ridging should resume in the SE with more of a battle ground taking place and more average temperatures dominating after the 10th.

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Notice the further east jet stream in the pacific which corresponds with MJO phases 8-2 and promotes an aleutians trough which we are seeing. The GWO supports this as we are seeing very high EAMT values pumping a rockies ridge.

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GWO:

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Preliminary 2013 Spring Forecast

Key Points:

• A quick transition to spring is expected in the southeast and along the east coast as an active southeast ridge is in place
• The northwest will be colder then normal with frequent troughiness and wet conditions especially in march and april
• Drought will continue to intensify across the southern plains states and florida with a strengthening ridge developing as we head into april and may
• The bulk of the severe weather this spring will be focused across the tennessee, ohio valleys and great lakes region with below normal activity in the plains states and eastern rockies
• Wetter then normal conditions are present across the great lakes, northern ohio valley and southern canadian prairies
• Dryness continues to increase across the southwest and gulf coast states as a weakening of the sub tropical jet stream takes place

ENSO

The state of the ENSO this spring will play a big part in my overall forecast. Right now we have a neutral ENSO state but the pattern is acting very la nina like due to the cooler then normal anomalies showing up in the eastern nino regions. Trade winds are dominating the equatorial pacific right now with positive SOI readings.

Despite all this we are not necessarily heading into a la nina. Right now we are seeing several conflicting signals with the MJO propagating westwards in the pacific. This is helping to move the warm water east from the sub surface. Some of the cold anomalies may shed away in nino 3.4  in the short term with an enhancement of sub tropical jet disturbances.

Moving into spring I don't think that this warming of SST's is going to last and the -PDO regime will help support the la nina. I do expect the MJO to return to phases 2 to 5 in the spring which favour a southeast ridge. I think that we will see a continuation of neutral ENSO conditions this spring although biased cold with a la nina look to the pattern. The MJO is the wild card here and if it stays in phases 2 to 5 we will definitely see the la nina pattern dominate with a ridge in the east and dryness in the south. My ENSO forecast is in line with the consensus:

The UKMET for MAM shows the dryness prevailing across the south and more moisture across the northern tier with an active northern jet. Notice the MJO phase 3-6 look to the pattern.

Monthly Breakdown

March

A quick transition from winter to spring will be in store to start of the month as ridging continues to strengthen in the southeast. This will be driven by the strengthening la nina pattern in the equatorial pacific and -PDO regime which favours increasing dryness across the plains states and a more active SE ridge. I am expecting warmer then normal temperatures across the southern plains, great lakes, southeast and ohio valley. Cooler then normal temperatures will dominate in the pacific northwest with a parade of storms diving into the area. This is caused by the very active northern branch of the jet stream which is driven by the cooling sea surface temperatures in the pacific. The negative PDO regime favors a -PNA pattern which causes troughiness in the northwest and warmth across the eastern half of the country. A relaxation of the -NAO/ AO combination is likely as the effects of the SSW ware off and the relaxation of the jet stream allows the -PNA to take over. The severe weather battle zone will set up in the middle across the Ohio/Tennessee valley's and eastern great lakes where a battle will take place between the warmth and the cold. This area will experience wetter then normal conditions in march. Below are my march analogs. I think ridging will be stronger and centred further southeast but this is very close to my current pattern ideas. Ridging in the bering sea will be a key feature this month with a strong trough in the gulf of alaska

This is in line with the latest SST's. Important to note is the strengthening -PDO supporting a gulf of alaska trough and ridge centred in the southeast u.s

April and May

Warmth will continue to intensify in the east with a strengthening ridge across the plains states. Little drought relief will be felt with warmer and drier then normal temperatures prevailing over much of the southern plains, midwest, southeast and east coast. Departures may be cut down at times in the eastern great lakes and interior new england with northern branch features moving along in the flow but warmth will prevail overall. The bulk of the severe weather will shift NE away from the heat ridge developing in the southern plains. I expect this area to set up across the eastern ohio/tennessee valley's and lower great lakes. Wet and cool conditions will continue along the west coast with some surface highs building down which may promote some cool nights in the southwest and pacific northwest. These wet conditions will begin to relax as we head into may with more seasonal values across the area. May can end up very close to last year in the east with early heat showing what may come later in the summer. I am expecting may to be warmer then normal across the eastern two thirds of the nation with severe weather quite active across the great lakes, ohio valley and interior northeast. Severe weather should shift north as the upper ridge in the plains steers  away systems from the northern branch.

Current U.S drought monitor shows the current drought conditions which should continue to intensify in the plains and florida common in -PDO years.

Here is my analog package for april at 500mb. I think the ridge will end up centered further SE than this. Heights may end up lower in northern new england with a +NAO overall and some northern branch systems moving through. I like the -PNA, and +EPO look to the pattern.

The CFSv2 is in line with my thoughts with dryness across the south and an active northern jet supplying some moisture to the ohio valley, pacific northwest and great lakes region.

Here is the CFSv2 upper pattern for MAM

My forecast for March, April and May

Temperature

Precipitation

Highlights

Feel free to post any questions or comments you may have!

Eastern Storm Threat Possible Jan 23-27

I am watching a potential storm in the 7-12 day period for the eastern seaboard. This threat lines up with the current low pressure bomb in the west pacific which usually telleconnects with an east coast storm system 7-11 days later. Although this storm will not be nearly as strong in the u.s, a significant system is possible on the east side of the trough that will deepen after the 20th of janaury.

Heres our west pacific storm:

Lower heights to the west of japan telleconnect with a trough centered over the great lakes region around the 22nd. A storm should form on the southeast side of the trough but phasing of jet stream disturbances are very difficult to forecast this far out and will change on the models. Track of the storm will be hard to pin point for several more days as models have trouble handling these disturbances but I want to warn eveybody about this threat. The european model is showing this storm developing at hour 240. Important to note is the classic banana shaped high which will help keep the cold air in place. Also important is the lack of a well defined 50/50 low which will limit downstream ridging and speed up the system. These details will have to be ironed out over the next week and will be crucial to the track of this system.

With plenty of cold air available to the north this storm should track along the baroclinic boundary with the large thermal gradient setting up near the eastern seabord. To see where this might set up lets have a look at the h5 pattern predicted by the european ensembles. Notice the west based -NAO blocking which will allow the storm to track further east. A SE ridge is present although shifted further south which may allow this storm to track further NW.

To sum up here are some keys points that I want to mention:

1. A significant storm is possible for the eastern third of the nation between the 22-27 of Jan

2. Track and strength of this system is very unceratin until we get closer to the event

3. Pleny of cold air should be present NW of the storm center

4. Phasing of jet disturbances, 50/50 low and -NAO positioning will be key

If you have any question or comments feel free to ask as always!

Early February Looks Stormy

AAM has moved into the negative territory with a very negative anomaly centred near 30N. This favours higher heights near alaska and a continuation of a negative EPO pattern. The 12z ECMENS EPO forecasts confirm this up until the 20th of the month. The -EPO signal is caused by the poleward movement of warm tropical air to higher latitudes.

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Mountain torque values have been on the rise but i believe the SSW has peaked and will begin to tone down at 10 and 30mb as we are seeing negative torque values showing up near 30N. Equatorward movement of frictional torque values favours a stormier pattern across the north pacific in the next two weeks with several systems moving along in the flow. A rossby wave train pattern has set up across the pacific.

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As a result a much stormier pattern will take place across the eastern and central part of the u.s between february 1st and 15th. Eastward propagation of the MJO in the southwest pacific will lose amplitude as it moves into phase 7 which looks very likely in the next 5 days. Major disagreements showing up between the ECMF, GEFS and the UKMET ENS MJO forecasts. I like a blend of the 3 but not quite as amped up as the GEFS and UKME. It does look like the MJO will lost amplitude in phases 7 or 8 which means that the GWO, SSW and pacific pattern will have more significant roles in the weather pattern for the end of jan and beginning of february. Eastward MJO progress should allow a kelvin wave to form around the date line as pressures rise across the maritime continent. Currently, easterlies are dominating across the equatorial pacific but a WWB in the western regions will cause a more nino like pacific pattern to set up. The current GWO phase is trending in that direction with a weak phase 5 setup. SST's can rebound in nino 3 and 4 with a brief SOI drop and a more active STJ for early february.

Arctic Blast On The Way

After this weeks january thaw a return to much colder conditions is in store for central and eastern north america as the frigid air in the west makes its way eastwards. Temperatures wil begin to drop off on monday and tuesday as a cold front moves through the east.

After this the polar vortex will begin to sink southwards into the upper great lakes region and into northern ontario. Now I want to break down what is occurring in the atmosphere to initiate this change to a much colder pattern.

Part 1: Major Stratospheric Warming Event
Temperatures in the middle and upper stratosphere have soared lately with near record warmth at 10, 30 and 50mb. This warming has reversed the wind direction in the stratosphere which will help to suppress  the troposphere and cause very cold air to rush down to the surface between the 18th-25th of january. As a result of this the Arctic Oscillation will crash and the polar jet stream will weaken allowing arctic air from the polar vortex to move south. Areas that will have to endure the brunt of the cold include the upper midwest, eastern canada, northern new england and the great lakes region.

Part 2: Tropical Forcing

As the stratospheric warming supports this major cold shot in the east the tropics will become more favourable as well. Right now the MJO is in phase 6 with convection centered across the maritime continent. A very strong MJO wave has formed as a result of some very strong solar activity. This wave is forecast to propagate eastwards into phase 7 and weaken meaning two things 1) The MJO will have less of an effect on our weather pattern 2) The MJO is moving into much more favourable phases for cold which will help to suppress the SE ridge. Less of a fight will occur between the warmth and cold air with the cold taking hold in the end.

The eastward propagation of the MJO will also help to create a kelvin wave in the west/central pacific which should help to drop the daily SOI numbers and warm the western ENSO regions. The kelvin wave should form once the MJO propagates east near the date line as pressures rise to the NW and a more westward wind alignment occur . West based warmth in the pacific supports cold across eastern north america which is why I believe that february will be a cold month from the rockies eastwards. 

Part 3: Atmospheric Teleconnections

As frigid air makes its way into the mid latitudes favourable changes in the pacific pattern will help to lock the cold air into the east for several days with temperatures dipping to the coldest levels so far this year. We are seeing changes in the PNA index, meaning that a ridge will amplify along the west coast by the 18th allowing the first shot of cold to move southwards. This along with enhanced blocking over the pole will allow a strong trough to form over the east and central part of the continent. The pattern change is supported by the european and GFS ensembles.

European Ensembles for the 18th show the - East Based NAO, -AO, -EPO and +PNA pattern:

850mb temperature anomalies respond accordingly:

A second shot of cold air will follow after the 20th and this will be aimed further south and east with frigid temperatures being felt in the ohio valley, east coast, midwest and great lakes. This shot of cold air will be more severe then the first one as the polar vortex takes a big hit from the SSW event which results in a complete collapse. Daytime highs will not get above 15F during this cold shot in new york city and chicago if this forecast verifies.

As you can see it is not just the modelling but it is also the physical drivers on the table that support the polar vortex collapse and turn to a much colder pattern in the east and central part of the continent. Feel free to post any questions and comments you may have!