Monday, February 28, 2011

Spring is Springing but Does Winter Have a Last Stand?

Spring is around the corner. Matter of fact we are only approximately 19 days away from the first day of spring. We have had temperatures recently to remind us that spring is indeed springing upon us…however…we must keep in mind that spring has not sprung yet and we technically are still in winter & is it possible that winter could take one last stand?

So lets look at the guidance for the period of March 6-8th,,

12zeuro850mbTSLPNA144

12zeuro850mbTSLPNA168

12zeuro850mbTSLPUS192

Now the above is the ECM and what the ECM does is it brings a primary up and towards the west of the region while bringing a cold front across the region. Then at 168 hours out another wave forms on that cold front and then moves up and along that cold front between 168 and 192 hours.

Now keep in mind when looking at the above that this was actually stated on this blog back on the 26th…

A more likely scenario is that there will be a northern area of low pressure that moves thru with an attending cold front with colder air behind that front. On that front a wave could potentially form and move up and along that front. The question then becomes how far east does that front make it? And what side of the front would the region lie on? Again all we are doing is speculating on the guidance above with the teleconnections that are in place at the time.

18zgfs850mbTSLPp06162

18zgfs850mbTSLPp06168

18zgfs850mbTSLPp06174

Now, as you can see on the 18 Z GFS..the GFS is also very similar in its depiction with the difference of the GFS does not bring the cold front all the way east..hence it is slightly warmer and there is no QPF on the western side of the storm system.

The means of the GFS however..seem to be more in agreement with the ECM.

18zgfsensemblep12156

18zgfsensemblep12168

18zgfsensemblep12180

So at this point and time the GFS means and the ECM are in fairly good agreement.

If we look at the GGEM..

12zggem850mbTSLPp06144

You can see it to has the same general concept with a wave and the cold front..with the secondary wave but it appears as though the GGEM could be playing into its biases of over phasing the energies that are involved.

So, while spring may be in the process of springing upon us ..it may be prudent to step back and watch the guidance to see if winter does indeed have one last stand and perhaps one last surprise for portions of the mid atlantic into the Northeast!

Feb 28-March 1st Rainfall

While HPC has been going back and forth with there rainfall totals..Here at R.W.S we are not changing a thing from what was issued on Saturday as  our final map. Just a few hours ago around 9 pm they had reduced rainfall totals over a good part of the region to only .50-.75…as of 1 AM ..they are now back to around an inch over most of PA.

I am not really sure what they had seen to make them change there minds to downgrade the rainfall amounts to begin with. The only thing that crosses ones mind here at R.W.S is the 00z NAM which only showed .25-.50 across the region with more to the north and more to the south.

RAD_MOS_NAT_8KM_WINTER_ANI

As you can see by the radar rain is overspreading the area and some of it is rather heavy. Now what we are concerned about for tomorrow is if you look off to the west just east of Oklahoma you are going to see a squall line developing. This squall line is producing a Tornado watch from parts of Ok northeast into Illinois and Indiana..

So here is the concern. We started talking several days about this storm taking a further north track then the last event which brought the heavy rains and the microburst wind damage into SNJ. And as you can see by the image below:

sfc_con_pres

This further north track is indeed occurring. Now what this has allowed last evening and the early morning hours here so far is for the warm air to start surging towards the north. Temperatures now are warmer then they were all previous yesterday..

sfc_con_temp

The concern is that this is going to allow the temperatures to probably climb into the 60s and approach 70 degrees and this is because of the warm front that is lifting north.

90fwbg

Now…with warm air surging northward ..it will be very vital as to how far north this warm front makes it before the cold front starts advancing towards the region. Remember part of severe weather development is the contrast in temperatures..so where that warm front makes it will be the dividing line between colder air to the north and warmer air to the south and could set the stage for some severe storms as that squall line comes towards the east.

So look for heavy rain in the early morning hours and then perhaps some sunshine before round 2 (squall line) moves back in providing more heavy rains along with the potential for severe thunderstorms which will contain strong gusty winds and at the present time can not rule out an isolated tornado.

Stay tuned for updates as needed..

Sunday, February 27, 2011

Feb 27-March 1st Severe Weather & Flooding Rains!

CURRENTFORECASTIMAGE1-9

Final rainfall map issued above. Winds with any thunderstorms will be on the order of 60 MPH or greater!

Is Winter Over or Does Winter Make Its Return Slowly over the next 10 days?

Guidance seems to be showing us lakes cutter after lakes cutter with heavy rain events..One thing that seems sure is that over the next 10 days ..there will be no shortage of rain and there will probably be an abundance of rain. However, there after is where things begin to get interesting.

For at least the past 4 consecutive runs of the GFS..the time frame after March 7th appears to be getting colder. Lets look at the following images..

06z

06 Z

12Z

12 Z

18Z

18 Z

18Z

00z

00z

What your looking at here is the 850 mb temperature anomolies and as you can tell at least the operational GFS is suggesting that the colder air could be making its return in the longer range. And the operational model is not alone as the GFS ensemble means are also showing the same scenario returning after the 7th of March.

Another thing that the guidance is beginning to hint at is the PNA which is strongly negative now starts to weaken and head up more towards neutral and the EPO  which is positive now is going to be going negative ..which means whenever the EPO goes negative it provides ridging in the west into Canada. Now keep in mind that a strong negative EPO would also indicate a strong SE ridge but the EPO is shown not to become over bearingly strong. The other thing that one notices is that the NAO which is strongly positive now is going to start to head into the negative realms before heading back into the neutral positive range.

00zensnao

Now this may become a significant factor around the 6-7th of March as you can see that is when we are dropping into negative and then starting to rise into that neutral positive. Chances are that during this time period there will be a big east coast storm. And guidance is suggesting this indeed will be the case..

00zgfs850mbTSLPp06174

00zgfs850mbTSLPp06180

00zgfs850mbTSLPp12192

00zgfs850mbTSLPp12204

Now..because this is in the long range of the guidance all we can do is merely speculate because nothing is set in stone this far out. However..the NAO is going to be negative at this time frame and if that is indeed the case then this could be a case of can the colder air come in before the low pressure moves into the area? If the cold air is delayed or a little late it could be a rain to snow scenario.That is one scenario.

A more likely scenario is that there will be a northern area of low pressure that moves thru with an attending cold front with colder air behind that front. On that front a wave could potentially form and move up and along that front. The question then becomes how far east does that front make it? And what side of the front would the region lie on? Again all we are doing is speculating on the guidance above with the telconnections that are in place at the time.

So as you can see..perhaps winter is not over after all & could make a return for the last 2-3 weeks of the month of march. It is something to keep an eye on and see where this leads over the next 10 days!

Saturday, February 26, 2011

Feb 27- March 1st Severe Weather

In our earlier update on this time period we mentioned how severe weather could very well end up being a factor. While we feel its still to early to issue any maps with any type of accuracy we thought it was interesting to find out that SPC now is on the same page thinking the same thoughts…

day3otlk_0830

day3prob_0830

As always we are ahead of the professionals with the forecast that we have in place. Stay tuned as we get closer to this event we will issue a map and let you the readers know what to expect!

Flood Potential Feb.27-29th

rain

Here We Go Again- Flood Potential Feb 27-March 1st

Once again the area is going to be under the threat for heavy rains from late on the 27th thru the 28th. This system that will be developing to our west will take a track similar to this last system ..however this time it may end up further north with a track across Northern Ohio and then ENE thru CNY spreading into the region another bout of heavy rain.

Due to the track being more northern then the last time that means the southerly flow will also reach further to the north so that the areas that seen snow this last system could end up with heavy rains this time. This is something we will have to watch and if this indeed does turn out to be the case then we will be talking about a pretty widespread flooding..

Temperatures once again look to be at 50-60 + from NJ thru Central Pa and south…and 40s north of there till you get further north where it will be in the 30s and then potentially below freezing in the state of Maine..

If guidance is correct we could be looking at these temperatures of 50-60 degrees dropping below freezing in just a matter of 6 hrs.

So this could potentially imply two things besides the rainfall anticipated.

1. Strong gusty winds. Once again we could have winds gusting between 40-50 MPH

2. Potential for thunderstorms..being that the front looks to come thru sometime around 00z we would have had the whole day to obtain day time heating.

So again this will be something we will have to keep an eye on.

So to sum things up we could be looking at another system providing strong gusty winds, heavy rain with the potential of wide spread flooding with rain totals on the order of 1-2 inches and the potential for severe weather as well.

Later today we will be issuing a map for this next system but we wanted to give the readers a heads up as to what to expect out of this! Stay tuned for more information!

Feb 26th Daily Weather Discussion

High temperature on the 25th was 54 degrees which was well above normal for this time of the year. Temperatures once again have tumbled and once again they will rise again, basically as the roller coaster ride of temperatures continues for the forseeable future.

Today there will be a chance of snow showers from about northern PA into NY. Then towards evening rain showers might develop over E C PA but they should remain all snow in NE PA. Sometime after 8 pm the rainshowers could turn to snowshowers in E C PA…just a T of snowfall anticipated in E C PA..and then the northern tier of PA points North have the best shot at steadier snows. Accunulations there should also be light in NE PA and NWJ with anywhere from a T to an inch or two. Further to the north into N Central NY would be the best chance at 2-4 inches of snow.

Temperatures single digits to the north into MAINE…south of there 20-30 ..then from a line from NYC into NE PA and south temps will range from 35-45 …colder north warmer as you go south.

Thursday, February 24, 2011

Snow, Winds, Thunder & Flooding all in one system!

Severe Zone

Winter

First severe map of the season and its in winter time instead of spring or summer. The area highlighted above is mainly highlighted for the area where the strongest winds are possible with the approaching cold front but also where there could be thunderstorms. Thunder storms will be dependent on whether we can get some clearing and daytime heating which will help to further destabalize things.

Otherwise  expect an area of low pressure to move from the Southwest to Ohio and continuing to move NE from there so its in a position over down east Maine by Saturday evening. Some of the southern regions of the snow zone will start with a wintery mix …mean while its possible in places like the poconos and NW NJ and western PA that we may end with a little bit of wintery mix or snow..Other wise we can expect heavy rain with the potential for flooding and thunderstorms thru the region except to the north where the cold air will be deeper and snow will take place.

Wednesday, February 23, 2011

Flood Potential Increases Across The Region!

We been talking about over the past 24 hours that one of the models between the ECM/GFS was either going to bust badly or one of them had to change its solution. The model which was showing the coldest solution has now changed its solution and actually caved into the ECM. So the snow potential out of this system has virtually disappeared in the past 24 hrs.

12zeuro850mbTSLPNA048

12zggem850mbTSLPp06048

12zgfs850mbTSLPp06048

12znogaps850mbTSLPp06048

12zukmet850mbTSLPp06048

As you can see virtually all models now have generally the same track with this area of low pressure. Some are slightly further west which would be considered the western extreme..but they all have one common theme and this is bringing warm southerly flow out ahead of the system with a large amount of precipitation as well.

GFS still remains the coldest and would suggest some snow across Northern portions of PA..so that is something we will keep an eye on.. however the European Computer model has temperatures ranging from 45-60 from just shy of the North Central PA/NY border covering all of central PA to eastern and NE pa and points east. With the more northerly extent of the system the stronger the low the stronger the southerly flow ahead of the system.

Precipitation amounts look to be on the order of 1-2 inches. Where there is a deep snowpack yet and with the warmer temperatures and the rain this could present some flooding problems ..especially across Western Pa.. and locations in Southern New England where they still have snowfall.

Stay tuned for more information on this developing storm!

Coastal Storm or Inland Low? Snows or Thunder/rain?

The time period we are talking about is the weekend. Friday into Saturday ..or perhaps late thursday night into friday night..

Generally this season models have been having a really difficult time with forecasting storms in the medium range or around 72 hours out which this is approx. As of 00z guidance tonight we have everything from thunderstorms with heavy rain potential to a snowstorm potential for those N & W of the major cities.

We have two major models that have been relatively consistent. The GFS/ECM but they have two totally different solutions.

00zgfs850mbTSLPp06066

You can see that the GFS is the model that would support a snowstorm for inland locations from about E Central PA and points to the west and north..

On the opposite side of the spectrum is the ECM which at 66 hrs (sorry its a pay site image) is over SW PA…quite the difference for 72 and under…

Looking at the rest of the guidance ..

00zukmet850mbTSLPp06060

UKMET which is not available at 66 hrs is shown here at 60 hours and this would be considered an extreme western outlier.

00zggem850mbTSLPp06066

GGEM at 66 hrs is over SE PA essentially which is closer to the GFS operational track…then it would be to the ECM operational track..However..its snows would be further inland then the GFS.

00znam850mbTSLPp06066

The NAM at 66 hrs at 00z is also on the eastern side of the solutions but also the snows would be further inland then what the GFS shows.

So we have the GGEM/NAM similar to the GFS but warmer and or further NE…

UKMET extreme western outlier..

ECM further to the west & warmer and also supportive of a thunder with rain event.

So we essentially have no model agreement and we are about 72 hrs out.

Normally the GFS would be considered an outlier with its colder solution..however..it has support from its ensemble means and more importantly only 3 out of 12 members are further west then the GFS op. This means that 9 members out of 12 support the OP and you would not expect this model to change all that much run to run..

As far as ensemble means the 00z GFS means and the 00z GGEM means essentially agree on the 60 hr position and 72 hour position but there is no access to the in between hours.

00zgfsensemblep12060

00zggemensemblep12060

You can see some fair agreement there between the two different means. This leads us to believe that the GGEM individual members probably closely resemble the GFS individual members as well.

So what causes the differences between for example the ECM /GFS? I believe the differences start at 48 hrs already..

00zgfs850mbTSLPNA048

00zeuro850mbTSLPNA048

You can see at 48 hrs already the GFS digs the energy further to the south and is also weaker with the system at that point and time. Now..what is interesting is that both the models show a strong negative EPO around this time period.

00zensepo

00zecmwfepo

As you can see by the images above. What this means is that you will have a strong southeast ridge in place. They also both show a rising NAO from neutral negative and a negative PNA..

Generally speaking ..the NAO rising from neutral negative to positive is a signal for a big east coast storm. Throw in the wild card on top of this of the MJO..

phase.Last90days

Which is in phase 7 and you have some more support for a GFS like solution as phases 7,8 and or 1 are the best for East Coast storms. The negative EPO also would be sending ridging out west which would cause this energy to dig further south as indicated by the GFS..

However..at the same time we can not simply just side with the GFS model even though it does indeed seem to have more support..fit the teleconnections better.

At this point and time we generally think that this should take a track from NC Arkansas  to Northern West Virginia.

The question then becomes does this continue to move NE from that point or does the confluence from the high pressure dropping into the Central states cause this to take a more easterly track? 

We are going to be honest and say that right now with guidance not in harmony it is just to early to know the complete answer at this time. The best bet scenario seems to be that the big cities would be rain..perhaps ending as snow and the inland locations (how far inland is not known yet) would be a wintery mix to snow scenario.

We are keeping in the back of our mind the past two systems which just delivered snow across the region ..and how at this time range they were modeled to far to the north and west..too warm and as rain..and the final result was snow!

So stay tuned for more information on this developing winter storm.

Tuesday, February 22, 2011

Snow has come North to ABE in Wave #2

001

002

Started snowing at 1:15 AM after hours of virga and a coating on the ground!

Feb 22nd Daily Weather Discussion

High temperature on the 21st @ KABE was 35 degrees. Snow has stayed to the south of this region thanks to the extremely dry air that has moved in aloft. Meanwhile the snow will continue across areas to the south where the air is a bit more moist..and will wind down by the early morning hours around 12 Z..Other wise it will be a partly cloudy day across the rest of the region. It will also be another cold day.

Temperatures will be in the teens north to the 20s pretty much elsewhere except south of the PA/MD border it will be in the lower 30s.

The weather looks to get pretty wild over the next 2-3 weeks so stay tuned to find out what “ups” and “downs” are ahead…

Sunday, February 20, 2011

Winter Has Returned As We Have Been Talking About Before The Rest!

As we have been talking about for some time now..winter is returning and snow is returning depending on where you reside. Low pressure which is forming over the Midwest is going to be moving towards the East and then Southeast. A second wave is expected to form along the frontal boundary and this wave should generally take a track similar to wave # 1 . The two waves combined will provide Wintery Weather across a good part of the region with wave # 1 greatest accumulations of snow will be from east central PA into NW NJ and then west wards into Northern and North Central PA and then into NY as well..

Basically this is a tricky forecast and has high bust potential because we are dealing with a SE ridge and a Arctic High to the NW. With over running events the precipitation can sometimes be faster then modeled and if this occurs ..presently there is some milder air still in place…which means that this could start off as liquid even in the areas with the higher snow totals which could cut down on the totals…If this occurs we believe it would be the lower end of the ranges that would come about in the end.

For wave 2…this should mainly effect east central PA and points south ..and this is expected because the cold air should be pressing south which would press the boundary further to the south. However..if this cold press to the south is not as strong as expected then the second wave would end up being further north ..so things will still have to be monitored for the second wave. The snow in SE PA , SNJ and DE would come from the second wave.

CURRENTFORECASTIMAGE1-9

So with all the above said this is the current thinking at this point and time.. Remember any deviance of the track north or south would effect these totals and this is combined for wave #1 and wave # 2.

Stay tuned for further information!

Feb 20th Daily Weather Discussion

High temperature on the 19th was 50 degrees. This high occurred right after midnight as thru out the day the temperature continued to drop.

Today we are going to be once again on the colder side of the equation with winds gusty early but calming down during the early part of the day..

By evening time we are going to have precipitation moving into the region with rain to the south of PA and into SE PA and snows to the North of that. In the overnight hours this snow will probably begin to mix with and change to sleet and freezing rain. We will have more specific details including maps later today after 12 Z..

High temperatures will be in the teens to 20s from Maine into Majority of the northeast with lower to middle 30s from SNE into East Central PA stretching back thru Central Pa and then lower 40s south of that line. Northern New Jersey will also be in the 30s and south of there in the 40s.

Saturday, February 19, 2011

Feb 20-22nd Updated Thoughts

As we have been talking about for several days now winter is about to return and those that were spoiled by the warmer weather and thinking winter was over are probably going to be in for a rude awakening. Temperatures today were dropping all day and were being ushered in with some very strong NW winds. Winds have been gusting into the 40s and 50s thru out the region which has been ushering in colder air. This colder air is going to set the stage for potential winter weather Sunday Night into Monday night and perhaps another round of winter weather on Tuesday…

Latest guidance as of 12 Z has actually started to trend further to the south with wave #1 and then for wave #2 the guidance is still split. We feel the reason that guidance is starting to trend south with wave #1 is because it was too far north to begin with. If you are going to have confluence strong enough to make the second wave south..then it only makes sense that with the storm being 6 hrs apart that the first storm would not be as far north.

12zeuro850mbTSLPNA048

12zgfs850mbTSLPp06048

12zggem850mbTSLPp06048

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12znogaps850mbTSLPp06048

As you can see by looking at the guidance above for wave # 1 ..the ECM is actually the model that is further to the south then the rest of the guidance..however..all of these models have trended further to the south with this first wave. Presently we think that the ECM probably has the best handle of the track with wave # 1 but we believe that it is probably too warm at this time range. This can be a bias of the ECM model and usually by about 24 hours out the model will actually be closer to reality with the temperatures.

We have been talking about how  it will depend on where the polar boundary sets up and this is the track that the systems should ultimately travel across. Right now we feel that boundary will probably set up just along or just south of the PA/MD border and that is pretty much what we have felt from the start of tracking these systems.

Now..as of 18 Z ..the NAM actually moved further to the North with wave #1..while the GFS actually moved further to the south from 12 Z..

18zgfs850mbTSLPp06042

Compare that to 48 hrs and you will see that it has come south. Now..you may be reading across the internet that this can be attributed to the models southeast bias at 18 Z runs. First..there is no truth to this statement. 18 Z runs are as valid as any other runs of the GFS. Second as we see above the ECM was further south then the GFS at 12 Z…and with the ECM in the short range being a better performing model it makes sense that the latest GFS has come further to the south.

The 18 Z GFS actually brings with wave # 1 about .50-.75 from E central PA and points to the North. Surface temps are below freezing in the same areas and 850s are as well so if this were to be pure snow those areas above would be looking at about 5-7 inches of snow. However..there could be some warm layer in there so ..the scenario would look like snow and some sleet/zr possible with wave #1 . To the south of those areas however..temperatures would be warm enough for rain or a wintery mix.

So at this point and time it appears that wave #1 will bring the areas from about central PA and north the best chances for some snow along with some ice potential.

This brings us to wave # 2. Models for the most part have been suppressed with wave # 2. Now there is some model divergence on this so..we will once again look at the guidance from 12 Z with wave #2 .

The NAM shears the system out and has it pretty well to the south with perhaps a light snowfall in Southern PA and then heavier amounts south of the PA/MD border..

12znam850mbTSLPp06072

GFS paints a similar picture as the NAM with wave # 2.

12zgfs850mbTSLPp06072

Now lets look at the foreign models..

12zggem850mbTSLPp06072

GGEM shows a stronger system with QPF more to the north then the american models above. Nothing impressive but a light snowfall for central PA and points to the south in PA.

12zeuro850mbTSLPNA072

ECM we see no surface reflection of the low however…compared to the two prior runs of the ECM..the QPF from the system is further to the north. As prior runs the furthest N was ABE for light QPF..now the furthest N is in NE PA. So while the American models are south ..the ECM is slightly further to the North and more similar to the GGEM.

Perhaps the most interesting foreign model of them all however is the UKMET..

12zukmet850mbTSLPp06072

UKMET has  a stronger system and would be a decent snowstorm across the region. This could potentially serve as a red flag to the ECM with its not strong enough nor far enough to the North.

So the foreign models actually give a fairly strong reason to continue to monitor storm or wave # 2. As well as the GFS means from 18 Z..

18zgfsensemblep12060

Presently it would appear as the second system would take a further south track and bring some lighter snows into SE PA , S NJ and DE and MD..

However..with the foreign models indicating further north and the track of the first wave coming further south (towards the PA/MD border) ..this second storm will likely depend on the boundary from the first storm and where it sets up.

Edited to add:

There is some more mis information going around on the internet. That is that once one gets inside 72 hours they should stop looking at the GFS means and start looking at the SREFS (NAMS ensembles) ..This simply is NOT TRUE! The SREF is the NAMS ensembles and the NAM was not created to be used beyond 48 hrs. So if we are talking about a system beyond 48 hrs..you would look at the GFS means before the SREF.. Under 48 hrs then you would look at both the SREF and the GFS means. So..please be careful with some of the information going across the internet!

Stay tuned for further updates.