Thursday, 31 January 2013

MJO, Stratosphere Support Cold... GWO not so much!

Conflicting signals showing up in the long range pattern. Current GWO in phases 7/8 strongly points towards HP setup between 60 and 30N which lines up with the below normal SST's in the eastern nino regions. Easterlies have set up from 120W to the date line which will help keep the la nina in place across nino regions 1,2 and 3.
 Reduced: 90% of original size [ 565 x 436 ] - Click to view full image
Attached Image
This pattern favours mid latitude ridging and troughiness across the northern latitudes which should make it more difficult for blocking to show up west of greenland. I can see some east based -NAO blocking showing up but nothing sustained. The PNA looks to stay neutral which should keep the mean storm track west of the appalachians in february. Frictional torque values are crashing which favours a SE ridge setup in the LR especially for the second half of february and most of march.
 Reduced 18%
Attached Image
773 x 1000 (107.54K)

Before this type of pattern sets up i think we have a 2-3 week period of winter weather coming up. The MJO is propagating through favourable phases although it is weakening through phase 1. With the MJO amplifying into phases 2 and 3 a trough will be favoured over the east after february 10th. Perhaps some east based blocking will set up allowing for some storminess before the MJO heads into unfavourable phases for march. Current OLR anomalies are enhancing the STJ which should allow more energy for systems to work with.
 Reduced: 93% of original size [ 546 x 546 ] - Click to view full image
Attached Image

The stratosphere supports this type of setup with warmth propagating downwards. Easterly wind anomalies are strongest from 70-100mb. This will help support ridging in the NW and a downstream trough from feb 10-20th.
 Reduced 29%
Attached Image
900 x 600 (45.96K)

Wednesday, 30 January 2013

Major Lake Effect Snow Outbreak

The NAM 4km WRF looks interesting with a WNW/NW flow dominating. 
Hour 22:
 Reduced 36%
Attached Image
1000 x 750 (210.85K)

Hour 31:
 Reduced 36%
Attached Image
1000 x 750 (193.71K)

Hour 54:
 Reduced 36%
Attached Image
1000 x 750 (188.21K)

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 

Tuesday, 29 January 2013

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.
 Reduced: 93% of original size [ 547 x 547 ] - Click to view full image
Attached Image

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:
 Reduced 25%
Attached Image
847 x 655 (31.38K)

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.
 Reduced: 79% of original size [ 641 x 496 ] - Click to view full image
Attached Image 

Sunday, 27 January 2013

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.
 Reduced: 93% of original size [ 546 x 546 ] - Click to view full image
Attached Image

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.
 Reduced: 84% of original size [ 604 x 626 ] - Click to view full image
Attached Image

This is what january looked like as a whole:
 Reduced: 90% of original size [ 565 x 436 ] - Click to view full image
Attached Image

Wednesday, 23 January 2013

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.
 Reduced 70%
Attached Image
2100 x 1126 (144.19K)

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.
 Reduced 38%
Attached Image
1024 x 768 (422.82K)

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.
 Reduced 34%
Attached Image
960 x 680 (197.74K)

 Reduced 18%
Attached Image
773 x 1000 (90.53K)

Saturday, 19 January 2013

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

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


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




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

Tuesday, 15 January 2013

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!