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Severe WX January 10-12, 2020 Severe Weather Forecast Thread

As expected, NAM is already underdoing sfc temps by 4-6 degrees across North AL, and that is with this morning's CURRENT 12z run. Runs 2-3 days ago were underdoing temps here by about 10-15 degrees.

This event is going to be a HARSH lesson for anyone who takes the NAM thermos at face value and wrote it off...
 
rolltide_130 said:
As expected, NAM is already underdoing sfc temps by 4-6 degrees across North AL, and that is with this morning's CURRENT 12z run. Runs 2-3 days ago were underdoing temps here by about 10-15 degrees.

This event is going to be a HARSH lesson for anyone who takes the NAM thermos at face value and wrote it off...
Click to expand...
It works the other way too, I remember non events that the NAM was overboard on CAPE.
 
Blue box out, first of the year. I wonder why the watch issuance and expiration times are being shown in CDT when we're on standard time? It's not even 8:45 AM yet.

Storm Prediction Center Tornado Watch 1

Severe weather, tornado, thunderstorm, fire weather, storm report, tornado watch, severe thunderstorm watch, mesoscale discussion, convective outlook products from the Storm Prediction Center.
www.spc.noaa.gov
 
Richardjacks said:
It works the other way too, I remember non events that the NAM was overboard on CAPE.
Click to expand...

That won't be the case this time however. A lot of those events where the NAM is overboard on CAPE is due to heavy rainfall early in the day over the risk area and not weaker WAA than advertised, and those heavy rainfall events are due to issues in the synoptic setup as a whole.

This is an absolutely pristine setup for uninterrupted WAA starting this afternoon and continuing into tomorrow.
 
Richardjacks said:
It works the other way too, I remember non events that the NAM was overboard on CAPE.
Click to expand...

Right. I am more used to NAM being hypelord on CAPE and busting (although that might be a warm season thing). Although, my concern with this event was always more the wonky wind profiles being displayed on the NAM forecast soundings. Based on the 12Z observed sounding from FWD, wind profiles (so far) are verifying more favorable that it was forecasting. Any veer-backing is up around 200mb where it's not too much of a deal breaker for mesocyclone strength/longevity.

d7f3ba44cd55fb6bdb2e9ef905322445.png
 
Atlanta at 7pm Saturday. The hodograph seems to becoming a little more worrying.
 

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"An outbreak of severe thunderstorms is possible later today through
tonight, with the most dangerous portion being tonight into early
Saturday morning with a potential derecho and embedded strong
tornado risk. Primary changes this outlook are to expand the
Moderate Risk east across the Lower MS Valley and increase tornado
probabilities for the evening/overnight period."

SPC Day 1 Outlook

Severe weather, tornado, thunderstorm, fire weather, storm report, tornado watch, severe thunderstorm watch, mesoscale discussion, convective outlook products from the Storm Prediction Center.
www.spc.noaa.gov

Derecho and strong tornadoes - not going to be a fun weekend!
 
rolltide_130 said:
I'm not really understanding the extreme NAM bias you've displayed leading up to this event to be honest. The NAM has gotten SCHOOLED by the other CAM models in recent cool season events, and just like ahead of 12/16 it's already been proven to vastly underestimate the thermodynamic profile ahead of this system to our west, and that trend will continue into AL.

Only looking at the NAM thermos during cool season events is a surefire way to get unpleasantly surprised when the event you've spent the last few days grasping at straws trying to downplay in ways that defy basic meteorological logic suddenly pans out, and everyone but you was expecting it...
Click to expand...

How is that post showing any bias for any model. That was interpreting what the 3km NAM was showing, not agreeing or saying it was correct. Which is why I added I hate it.
 
rolltide_130 said:
I'm not really understanding the extreme NAM bias you've displayed leading up to this event to be honest. The NAM has gotten SCHOOLED by the other CAM models in recent cool season events, and just like ahead of 12/16 it's already been proven to vastly underestimate the thermodynamic profile ahead of this system to our west, and that trend will continue into AL.

Only looking at the NAM thermos during cool season events is a surefire way to get unpleasantly surprised when the event you've spent the last few days grasping at straws trying to downplay in ways that defy basic meteorological logic suddenly pans out, and everyone but you was expecting it...
Click to expand...

I'm trying to understand where all this NAM hate comes from. It's showing just about the same amount of surface Cape as the CAMs, in fact more than some of them.

sbcape.us_se.png


sbcape.us_se.png


sbcape.us_se.png


sbcape.us_se.png


sbcape.us_se.png
 
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