Thursday, March 31, 2011

Storm Will Still Happen Just Not What Was Originally Expected in Southern Areas!

RAD_MOS_NAT_8KM_WINTER_ANI

Instead of complaining about a busted forecast we wanted to point out the reason why things are not going to transpire the way that they were originally being modeled. This was originally pointed out by DT so all credit goes to him for noticing it even though the models did not catch on to it till today. Notice looking at the radar the moisture that is diving NE across ARK? This is from what is called a Kicker low and the problem becomes there is not enough wave length space between that kicker low and the low pressure trying to develop. So this does not allow the low pressure to do negative tilted soon enough ..which causes its rapid development to be delayed until it gets past our latitude..and essentially till it nears Cape Cod..

In other words..things happen to late. Basically since the storm is going to be weaker at our latitude ..the precipitation is going to be weaker…the temperatures are going to be more marginal..IF this storm would had deepened where it was being modeled to , up until today, off the coast of the Delmarva /SNJ area then we would still be looking at and talking about a Major snowstorm for areas further south.

Just so happens that its all coming together too late so those to the south do not benefit but the further north you go and are closer to that deepening..you will benefit.

So with that said the area from PA into NW NJ has the biggest bust potential… there is a chance that the storm does not gather enough moisture to even reach the totals that are shown ..especially Lehigh County area ..into NW NJ..or the temperatures may be to warm.

Highest totals still once again will be in highest elevations and the lowest totals in the lowest elevations.

CURRENTFORECASTIMAGE1-9

We will continue to monitor this and Nowcast the scenario in case the chance that there is more surprises in store with this developing system.

Real Wx Services Cancels The Level 3 Alert!

As of 2 PM real wx service is cancelling the Level 3 Alert! Latest guidance has come in and now keeps the system weak and east and does not deepen the system until it is up near or close to the state of Maine. Outside of extreme SNE most areas will end up seeing very light precipitation in the form of rain showers and if cold enough snowshowers.

Please disregard the previous map that was issued.

Not one to make excuses on a busted forecast but this one the models truly have performed horrible.

Its ironic that mother nature gets the very first APRIL FOOLS day joke in!

Again, we apologize for not seeing this sooner but we are not going to continue something guidance does not support!

Potential Warm Up & Severe Weather Possible!

Its pretty much a given that once the European Computer Model depicts a Great Lakes Cutter..it almost never drops away from that idea. So for the purpose of this discussion we are referring to the ECM 00z .

We have talked about how this current system that will be coming thru from the 31st to April 2nd time period was going to be a pattern changer & this is exactly what the 00z ECM is showing.

00zeuro850mbTSLPNA120

00zeuro850mbTSLPNA144

As you can see ridging is going to be coming into the east with an area of low pressure tracking up towards the Great Lakes region. Now what is so special about this? Well you can see colder air coming down behind this system..This colder air looks to be only temporary ..However..if the ECM is correct… You should prepare for and expect a severe weather outbreak!

Why? I am going to use ABE as an example of what the ECM is suggesting. At 18 Z Wed the ECM has the surface temperatures in the lower 70s. In a 12 hr span these temperatures drop to the upper 30s..This would be a 34 degree drop in temperatures in a 12 hr period.

On top of that the 850s are in the 15 degree C range..to drop below 0 over the next 12 hrs.

Again..if the ECM is correct with its scenario we can expect a Severe Weather Outbreak the 6th of April!

Wednesday, March 30, 2011

Real WX Services Level 3 Alert For Late March 31st into the 1st Of April.

As we have been talking about some time now ..the region is getting ready to deal with a Spring Season Nor’easter that is going to have more Winter like effects over parts of the region.  This forecast is based on a blend of the ECM/ECM means and the GFS Means.

Low pressure is going to develop off the coast of Hatteras and move up and along the eastern Seaboard. If you are generally along the coast you can expect rain out of this system and in the order of 1-2 inches depended on where you are located.

Before this happens however..another area of low pressure may bring some QPF into the region starting later this evening and that will probably be in the form of rain..if you are in higher elevations it is possible that this may take a more wintery form. The real show though is going to be on Thursday Night into Friday…

As this low pressure moves up the coast it is going to deepen rapidly. This will allow dynamics to come into play with the upper levels being colder will pull the colder air down towards the surface resulting in locations going from rain to a heavy wet snow. This is the type of snow that will cling to trees and powerlines so it is possible that locations may lose power as well as have some fallen trees.

Winds will be another issue as they may be in the range to 15-25 MPH with gusts as high as 35 MPH which in heavier snow will cause visibility problems.

final

As usual this time of the year the highest amounts will be in the higher elevations. Because this show will be falling in the overnight hours it is also very possible this will cause some slippery roads. Majority of the accumulations should be however on the grassy areas.

Stay tuned as the models still remain in less agreement then they should be.

Tuesday, March 29, 2011

March 31- April 1st Update & Discussion

Note:  

This is a very early preliminary map and is HIGHLY subject to change. This also is a very high bust potential forecast and I am going to start off by explaining why..

The models over the past several days have really been showing the potential of two waves..one would be wed night into thur and the other would be thur night into friday. Models have been mainly concentrating on the second wave for thursday night into friday while more or less making the first one of little to no effect…NOW it is possible that this could reverse itself and it could actually be the first one that becomes the more important wave. The 18 Z GFS means is the first to actually suggest this to my knowledge..

18zgfsensemblep12036

Now compare that to 06 Z means at the same time ..

06zgfsensemblep12048

Notice how this low is now more AMPED up? This is something that we are going to have to keep an eye on over the next 24 hrs of model runs.

Due to the uncertainty caused by the 18 Z GFS means we are only going to be issuing a Level 1 Alert at this point and time. There is little to no doubt in our minds that a significant East Coast System is going to occur but the question that really needs to be fine tuned is when? Wed night –thurs-thurs night to friday or wed night –friday?

Lets look at the latest guidance from 12 Z ..

478_100

622_100

12 Z GGEM has a significant system off the east coast that gets down to 983 mbs by 78 hrs with a heavy QPF axis across E PA and points to the east and northeast.

slp12

slp14

post-1547-0-91212900-1301415378

Different views of the 12 Z UKMET which also shows a significant system along the east coast ..tucked in south of LI at 985 MBS.

12zgfs850mbTSLPp06060

12zgfs850mbTSLPp06066

12zgfs850mbTSLPp06072

12zgfs850mbTSLPp06078

12 Z GFS also has a Potent system that gets down even deeper to 978 MBS and tracks just off the coast. Temperatures on the GFS are marginal at the surface and 850s are cold enough N & W of the major cities to support a heavy wet snow fall.

I_nw_g1_EST_2011032912_072

I_nw_g1_EST_2011032912_076

Now these here at the 12 Z GGEM precipitation type maps for 12 Z and 16 Z Friday. As you can see the GGEM is mainly a snow/sleet storm across the interior with rain along the coast from  Central NJ south. This is from a warm biased model which has to lead some thinking that temps at the surface could be a tad colder then some of the other guidance at the surface.

12zeuro850mbTSLPNA048

12zeuro850mbTSLPNA072

12 Z ECM is probably the model that has made the biggest turn around since last night. It brought little less then .25 QPF to ABE for example and today at 12 Z it brings 1.40 QPF to ABE with marginal temperatures of 32-34 and 850s generally cold enough for an all frozen event N & W of the city.

So with the 12 Z guidance what we have is the GFS that would be marginable with snow/sleet N & W and wintery mix rain in the big cities.

UKMET would be rain in the big cities with snow inland N & W…

ECM would be snow and sleet N & W with wintery mix/rain in the big cities.

GGEM would be snow/sleet N + W and wintery mix in the big cities.

Now..another word of caution is the ECM ensemble means. These are reputably the better performing model ensembles that outperform all other models including the OP ECM…if the ECM ensemble means were to be correct..

12zecmwfens850mbTSLPNA048

12zecmwfens850mbTSLPNA072

Then we may have to push some of the heavier amounts to the SE into the big cities. Not enough evidence for this at this point and time.

So we have taken a blend of the models and what they show above and put together a preliminary map ..so that people know ahead of time that this could be impacting the region with heavy snows and rains as well as strong gusty winds…

CURRENTFORECASTIMAGE1-9

Again this is very preliminary and refer to the special Note at the top of this post.

Stay tuned for further updates and if necessary updates to the level of Alert.

Monday, March 28, 2011

April 1st Time Period-Consensus?

We have been talking about this time period for some time now. I actually think we were the first probably to start talking about this system and its potential based on the Heather A signal of the rising NAO from a negative state. We have been talking about the potential for a significant storm system along the east coast due to this signal in the teleconnections.

Some folks in the weather forecasting business have been saying things such as “Nothing supports a Major Storm” or perhaps “ or “consistency of a model does not matter”..

To those folks we would suggest researching Heather Archambault and study what she has found in reference to when the NAO is transitioning from negative to positive!

ITS ALSO BEEN NOTED BY HEATHER
ARCHAMBAULT THAT LARGE PRECIPITATION EVENTS OFTEN OCCUR DURING
PATTERN CHANGE

 

Perhaps this is something that they are not familiar with? Consistency in a model is also something that is very important. For example..You can not base a forecast on a model that at 00z calls for 1-2 feet of snow and at 12 Z now says an inch or less and then at 00z now says a wind driven rain storm. When forecasting the weather one has to take into consideration all the guidance available and then scour out those that do not make synoptic sense and are contrary to what teleconnections are in place and then to make that forecast take a blend of those models that do fit the bill. To do anything else is quite frankly WEATHER SUICIDE!

So with that out of the way lets look at the latest guidance..as of 12 Z and 18 Z.

slp19

slp20

First up is the UKMET. This model has been by far the most consistent model when it comes to showing a potent system effecting the east coast. It has been shifting east. However..it has not gone from showing a non event to an event or reverse. The consistency does not mean its correct ..however..the UKMET would definitely be representative of the type of event that Heather A talks about.

ngp10.prp.102.namer

ngp10.prp.108.namer

ngp10.prp.114.namer

Nogaps at 12 Z..there is no doubt about the NOGAPS and what it is showing. 850s are plenty cold enough and it as well is showing a potent storm system (sub 992) moving up and along the coast. As of 18 Z this model has gone well OTS. Often this model will do that on off hour runs..so we will have to see what the 00z model does later this evening.

12zeuro850mbTSLPNA072

12zeuro850mbTSLPUS096

(not sure what happened to this image)

12zeuro850mbTSLPNA120

Now..the 12 Z ECM seems to be showing two sustems within the 72 hr to 120 hr time frame. However…with system number 1..the QPF is quite paltry and surface temperatures are marginal at best ..but it seems to focus more on the wave at 72 hrs out (wed) then the latter wave for friday /sat.  At this present time it is the only model that is showing any measurable QPF with the wed/thurday event.

The next wave ..due to the first wave..deamplifies things and never pulls the baroclinic zone back in to allow the 2nd wave to effect the east coast.

Its ensemble means pretty much support the operational run but would argue for perhaps a more stronger system and west at 72 hrs . The means do show the second system from 96-120 hrs (the one the rest of the guidance focuses on) .

12zecmwfens850mbTSLPNA072

12zecmwfens850mbTSLPNA096

12zecmwfens850mbTSLPNA120

The problem with the operational ECM is its too much of a strung out system. Pretty weak area of low pressure not able to get organized due to what is mentioned above.

12zggem850mbTSLPp06072

12zggem850mbTSLPp06084

12 Z GGEM has the first wave going OTS or to the south and then OTS..

12zggem850mbTSLPp06096

12zggem850mbTSLPp06120

Second wave never really gets organized..generally because the trough is so broad and there are so many shortwaves within the flow that the model does not know what to focus on.

12zgfs850mbTSLPp06072

12zgfs850mbTSLPp06096

GFS @ 12 Z had two systems effect the region. Which is similar to what the ECM showed but the GFS was pretty cold overall and to the N & W of the major cities could argue for a wet snowfall. Then it had another system follow thru:

12zgfs850mbTSLPp06120

This followed up behind the previous low and was a fairly amped up system. Temperatures were fairly marginal.

Now the 18 Z GFS has changed its tune a little and no longer has two systems (like the 12 Z and the 12 Z ECM) but has one system.

18zgfs850mbTSLPp06072

18zgfs850mbTSLPp06084

18zgfs850mbTSLPp06096

This system forms over the southeast and essentially moves up the east coast along the coast. Pretty far west with its track but pretty well amped up and this causes the 850s and surface temperatures to remain pretty cold. Verbatim the 18 Z GFS delivers almost 1 inch of QPF to the ABE region which would support a wet snow event.

So there we have the break down of all the latest model guidance. The question still remains..will this be one system or will this be two systems within the time frame?

Well..if you believe the European Computer model there will be two systems ..one brings a shot of rain to the big cities on wed-thursday with snow further north possible and the other (operational) is  a non event..

Majority of your people that are following the weather are essentially hugging the ECM and that comes right down to the pro mets with various agencies such as the NWS…some private pro mets as well.

Here at R.W.S we recognize there is no such thing as hugging a model.

We see no reason to change our thinking of a significant system moving up along the east coast. That significant system will more then likely be the friday/saturday time frame in which at that time depending on what sector you are in could mean a significant wet snow storm ( Far N and W of I-95)  or if you are in the warm sector would imply flooding situation with some heavy rains. (along the immediate coast)

With striving for more accurate forecasts and it only being monday ..it would be foolish to start talking about amounts etc..However…chances are pretty good for a significant east coast system in this time frame.

Stay tuned for more information on this developing situation.

Sunday, March 27, 2011

Major Changes on the 18Z GFS-Similar to 00z ECM!

Perhaps to add more confusion to this already confusing forecast..the latest data on the 18 Z GFS comes out very similar to last nights 00z ECM. One difference being the heaviest QPF on the GFS is more to the east..

18zgfs850mbTSLPp06120

18zgfs850mbTSLPp06126

18zgfs850mbTSLPp06132

18zgfs850mbTSLPp06138

As you can see the GFS has switched gears and switched over to a Major Coastal storm forming and moving up along the coast as it deepens down to a sub 980 MB storm.  In our opinion a sub 980 mb storm should have more QPF associated with it on the western side of the system but those details will be ironed out as we head closer to the potential event.

Now lets look at the means of the GFS..

18zgfsensemblep12120

18zgfsensemblep12132

18zgfsensemblep12144

Very strong signal on the GFS means for a significant Nor Ester.

Now, people are starting to ask “Well when does the 18 Z GFS ever come true?” Well first of all lets look at the ECM means to answer this question:

12zecmwfens850mbTSLPNA096

12zecmwfens850mbTSLPNA120

12zecmwfens850mbTSLPNA144

You can see that the ECM has system #1 at 96 hours and it has a follow up system at 120 hrs that moves up the coast. These ensemble means give credence towards the 18 Z GFS & its means and being that the OP ECM essentially lost the 2nd system..& its means has it…we generally expect tonights 00z ECM to go back to a solution quite similar to last nights run.

The potential does exist for this storm to drop some heavy rains and snows across the region. It is still to early to determine where the rain snow line sets up and whom will get what..

Stay tuned for more information on this developing late winter storm!