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The Big One - Forecast & Discussion


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Thanks Phil! (Didn't see the post in the other thread) I remember the 09 storm well. We have colder temps this time so that is encouraging. 

 

Yes colder temperatures will help... the snow in the 09 event was essentially cement with 6-8:1 ratios in incredibly heavy snowfall rates (not to mention thundersnow!). This event will have similar amounts yet with colder surface temperatures... a recipe for disaster. 

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First thing I noticed this morning was the GoM convection. That's always a red flag. However, I don't think it will necessarily play a big role in the Carolinas with this event. When the phasing occurs later today, we should see the area of precip in N AL and N GA really blossom nicely.

 

In fact, the RPM has the Gulf coast convection indicated very nicely in the runs this morning.... the eastward progress of the convection is just a little faster in reality than on the model. 

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First thing I noticed this morning was the GoM convection. That's always a red flag. However, I don't think it will necessarily play a big role in the Carolinas with this event. When the phasing occurs later today, we should see the area of precip in N AL and N GA really blossom nicely.

 

In fact, the RPM has the Gulf coast convection indicated very nicely in the runs this morning.... the eastward progress of the convection is just a little faster in reality than on the model. 

 

I agree Matthew, The convection is not going to play a big role in our area with this event. The system is moving right on schedule and I expect to see the radar beginning to fill in over the next few hours as the energy moves east, begins to strengthens, and the surface low begins to deepen.

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Here is the pre-eminent paper on this topic. http://journals.ametsoc.org/doi/pdf/10.1175/WAF986.1

 

What you look for is if the convection is moving out faster from the parent storm system then what the model is forecasting. In those events then the model is underestimating the impact of the stabilization on the atmosphere that the convection has and will most likley overpredict QPF.

 

And in the other hand if the convection is slower than what was modeled QPF downstream may end up being greater than modeled thanks to better moisture inflow.

 

Looks like the 12z NAM-4km to me is pretty close to what is going on and therefore its modeled QPF may be accurate.

 

This is a tricky topic and you cant just say just because there are storms in the gulf moisture is robbed. There are almost always storms in the Gulf with a southeast winter storm.

 

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Here is the pre-eminent paper on this topic. http://journals.ametsoc.org/doi/pdf/10.1175/WAF986.1

 

What you look for is if the convection is moving out faster from the parent storm system then what the model is forecasting. In those events then the model is underestimating the impact of the stabilization on the atmosphere that the convection has and will most likley overpredict QPF.

 

And in the other hand if the convection is slower than what was modeled QPF downstream may end up being greater than modeled thanks to better moisture inflow.

 

Looks like the 12z NAM-4km to me is pretty close to what is going on and therefore its modeled QPF may be accurate.

 

This is a tricky topic and you cant just say just because there are storms in the gulf moisture is robbed. There are almost always storms in the Gulf with a southeast winter storm.

 

Yep, when it is orientated NE-SW, it can actually enhance QPF downstream. Bottom line is I don't think it's a big concern this time around. But we will see.

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FWIW

 

The discussion earlier about the SLP track by the euro not being correct. Well its true. The SLP should remain completely offshore of Wilmington and Hatteras.

 

The primary LP is forming where Raleighwx(allan)  showed the pressure drops on the posted map.

The primary is in the GOM transferring to the secondary(which will be the primary) ESE of Jacksonville, FL.

 

 

post-7245-0-70547000-1392218577_thumb.gi

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Does that mean Atlanta turns out OK?

 

I believe so. I believe the lull is due to a slight delay in the energy rounding the base of the trough. It is just now occurring and will be helping the coastal storm strengthen. This will help to develop very heavy precipitation on the northwest side of the storm. The storm is just beginning for most as the upper level disturbance swings through.

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