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Do We have one More in Us?


Damage In Tolland

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Holy fook what a bomb Jerry... Had to break my weeks-long silence

Just about every run of the Euro and GFS along with ensembles for past 36 hrs showing this... We haven't had a signal like this for a while.

Box seems confident of some snow though waiting for pacific energy to reach West coast.

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Definitely looks like convective feedback issues on the 00z CMC. Similar to the 12z ECMWF it spontaneously develops of a 500 hPa vorticity maxima from an MCS that develops off the southeast coast. Be very weary of these types of solutions since global models like the CMC and ECMWF are within the "no mans land" resolution wise when it comes to resolving convective features. We still need convective parameterization to resolve convection properly, yet we are getting to the point where the resolution in the models is high enough that we can resolve some convection without the need of parameterizations. Thus in some cases, convection gets over accounted for by the parameterization and you get the simulation overproducing precipitation, leading to positive feedback (more height falls, stronger trough, more forcing for lift ect.)

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Definitely looks like convective feedback issues on the 00z CMC. Similar to the 12z ECMWF it spontaneously develops of a 500 hPa vorticity maxima from an MCS that develops off the southeast coast. Be very weary of these types of solutions since global models like the CMC and ECMWF are within the "no mans land" resolution wise when it comes to resolving convective features. We still need convective parameterization to resolve convection properly, yet we are getting to the point where the resolution in the models is high enough that we can resolve some convection without the need of parameterizations. Thus in some cases, convection gets over accounted for by the parameterization and you get the simulation overproducing precipitation, leading to positive feedback (more height falls, stronger trough, more forcing for lift ect.)

 

 

I wish we had mets like you in our sub forum..

 

Good luck guys!

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Definitely looks like convective feedback issues on the 00z CMC. Similar to the 12z ECMWF it spontaneously develops of a 500 hPa vorticity maxima from an MCS that develops off the southeast coast. Be very weary of these types of solutions since global models like the CMC and ECMWF are within the "no mans land" resolution wise when it comes to resolving convective features. We still need convective parameterization to resolve convection properly, yet we are getting to the point where the resolution in the models is high enough that we can resolve some convection without the need of parameterizations. Thus in some cases, convection gets over accounted for by the parameterization and you get the simulation overproducing precipitation, leading to positive feedback (more height falls, stronger trough, more forcing for lift ect.)

 

I was looking at this too- but interestingly enough, there are very similar signatures in particular runs from both the European and GFS deterministic runs. Looking at vertical motion, it does appear that there will be strong lift over New England during the time where the GEM produces that intense precip band. It'll be interesting to see what the RPM does with this beast when it gets into the right time-window. I'm not a fan of the two discrete areas of precip in the GEM though- looks odd. 

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Currently, models are pushing the main low track Slightly westward of prior positions on each successive model run. I use my own in-house contour model to map out the probability of the low center passing over specific areas. This is what has happened over the past few runs ( probability percentages are deduces from taking the median number at bottom of legend and multiplying by 10):

 

This image was from this morning's run of the American model (GFS 06z 3/21/2014) And showed progress to the west of low track probability from the previous contour initialization:

 

http://weather-talk.net/32614-storm-track-probabilities-updated-3212014/

 

Prior initialization of this model probabilities are included in the tabs area.

 

 

As you can see this run was a bit more east than this morning's model run. The percentages of the low making it near the benchmark 70/40 position are increasing as time continues to tick away. Even the National Weather Service has issued a statement concerning the "bomb" likely passing just shy of the 70/40 per model guidance. Even though this is likely to change in one direction or the other, it is interesting to see such a powerful cyclone developing. Typical of March, these monster storms typically skirt out to sea to our south, or track a bit farther inland, like the 1993 superstorm.

 

make no mistake, this is not a history lesson, nor is it to educate your folks who already know this information. this is to point out a very real and credible threat of a powerful storm moving close enough to New England on the 26th to give some headaches at best, and a massive blizzard at worst.

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Days and days and days and day....................

 

Quite the breeze overnight.

 

30.4/22

Agreed, plenty of time to watch the dynamics of this one. I never base a storm days out on model position. I look at 500mb, wind direction, and 850mb temps. Probabably the only model data I ever want to use.

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Definitely looks like convective feedback issues on the 00z CMC. Similar to the 12z ECMWF it spontaneously develops of a 500 hPa vorticity maxima from an MCS that develops off the southeast coast. Be very weary of these types of solutions since global models like the CMC and ECMWF are within the "no mans land" resolution wise when it comes to resolving convective features. We still need convective parameterization to resolve convection properly, yet we are getting to the point where the resolution in the models is high enough that we can resolve some convection without the need of parameterizations. Thus in some cases, convection gets over accounted for by the parameterization and you get the simulation overproducing precipitation, leading to positive feedback (more height falls, stronger trough, more forcing for lift ect.)

 

For the ECMWF, the convective scheme is coupled with the larger scale so changes in stability and surface fluxes from the "non-convective" part (even due to the fake "convection" produced by higher resolution) of the generated precipitation will lower the amount of precipitation (or cloud base mass flux) produced by the convective scheme.

 

This document has more information about the ECMWF convective scheme.

http://www.ecmwf.int/newsevents/training/lecture_notes/pdf_files/PARAM/Atmospheric_moist_convection_v9_Bechtold.pdf

 

I think a bigger issue may be the parametrization of ice production in the clouds, which is poorly understood and which the models are highly sensitive to. An error in the bulk ice growth could then lead to erroneous convective feedback.

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