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Weekend Storm Discussion Part II, 2/18-2/19


stormtracker

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I kind of discussed it to you in post 720 ;)http://www.americanw...ost__p__1381549

But in short, how moist convection develops across the warm sector in positive tilt waves can have large influences in how energy is distributed during cyclone development. Large MCS's that develop along the warm front can displace large amounts of energy away from the cyclone center/upper shortwave/anomaly which can inhibit northward moisture transport as well as change advective processes which also play a role in cyclone development. Negative tilt troughs/waves are not affected nearly as much in a negative manner like this, and in fact, usually are enhanced by the presence of deep, moist convection since it has a tendency to "feed" directly into the upper cyclone which results in rapid intensification/bombing.

In case anyone is reading who wants a primer on these terms, this may help:

http://www.theweathe.../habyhints/127/

or

http://www.usatoday.com/weather/tg/wtrough/wnegtilt.htm

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Here's a snippet from HPC's latest discussions:

"

HOWEVER...MUCH UNCERTAINTY REMAINS...INCLUDING THE

INITIALIZATION/BEHAVIOR/EVOLUTION OF SEVERAL SMALL-SCALE SHORTWAVE

TROUGHS ACROSS THE NORTHERN PORTIONS OF THE CONUS AND SOUTHERN

CANADA...WHICH WILL HAVE A DIRECT BEARING ON THE PRECISE

TRACK/DEPTH OF THE LOW. ADDITIONALLY...MUCH IS UNCLEAR ABOUT THE

ANTICIPATED QPF AND INFLUENCE FROM CONVECTIVE PROCESSES AND

ACCOMPANYING NORTHWARD MOISTURE FLUX FROM THE GULF OF MEXICO. IN

SUMMARY...THE ACCOMPANYING SPLIT-FLOW REGIME APPEARS TO HAVE

LIMITED PREDICTABILITY

...AND AS SUCH...A DETERMINISTIC CONSENSUS THAT MAXIMIZES THE USE

OF HIGHER SPATIAL RESOLUTION WHILE PROVIDING MULTIPLE DYNAMICAL

CORES/MODEL PHYSICS PACKAGES TO INCREASE THE DISPERSION...SEEMS

MOST PRUDENT. THIS APPROACH IS BEST APPROXIMATED BY THE 12Z

GFS...AND IS SUPPORTED BY THE GFS/ECMWF ENSEMBLE MEANS...ALBEIT

WITH LESS DEFINITION. REFER TO THE QPFPFD AND QPFHSD FOR MORE

INFORMATION ON QPF AND WINTER WEATHER PREFERENCES.

CONFIDENCE: ABOVE AVERAGE ON TRACK...BUT BELOW AVERAGE ON TIMING"

http://www.hpc.ncep.noaa.gov/discussions/hpcdiscussions.php?disc=pmdhmd

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Help a dummy out here. What are they saying?

Here's a snippet from HPC's latest discussions:

"

HOWEVER...MUCH UNCERTAINTY REMAINS...INCLUDING THE

INITIALIZATION/BEHAVIOR/EVOLUTION OF SEVERAL SMALL-SCALE SHORTWAVE

TROUGHS ACROSS THE NORTHERN PORTIONS OF THE CONUS AND SOUTHERN

CANADA...WHICH WILL HAVE A DIRECT BEARING ON THE PRECISE

TRACK/DEPTH OF THE LOW. ADDITIONALLY...MUCH IS UNCLEAR ABOUT THE

ANTICIPATED QPF AND INFLUENCE FROM CONVECTIVE PROCESSES AND

ACCOMPANYING NORTHWARD MOISTURE FLUX FROM THE GULF OF MEXICO. IN

SUMMARY...THE ACCOMPANYING SPLIT-FLOW REGIME APPEARS TO HAVE

LIMITED PREDICTABILITY

...AND AS SUCH...A DETERMINISTIC CONSENSUS THAT MAXIMIZES THE USE

OF HIGHER SPATIAL RESOLUTION WHILE PROVIDING MULTIPLE DYNAMICAL

CORES/MODEL PHYSICS PACKAGES TO INCREASE THE DISPERSION...SEEMS

MOST PRUDENT. THIS APPROACH IS BEST APPROXIMATED BY THE 12Z

GFS...AND IS SUPPORTED BY THE GFS/ECMWF ENSEMBLE MEANS...ALBEIT

WITH LESS DEFINITION. REFER TO THE QPFPFD AND QPFHSD FOR MORE

INFORMATION ON QPF AND WINTER WEATHER PREFERENCES.

CONFIDENCE: ABOVE AVERAGE ON TRACK...BUT BELOW AVERAGE ON TIMING"

http://www.hpc.ncep....php?disc=pmdhmd

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Help a dummy out here. What are they saying?

In extremely simple terms, there are alot of small features in the atmosphere in this setup. Small shifts with any of them can cause large changes in the modeled evolution of the storm. Not getting everything just right at initialization of the model run can exaggerate the error as you go forward in time. Error is probably a bad term to use because it's very difficult (or impossible) to replicate the atmosphere perfectly when initializing a model run.

Think of it like an NCAA basketball pool. It's incredibly hard to pick all the winners in the field when there are 64 teams. It's much easier to get the final right. The current pattern has 64 teams.

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I kind of discussed it to you in post 720 ;)http://www.americanw...ost__p__1381549

But in short, how moist convection develops across the warm sector in positive tilt waves can have large influences in how energy is distributed during cyclone development. Large MCS's that develop along the warm front can displace large amounts of energy away from the cyclone center/upper shortwave/anomaly which can inhibit northward moisture transport as well as change advective processes which also play a role in cyclone development. Negative tilt troughs/waves are not affected nearly as much in a negative manner like this, and in fact, usually are enhanced by the presence of deep, moist convection since it has a tendency to "feed" directly into the upper cyclone which results in rapid intensification/bombing.

Good post. Model MCS in the wrong place can also screw things up in terms of how fast the storm translates ewrd.

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there is hope for you guys

* IMPORTANT COMMENT ON EURO 12Z EMSEMBLE ** it is WETTER and has 0.25" as far north as md pa border and its cold with a lot of heavy precip over central and eastern VA 7PM Sunday evening-- all of it snow

I don't know where he is getting that. Earthsat is only out to 36

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