March 25-26 Potential Bomb Part III

[earthlight]

So I'm going out on a limb here. I realize it's a lonely camp, and as such if I'm wrong I'm subject to getting my head chopped off. BUT, I have a sneaking suspicion we see a last minute trend west, beginning tonight. I have little to support this other than the drop off in the NAO over the next 2 days, which will be going from 1, approximately to 0.5; however, I believe this to be quite important. While this may not seem like much, the slowing down of the westerlies, may be enough to get this system to slow down to a point where it can get the positive feedback going faster at an earlier stage (lower latitude). In my experience, the models, in general, are notoriously behind shifts in the NAO. I'm not expecting anything significant for interior sections, but would not want to rule out a trend toward the BM. Coastal sections, namely LI, Eastern Conn, RI, and eastern Mass. should all stay vigilante imho. I do not have high confidence in this (for obvious reasons: model consensus etc.), it is just the way that I'm leaning at the moment.

 

I'm usually right there with you when it comes to western trends. I've seen forecast models completely crap the bed on situations similar to this especially the last several years. I don't know exactly what causes it, whether it be convective feedback, difficulty handling the baroclinic zone, or whatever -- but these storms just love to tuck in near the coast the past several years and I have been a huge preacher of that. I stayed up until 4am three days before Boxing Day arguing that it was coming west. 

 

But this one doesn't do it for me and it has nothing to do with dynamics, latent heat release or anything of the sort -- in fact it has to do with simple things going back to the height field orientation and jet positioning. The 500mb flow is simply oriented too much on a NW to SE trajectory on the eastern periphery of the west coast ridge for there to be any major trend toward amplification. The lead shortwave is not helping as it has continued to trend a bit flatter and faster, moving along the southeast trajectory into a generally flat flow over the Tennessee Valley.

 

 

The mid and upper level jets over the Mid Atlantic at that time are oriented from west to east and very unfavorable. It is not until the second shortwave and jet streak move in that the entire setup becomes more conducive for rapid strenghtening/development of the surface low. And unfortunately for us, that occurs just a hair too late once the storm has already passed our latitude.

 

There could be a westward trend at the last minute and I still don't think we would reap the benefits of it for these reasons. Just my two cents. 

[Weathergun]

250mb jet streak still too far east, for the storm to closer to the coast:

 

 

 

[IsentropicLift]

Going out on a limb here, something happened on the NAM between hours 48-51 at H5. Almost as if a piece of the vorticy broke off and escaped east. Then the whole low gets tugged east with it. Seems very strange to me considering the amount of phasing going on here. I thought for sure this run was going to nail SNE.

[user13]

250mb jet streak still too far east, for the storm to closer to the coast:

 

 

Yea our classic storms have it just under li

[SnoSki14]

Eastern areas should still keep an eye on it, the NAM did move it west somewhat. Still think a few inches are possible with the inverted trough but those are so hard to forecast. You usually don't even see it show up on the globals until immediate range. 

[PB GFI]

I'm usually right there with you when it comes to western trends. I've seen forecast models completely crap the bed on situations similar to this especially the last several years. I don't know exactly what causes it, whether it be convective feedback, difficulty handling the baroclinic zone, or whatever -- but these storms just love to tuck in near the coast the past several years and I have been a huge preacher of that. I stayed up until 4am three days before Boxing Day arguing that it was coming west. 

 

But this one doesn't do it for me and it has nothing to do with dynamics, latent heat release or anything of the sort -- in fact it has to do with simple things going back to the height field orientation and jet positioning. The 500mb flow is simply oriented too much on a NW to SE trajectory on the eastern periphery of the west coast ridge for there to be any major trend toward amplification. The lead shortwave is not helping as it has continued to trend a bit flatter and faster, moving along the southeast trajectory into a generally flat flow over the Tennessee Valley.

 

 

The mid and upper level jets over the Mid Atlantic at that time are oriented from west to east and very unfavorable. It is not until the second shortwave and jet streak move in that the entire setup becomes more conducive for rapid strenghtening/development of the surface low. And unfortunately for us, that occurs just a hair too late once the storm has already passed our latitude.

 

There could be a westward trend at the last minute and I still don't think we would reap the benefits of it for these reasons. Just my two cents. 

John , If there`s a further correction west  , its between 48 and 54 hours  look at the  18z  between 54 and 60  hours the center corrects 100 miles west  .

Is the models 1st attempt to not send the center out over the top of the convection ? but keep it closer and ride the arctic front .

 

Centers sometimes off OBX let the best convection run off  only to separate itself and deepen NE .

We`ve so many times centers early on get modeled to run east with the convection , only to let Them release east .

I am not saying this comes really far west , but I  would like to see the rest of the suite to see if the NAM is showing us something .

Maybe its nothing , but it didn't run the center to Bermuda , so one last shot may be In the cards . IF not then I will fold up shop .

[NYC Weather Lover]

Just saw Craig Allen, and he showed the RPM model. I'm sorry but the the model has to be somewhat reliable if TV mets use it to inform the public. If it's not reliable then why don't meteorologists use the European or GFS model to inform the public?

[IsentropicLift]

The 4k NAM brushed the coast with the developing CCB.

[WintersGrasp]

NAM would be 20-35" for extreme eastern ME to Nova Scotia

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[earthlight]

John , If there`s a further correction west  , its between 48 and 54 hours  look at the  18z  between 54 and 60  hours the center corrects 100 miles west  .

Is the models 1st attempt to not send the center out over the top of the convection ? but keep it closer and ride the arctic front .

 

Centers sometimes off OBX let the best convection run off  only to separate itself and deepen NE .

We`ve so many times centers early on get modeled to run east with the convection , only to let Them release east .

I am not saying this comes really far west , but I  would like to see the rest of the suite to see if the NAM is showing us something .

Maybe its nothing , but it didn't run the center to Bermuda , so one last shot may be In the cards . IF not then I will fold up shop .

 

I think it would have to happen earlier than that actually...from 30 to 36hours when the surface low develops a few hundred miles off the southeast coast. That needs to be changed completely but it won't be unless there is a significant model error in all regards, mainly including the mid and upper level jet positioning. There will always be convection when you have a developing surface low and incoming vort..and I don't think that is attributing to the model being too far east. 

 

Here is where you need a correction. The surface low is way too far east for us and the mid level flow too flat. 

 

[IsentropicLift]

I want to see the GFS/GGEM bump NW. That will raise an eyebrow.

[user13]

Going out on a limb here, something happened on the NAM between hours 48-51 at H5. Almost as if a piece of the vorticy broke off and escaped east. Then the whole low gets tugged east with it. Seems very strange to me considering the amount of phasing going on here. I thought for sure this run was going to nail SNE.

That seems to be connected to the thunderstorms at the surface...If they fire up any differently than modeled the surface low could initially be further north

[earthlight]

I want to see the GFS/GGEM bump NW. That will raise an eyebrow.

 

This thing doesn't close off at 500mb on any model until its in the Gulf of Maine...and the initial surface low develops 100-200 miles too far east off the Southeast US Coast. A bump NW doesn't help. We need a significant change in the modeled mid level interactions and upper level jet structure. 

[Mitchel Volk]

The reason for the vorciticy jump is the the eastern low is developing up to the 500 MB level very quickly. I still think NYC will only see some snow showers with little or no accumulations. The ECMWF has way to much QPF, it is doing the same thing the it did with the other misses to our south. We are in a more standard NYC pattern where the models look promising but it just not happen. Earlier this winter were very lucky until the middle of February. Then we went to a standard cold pattern for NYC. The positive NAO Pattern is the main reason why we are not getting any blockbusters lately.

[user13]

This thing doesn't close off at 500mb on any model until its in the Gulf of Maine...and the initial surface low develops 100-200 miles too far east off the Southeast US Coast. A bump NW doesn't help. We need a significant change in the modeled mid level interactions and upper level jet structure. 

Any chance the actual surface low forms near the convection off the SC coast and the models are just seeing a very intense mesoscale low?

[ag3]

Looking at the Rgem 700rh maps, it appears it's forming a nice trough at hour 48.

[ag3]

This is somewhat intriguing:

[Weathergun]

Any chance the actual surface low forms near the convection off the SC coast and the models are just seeing a very intense mesoscale low?

Slp develops where 925mb Theta-E advection is strong:

 

[ag3]

Double barrel low showing up on the Rgem:

[Isotherm]

The reason for the vorciticy jump is the the eastern low is developing up to the 500 MB level very quickly. I still think NYC will only see some snow showers with little or no accumulations. The ECMWF has way to much QPF, it is doing the same thing the it did with the other misses to our south. We are in a more standard NYC pattern where the models look promising but it just not happen. Earlier this winter were very lucky until the middle of February. Then we went to a standard cold pattern for NYC. The positive NAO Pattern is the main reason why we are not getting any blockbusters lately.

 

 

The problem with the previous storm this month and the upcoming one as well is mostly related to the PNA ridge being progressive and de-amplifying too quickly in my view. And this is due to the recent more progressive north pacific pattern with short waves crashing into the NW US, thereby shifting the entire downstream ridge / trough pattern too far east. The last missed storm was due to the PNA ridge rolling over and preventing energy from ejecting (due again to an active flow into the NW US). This storm will have a more meridional pattern but again it could be slightly too progressive. I don't believe the real issue is with the NAO/Atlantic with the current situation. Some east based blocking could have helped slow the upper flow for sure, but the PNA spike now is not as impressive as we saw for a couple events this winter.

 

Back on January 22 we had a very favorable western PNA ridge without a negative NAO. I disagree that we got "lucky" through mid February. Several events in early December and in February were related to the -EPO / +NAO induced gradient-baroclinic zone running through the SE US, and the January events were mostly due to an amplified western ridge which was slightly less progressive than the current pattern.

 

[user13]

Slp develops where 925mb Theta-E advection is strong:

 

Hmm thanks for that. Then I guess the question should can the EPT be skewed by really strong thunderstorms? Looking at the 4k it looks even more curious...

[PB GFI]

Hard to imagine it doesn't snow on Long Island looking at this .

 

[Isotherm]

The problem with the previous storm this month and the upcoming one as well is mostly related to the PNA ridge being progressive and de-amplifying too quickly in my view. And this is due to the recent more progressive north pacific pattern with short waves crashing into the NW US, thereby shifting the entire downstream ridge / trough pattern too far east. The last missed storm was due to the PNA ridge rolling over and preventing energy from ejecting (due again to an active flow into the NW US). This storm will have a more meridional pattern but again it could be slightly too progressive. I don't believe the real issue is with the NAO/Atlantic with the current situation. Some east based blocking could have helped slow the upper flow for sure, but the PNA spike now is not as impressive as we saw for a couple events this winter.

 

Back on January 22 we had a very favorable western PNA ridge without a negative NAO. I disagree that we got "lucky" through mid February. Several events in early December and in February were related to the -EPO / +NAO induced gradient-baroclinic zone running through the SE US, and the January events were mostly due to an amplified western ridge which was slightly less progressive than the current pattern.

 

 

 

 

In fact looking at the ECMWF ens H5 progression, east based -NAO blocking does develop immediately prior to this upcoming storm, with a connection of higher heights in the Scand. region / north of there. Overall, the pattern's a fairly conducive one for a storm developing, but the slightly too progressive PNA ridge could cause a near miss.

 

 

[ag3]

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[snow1]

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That's very light snow that won't accumulate.

[Overcast]

That's very light snow that won't accumulate.

Think its the double barrel low that is the attention grabber here.

[Sn0waddict]

That's very light snow that won't accumulate.

The low is still developing. A few panels later that would be a very good snowstorm for at the very least Eastern LI/CC

[PB GFI]

That's very light snow that won't accumulate.

Don't look at the precip - look at where at that SLP is early in the run .

[Ralph Wiggum]

.

Road trip to OC, MD?

[Isotherm]

That's very light snow that won't accumulate.

 

 

You're missing the point, it's a surface low pressure center rather than the inverted trough look. If it's correct, that's certainly something worth noting. The double barreled look has been hinted at by some guidance for several days. We'll see if it comes back or not.