Tuesday, 24 June 2014

Why will El Nino turn out potentially weaker then expected?

After expectation's were very high coming off a record breaking oceanic kelvin wave this past spring, tides have turned in the ENSO department with the prospect's of a strong el nino dwindling. Below are some of the factors I am looking at regarding ENSO:

1) Solar flux has dropped at or below 75 for the first time since november after a double peak this winter/spring period signifying a long and weak cycle. This should have some implications on ENSO this upcoming fall/winter.

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2) Despite negative 200mb CHI propagation into the central/eastern pacific this week, any WWB's over the WPAC are expected to remain weak/stationary over the next week. This displays that even period's which favour el nino strengthening are failing to produce major changes to the subsurface anomalies.
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3) Cooler than normal subsurface SST's have replaced the strong downwelling OKW that formed in the early spring period.

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4)AAO/Atlantic circumpolar wave forcing has helped keep the western IO cool while SST's in and around the maritime continent are well above normal. This makes it very difficult to keep the SOI predominantly negative. SOI values are expected to remain negative through early July with a reversal to positive values expected after ~7/3 as the MJO wave propagates east.

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5) A weak K/O current this spring means the JJA "summertime" AO anomaly should remain predominantly positive correlating to this SST anomaly setup.

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6) Underwater currents have shifted to an easterly anomaly after it was initially suspected that the base state of the pacific changed to a mean westerly anomaly as a result of the mega downwelling OKW in the spring. Obviously that claim was proven false.
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For these reasons i'm expecting a weakening and retrograding el nino anomaly as we head into winter. In the end, moderate ENSO strength is likely IMO in the trimonthly ONI dataset (+1.0 to+1.5c peak). Any questions/comments, feel free to shoot away in the comment section below.

Sunday, 22 June 2014

Are back to back Nino's on the way?

Looking at years following at least three winters with negative ONI conditions and at least one winter with ONI values <-1.00 for 3 or more trimonthly periods we get the following years as past analogs.

1957-58(Moderate El Nino) and 1958-59(Warm Neutral)


SST anomalies from 1957-58 on the right and 1958-59 on the left



1976-77(Weak/Moderate El Nino) and 1977-78(Moderate El Nino)

SST anomalies from 1976-77 on the left and 1977-78 on the right



1986-87(Moderate El Nino) and 1987-88(Moderate El Nino)
1986-87 on the left and 1987-88 on the right

2002-03(Moderate El Nino) and 2003-04(Warm Neutral)


1918-19(Moderate El Nino) and 1919-20(Weak El Nino)


1911-12(Moderate El Nino) and 1912-13(Cool ENSO Neutral Conditions)

As you can see, all of these setup's have a secondary el nino(sometimes considered warm neutral) that is weaker in terms of anomalies when compared to the first nino. The 1911-12 and 1912-13 couplet is the only exception, with ENSO neutral conditions occurring in the second winter(1912-13).

Complications
Now comes the question whether the current pattern we are in is considered a period of 3+ years with cooler then normal ENSO conditions. Unlike most negative ONI periods including 1 or more la nina events, trimonthly ONI managed to spike at or above +0.5c for two trimonthly period's in the fall of 2012. Although by official standards this is not considered an el nino, it can significantly alter the global climate system. The question for me was if I could find a good analog to see if it made a difference to the ENSO state following a long cool ENSO period with an el nino year afterwords. After some research, the mid 1930's matched up pretty well. Below are the ONI values in this period courtesy of Bob Tisdale. Note the long period of negative ONI values from late 1932 through mid 1939. This period included several spikes into warm neutral conditions(similar to the 2012 period) although official nino status was never met. Coming out of this period was not only a double nino, but a triple nino.


Implications
So what would be some potential effects of a double el nino if analogs hints verify?

1) A temporary spike in global temperatures.

2) Longer lasting temporary +PDO regime within a multidecadal -PDO phase. This means a relief from  drought conditions that currently exist over the SW and southern plains states.

3) Strength of ENSO in the 2015-16 winter could dictate the H5 pattern across the eastern U.S(stronger events correlate to very cold temperatures east of the rockies e.g 77-78 and 69-70 while warm neutral events correlate to warmth e.g 03-04).

4) Continued below normal ACE/tornadic activity over the next 2 years with a significant spike to follow.

Questions and comments are encouraged in the section below. You can tweet me with your questions, @blizzardof96.

Thursday, 19 June 2014

Early Thoughts on Winter

Few comparisons I made on twitter this morning, using an ONI base state between +0.7 and +1.5c. All el nino/-QBO years are on the right with nino/+QBO years on the left. We should be in a -QBO shear phase this DJF nearing the -QBO peak late winter. Note how the -QBO years tend to have a pretty strong -NAO block with lower heights surrounding the block and a -SAM/+PDO state in the means. Whether solar activity increases or decreases heading into winter will be very important as you run the risk of ending up similar to 91-92 although it's definitely not a guarantee either way.

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The PDO dataset is also pretty interesting with the positive years on the right. I am expecting the PDO to remain positive through next winter as the nino continues to gradually strengthen. This is consistent with the NMME/JAMSTEC suite's. Note how PNA and EPO ridging is stronger in the +PDO years and the state of the NPAC is completely opposite. This tends to favour areas further SE for the heavy snow's(mid atlantic and southern parts of the Northeast) as it takes any nina component out of the pattern.



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The few things i'll be monitoring besides solar:

1) Positioning of the NPAC warm pool. If it can retrograde, look for the storm track to want to shift further west. If it continues to shift East into a more classic +PDO horseshoe position, as I am expecting, the mid atlantic will be more favoured in terms of storm track/snow interests.

2) The warm SST's off the east coast tend to pump up a stronger SE ridge like 51-52 saw in the December-January period. 

3) Keeping an eye on the positioning of the nino. Currently favouring a slightly west based nino although it could very well end up providing more basin wide like forcing.

4) We just came out of a long lasting la nina period. ONI spikes coming after at least a double nina look like this with no ENSO sorting:
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5) SLP pattern across N Siberia in October. This goes hand in hand with SAI feedbacks, which looks at snow cover growth in october over southern siberia.

Below are Positive AO El nino december heights at 250mb with Oct SLP anoms on the left. Notice the negative SLP anomaly across N Siberia and the response across North America.
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-AO years are completely opposite in December. 8 of those 10 +AO December years remained persistent with a +AO in January as well. In feb it mattered little as troughiness still dominated over the northeast/great lakes. Any questions about the upcoming winter? Feel free to shoot me a question in the comment section below or you tweet me @blizzardof96.

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Monday, 19 May 2014

Summer 2014 Outlook Part 1

The time has come, the time that we wait all year for. The summer season is upon us and many are wondering what is in store for parts of north america this upcoming summer.  This season, I decided to break my outlook up into two parts, with part two coming out sometime before the start of June. The discussion below(part 1) deals with a case study I have been wondering about regarding vastly different H5 pattern's among different East based or basin wide el nino events. The "going rule" that most people usually go by is that East Based nino's involve a North Pacific high that is based further west then WB nino's which brings down the PNA overall and pumps the SE ridge.  In addition, East Based nino's tend to force a stronger South-American hadley cell which curbs any North Atlantic blocking. This assumption is usually correct but significant year to year variability is present so that one cannot just say WB nino's are always cold and EB nino are always warm east of the rockies. In the discussion below I will go into detail on what factors you can look for when differentiating between a warm and cold EB/Basin wide nino event.


First off, I want to get a clear picture on where we are headed in the ENSO department before delving any further. Right now, the state of the pacific is undergoing significant change. Warm water continues to invade the ENSO domain, especially across eastern and central areas. Nino 1+2 has surged to 1.3c above normal as of today's update while nino 3.4 is at 0.4c above normal.

SST change since 4/16 is listed below, via the CPC. Notice significant warming of Eastern ENSO regions with slight warming across nino 3.4 and nino 3. This sudden SST warming off South America is a result of an anomalously strong downwelling Oceanic Kelvin Wave(OKW) that formed in February and is continuing to propagate eastwards in the Tropac. This OKW was so strong that it actually modified the base state of the Pacific, causing sub-sfc currents to favour a mean westerly direction. It also helped weaken the upwelling OKW that is following it so that it only acted as a slow down to the upcoming nino instead of denting the anomalous sub-sfc warm pool. For these reasons, I am favouring a high end moderate or low end strong el nino which is on the higher end of the model guidance currently.




Sub Surface Temperature anomaly loop via NOAA
With that in mind I am expecting an east based event in June which slowly transitions to basin wide as we head towards july/august.   For the purpose of this outlook I will be examining years that are EB/Basin wide as that is our expected ENSO positioning this JJA. Bolded/underlined are the years with above normal 500mb height anomalies in the means east of the Minnesota to Texas corridor. Most years did vary from month to month. For example, 1957 had a cold august while June and July were much above normal temperature wise in the east/lakes. I was pretty pleased with my dataset, as even though the sample size was small the numbers were pretty even (4 above normal, 5 below). Beforehand, I did note that there was no conclusive trend with PDO, AMO and solar when related to both dataset's which means that other factors are at work here.

a) East/Basin wide events listed below, with solar mins and maxes noted

East: 1997(Below Normal)  *Smin
East: 1983(above normal)
East: 1972(below normal)
East: 1957(above normal) 
Basin Wide: 1987(above normal)  *Smin
Basin Wide: 1991(above normal) *Smax
Basin Wide: 1965(below normal)  *Smin
Basin Wide: 2009(below normal) *Smin
Basin Wide: 1982(below normal)  *Smax

200mb height anomalies for the JJA period
Group a) which included the below normal EB/BW Nino years. Notice how circumpolar troughs dominate the 30-80N region with slightly above normal heights over the Tropical Pacific.
Group b) Well above normal heights were present along the equator with a strong Great lakes ridge and -PNA pattern.

500mb Omega Anomalies

Colder then normal EB/BW El nino years

 Notice the very strong forcing between the dateline and ~120W in addition to strong African uplift. Weak negative Omega anomalies were present across the northern and Western IO. 



In the above normal EB El Nino years, IO forcing was significantly stronger and extended further east both South and North of the equator. African forcing was significantly weaker then the other group of year as the AEJ(African Easterly Jet) was displaced south in the means.




So how can we actually tell whether this year is headed towards the above normal years(enhanced IO forcing, -PNA, weaker African forcing and +NAO) or the opposite pattern. One thing we look for is persistence as the atmosphere loves to repeat itself, even with changing indices. Below is the H5 pattern for the above normal years in MAM. Notice a very similar type of pattern as noted above.
A strong upper level trough is present across the southern Bering Sea and Sea of Okhotsk in addition to a strong eastern U.S ridge/SW trough.
In the below normal years note the very strong bering sea high which is exactly opposite of dataset 1. This is a very encouraging signal as it makes it easier to differentiate between years that will take path a) or b) as the correlation is high.


OLR Anomalies
In the below normal years tropical forcing was strong across the Southern IO and the African sector in addition to off equator forcing near hawaii. This favours below normal temps across Eastern NA as it weakens the East Asian Hadley cell, increases East Asian cyclogenesis and strengthens the downstream North Pacific high. Also notice how -OLR anomalies extend west of the dateline.
In the above normal years many aspects of tropical forcing are similar(Positive OLR over the central and northern indian ocean). The main difference is that the forcing over the central/eastern tropical pacific is based right along the Equator while the below normal years had more subtropical uplift. The -OLR anomalies also don't extend as far west once you get beyond the dateline.

So how has this year looked so far? If we take a look at tropical forcing notice how -OLR anomalies are virtually non existent across Indonesia.  Notice how Tropac forcing is weaker(more consistent with the below normal years) and also extends further West of the dateline(consistent with the below normal years).

At H5 a Strong North Pacific high, -WPO and tendency for strong East Asian troughiness is in place. This also mirrors the below normal years. 
The West Pacific jet packet amplified anomalously as well.
To conclude part 1, I am expecting this year to behave similar to group A or the Basin wide/East Based nino years that have below normal temps in the JJA means over the Eastern midwest, great lakes, ohio valley and eastern CONUS while the western CONUS enjoys above normal temperatures. In subsequent updates, I will go into further detail regarding the month to month/regional breakdown with precipitation and temperature analysis. I will also talk about some of the closer analogs that I am looking at, in addition to other factors such as the QBO, PDO and solar activity. Any questions, comments etc are more then welcome and I will try to answer them as soon as possible. You can tweet me @blizzardof96 with questions as well.

Friday, 29 November 2013

What's going on across the stratosphere?

With regard to any significant SSW occurring this winter, its looking very slim in DEC/JAN given the indices on the table this year. For +QBO, -PDO, N/- ENSO and years with the JAN SSN below 95 no significant warming's have even occurred since 1950 in DEC/JAN. In february their are a few exceptions, one begin 08-09 which had a strong East Pac ridge, definitely aiding in the wave 2 response. 00-01 is another example of this, although the PDO was neutral/positive and the QBO was transitioning from positive to negative. The common denominator in these two years is a strong Kamchatka PV lobe and bering sea/GOA ridging. Unless we see an uptick in the PDO/ENSO domains, or a quick downturn in the QBO by feb a major warming in the DJF period is going to be tough to come by. EP heat flux anoms are already starting off winter well below normal ever since the wave 1 response in late october. Our best shot will probably be a wave 2 warming in Feb if we can keep the EPO ridge consistent which becomes more likely given the +QBO/N ENSO and -EPO persistence. If this doesn't work out then their is always the FW question in March/April that should arise with a mean state similar to our current one. This SSW timing is much more favoured given the current setup and could have impacts on spring, especially with the warming ENSO region expected and a transitioning QBO index(favourable for high heights across the NAO/EPO region's).

Feb 2001
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Feb 2009
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Tuesday, 26 November 2013

Snowstorm Forecast Nov 26-27

Winter Storm Discussion

After a long summer, winter is back and so is snowstorm tracking across eastern canada. A low pressure area formed across the central gulf coast yesterday night and has since began its trek eastwards, now stationed across western NC according to noaa mesoscale analysis. Snow will begin to break out across the niagara region over the next few hours with snowfall moving into eastern ontario and southern quebec in the 7pm-10pm timeframe. The snowfall is expected to come in two waves, with a secondary low forming and riding along the east coast tomorrow bringing a reinforcing shot of precip to Eastern ON/QUE by tomorrow afternoon and evening. The heaviest snow is expected to fall southeast of ottawa and west of montreal in an area from east of kingston up towards saint jerome, the laurentian's and the eastern suburbs of ottawa. Over this area, a general 25-35cm's of snow is expected to fall, with isolated amounts in the 40cm range.

For the city of montreal itself, precipitation type will be a huge issue and likely a headache for EC and many forecasters across the area. Precip should start off as snow in the city with 7-15cm of snow likely before a change over to rain and maybe a brief period of ice pellets between 7am and 1pm. The east end will be seeing a longer period of mixing while the west island gets less. Higher elevations NW of the city should be the jackpot zone with all snow, nice isentropic ascent and a plethora of moisture available. After the change over to rain, another 5-12cm is likely in the afternoon/evening hours with a change over back to mostly snow occurring around the 12-2pm time frame. RGEM/GFS have this changeover a little bit earlier with only a brief period of RN/PL in the early morning hours. I am going with the RAP/NAM WRF/NAM/SREF consensus for now, based on surface analysis at the current time. For the GTA, looks like the heaviest precip will fall overnight, mostly in the form of 10:1 ratio snowfall. Expecting 2-9cm amounts over the city, with highest amounts over the east end(oshawa area). In terms of the ottawa valley, I am expecting a solid 15-25cm of snow with some isolated 30-35cm amounts over the east end. Perhaps ratios are a little bit better then 10:1, but not by too much.

With that being said here are my forecasted snowfall totals across eastern canada. Questions, comments ETC are encouraged.

Kingston: 20-30cm
Ottawa: 15-25cm
Montreal West Island: 12-25cm
East Montreal: 8-20cm
Belleville: 10-20cm
GTA: 2-9cm
Hamilton/Burlington: Trace-4cm
Niagara: 5-12cm
Quebec City: 8-18cm, locally 20cm
Trois Rivieres: 7-15cm, locally 15-20cm

Friday, 22 November 2013

Lake Effect Snow Outbreak for Southern Ontario

I thought that I would post my thoughts on this LES potential, now that Travis has shared some of his thoughts. I'm thinking that the flow align's a little bit further west then he is thinking. This outbreak looks like it has huge potential, greater then we have seen in a while. Params look to set up really nice as previously discussed. High Delta T values will set up some very intense squalls as extreme instability develops along side a very saturated BL, low shear values and continuing cold air advection through sunday morning.

Georgian Bay
From late afternoon saturday into early the evening hours it looks like cells set up in a WNW fashion(collingwood/wasaga band south towards stayner, angus and Bradford/Newmarket) before shifting further to the SW once the flow shifts to the NNW by late evening into the overnight. This squall should be able to briefly move through the GTA/hamilton area's as well before building back to the West. These squalls should sit in this type of position through sunday morning with a band extending through meaford/collingwood and down towards shelbourne and perhaps as far east as alliston. Don't think areas east of barrie see very significant accumulations with this outbreak besides some weaker squalls after the immediate passage of the cold front saturday evening/afternoon. Barrie is in the 5-10cm zone. The squalls should build back to the NE sunday afternoon with the flow lining up in a more NW direction as the high moves through, but this will only last for a few hours before shear starts to rebuild.

Lake Huron

BL lapse rates should remain rather steep throughout tomorrow evening into the overnight and through sunday morning with some wavering of the band from more of a goderich, st mary's, tillsonburg position before shifting further south into the london/strathroy/lambton shores areas. Going to see this band waver considerably throughout the duration of the event as winds shift between these two positions. Thinking thundersnow is possible especially in areas North of London, may even get into the city, where 10-25cm is likely IMO.
Here is my Forecast Map. Thinking a trace-5cm is possible outside the blue zone with the area shaded in pink, including the GTA and hamilton.

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Wednesday, 20 November 2013

December Update

Contrary to any previous ramblings, I am all in for a below normal december based on the current look to the pattern. The NE pacific warm pool will help encourage strong ridging over the aleutians(we are seeing hints of this already with Ca air masses packing a punch from the prairies on east). We are already seeing record cold showing up across the NWT, AB and BC. The bering sea ridge will shift at times into the GOA(when tropical forcing is favourable) creating more of an el nino/la nina hybrid sometimes. Biggest risk right now is if the GOA warm pool backs further west which would have a tendency to shift the coldest anoms into the W and SW part of the continent(unlikely scenario at this point). 
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Indications are pointing towards a favourable GWO in Dec with +AAM dominating the 35-55N belt and easterly momentum dominating the subtropics. This will help encourage the MJO to move into more favourable phases. Roundy plots show this evolution just before christmas with a wave moving across the pacific in tandem with the active KW phase plot.
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In terms of the AO, it should stay predominantly on the positive side this winter with little in the way of any major SSW's unless we see a late winter final warming which could have implications on spring. An overall +NAO and +AO means that we can see some larger temp swings with more of a progressive pattern setting up on average. In terms of the +QBO, Neutral ONI and Smin induced -NAO pattern, we will need to see where the PV sets up in december to see if that theory can prove itself valid. Early indications have the upper vortex over the greenland/siberia area with most of the blocking confined to the bering sea. 

Saturday, 16 November 2013

Major Severe Weather Outbreak Looms


With a moderate risk out now from the SPC, the weather world is buzzing about the current severe weather outbreak on the way for the lower great lakes region. It has become apparent that a very significant outbreak of severe weather is on the way. Throughout the day today and into tonight, warm and moist air will be advected northwards through the ohio and tennessee valley's. Dew points are well into the 60's and even 70's across south texas based on current observed data. These readings will be transported well to the north due to strong forcing from the low level jet. 
By tomorrow morning temps are expected to reach 70f in the chicago and lafayette area's with 60's extending east towards detroit and columbus. This should provide ample moisture to set off discrete cells especially if skies can clear out ahead of the front. Surface-500mb bulk shear is in access of 50kts as well, with significant speed and directional  wind shear with height.

Note the very dynamic upper level jet streak that is going to be penetrating this warm sector. SRH values will likely be above 350 near Chicago with EHI values >3 ripping right through the chicago metro area. The cells along the cold front will most likely stay discrete as they move through the Chicago area before organizing into a squall line setup over Michican, Ohio and S ON.




 This means that we see an elevated tornado threat across IL,IN, and KY before it transitions to mostly a damaging wind threat over OH/ MI and ON. The tornado threat will still translate east as meso-vortices can form along the front and jet dynamics remains very favourable for rotating thunderstorms. Peak Gusts to 115km/hr are possible along the intensifying front, as the surface low deepens below 980mb.



Stay safe out their this sunday! Will continue to update blog when needed.