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Plains Weather Discussion


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New 00z GFS still develops a secondary low. Gonna be interesting to watch.

It's more the primary low pressure, actually, as the UL energy translates eastward and induces leeside cyclogenesis, which then speeds NE and rapidly deepens as the associated vort max slows down and tightens due to the long wave trough being squeezed by the ridge on the east side.

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It's more the primary low pressure, actually, as the UL energy translates eastward and induces leeside cyclogenesis, which then speeds NE and rapidly deepens as the associated vort max slows down and tightens due to the long wave trough being squeezed by the ridge on the east side.

Yeah it deepens pretty intensely too. Impressive.

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New 00z GFS still develops a secondary low. Gonna be interesting to watch.

Definitely interesting... but instability looks meager, to say the least, if you believe the GFS thermodynamics. With the brunt of the cold air aloft sliding north and west of the warm sector, as usual, this isn't difficult to believe.

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Definitely interesting... but instability looks meager, to say the least, if you believe the GFS thermodynamics. With the brunt of the cold air aloft sliding north and west of the warm sector, as usual, this isn't difficult to believe.

For the Plains on Wednesday, I'm assuming you are referring to?

Also, that's a pretty big "if" you are highlighting there. :lol:

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DAY 4-8 CONVECTIVE OUTLOOK

NWS STORM PREDICTION CENTER NORMAN OK

0351 AM CDT SAT OCT 20 2012

VALID 231200Z - 281200Z

...DISCUSSION...

00Z ECMWF/GEFS/UKMET IMPLY THAT THE LONGWAVE PATTERN THROUGH THE

MIDDLE PART OF NEXT WEEK WILL GENERALLY BE CHARACTERIZED BY LONGWAVE

TROUGHING OVER THE WESTERN/NORTH-CENTRAL CONUS...ALTHOUGH THE EXACT

DEGREE OF AMPLIFICATION IS A BIT UNCERTAIN /00Z ECMWF REMAINS LESS

AMPLIFIED VS OTHER GUIDANCE/.

THE PRIMARY FOCUS FOR THE PERIOD WILL BE SEVERE POTENTIAL ON DAYS

5-6 WEDNESDAY/THURSDAY. AS AN UPPER TROUGH/COLD FRONT SHIFT EASTWARD

AND ENCOUNTER A RELATIVELY MOIST AUTUMNAL AIRMASS...ORGANIZED SEVERE

TSTMS COULD OCCUR ACROSS PORTIONS OF THE UPPER MIDWEST/MIDDLE MO

VALLEY ON DAY 5/WEDNESDAY...AND PERHAPS THE UPPER/MIDDLE MS VALLEY

AND LOWER MO VALLEY ON DAY 6/THURSDAY. WHILE AT LEAST SOME SEVERE

TSTMS ARE PROBABLE ON THESE DAYS PROVIDED SUFFICIENT

MOISTURE/INSTABILITY...GUIDANCE VARIABILITY REGARDING UPPER TROUGH

AMPLITUDE/TIMING PRECLUDES A DELINEATION OF ANY SPECIFIC SEVERE RISK

AREAS AT THIS TIME.

..GUYER.. 10/20/2012

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Still looks like we could see something, just not as far south and not as ominous.

Lots can still change, with such a large trough, there would be many embedded vort maxes and s/w that can easily be missed by the models, which can have huge impacts on how dynamic the resulting low level response can be.

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haha Euro at 240 is just awesome for the East Coast. What's it do, combine with a hurricane?

GGEM does at 192, Euro does not, just that amplifying eastern trough closes off and begins to lift northeastward (close to a Miller A track), there could be some kind of Fujiwara interaction as well.

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DAY 4-8 CONVECTIVE OUTLOOK

NWS STORM PREDICTION CENTER NORMAN OK

0358 AM CDT SUN OCT 21 2012

VALID 241200Z - 291200Z

..DISCUSSION

IN GOOD GENERAL AGREEMENT...00Z ECMWF/GEFS/UKMET IMPLY THAT THE

LONGWAVE PATTERN THROUGH THE MIDDLE/LATE PART OF THE WEEK WILL

GENERALLY BE CHARACTERIZED BY LONGWAVE TROUGHING OVER THE

WESTERN/NORTH-CENTRAL CONUS. A SUBSTANTIAL LEAD PORTION OF THIS

TROUGH IS EXPECTED TO STEADILY SPREAD NORTHEASTWARD FROM THE CENTRAL

ROCKIES TO THE NORTH-CENTRAL CONUS/CANADA BETWEEN DAYS 4-6

WEDNESDAY-FRIDAY...DRIVING A COLD FRONT EAST-SOUTHEASTWARD ACROSS

THE CENTRAL CONUS.

AS THIS UPPER TROUGH/COLD FRONT ENCOUNTER A RELATIVELY MOIST AIRMASS

FOR AUTUMN...AT LEAST SOME SEVERE TSTMS ARE PROBABLE ON DAYS 4-5

WEDNESDAY/THURSDAY. INITIALLY...ORGANIZED SEVERE TSTMS COULD OCCUR

ACROSS PORTIONS OF THE MIDDLE MO VALLEY/UPPER MIDWEST ON DAY

4/WEDNESDAY. CURRENT INDICATIONS ARE THAT THE SEVERE RISK COULD

SPREAD EASTWARD/POSSIBLY BECOME A BIT MORE WIDESPREAD INTO DAY

5/THURSDAY ACROSS THE MIDDLE/UPPER MS VALLEY...PERHAPS AS A

FAST-MOVING/LOW-TOPPED SQUALL LINE. WHILE AT LEAST SOME SEVERE TSTMS

ARE PROBABLE ON THESE DAYS PROVIDED SUFFICIENT

INSTABILITY...LINGERING GUIDANCE VARIABILITY REGARDING UPPER TROUGH

AMPLITUDE/TIMING AND THE EXACT DEGREE OF DESTABILIZATION PRECLUDE A

DELINEATION OF ANY SPECIFIC SEVERE RISK AREAS.

..GUYER.. 10/21/2012

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Based on solely the 00z NAM, the northern target looks interesting, but I'm not sold on a huge tornado threat. The moisture looks to be there and the instability will probably be more than sufficient, but I'm not loving the shear profile when the best instability is in place. EHI values are impressive, but the values seem to be inflated mainly because of the instability and not so much the helicity. 0-1 km helicity in Iowa is not very promising, but the 0-3 km is OK. Right now, everything looks fairly linear to me. The 850 vectors look great at 18z but start turning too much at 21z when the best ingredients are together. This system is a bit more interesting to me, northern Plains-wise, than the last one, however.

This has just been a quick cursory glance, however, as I refuse to look at these setups closely sooner than around 36-48 hours at this point, lol.

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