Thursday, December 18, 2014

Where We Have Been and Where We Are Going

     So, lets cut right to the chase shall we. The question that is on many minds, where is the snow? Well, its in Maine, head north !  Before I can get into that lets discuss how we have gotten to where we are now this season. First there was a drought, but we have certainly have taken care of that for the most part during the past 60 days or so with well above normal precipitation observed for most locations in Southern New England. In the temperature department , November featured below average temperatures for most the area, now into December we are seeing slightly above avg temps. I thought it would be a bit cooler, but it has not. The Climate Prediction Center has been right on though for the most part. We will see how the rest of the month shapes up, but I can tell you there are very good signals of cooler air heading into January. It has been a fairly "normal" period of weather in recent months, no real extremes occurred other than some daily precipitation records. The map below shows the daily high and low temps for Hartford CT since October. Nothing really jumps out in either direction and only one extreme was reached, and that was a record high of 67° on November 12. 

Click on images for larger views

November did feature a few snow "events" though. Four for some communities ! That is quite rare, and actually many folks across SNE saw more snow in November than what they have received thus far in December. Thankfully no snow was observed in October this season which is a good thing as many of you know I have a strong belief that seeing snow during October is a  curse for snowfall ahead. So as we sit here today on December 18, just a week away from Christmas and most SNE locations are right around either side of avg snowfall to date thus far, though I feel we need to get a decent storm in here before the month comes to a close if you really want that "big" winter. Why? A look back in time to past seasons shows that this month is critical towards the big one. Using Boston for December, the years between 1996 and 2003 there was not one December that featured more than a total of 10" for the month. Only ONE of those seasons finished above normal. 1981-1992, same thing , not one December even hit 10" of snow and only 2 of those seasons even finished above avg which is around 42" . History says we really need to get one before December wraps up. 
So that's a little write up on where we have been and now to touch on where we may be heading. We know for the past two months it has been quite active but we have lacked cold high pressure along the Canada/New England border that is necessary to lock in cold air as storms approach. You see, when coastal storms approach, they come with mild air from the tropics or sub tropics and from the moist Atlantic Ocean, its what feeds storms into cyclogenesis and when you lack a dome of *established* cold air, it is very hard to get a true SNE Snowstorm in the month of December. There is another wildcard this season so far too and that is well above avg SST's (sea surface temperatures) off the Mid-Atlantic coast right up into the Gulf of Maine. What this means is any onshore wind flow (which usually occurs as a storm is approaching and during it for a time till winds shift) brings milder air into coastal locations. Inland areas are less effected but still to an extent depending on the intensity of the winds and direction. We really need to get these ocean temps down before we can get too excited along the coast for "snowstorms" .
Here is a map showing those current SST anomalies. You can clearly see they are running well above avg.

The Pattern ahead looks to remain very active, but as discussed previously , its been mild for December for many so far, how do we change that and where do forecasters look for that big "pattern change" ? Well, there are a few places, 1st off models, but most of all teleconnections and more specifically The Arctic Oscillation (AO) and the North American Oscillation (NAO) . What you look for in a big pattern change is sharp changes in these phases, the graphs below show that we are heading in that direction and in a favorable direction with AO projected to head down as well as the NAO which will provide for some much needed Greenland Blocking . 

There is the hope for the snowlovers right there as we move into January, so lets see how this pans outs. Models are suggesting a huge dip in the jet stream in the days ahead but they are not in total agreement as to where the eastern edge of the dip/trough sets up and its eventual tilt which is very important along the East Coast. The Image below is a projection from the GFS model showing the 500mb height anomalies for Christmas Eve time frame. Notice the big ridging off to the northeast producing a high block, keeping storminess over the Northeast US. It's tilt is not quite ideal but could do the trick. Think of the red, yellow & orange (& green here) as a brick wall. We just have to watch trends, it already has shifted a bit in recent days. 

There are the signals that should bring us into a more conducive Winter pattern. Very anomalous. Often anomalous projections lead to anomalous results ! 
The forecast ahead is very difficult, but we will likely track a wave of low pressure up the coast Saturday into Tuesday that looks to bring some rain and snow to some area, most likely Tuesday before the potential of a very large storm system that likely will move off to our west keeping us in the warm sector and mostly rain and wind on Christmas Eve into early Christmas morning as Santa is making his deliveries which the big fella will have a hard time doing over the Northeast, but something tells me he will get er done. Is there a chance the storm trends colder? Outside shot, yes. We would need to redevelop a new coastal low for that to occur, while that may happen, the negative tilt to the jet would still bring in marine air in regardless. This storm does bring BIG changes in its wake though and don't be surprised to see a few festive snow flakes flying around on Christmas Day ! Now that would be nice. Maps below are for Christmas Eve. Someone is going to have to get Santa a windbreaker for his flight into the Northeast   

A reminder: The first official full day of Winter occurs on Monday December 22 and will end on Thursday March 19th. The Southern New England Weather forecast remains calling for below normal temperatures and snowfall near either side of average. Thank you for reading.   ~Anthony 

Monday, April 14, 2014

Winds of Change

The winds of change are upon us ! They brought many 70's the past couple days and will bring other changes over the next couple of days but you may not like them this time.
A powerful early Spring cold front will be approaching the region Tuesday bringing with it scattered early downpours which will become more widespread as Tuesday wears on. Overall the entire region is prone to about an 1-1.5" of rain with a few isolated higher amounts possible, especially over Connecticut.  For this reason there is a  * Areal Flood Watch* is up.  And If you think the winds were strong today, wait till tomorrow and tomorrow eve.
They will scream from the south with gusts between 40-55 mph. A few isolated higher gusts are certainly possible over the hills and over Cape Cod & the Islands. I would expect at least widespread Wind Advisories to be issued for tomorrow shortly. For now though, Gale Warnings are up for the waters just off our coastlines from 2pm Tuesday through 6am Wednesday.  Gusts of this magnitude are certainly capable of isolated damage and power outages. As the strong cold front passes the region late Tuesday into Wednesday wind will shift to the west/northwest and still be gusty especially early on Wednesday as they usher in much colder air. Its during this time (late Tues night-early Weds) that some cold air aloft will creep in and marginal surface temperatures snow for may will bring the potential for heavy rain to turn to some wet snow flakes over the higher elevations and western Southern New England. Believe it or not the potential is there for a slushy inch or two ! Some wet flakes could even make it all the way to to the coast. Wednesday we are left with morning lows near freezing and high temperatures that will struggle to get of the upper 40's and low 50's with developing sunshine during the afternoon. A frost is likely Thursday am and again highs struggling to get out of the upper 40's and low 50's even with quite a bit of mid April sunshine. Quite impressive!   Cool weather looks to rule right into the coming weekend.    ~Anthony

Saturday, March 22, 2014

Forecast Thoughts For Potential Major Nor'easter Tues-Weds 3/25-26

   Highs today were near 60° for portions of the area but all eyes continue to be on what now appears to be a significant early Spring Nor'easter for much of the region later on Tuesday into Wednesday morning with the brunt of the effects expected over the eastern sections of Southern New England.
Click on all images for a larger view
   OVERVIEW: Arctic air looks to settle in Sunday eve and especially Monday where we could see record low maximum temps and begin to set the stage for a decent snowstorm  and what looks to be the first significant one since Feb 18th I believe. Northern energy for the pending storm is now entering the Pacific Northwest and will dive SE towards the Southeastern US states and merge with a southern based sub-tropical jet and form a storm off the Carolina's early in the day on Tuesday as the upper levels of the atmosphere dig a deep amplified trough over the East Coast Tuesday eve sending a phased storm off to the north/northeast that will undergo meteorological bombgenesis in response to rich Atlantic Ocean moisture and a clash of above normal sea surface temperatures and below normal SST's along its track and an assist from the Gulf Stream. Low pressure will pass just outside the 40/70 benchmark early Wednesday somewhere around 970 millibars, perhaps even lower  before heading towards Nova Scotia late Wednesday.
   TIMING : Flurries and light snow could break out as early as Tuesday am as upper level energy over the Ohio River Valley starts to interact with building moisture off to the south as the main storm takes shape near or off the Outer Banks of North Carolina. Flurries, perhaps a period of light snow should continue through the daylight hours before intensity will pick up south to north through the evening hours with the peak of the storm occurring overnight Tuesday into early Wednesday before  it pulls off to the northeast.
   IMPACTS & EFFECTS: Very strong signals continue to indicate the most significant effects and impacts will be felt near coastal locations. The heaviest snow and strongest winds are likely near the coastal plain. Banding of heavy snow is likely for eastern SNE especially near and inside interstate 495 in eastern Massachusetts as this area will be closest to the storm center and in the area of greatest signaled vertical motion. Unlike previous storms where there had been a sharp cutoff due to incredibly dry air contrast to the north and northwest of the storm, this one will have decent mid level moisture at least at the get go to spread light accumulating snow to the entire region before the storm really blows up and pulls the heaviest snow and banding closer to the coast and especially over the Cape and Islands. It will be very hard to see thermal profiles rise to the point where any mix would be involved so this is a predominantly snow event. Winter Storm warning headlines are very possible and even a Blizzard Watch could be warranted near the eastern Shores. The other issue and it could be a BIG one is the potential for powerful sustained  winds, again affecting the coast the most. There are strong signals of potentially damaging wind gusts along the immediate shore to Cape Cod and the Islands as the storm continues to intensify passing by.  There is a big difference between a weakening storm system and an intensifying one  like this will be . Enough signals have been there that I feel  *High Wind Warnings* are likely near the shores with even  *Wind Advisories* possibly further inland. Images below show the sustained and gust potentials during the brunt of the storm overnight Tuesday into Wednesday morning.
Wave heights are expected to grow to 15-20 feet near or just off our coastlines. The Wednesday high tide cycle will have to be closely monitored for likely splash over and potential for moderate coastal flooding. This aspect is very dependent on exactly how close that low center comes. There is great agreement as of now but slight shifts are still likely.
   So now to answer the big question I am sure many of you are asking. How much snow?  Its still a bit early to tag numbers for certain locations, however,  I believe I will be able to estimate further by this time tomorrow. In the map below it shows the best probability of seeing and exceeding 6" of snow. Confidence is quite high here, and if it  all comes together, as it has the potential to do so, someone will come away with a foot, perhaps a bit more when all is said and done Wednesday ino mid-day over eastern SNE.
Thats the skinny on the system as I see it right now. I do not expect many drastic changes but do stay tuned to me on twitter and facebook if they should arise between now and then. The good news is we could hit 60° by Friday with a better chance Saturday and we may finally be able to put the snow behind us and move forward to enjoy 'Spring'. Thank you for reading     ~Anthony