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OKpowdah

Moderator Meteorologist
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Everything posted by OKpowdah

  1. OKpowdah

    January 2014 pattern discussion

    Over-amplifies literally every single trough that digs from the Plains to SE. Every time, I swear.
  2. OKpowdah

    January 2014 pattern discussion

    That's not just an extreme cold outbreak, that has longevity followed by activity in the stratosphere that would lock that in place into February, with storm potential all the while. Probably would be talking about a very extensive snow pack east of the Rockies ...with the related positive feedback into supporting arctic surface temperatures.
  3. OKpowdah

    January Forecast Discussion

    Absolutely. And your emphasis of the importance of the PV enlongation is spot on. That's when we can actually get some real perturbations on the flow
  4. OKpowdah

    January Forecast Discussion

    It'll snow. It'll snow more in February
  5. OKpowdah

    January Forecast Discussion

    For a downwelling SSW, true -NAO blocking develops in February
  6. OKpowdah

    January Forecast Discussion

    Great discussion! Only issue I have with getting excited for big snow storms in this pattern is the lack of true blocking over the N Atl to Greenland. Heights rise over N Greenland but we're maintaining this N Atl ridge pattern. So we drop this anomalous trough into the eastern US, up against the ridge, and upper level winds are screaming from the S/SW. Certainly a baroclinic environment, and the monster ridge in the west favors amplifying disturbances, so east coast cyclogenesis potential looks great. But without more of a block to the NE, looks like a pattern that'll have 980mb lows zipping by with 6 hours of snow. Granted that can easily be a 10" storm, but in the great quest for a MECS, I would want more blocking.
  7. OKpowdah

    January 2014 pattern discussion

    lol seriously, that's what you need. A nice STJ connection, boom. Especially once ridging bridges across Greenland and the Baffin Island in early February
  8. OKpowdah

    January 2014 pattern discussion

    I love at hr312, with no blocking in the Atlantic, surface low tracks north of New England, and it's all warm conveyor belt precip running over the cold front. And still it's all snow for most people. Just imbedded in the arctic air.
  9. OKpowdah

    Winter 2013-14 medium range discussion

    Yeah honestly even if ridging retrogrades over Greenland, that Atlantic ridge isn't going anywhere. It'll just be raging southerlies over the western Atlantic at 500mb.
  10. The loading patterns of various teleconnections (like EPO, NAO, PNA, etc) are based on the leading modes of variability over a specific domain (could be the Northern Hemisphere, Pacific+North America domain, Atlantic domain, etc). This is done through computing the EOFs of 500mb height (or SLP) climatology. So then to calculate the daily index value, you project the daily 500mb height pattern onto the loading pattern. So basically when the current pattern matches the loading pattern, the projection will be positive, and when the current pattern is opposite the loading pattern, the projection will be negative.
  11. Highest GOA heights, but that's not the loading pattern for the EPO http://www.esrl.noaa.gov/psd/forecasts/reforecast2/teleconn/images/epo.composite.gif
  12. I figured we could use a thread to post general obs and short term discussion in the southern / central Plains area. Basically a thread to cover the garden variety slight risk days, so we don't clutter the long range thread with that stuff. SPC has a slight risk up for most of Oklahoma for late today and tonight. Last update included a small 30% hail area. DAY 1 CONVECTIVE OUTLOOK NWS STORM PREDICTION CENTER NORMAN OK 1118 AM CDT FRI APR 26 2013 VALID 261630Z - 271200Z ...THERE IS A SLGT RISK OF SVR TSTMS LATE THIS AFTERNOON THROUGH TONIGHT ACROSS MUCH OF OK... ...OK... MORNING WATER VAPOR LOOPS SHOW A WELL-DEFINED SHORTWAVE TROUGH OVER EASTERN NM AND THE TX PANHANDLE. THIS FEATURE WILL TRACK EASTWARD AND ACROSS THE SOUTHERN PLAINS TODAY INTO TONIGHT. AHEAD OF THE TROUGH...SOUTHERLY LOW LEVEL WINDS ARE TRANSPORTING MOISTURE NORTHWARD ACROSS TX/OK WITH DEWPOINTS RISING THROUGH THE 50S. LOW CLOUDS ARE SLOWLY ERODING OVER WESTERN OK AND WESTERN NORTH TX...BUT ARE LIKELY TO PERSIST MOST OF THE DAY OVER THE BULK OF OK. THIS WILL LIMIT DAYTIME HEATING AND KEEP A SUBSTANTIAL CAPPING INVERSION IN PLACE THROUGH 00Z. BY EARLY EVENING...LIFT ASSOCIATED WITH THE NM/TX TROUGH WILL OVERSPREAD THE MOIST AXIS OVER OK. LARGE SCALE ASCENT WILL LIKELY RESULT IN A RAPID WEAKENING OF THE CAP AND SCATTERED THUNDERSTORM DEVELOPMENT OVER NORTHWEST AND CENTRAL OK. FORECAST SOUNDINGS SHOW STEEP MID LEVEL LAPSE RATES AND ELEVATED MUCAPE VALUES OF 1500+ J/KG. FAVORABLE EFFECTIVE SHEAR VALUES WILL PROMOTE SUPERCELL STORM STRUCTURES CAPABLE OF HAIL. WHILE DAMAGING WINDS AND TORNADOES ARE NOT OUT OF THE QUESTION...IT APPEARS THAT LARGE HAIL WILL BE THE MAIN THREAT TODAY. THE SUITE OF STORM-SCALE MODEL SOLUTIONS THIS MORNING /NAM NESTS...NMM...NSSL...HRRR/ SHOW STRONG AGREEMENT IN A NARROW CORRIDOR OF GREATEST RISK OF SUPERCELL STORMS THIS EVENING AFTER 00Z. THIS AREA OF WESTERN/CENTRAL OK HAVE BEEN INCLUDED IN A 30 PERCENT HAIL RISK. ..HART/GARNER.. 04/26/2013 Here's the impulse on water vapor: 12z sounding from Norman:
  13. OKpowdah

    Emerging signal for storminess Jan 6-8

    Rain has flashed over to heavy snow in Keene,NH! Thick fog of flakes right now.
  14. OKpowdah

    Winter 2013-14 medium range discussion

    The wave 1 response has been a little stronger than I was seeing forecast. Hence the warming in the far upper reaches of the stratosphere right now. But it won't be enough to get things going. But we maintain this wave 2 amplitude for a while, keeping the vortex stretched across the pole, with notable mid latitude heat flux. I think better potential for a SSW in mid February. Also supported by the QBO easterly shear zone dropping to around 30mb in February. This phase in February and March is statistically most favorable for a negative AO. 2006-7 is a really interesting analog for comparison. First, generally cold vortex sticking near the pole, with the same MQI phase. December 2006 to early January saw similar small preliminary disruption of the stratospheric polar vortex. The MAJOR difference being that the PV slid to the other side of the pole. It's actually really really cool. So the 500mb pattern is IDENTICAL over the North Atlantic and Europe (+NAO with cold vortex), and completely OPPOSITE over the Gulf of Alaska up through the Bering Strait. Well we saw what a massive difference that made in terms of sensible weather over the US!! Anyway, we know how the AO turned on a dime in the second half of winter in 2007. As I said, I think that flip looks good this winter too.
  15. OKpowdah

    December pattern discussion, part II

    Anyone notice the 1068mb+ high, with -40F 2m temps working south over the Rockies at hr300 on the 00z GFS pic.twitter.com/6yTD0BQyig
  16. Anyone notice the 1068mb+ high, with -40F 2m temps working south over the Rockies at hr300 on the 00z GFS pic.twitter.com/6yTD0BQyig
  17. OKpowdah

    December pattern discussion, part II

    This could be explained by the fact that a positive AO (or high index annular mode) is basically amplified climatology, whereas a negative AO can be more significantly anomalous from the background state. Can this be replicated in ENSO data? Tend to get slightly more extreme El Ninos than we do La Ninas. Of course all this is based upon the methodology of how we measure these oscillations.
  18. OKpowdah

    December 17th Clipper Discussion

    Disagree. HRRR especially is trimming back every run. 3-5" looks good to me with a few spots hitting 6" in eastern NH / NE MA.
  19. OKpowdah

    December 17th Clipper Discussion

    HRRR keeps getting a little faster / less amplified.
  20. OKpowdah

    December 17th Clipper Discussion

    I have to get from MHT to Keene at 930pm tomorrow. Little worried just because these systems can easily become over-performers. All it takes is a little sharper shortwave initially, and things take off on the coast quickly. GFS is definitely the sharpest, because it doesn't have that lead impulse at all, for some reason. NAM uses the lead impulse in a big way, but QPF bias applies.
  21. OKpowdah

    Dec 14/15 winter storm Obs

    There's your forcing for that mega band moving north from CT into MA now. 0-3km SRH >2000J/kg = very strong WAA pic.twitter.com/TDdINq3hTD
  22. Has been a pretty clearly understood relationship, but here's what I've found with my re-definition of the QBO in phase space: Phase -90 corresponds to an easterly QBO and phase +90 corresponds to a westerly QBO. Notice that the strongest association to a -AO occurs not at the QBO min, but actually closer to the easterly shear phase. Same with a +AO, the strongest association is closer to the westerly shear phase
  23. OKpowdah

    Winter 2013-14 medium range discussion

    Except when it comes to highly amplified disturbances, which is really when you're concerned anyway if you want big snow. Pacific is great in dictating the arctic connection to the US, but the Atlantic dictates the evolution of s/w's across the US ... do they break into the Great Lakes, or does downstream forcing trump nonlinear growth.
  24. The divergent wave activity vectors over the central Pacific are associated with wavebreaking. In this case there is cyclonic wave breaking over the central Pacific which is the beginning of the new wave train across North America and the pattern change this week.
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