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RE: ForecastBuilder CRON - Always generates MaxTwAloft and ProbRefreezeSlee

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JM
Joseph Moore, modified 8 Years ago.

ForecastBuilder CRON - Always generates MaxTwAloft and ProbRefreezeSleet?

Youngling Posts: 72 Join Date: 11/1/13 Recent Posts

I've noticed that the ForecastBuilder CRON always generates MaxTwAloft and ProbRefreezeSleet throughout the entire Period 2 to Day 7 length. This seems to be in conflict with the ForecastBuilder/PoWT Methodology per the provided training, and against how we've been using PoWT in practice.

In the training, we're told to only generate a MaxTwAloft grid if a warm layer is expected aloft. Then, and only then, should there be a consideration about the possibility of sleet via ProbRefreezeSleet - a fairly rare case per the training videos.

Why is MaxTwAloft and ProbRefreezeSleet being generated on the CRON without any input from the forecaster or any regard for the actual presence of a warm layer aloft? To be meteorologically consistent shouldn't this be input "manually" through the period as the actual forecast conditions dictate? Otherwise this results in more complicated weather being generated when in fact it may not be possible and/or expected by the forecaster.

AJ
Andy Just, modified 8 Years ago.

RE: ForecastBuilder CRON - Always generates MaxTwAloft and ProbRefreezeSlee

Youngling Posts: 89 Join Date: 6/2/15 Recent Posts

Joseph,

  The MaxTwAloft and ProbRefreezeSleet are always generated for period 2 - day 3 if during the time period hourly temps are found < 40. These are needed to diagnose the environment for potential freezing rain/sleet scenarios. Additional code was added within the PoWT methodology last winter to allow for rain/snow scenarios given the presence of these grids, as well as scenarios where you have a cold rain situation (deep isothermal layer situation holding above zero).  Another reason they need to be populated is for consistency in SnowAmt/IceAccum. If some offices populated them and others did not, then you could get dramatic differences in SnowAmt/IceAccum due to % of QPF going to differing p-types.

  A fix is in place with the next ForecastBuilder release for the presence of the top-down grids beyond day 3.

 

JM
Joseph Moore, modified 8 Years ago.

RE: ForecastBuilder CRON - Always generates MaxTwAloft and ProbRefreezeSlee

Youngling Posts: 72 Join Date: 11/1/13 Recent Posts

Thanks for the reply, Andy!

So there was a change where it's now okay to have MaxTwAloft and ProbRefreezeSleet even if it's freezing rain/sleet are not expected? I wasn't aware of that - previously the training and my experience made me think that these grids should only be used when mixed precip beyond rain/snow is expected, since it can not only complicate the grid but also makes MergeWx slower.