Tuesday, February 26, 2013

Winter Storm Update for 26th and 27th of Feb

Taking a brief look at guidance ... We are going to look at the 00z NAM and 00z GFS along with the 00z GGEM all at 30 hours...



All guidance takes the primary low to the west of the area ..over the Ilinois, Indiana area. Meanwhile a secondary is going to develop but this is going to develop inland. This sends the 850 freezing line well to the north of the area. High pressure to the North will initially keep some lower level cold air in place ..but this high pressure will start to slide off to the east and will bring an easterly wind. So we are going to have a wide range of precipitation types from plain rain to Snow, Sleet. & Freezing rain. The areas that will be frozen will be to the north across the northern tier of PA and in the higher elevations in central PA..Its quite possible that these places could turn to rain as well ..but initially it will fall as snow and ice across those zones. Travel could become slippery. Even though we have warm air advection and winds switching to the east we still have some colder air trapped at the surface and hence despite 850s being mild the winter mix precipitation.
Current radar above shows the storm getting itself organized over the southeast part of the US . Those locations that receive all rainfall look to receive on the order of around an inch. However south of PA may see more then an inch of rain in Eastern Md..  NYC residents can expect to see all rain out of this system ..those in NW NJ can expect to see a winter mix which could leave between a T-3 inches of snow/sleet.

There after some colder air will come in behind the system and will shift the axis of the trough further to the east so the weather will quiet down some as any storms should stay out to sea. 

Friday, February 22, 2013

Pattern Update -What is Ahead?

We been trying to put the pieces together on the weather pattern and where we are heading to over the next 10 days or so. We generally when doing this rely on two things:
1. The guidance that is available 
2. The teleconnections 

#2 being the greatest tool because it is what drives the weather patterns that we have. One of the main things we are seeing in the guidance appearing is the blocking showing up. You can see this really quite well in the below figure...

We have seen this signal come up other times this season but as we got within 84 hours ..the blocking would weaken and it more or less would become a "fake block" and not an actual true blocking pattern. So we will have to keep an eye on whether this blocking indeed happens as modeled.
Now when we turn to the teleconnections we get a muddled picture. The muddled picture comes in with the MJO. The current MJO is in phase 4..

Lets look at the what Phase 4 means in the month of Feb..
Now majority of your guidance takes the MJO into phase 5 ..from there it looks a little more uncertain but it looks like it could go into the COD which is commonly called the circle of death which is when it has less influence on the weather patterns. But this is what Phase 4 looks like in March...
The following will be Phase 5 for February and then March..
You can see what happens is the Southeast ridge is very much alive in Phases 4 thru 5. This would represent a warm up in temperatures across the region.. However..it is when the MJO reaches the COD that things become more interesting. This is when the MJO has the least influence and this is when the rest of the teleconnections will become important as to whether they actually happen as suggested.
Two different sources we can turn to for the teleconnections one being CPC and one being ESRL. So when we look at the NAO we see the following...

ESRL 
 ESRL NAO shows a very negative NAO and it stays this way thru the chart .
CPC shows a negative NAO as well and majority of the ensemble members keep the NAO negative though they try to raise it up towards neutral. 

The PNA (ESRL) 
 The PNA we diverge a little bit between the two sites with the top showing the PNA as negative to start but then going positive while the chart below shows more of a neutral but members taking it positive before going back towards neutral.
The AO 
The AO is negative and is generally expected to stay negative when looking at the above chart. So we are dealing with a negative NAO a negative AO, blocking (as being modeled) and a + PNA. 
All these teleconnections point towards a colder time period of weather upcoming if they indeed come to fruition. 
However, at the same time we are going to be having a MJO in phase 4 and 5 until it moves into the COD. So in the short term we will be moderating in temperature wise but the big ??? mark comes in when the MJO reaches the CDO. 

With those teleconnections shown to be in place this would put the mean trough into the east and this would end up putting ridging into the west coast. This in tandem with a active southern Jet Stream could lead to some interesting times along the east coast for those that are snow and cold lovers. 
Just to give you an idea and this at this point and time is just for entertainment purposes only to show you the potential that could lie on the table with the blocking, negative NAO, AO and + PNA in place. This was the 12 Z GGEM 10 day map:
It should be noted that the 00z GGEM has lost this feature however but still has the trough carved out over the region. The ECM was also close to showing something big on the 12 Z run but mainly New England ended up being the jackpot in that model run. 
The question or not to whether the upcoming pattern will deliver or not is highly dependent on where the trough axis sets up. If it sets up to far to the east anything trying to round the base of the trough would end up being to far east. If it ends up setting up further west then anything that rounds the base of the trough would move up the eastern seaboard...
So in summary we will be moderating and in that moderating time we will have two mainly rain storms to deal with (outside of Northern and Central New England) but there after is where the potential lies for things to get interesting based on what is being shown right now for about 7-10 days down the road. As always though the weather constantly changes and if that blocking fails to form and the MJO re emerges or stays in the warmer phases then winter would essentially be done for PA and points south and some parts in those areas are still waiting for winter to begin!

Thursday, February 21, 2013

Feb 22nd-23rd Winter Storm

Low pressure is taking shape over the south central part of the USA. This low pressure area is expected to head up towards the Great Lakes region, pushing a warm front across the area and then  drag a cold front across the region.
. This cold front will advance towards the region and a wave of low pressure will form over the southeast and move to a position off the southern New Jersey Coast. Due to the warm front moving across the region we will have what is called Warm Air Advection precipitation breaking out across the region. 
The air mass in place is very shallow across the central and western part of the state so as the warmer air moves over top of this shallow cold air it will result in some winter mix precipitation. We are not expecting a large amount of ice or snow but an inch or two of snow could fall and up to a tenth of an inch of ice is possible. Untreated roadways could become slippery. 
Further east this cold air will scour out fairly quickly due to easterly winds and warming temperatures so locations may start as a mixture of snow sleet and rain but quickly transition over to rain . Extreme Southeast PA should remain all rain.
For areas further north of PA.. we want to wait one more cycle run of the guidance to see how far north the warmer air is anticipated to advance. 
For those that live in the NYC /PHL area this will be an all rain event. Rainfall looks to be generally .75 to around 1.25 inches. 
The areas that look to be all snow would be Northern New England.. 
Southern New England looks like there could be precipitation type issues as well.. which is one reason why we are holding out one more model cycle for places further north..

Tuesday, February 12, 2013

Valentines Day Snow Event

With what was a historical east coast snowstorm in the past week.. we are talking about a snow event once again. However, this time around this will not be a historical storm or even a Major Snowstorm but will be more of a light to moderate event depending on where you are located.

We will start this off by saying all models essentially agree on the track of the system ..the problem is that the models do not have a lot of QPF with them. They have cut down on the QPF by having a more weaker southern stream vort and the quickness of this system.

Briefly looking at this system we will start with the wettest model and end with the driest model ..

The above is the 00z UKMET and this falls in as the wettest model and the furthest north model. 
00z GGEM has about a 7 hour window of snowfall (a quick hitter) and it starts as rain in locations like southern NJ , De etc

GFS & NAM are overall quite similar ..the one difference being that the GFS is slightly further north with the QPF shield then the NAM. 
Finally the ECM which is actually the furthest south of all the models and barely brings any QPF up towards KPHL.

When putting together the map we have left the ECM out of the equation and have used more a blend of the NAM/UKMET/GGEM/GFS.
This will not be a major snowfall as we mentioned but more in the way of a nuisance event 
We expect the National Weather Service to issue winter weather advisories for this event. 

Thursday, February 7, 2013

Major SNOWSTORM For The Northeast Region



The first major snowstorm of the season is now presently taking shape across the southeast. There are actually two pieces of energy that will be responsible for creating this storm system that will be effecting the East Coast. One piece of energy (the primary) will be moving across the Ohio Valley while a coastal low will take shape over the Southeast and really start to rapidly intensify as it moves up along the east coast. The Northern stream system will then phase with the southern stream energy creating what looks to be Blizzard like conditions from NYC to the Boston and Cape Cod areas. There could be as much as 18-24 inches of snow with locations exceeding two feet.

A quick look at the guidance shows the following:


As you can see the ECM is showing a powerful Noreaster along the NE coast and the ensemble means are just as impressive..
Below is the GGEM at 48 hours and you can see this is in agreement with the 12 Z ECM and ECM ensemble means...
12 Z GFS is also in agreement with the Canadian and the ECM and the ensemble means..

18 Z Guidance has not moved away from this scenario. The NAM has finally come on board with this system...

And here is the 18 Z GFS 
As you can see all guidance is in agreement on a strengthening Noreaster that will be effecting the northeast.
Starting time will be between 3 am and 6 am for the ABE region and last until 6 AM saturday morning. The ECM drops 1.03 QPF across this part of the region which would place us squarely in the 6-12 range.
In addition to the heavy snows will be the winds which will gust from 35-45 MPH. From NYC to Boston expect Blizzard conditions to occur with winds Gusting up to 60 MPH ...

Monday, February 4, 2013

Pattern Update as Of Feb 4th 2013

The weather world all over is asking the question of where are we going..is winter over? Majority of winter has been above normal..the months of December and January. Many people hung their hats onto the CFSv2 which was showing a colder then normal January and this turned out to be the opposite of what the CFSv2 was forecasting.
Now we are starting to see that Feb is going to be colder then normal and snowier then normal. We have had a couple clippers that have dropped light coatings of snow but with the MJO moving thru phase 8 and now going to be making its way into Phase 1 ..we should be going into a moderating trend with the return of the SE ridge. 

Lets look at what we just came out of 

Rather cold pattern that we just came out of and indeed we had a stretch of about a week of cold weather , then a brief warm up and back to the cold weather... but now we are looking at the MJO moving into phase 1...
When we look at phase 1 we see that the coldest anomalies are in the southwest region into the west..
While in the east it becomes a warmer phase. Along with the warmer comes also a more active phase where the southern Jet stream has a chance to kick back into action but also with Phase 1 we see the Southeast Ridge come back into play and we are seeing that on the guidance . However before we get to the guidance lets look at where the teleconnections actually are..

NAO
The North American Oscillation is positive and its forecasted to go back down to neutral but then it looks to remain neutral to positive with a few members taking it neutral negative.

AO
AO is currently positive expected to go negative but then members are divided on whether we stay negative or go back to positive but at the present time the AO is positive.

PNA 
PNA is neutral positive and looks like it is generally forecasted to stay that way by looking at the image above.

Remember a negative AO means a discharge of cold air into the USA
A negative NAO means a colder pattern in the east 
And a positive PNA means troughing out east and ridging out west. 

With both the AO and NAO positive this means that temperatures are going to be moderating and with the PNA only neutral positive it means any troughs are not going to be deep in nature but rather more flat in nature with a progressive flow prevailing. This is going by the teleconnections alone ...
So now lets look at the guidance and we will start with the ECM 



You can see that the ECM is indeed forecasting the region to start warming up at about 144 hrs out and keeping the east coast under the influence of the southeast ridge. 

What about the GFS does this also agree with the ECM? 




You can see that the GFS is in fair agreement with the ECM in warming things up. This makes complete sense when looking at the teleconnections and looking at the phase of the MJO with it heading into phase 1. 

We also said it means a more active pattern ..Here is 192 hours on the GFS 
And here is 228 hours out on the GFS 
ECM also has a similar set up at 192 hours out ..
And a storm coming from the SE at 240 hours out..
So, indeed it looks like we are going into a more active period but with a forecast of warmer temperatures on the horizon we would be looking at more in the way of rainfall then snowfall (interior Northeast could be exceptions) 
You can also see that the Climate Prediction Center agrees with this thinking as well with there latest outlook for Days 6-10 and 8-14 ..
 So the groundhog could be completely correct about an early spring at least for the time being as teleconnections and guidance show a warm up on the horizon and a return to a more active period of weather.