Pattern, Pattern, Pattern–Pattern Change Coming?

This has been the question since the beginning of November. We all remember being told that the pattern was going to change and the pattern was going to change to a colder and snowier pattern starting in Mid November. When that did not happen we were told it was going to occur in Mid December. When that did not happen we were told it was going to occur in Mid January! Here we are at January 23rd and we still have not had a pattern change to one that is locked in sustained cold and snowier weather.

Matter of fact lets look at some departures. Overall October snowfall counts towards the season but lets assume that this snowfall did not occur and we just look at the Winter beginning with Dec 1st..

ABE 3.4 inches this is 9 inches below normal..

PHL. 2.5 this is 5.5 below normal

NYC 4.3 this is an inch below normal

Newark NJ 3.7 which is 2.2 below normal

Boston MA 6.6 which is 3.5 below normal..

Now lets look where we have been as far as temperature departures..

November 2011

December 2011

First 23 days of January..

The moral of the story since at least November 1st has been above normal temperatures.

Now is there a reason for this? Well, there are a couple reasons…

First one is the MJO. The MJO has not been able to get into any favorable phases. When it does not get into a favorable phase it ends up extremely difficult to get any type of teleconnections in place for colder and snowier weather. When you have convection near the date line this helps to bring about a + PNA ..We have not seen that because the MJO has been in phases 3-6 all winter long..

So where is the MJO currently?

Phase 5 of the MJO. Now we are not going to look at MJO forecasts because they have not been verifying well but we will look at the 500 mb anomalies for Phases 5 and 6 for January and February to see if they indicate a turn towards colder and snowier..

The above is January Phase 5 and 6. Certainly not reflective of a cold pattern..But what about Feb?

So what we notice is that we do not get any help from the MJO in phase 5 or 6 in January or February.

So now we have to look to the teleconnections..

Remember the following: A negative NAO represents colder weather in the east. A positive PNA represents ridging in the west and troughing in the east. A – Ao represents colder air discharging south into the USA..A – EPO also represents colder air discharging into the USA… Keep that in mind as we look at the teleconnections. We are using the ensemble means from 12 Z of the GFS/ECM..

GFS AO

GFS EPO

GFS NAO

Now these are the first three teleconnections off the GFS ensemble means which are the AO & EPO and the NAO.

Notice the AO goes positive? The EPO is positive (till the very end) and the NAO never goes negative but at the most neutral negative to neutral positive. These three signals are not cold weather signals..

Finally the PNA. Now this is a signal that would put the trough on the east and the ridge on the west once we are further out in the models range.

The problem is that the GFS ensembles has been trying to bring the PNA positive before..and it has failed to happen.

Now lets look at the ECM teleconnections..

AO is going from negative to slightly positive and then stays at neutral negative to neutral positive thru the next 240 hours. This would represent cold air having a very difficult time sinking southwards.

EPO ..completely positive. Again this is not another cold signal on the guidance.

PNA mainly negative but at times flirts with positive. This would indicate more in the way of transient troughs when it is positive… transient colder air associated with those troughs.

Finally the NAO which is shown to be in the positive to neutral negative and then neutral positive range.

Outside the PNA signal on the GFS ensemble means there is NOTHING to indicate that we are heading into a pattern change to more cold and more snowy sustained weather.

Rather the signals indicate what we have been dealing with all winter long. And now lets take a look at the real MCCOY of a reason as to WHY we have been so warm this winter!

To do this we are going to once again use the ECM ensemble means but each image has been illustrated on to try and make it easier for the readers to understand..

Now, wait , wait but I thought the GFS shows a pattern change occurring? Does the GFS agree with the above?

So you can see that on both the GFS and the ECM thru at least the next 10 days which take us into the first week of February we continue to deal with the pattern we have had in place. That is the Alaskan Vortex.

Until that feature is GONE or retrogrades west…and ridging builds into that region ..we will continue with the theme of above normal temperatures with transient shots of colder air.

What about snowstorms? Until the pattern would change…we will have to depend on perfect timing of shortwaves with the colder air time periods.

If anyone is trying to say that this has not been a sustained warm pattern overall…they are either kidding themselves or just trying to gain popularity!

We will not look beyond 10 days because that would depend solely on the Global Forecasting System which changes every 6 hrs.…

January 26-27th Storm System

This is the next storm system that will begin to take shape across the TX region by 18 Z Wednesday. By 00z Friday we will have one area of low pressure over SW TX with another area of low pressure to the SW of that with a warm front stretching west to east near the PA/MD border..
This low pressure will take a track right across Eastern PA lifting a warm front north in the process. In the light green rain area there may be enough cold air at the surface to start the precipitation off as a little wintery mix but by far the best chances for anything frozen wise will be further to the north which is indicated by the snow on the map. At the present time we are thinking this is a 2-4 inch snow at the most with even some ice potential in that snow region. This is something we will have to watch and it is not reflected in the map at this time.

January 22nd Severe Weather Event!

Seems we have a severe weather episode on our hands today the 22ND. A upper level trough will be moving out of the Rocky Mountain region towards the east and the guidance shows a strong lower level jet of at least 70 knots and a upper level low should close off over the Midwest. This should cause moisture return over the region.
GFS is also showing dew points across the region in the 60s to around 70 across the region.
Mid level lapse rates will be 6.0-6.5
CAPE or convective potential energy is not all that impressive only up to about 1500
Lift Index is as negative as -8 across parts of the region
The interaction between the mid level jet being just as strong as the low level jet should create sufficient low level shear.
Another factor is the SWEAT index.. this is one of the indicators that we like to look at to determine tornado potential and on the NAM at 00z we see that the area from Eastern TN to ARK and south into Louisiana is at 400 or above. When looking at the GFS we also see that same general region under high SWEAT of 400 or above.
Yet one other factor for tornados is the Energy Helicity Index and you generally want to see this at 1.0 or above and that would cover the SE part of ARK and into Louisiana on the 00z NAM. So these regions should be the greatest threat for tornados while the rest of the region should be more along the lines of straight line winds and large hail.
In addition to all the above the culprit or trigger will be a strong cold front which will be clashing into warmer moist air and this cold front should be thru the region shown above by 7 AM Monday morning.
If you are in these areas be on the look out for severe weather and as always if you see a tornado warning or a tornado on the ground and headed towards you take shelter immediately!

Update for Jan 21st Winter Storm

After viewing the ECM & the rest of the guidance ..this is the final map being issued..we cut out the ice in all locations but PA/SW
In addition to this map ..
NW NJ and Central NJ & NYC 3-6 inches ..In NW NJ up to 8 inches
CT 3-6 inches
SNJ and south into DE T-2 inches
SNE would be in the 3-6 inch range with the isolated higher amounts

Winter Storm This Weekend of the 21st!

In addition to this map above:
NYC 1-3 inches snow to wintery mix
CT 4-8 inches mainly snow-some sleet (away from coast)
NW NJ 4-8 inches
Central NJ 3-5 inches with .10 ice potential
SNJ and south less then an inch with a turn to rain
Discussion: This is what we like to call a southwest flow event . What this means is that this is a purely driven warm air advection event meaning warmer air flowing in aloft over top of the colder air at the surface..
Cold air is being supplied by a shot of arctic air ..however this arctic air is not nearly as impressive as the arctic air that came in at the beginning of January. So this is really a modified arctic air mass in place with a mediocre high pressure to the North but ..cold enough that we will see a moderate snow storm in what has been an overall warmer winter. We will take what we can get I guess you could say.
Guidance such as the ECM does bring the 540 line to close to the Lehigh Valley region and the GFS and ECM also bring close to or slightly above freezing at the 925 mb level which is the reason for the winter mix expectation as well as the snow!
By 12 Z Saturday morning a weak wave of low pressure will be located over eastern KY with a warm front extending to the east of it. This low will generally move in a east northeast fashion...to a position east SE of Long Island NY by Saturday evening.
What could go wrong?
1.Models tend to under do mid level warming ..so if the mid level warming ends up being stronger then snow totals would be lower and ice would be more of a factor..
2. Winds will be out of the east. This means that the boundary temperatures could end up being progged to cold ...
This is not exactly the most perfect set up ..it is more a threading the needle type scenario.
As is we expect start time to be between midnight and 3 AM and end time to be before midnight on Saturday night.
Travel will become tricky and slippery so if you have to be out and about take caution!
We encourage all members to post and submit snow totals on the page as well as snow photos on the page!

January 13th Arctic Cold Front Rains and Snows

Not going to put to much discussion behind this we have a deep cyclone located near the great lakes which is going to track ENE the air mass that is out ahead of this is relatively mild and the colder air coming in behind the front will not really benefit the eastern side of the region but more or less benefit the western regions as cold air flows over the relatively warm/unfrozen lakes which will enhance the snowfall along the western regions.

You can also look at the critical thickness lines and nearest surface freezing temps and nearest freezing levels..

Essentially on the eastern side rain will move back into the region and mix with and end as snow showers with less then an inch of snow possible ..

January 11-12th Winter Storm

Low pressure is beginning to take shape this evening down over the south central states as of 00z this evening. This low will lift NE and should be positioned over central Tennessee by 12 Z Wednesday. By 00z Thursday we should have a dual structure low with the primary over NE KY and a secondary developing to the southeast of the primary over the Carolina regions.

The primary should lift north into Ohio while the secondary should track right across SE PA.

With no blocking this is going to be a relatively quick moving system..however it will bring a swath of heavy rains and winter precipitation. The air mass that is out ahead of this storm is not fresh cold arctic air but rather modified cold air from the last shot of Arctic air that went thru.Southwesterly flow /WAA warm air advection will flow into and across the region ..

We will have some CAD in effect ..this CAD will basically effect the higher elevations (NOT SHOWN on the map) where they could have a wintery mix..for snowfall you are going to have to go to NNY state and points NE.This is where the 540 line is located. In places like NE PA you potentially could see a wintery mix but we are expecting a change over to rain.  We are expecting snowfall to be in the range from 1-4 inches in the southern locations to 4-8 inches in the more northern locations.

The big cities of the Northeast and I 95 corridor we are expecting all rain with anywhere from 1-2 inches. Colder air will come in behind this system & we will talk about that aspect of the forecast later tonight…

Cold & Snowy Or Walking the Line?

We are going to start this off with taking a look at the first 8 days of January 2012. As you can see there has not been much change from November 11 and December 11. The region is still running above normal temperature wise. It is important to keep this in the back of your mind as we move forward in this update.

However..indications are that another shot of arctic air is going to make its way into the region. Models agree on this…lets look..

So yes without a doubt the guidance is suggesting that another shot of arctic air is going to invade the region. However..the question becomes whether or not this arctic air is going to be sustained…or if it is going to continue to be a transient pattern where shots of colder air come into the region followed by warmer air or moderation?

So the first thing that we are going to look at is the Madden Julian Oscillation to get the background of what is happening..

What we are looking at now is the GFS ensemble means MJO and the ECM MJO. And as you can tell the GFS takes the MJO into phase 7 and 8… this would be an excellent pattern for snow and cold lovers in the east..

You can see both of these translate into a colder pattern in the east with a trough to the east and a ridge to the west which would give plenty of opportunity for snowfall across the east.

However..on the other side of the spectrum is the ECM which keeps the MJO in the Circle of Death and then brings it out into phases 3-5.

As you can see these would not be favorable phases for the east coast and would indicate warmer then normal anomalies.

So what we have here is a classic model battle when looking at the Madden Julian Oscillation. So now we will look at the teleconnections from the GFS and the ECM to see what we can glimmer from them..

Now as we look at the above we see that the GFS is showing :

1. A positive WPO turning strongly negative (keep this in mind)

2. A strongly negative Arctic Oscillation (supporting cold pattern)

3. Positive EPO to negative to Positive (supporting warm to cold to warm)

4. Positive NAO to negative back to positive…(supporting warm to cold to milder)

5. A PNA that is mainly positive (trough in the east) but at times negative (ridge in east or more zonal flow)

Now lets look at the ECM teleconnections:

Well from looking at the above teleconnections on the ECM @ 12 Z we see the following:

1. NAO ..mainly positive with brief – east based NAO

2. AO is mainly positive with a brief flirt in the negative territory..

3. EPO going from positive to negative but mainly negative..

4. PNA going from positive to negative and quite strong negative

5. WPO going from positive to off the charts negative!

So as you can see the teleconnections differ as well on the guidance and I think that can be contributed to the evolution on the Madden Julian Oscillation chart above. Now lets go back to that:

Look at the one that is for the GFES and notice the green line. That is the NVEP GFS ..do you see how it showed it going into the COD and then kind of making a due north turn and heading into phase 7? Now look at the red line and look for the #8..that is where the MJO is as of Jan 8th and you notice two things:

A. Its on the INSIDE of the circle not like on the outside as the GFES means shows and:

B. It never made that due N turn into phase 7 so the NCEP GFES is already in error with the MJO.

Now…lets go back to the guidance and see what is happening on the ECM as of 12 Z..

Now this here is the ECM 850 mb anomaly temperature departures and as you can see they are indicating warmer departures moving into the central part of the USA and heading towards the east…

This here is a look at HPC and the positive departures for day 6 and day 7. Looks quite familiar to the ECM up above one could say…

So..in summary so far we have a classic model battle between the GFS & the ECM…Remember the beginning of this update the departure map for the first 7 days of January? Remember how it has been warmer then normal…Well..if one were to follow and believe the GFS we should have been colder then normal… but the reality is we have been warmer then normal.

So why the difference between the models? DT talked about what could go wrong in a post a few days ago and the next two images are from wxrisk.com Dave Tolleris..

Remember above both the ECM and GFS are showing a fairly strong – WPO but the ECM is the strongest by far.. this is what this would look like:

And you can see this “gradient” pattern setting up on the ECM today at 12 Z

Notice the ECM  has +12C 850 temps in Kansas with -24C temps at 850 touching the border of the US at 192 hours? This is what you call a gradient pattern. It represents a difference in thermal or temperature profile over a short distance..

If the ECM has the correct idea then we will look like this:

This would be due to the – WPO which both the ECM and GFS are showing. IF IF the NAO goes negative like the GFS is suggesting and the AO then the colder air would be more along the east coast..

If the ECM ideal is correct with a strong negative PNA and – WPO and positive AO and mainly positive NAO then the above image would be how things would play out.

So in summary ..we here at Real Wx Services do not like the GFS and how it tanks the AO and the NAO. We feel the ECM has a better grip on the weather pattern…

One fly in the ointment is the stratospheric warming. If this begins to down well and we can obtain blocking over the Davis straights then this to would cause the above to end up falling by the wayside…

However..all a strat warming down welling implies is that the NAO would go negative and the AO would go negative –it does not guarantee colder air into the east but somewhere in the USA. If the EPO is negative and the WPO is negative as strongly as suggested this could still cause the above image (WPO classic pattern) to occur…

So we are anticipating arctic air to invade the region in about 3-5 days ..but we are anticipating it to be transient in nature with the potential of warming up (moderation in temps) again before cooling down.

Latest ECM weeklies which have been verifying well also support this discussion…