Sunday, 24 February 2013

Eastern Canada, Brace Yourself Again!

Winter Storm Forecast Discussion:
Meteorological Synopsis

A 996mb storm is currently located across SE new mexico and is expected to move northeastwards towards the lower great lakes region. Snows are already breaking out across the eastern rockies as the storm taps into cold air from the north. A swath of snow will develop along the rim of the cold air which will effect southern and eastern ontario starting early wednesday morning and continuing into thursday for southern quebec. The storm is expected to occlude as it does so which will cause a prolonged period of wintry precipitation (12-24 hours). Heavy wet snow will begin to develop across southern ontario by 3am wednesday as boundary level temperatures stay well below zero. Moderate to heavy snow will work into the ottawa/montreal regions by the afternoon hours. This type of snow will be quite moisture laden sticking to any exposed surfaces including trees and power lines. Power outages will become a concern from kitchener through the GTA and up towards kingston as winds gust up to 60kph at times. By wednesday evening precipitation will begin to taper off across southern ontario but light to moderate snowfall may add an additional accumulations wednesday evening/night.

Forecast Risks and Uncertainties:

TROWAL- A trough off warm air aloft will form south of lake erie allowing for intense lifting to occur along the west end of lake ontario. The location of this deformation band will determine who picks up 30cm+ from this event. The 0z european run showed this band pivoting over the GTA but the current run has shifted this 25-50 miles further NE. If the next run of the euro returns to its original ideas accumulations will have to be taken up along the west end of lake ontario.

Dry Slot- Some models are pointing towards a dry slot potential across the area. Dry air intrusion will occur because of the strength of the storm. The strength and location of the secondary low will determine the strength and duration of this. If the secondary tracks further west we will see longer duration precipitation moving into S, E On and quebec. I think most areas from kitchener to kingston see a primary thump of 14-20cm from the main band with additional wrap around precipitation afterwords. Ottawa, montreal and SW ontario will see slightly weaker returns on the primary band.

Temperatures- I think boundary layer temperatures are supportive of predominantly snow from london to montreal and ottawa. I think southern niagara, windsor and areas directly along lake ontario will see some mixing but most of the province should stay as all snow. The heavy precipitation caused by the storm will help cool the column especially in the heavier bands. Ratios should stay between 8-10:1, being highest at night or when the sun angle is lower.

With all these factors in front of us here are my forecasted amounts across the effected area:
Toronto downtown: 15-25cm, winds gusting to 60kph
Toronto (St Clair to Steeles): 17-27cm
York Region: 20-30cm
Hamilton: 14-24cm
Guelph/Grimsby: 15-25cm
Kingston: 20-30cm
London: 11-21cm
Bruce/Walkerton/Mount Forest: 5-15cm
Barrie: 15-25cm
Windsor: 10-20cm
Montreal North: 15-25cm
Montreal South Shore: 10-20cm
Newmarket: 20-30cm
Ottawa: 10-20cm
St Catherines: 13-23cm

If you have any questions, comments or would like a forecast for your area just ask away! I will update snowfall amounts if needed tuesday evening.


Tuesday, 19 February 2013

Southern Ontario Lake Effect Snow

Some key points I wanted to make on the upcoming lake effect snow outbreak across southern ontario

1. Wind alignment starts of as WNW before transitioning to NW and NNW later tonight and into tomorrow morning. Up to 40cm of snow may fall in areas along the shores of GB and lake huron with 850's crashing below -15c and favourable wind alignment aloft. Boundary level moisture will be present from 600 to 800mb with little to no wind shear throughout the region. All these parameters coupled with ice free lake huron and GB will allow for significant LES to set up across southern ontario.

2. I think the GB squall will be strongest and most extensive from midnight tonight through 8am tomorrow morning. This squall should extend into york region and the GTA in the early morning hours wednesday and thursday with accumulations up to 10cm in some spots. This band will weaken but continue to stay active across the barrie, meaford and wasaga areas into mid day wednesday. It should intensify again in the evening hours with significant impacts from meaford to collingwood stretching east to wasaga. I expect a re-intensification wednesday night into thursday morning with further impacts possible across york region again.

3. I am expecting the lake huron band to be stronger with several waves of snow squall activity from tonight into tomorrow afternoon with weakening by 1pm. This zone will set up from owen sound south to london including goderich, kincardine, walkerton, hanover, huron east and lucan. We are already seeing a first band of snow setting up across this region. Northern parts of this zone will get into the second heavy band from midnight to 4am. It should shift into the goderich and kincardine areas by 7am and lasting into the early afternoon. I think the most impacts on london will be from now until 11pm with a WNW flow dominating but they should avoid the second band for the most part. I think weaker but consistent bands of snow will continue to set up through wednesday afternoon and evening from blue water to kincardine. Another intense band should set up through the city of london wednesday night into thursday morning which will be their best chance at heavy snowfall from this event as the flow switches to NW. I am expecting the heaviest accumulations to stay NW of the city but 13-23cm in the city itself.

Here is my snowfall map for this event. In the GB and lake huron squalls i can see some 35cm accumulations locally but most accumulations should stay below 30cm in the dark purple zones.
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Sunday, 17 February 2013

Wet Snow Event for Ontario, Quebec

Here is my forecast map for this event:
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Key Points
1. Precipitation will stay predominantly as rain from windsor to london. On the front side some mixing with wet snow is likely before the change over. On the back side of the system snow showers will wrap around through the area under the upper level low. 850mb temperatures will hover just below the freezing mark but 925mb temperatures are above zero for most of the event.

2. A line from cambridge/kitchener east to oshawa will see wet snow with this system, mixing with rain at times especially in the morning hours on tuesday. The time of day will be in our favor with 850mb temperatures below zero for the entire event. 925mb temperatures will hover just around the freezing mark with the exception of areas right along the lake shore who will experience mainly rain with this event. I can see 3-8cm accumulations across the area including the GTA north of the lake.

3. From orillia northeast to ottawa and montreal this should stay predominantly as a snow event. Snow will be wet at times especially in areas close to the mixing boundary outlined on the map. I think ottawa, north bay and sudbury have a shot at 10-15cm but i am going with a general 6-15cm across the area. The montreal area may experience some mixing issues with higher boundary level temperatures but precipitation should stay mostly as a wet snow(4-10cm).

Feel free to ask any questions you may have! 

Friday, 15 February 2013

Stormy Pattern Reverses By Mid March

The next 3-4 weeks will be pretty exciting for winter weather lovers across most of the nation. Blocking will be a key player with the MJO headed into unfavourable phases after the 20th of february. The wave will weaken as it propagates eastwards towards indonesia and the philippines which should keep the impacts much smaller. A less active SE ridge will hold until mid march.
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From Feb 20th-March 10th the mean trough will set up in the rockies with a strong blocking high across east hudson bay. Another key player will be the strong trough east of hawaii which will help enhance STJ disturbances. This will cause the mean storm track to set up across the ohio valley, interior northeast and great lakes with phasing possible if the timing is right. The recent SOI drop has definitely enhances STJ moisture which should make for an interesting few weeks as numerous storm systems move across the CONUS. Many storms will take a more southerly track with weakening as they move north into the eastern canada block.
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As we head into week two and three of march I do believe the SE ridge will begin to take over. Warmth will dominate the east as the stratosphere has cooled rapidly and the la nina continues to intensify. The IOD also looks to be transitioning into a negative state which will help contribute to mid latitude ridging. The GWO continues to stay in la nina phases with very negative MT anomalies and a northward momentum transport. This is responsible for the very active rossby wave train in the pacific and inevitable SE ridge strengthening that should occur in march. The GWO will head into 3/4 with strengthening IO convection.
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Currently we are seeing a CCKW propagating eastward in the central atlantic which may help amplify the MJO in a couple of weeks as convection increases in the IO region. The -NAO/ phases 1-2 of the GWO will keep the pattern very stormy over the next few weeks from the plains east. By mid march tropical forcing will cause the wintry pattern to break down especially if the MJO re-amplifies in the IO.
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Wednesday, 6 February 2013

Snowstorm On Its Way For Eastern Canada

Winter Storm Discussion: Feb 7-8

Meteorological Synopsis
An alberta clipper system is currently located across the dakotas with a minimum central pressure of 1009mb. Snows are breaking out already in advance of this system across the american midwest. This system is expected to move towards the eastern great lakes region on thursday, bringing heavy snowfall along with it. This is not your typical alberta clipper because it will be phasing with a disturbance currently over the western gulf of mexico. This system will move up towards the eastern great lakes and bring with it plenty of moisture from the gulf. These two storms will phase across the interior northeast leading to intense lifting along the northwest side of the system. This zone will be located along the shores of lake ontario as well as most of southern ontario from london/kitchener northeast towards toronto and ottawa. As this phasing occurs the upper trough will go negatively tilted leading to the heaviest snowfall friday morning into the noon hour. All of the major models are showing heavy snowfall across ontario and southern quebec with the european/NAM the most bullish on amounts(30-50cm from toronto to ottawa). The GFS is also showing widespread 25-40cm amounts.

Light snowfall will begin to take place thursday morning and afternoon with heavier snowfall beginning thursday night from 8-10pm as the deformation band gets well established across southern ontario. Eastern ontario will get in on the heavier snow around midnight thursday. Moderate to heavy snowfall will continue through friday morning with gusty winds and blowing snow probable. On friday morning, convective bands of snow will intensify on the south side of the storm leading to the heaviest snowfall rates from 8am-1pm, where several cm's can pile up per hour. Location of the convective and deformation bands will be key as this area will bear the brunt of the storm. 

Risks and Uncertainties
1. Thunder Snow- I think the potential is there for isolated thunder snow friday morning but it should stay isolated across the area. This process will come down to nowcasting to see if some convective bands can become established and move into the cold air. If this comes to fruition snowfall totals will be enhanced in effected areas. We will need to follow guidance from the RUC and RAP to see if this setup is possible.

2. Lake Effect Enhancement- As the system tracks to the south of the great lakes a SE, E and then NE wind will rotate around the storm centre which may lead to some higher snowfall totals along the west end of lake ontario. According to the latest skew-t charts, it does look like quite a bit of wind shear will develop between 900mb and 700mb which should limit intense LES in my opinion but nonetheless some lighter bands may organize along the lake shore with delta-t values and surface winds very favourable. Again we will have to use the short range models for guidance.

3. Snowfall Ratios- I do believe snowfall ratios will be more favourable then 10:1 across most of the province. On friday morning surface temperatures will remain below the -10C mark from toronto northwards. 900-600mb temperatures are very cold with the highest vertical velocity values at this level. I think 12:1-16:1 ratios are likely from toronto to ottawa in this setup which can increase snowfall amounts.

With all these factors in front of us here are my forecasted amounts across eastern canada
Toronto: 17-27cm
Ottawa: 17-27cm
Kingston/Belleville: 17-27cm
London: 14-20cm
Windsor: 8-15cm
Montreal: 15-25cm
Barrie: 14-20cm
Hamilton: 15-25cm
Newmarket: 17-27cm
Mount Forest: 14-20cm
Guelph: 15-25cm
Niagara/St Catherines: 15-25cm
Cobourg: 20-30cm

If you have any questions, comments, criticism or would like a forecast your area please ask and I will be happy to answer.

Monday, 4 February 2013

Indicies, Stratosphere, Tropics strongly support stormy pattern

Some interesting trends from the GWO today. We are entering phase 1 which corresponds well with the negative torque values showing up between 30 and 60N. A negative peak has been reached and a recovery will take place from the deep negative torque anomalies as the MJO propagates into phase 2. Convection is already beginning to develop in the western IO which should allow the GWO to continue propagating quickly around the COD as is the MJO.
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Notice the negative OLR anomalies propagating away from africa and redeveloping towards the IO. We are already beginning to see a response from the MT values with some positive values developing near 30 and 70N.
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A positive trend will continue to develop because of the positive temperature anomalies located at 70mb. This will continue to promote wave breaking events across east asia keeping the PV weak and unable to recover until the warming subsides. This will help prevent long lasting warm spells in the east until march.
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With a more favourable NAO and AO in the 10-20 day period blocking does look to return across greenland and the north pole. In this period I see a cold pattern nationwide as the hangover effects of the SSW and favourable MJO continue. It looks like the cold will be centred in the western lakes, northern plains and rockies as a -PNA is favoured in phases 2-4 of the GWO. Pieces of the arctic air will move eastwards at times into the GL's and northeast but a very cold pattern does not look favourable. Stormy conditions are likely across the ohio valley, great lakes and northeast with the mean trough to the west and a favourable MJO wave that wants to stall across the eastern indian ocean(phases 1-3) according to the latest OLR forecasts from roundy.
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Sunday, 3 February 2013

March Analogs

I did some research today and came across some close matches to my march thoughts.
Here's my Analog Package for March:
Temperature Departures

500mb Pattern

Matches pretty well with phases 4-6 of the MJO which is where i think we are headed for march.
Phase 5 upper pattern in march

February Analogs

My GWO analogs keep most of the cold air locked up in the plains and upper midwest for february with a ridge in alaska and troughiness across the northern tier. I used years with similar AAM values from december as well as similar phases, amplitude, torque and tendency.
500mb upper height anomalies for feb have a very +NAO, +AO, active SE ridge, -EPO and neutral to -PNA. I think the +NAO is overdone but the rest is in line with my thinking.
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Although departures will start off colder then normal in the east ridging will begin to form again in the 6-10 day period with a stormy/volatile pattern taking place. I don't see sustained blocking showing up in february and if so it should remain east based. A more progressive pattern will take place for the first ten days of february with a fast moving MJO. As the MJO moves into phases 2 and 3 i can see more blocking showing up across eastern greenland and an attempt at a positive PNA spike. By week four the MJO should propagate into octant 4/5. This coupled with negative frictional/mountain torque values will form a strong ridge in the east to end off february. I do think colder then normal temperatures are on the way from the 13th-20th of the month centred in the northern plains, upper midwest and great lakes. With a more active southern branch and phases 8-2 of the MJO, storminess is likely across the northeast,great lakes and ohio valley in this period. 

Here is my analog package centered on the u.s:
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Saturday, 2 February 2013

Atlantic Canada Blizzard Forecast

Atlantic Canada Winter Storm Discussion
An alberta clipper system located across the ohio valley has a current minimum sea level pressure of 1016mb. This system will move off the eastern seaboard later tonight and then begin its movement towards atlantic canada. As this system does so it will phase with polar vortex energy diving south from hudson bay as the trough axis goes negative. This will create a huge amount of lift as the system interacts with the very impressive pressure gradient setting up along the east coast with cold arctic air to the north and warm SST's to the SE. The system will move along this boundary and bombogenesis will take place which means that the area of LP will deepen by more then 24mb in a 24 hour period. More then a 70mb pressure gradient will take place between the storm and a blocking high to the northeast. This block will prevent the system from exiting to the northeast, causing it to stall out and move NW. All of these atmospheric factors will create high snow amounts and blizzard conditions where enough cold air is in place.

The storm will begin to deepen sunday night and really get cranking monday morning. Across nova scotia, light to moderate snows will break out across the province sunday night with the heaviest precipitation to the south. A changeover to rain will occur for the central and northern part of the province early monday morning as warm air gets pulled up from the southeast. As the storm begins to intensify further and the LP center moves NE, temperatures will begin to crash very quickly leading to a change over to heavy snow and blizzard conditions across cape breton island, halifax and central NS. I think the change over will be very quick across halifax and more significant to the north. As the system begins to move to the north white out conditions are likely across labrador, gaspe, PEI, cape breton and halifax. Precipitation will stay as all rain for most of newfoundland. Winds will be very strong with this system and gusts can exceed 100kph at times, especially across eastern cape breton island, PEI and western nova scotia. With strong winds comes very impressive blowing and drifting snow. Motorists are asked to stay off the roads with visibility of less then 1/4 of a mile monday afternoon and evening across PEI, cape breton and central NS. Snow drifts may exceed 2 feet in areas that pick up significant snows and are exposed to strong winds.

With all of this being said here are my snowfall accumulations for cities across Atlantic Canada
Halifax: 10-20cm of snow, wind gusts up to 60kph
Cape Breton: 15-25cm of snow, wind gusts up to 105kph in the east
Sydney: 10-20cm of snow, wind gust up to 90kph
Gaspe: 7-15cm of snow, wind gusts up to 90kph
Charlottetown: 20-30cm of snow, wind gusts up to 75kph
Moncton: 5-15cm of snow, wind gusts up to 60kph

Cap-Pele: 10-15cm of snow, wind gusts up to 70kph
Antigonish: 12-18cm of snow, wind gusts up to 85kph
Yarmouth: 8-15cm of snow, wind gusts up to 85kph

My Track and Intensity Forecast:

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If you have any questions or you would like a forecast for your area just ask away! 

Friday, 1 February 2013

Long Range Thoughts

The current MJO wave is propagating through phase 8 with negative 200mb velocity anomalies near 120W. As it heads into phase 2 and 3 it will set up a wetter pattern across NA. A wetter pattern from feb 10-25th is supported by the current rossby wave train development near 120E and 30N. Propagation eastward is occurring and it should enter the eastern u.s around the 14-16th of february with a cold shot to follow. The GFS ensembles support this after some moderation from our current cold pattern. The pattern favours warmth overall with negative frictional/Mountain torque values. Areas to the NW of the BZ(Great lakes, Midwest) can cash in on some snowfall accumulations with a more active STJ and east based blocking in this period. 
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The RWT near 60E will cause yet another shortwave to move into the east from the 19th-21st.
GFS ensembles for the 15th:
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Our current Pattern favours SOI drops with cool water NW of australia and warmer water SE. Daily SOI value at -26.1 driven by the MJO with enhanced convection southwest of australia.
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Notice the higher then normal pressures north of australia. A similar pattern will continue throughout the week which supports a bit of an el nino comeback. Subsurface warmth is beginning to emerge especially in the western enso regions but the question remains if it can move up to the surface. In the long range the MJO will go towards la nina phases, enhancing easterlies and suppressing any WWB's caused by the eastward propagating KW.
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