February 27th-28th 2023 Winter Storm

sroc4 wrote:Morning Folks.  Lets get right into it.  I'm pretty confident we are going to see accumulation snow Monday night into Tuesday morning if you live north of, draw a line SW to NE, between say Trenton NJ to Sandy hook out to Montauk point.  South of there will struggle.  

A few key points:  
1) We have needed to see our 500mb energy stay south of Long Island.  All models have trended to this soln; however, there are still subtle differences to just how far south and how strong and concentrated vs more strung out is it between models.  (Below is GFS and Euro 500mb vort maps.  Notice these differences)




2)  Point two:  If you have been following along this past week I have wanted to see the SOI remain negative through the weekend.  Reason for this is that all winter it has remained in mod positive territory which is a La Nina base state.  Combined with the MJO prev running through warm phases 3-4-5-6, this base state of the atmosphere typically allows any energy coming out of the SW CONUS to amplify over the center of the country which pumps the SE ridge, allowing the energy to bully its way into the great lakes; flooding the entire NE region with warm air ahead of our systems.  




Unfortunately the SOI has trended back into positive territory over the past 3 days after only spending 3 days in the negative.  https://www.longpaddock.qld.gov.au/soi/.  My concern with this would be that if nothing else changed then the prev atmospheric forcing pattern that has been entrenched all winter would settle back in allowing this Mondays potential to trend right back to the GL cutter soln.  BUT hold on because even though the SOI isnt ideal there are afew other big picture items that are likely to allow this to happen for Monday AND maybe even allow for the potential for the March 3rd-4th come to fruition as well.  One at a time though.  

3) Take a quick look back at the last two maps and notice the big circle to our NE.  This is our 50/50 low. If you look at the Anomaly map notice just how green the colors are in the center.  Also note the Reds to the north(our -NAO).  Up until now with the aforementioned pattern entrenched, La Nina base state and MJO in warm phases, anything that has resembled a 50/50 low in the past had been easily booted as our system amplified over the central CONUS an the SE ridge flexed.  But this time is def diff.  Reason?  the Stratospheric warming that has occurred.  That's right Mugsy had been talking about this quite a bit a few couple of weeks ago, and its effects are clearly going to help us here.  

Lets explore just how real quick.  How exactly does a strat warm event help?  This illustration is somewhat oversimplified but gets the main point across.  Here is a little mind exercise.  I want you to pretend you are an alien hovering high above earth centered over the north pole looking down and this is what you see.  



What you are looking at here is the temp profile for the strat at about 50mb or approx 63,000 feet above sea level.  Now I want to think about the fact that when air warms it expands, and when it cools it contracts.  Ok.  Still looking straight down at this map from space pretend that that the circle is a balloon filled with air in the stratosphere.  Immediately below the balloon is another balloon over the north pole in the troposphere.  Now I want you to take your space ship from hovering directly over the top of the north pole and now fly it such that you are now hovering centered over the equator.  Now we are perpendicular to the north pole.  So what we are visualizing here is two balloons stacked directly on top of one another centered over the north pole.  

Now when we have a strat warming event I want you to visualize the fact that the air within the strat balloon is going to expand.  now reference the image below.  As the strat balloon expands it cannot expand further out higher in altitude because its out into space.  So instead it begins to expand outward and down.  As it expands down in height you can now visualize that the result is going to be to compress the tropospheric balloon below it.  As you press on the center of the trop balloon, since it can compress into the surface of the ground you can imagine the balloon only being able to expand outward.  (Put a balloon on a table and press down into the center of the balloon with a fist.  You can see the balloon expand outward right?).  



With this visual, understand that when the strat warms over the N pole like this it in essence dislodges pieces of the tropospheric polar vortex(arctic and polar air masses) southward in latitude because of the downward pressure exerted on it by a warming and expanding strat Polar vortex.  Again keep your balloon analogy in mind here.


So how does this tie into our discussion about Mondays snow potential?  Despite the fact that the SOI, or more appropriately put the Trop Pac forcing is still less than ideal, the DEEP 500mb trough in our 50/50 region combined with the -NAO is NOT going to budge much because of the force exerted on the troposphere from above.  




 THIS right here is a fundamental difference and key factor as to why this is different setup with a likely different outcome than what we've seen all winter and why accumulating snow is going to happen for many of us on this board.  

So to bring this back around instead of our amplifying system over the central CONUS pumping the SE ridge and bullying its way into the GL its going to run into this 50/50low/-NAO block that isnt going to move much due to the forces exerted on it from the Strat.  The result is our closed ULL w'll head into the Ohio valley before running into the block, opening up, and forced ESE, and exit the coast S of Long Island.  At least thats the current consensus on the models.






Its a comlpex set up as you can see by the three LP look.  There is a HP to our north with exceptionally cold air to work with as seen by this 850mb temp anomaly map.  This air mass is Arctic in origin and as you can see is about 12-20*C below normal at its center.    



Some of the finer details that need ironing is the fact that the surface and low mid levels will have a SE and ESE wind flow which will likely keep the surface temps above freezing along the coastal plain.  Just how deep this above freezing layer is will dictate just how far away from the 10:1 snow ratio will be.  I would strongly urge you all to reference the Kuch-era snow maps instead of the 10:1 maps as it is likely giving a better representation of the 6:1-8:1 ratios for the coastal plain.  Once you get N of the Ct Coast the ratios are going to go up.  Its still possible that we get even worse ratios along the coastal plain if the soln is closer to the GFS than Euro regarding strength and position of the energy.  

Obviously no amount of snow is going to change my outlook on winter, but I am at least a little excited of the prospects of enough snow to cover my grass.  

WE TRACK!!!!
 

heehaw453 wrote:Latest HRRR.  Bottom line is the trajectory of the L pressure is favorable around I78 on northward.  That doesn't mean a warm nose won't invade if there is slow consolidation or rates aren't ideal.  Shave off an inch if your near coast or your mid-levels are flirting with freezing. Have to look at soundings for your area. This is probably a bit overdone in all honesty.

heehaw453 wrote:Latest HRRR.  Bottom line is the trajectory of the L pressure is favorable around I78 on northward.  That doesn't mean a warm nose won't invade if there is slow consolidation or rates aren't ideal.  Shave off an inch if your near coast or your mid-levels are flirting with freezing. Have to look at soundings for your area. This is probably a bit overdone in all honesty.

Frank_Wx wrote:The HRRR feels like an anomaly / extreme outlier. The 00z NAM did not look too great for coastal sections. Looks like a couple of inches at best.

sroc4 wrote:Upton. Personally I think this is too aggressive

frank 638 wrote:

sroc4 wrote:Upton. Personally I think this is too aggressive

I still don’t understand why national weather service weather weather channel has me for 2-4 inches of snow . Compared to 1010 wins they say coating to a inch followed by quick change over to rain for the city and coast

sroc4 wrote:Upton. Personally I think this is too aggressive

heehaw453 wrote:The HRRR continues dipping the mid-levels lower.  That will matter for northern Ocean Cty. Can't underestimate closing off the mid-levels in the right location.