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Mid January/Mid February Medium/Long Range Discussion


WinterWxLuvr
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1 minute ago, C.A.P.E. said:

This is probably as good a run as is possible for the coastal plain with this crappo setup, and it still produces only light snow. Thus why I have been out since the beginning.

I agree that we’re probably tracking a rainstorm at best, but it’s been interesting nonetheless.  

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4 minutes ago, Weather Will said:

WB GFS 18z....looks like we are close to a phase and a negative tilt....experts?

3A46E221-076E-427D-9D05-683832580842.png

I may not be that much of an expert (nor do I play one on TV, and have not stayed at a Holiday Inn Express)...but my 2 copper coins worth:  The "main" southern stream trough actually has a neutral tilt (aligned more or less north-south).  The northern stream energy up around WI is neutral to slightly positive tilt.  But it sure looks like it's getting close to phasing with the southern stream...which, if it did, would probably result in a closed off system that becomes negatively tilted.

(Note:  "positive" tilt, trough aligned more southwest-northeast in the flow..."negative" tilt, aligned northwest-southeast, and can become closed off..."neutral" tilt, aligned more north-south.  Generally speaking, a positively tilted trough is weaker, and the energy can tend to get sheared out.  A negative tilt or closed low implies a slow moving or intensifying system, or perhaps phasing if there's more than one stream...these tend to be much stronger.  A neutrally tilted trough is kind of, well, neutral or "in the middle", could imply a trough that's amplifying and potentially can become negatively tilted.)

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22 minutes ago, Weather Will said:

WB GFS 18z....looks like we are close to a phase and a negative tilt....experts?

3A46E221-076E-427D-9D05-683832580842.png

The separation of energy on this run is still too far apart for the MA. By the time the N/S vort catches up with the S/S vort, the phasing energy is too far to the east. The snow we see breaking out over WV is from strong PVA on the base of the trough coupled with upslope flow over the higher terrain. Wind direction shifts to the NW across the Piedmont as N/S finally makes its run at the S/S, but that provides a down-slope component locally, drying out the precip shield on the western side. In order for the area to be in game with the storm, you need the S/S vort to lag by 6-12 hrs, or for the N/S to speed up and promote phasing while the S/S energy pivots through western NC. It's all just too late for it impact the MA, and even most of the EC for that matter. Not until the Maritimes do you see the anchor set up and start pulling back to the NW. LI, Cape Cod, and Down-east Maine the only true beneficiaries. 

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1 minute ago, Ji said:

The ss vort was much stronger on this run and was able to produce an event without a phase

That was a positive takeaway for the run, but issue becomes when the winds shift west/northwest, down-sloping takes over and it all dries up quick. If that S/S vort can tilt negative or pass further to the northwest, more precip can be thrown back for the inevitable cutoff. 

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