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    Oklahoma City, OK

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  1. Severe potential 2/24

    Can't rule out QLCS tornadoes on Saturday, and/or a few embedded supercell structures, but the storm mode looks largely linear. Low level instability does not look as impressive as some of the more severe analogs and issues in the mid-level wind fields suggest the window for any discrete supercells will be minimal at best. Even the agressive 3km NAM shows a linear storm mode, with some cellular elements within the larger scale line. Essentially it shows no open warm sector activity, where the parameter space and backing of near-surface winds are maximized. A typical forecast sounding ahead of the line (late afternoon in southern/eastern Arkansas) looks like this: The 0-2km wind fields are quite favorable, but then above that it gets junky looking. With all of that said, such considerable low level shear, combined with seasonably impressive low-level moisture and <1km LCLs suggest an elevated potential for tornadoes, although they'll probably be short-lived and embedded within a line.
  2. November 5th, 2017 Severe Weather Event

    Not only are steep mid-level lapse rates noted across MO/IL, but the 12z SGF sounding sampled nearly dry adiabatic lapse rates from 800-550mb, supporting a mean 850-500mb LR of 7.8 C/km. Seasonably large CAPE profiles will easily be realized downstream as a result, even if there is only partial sunshine today from MO into central/southern IL.
  3. November 5th, 2017 Severe Weather Event

    Tornado potential will likely come down to storm mode and interactions. Two regimes will be favorable, assuming cell(s) can remain at least somewhat isolated. Midday through mid-afternoon favors central IN to western OH along an effective warm front/moisture gradient. Here, shear looks to be greatest, both in terms of stronger 0-2km flow and vectors being more orthogonal than points west. With that said, instability appears to be on the lower end of the spectrum, in the range of about 500-1000 J/kg. Cells may tend to outrun the favorable thermodynamic environment. Mid to late afternoon targets the southern third of IL and possibly into portions of eastern/southeastern MO. Model data and trends suggest unseasonably robust instability will develop immediately ahead of the frontal boundary, with 1500-2500 J/kg CAPE and dew-points in the upper 60s (a tick higher than IN/OH). With that said, angles created by the shear vectors and front will be smaller than points east, but will be conditionally favorable for tornadic supercells. It's one of those events where the ceiling is fairly high, but only if storms remain discrete. There is not much room for error, but one cannot help but be intrigued by this sort of parameter space in the region in November. One scenario features messy storm modes with too many storm scale interactions for a widespread tornado event. There could also be a rogue cell that either fires in the warm sector/near the warm front and goes to town. Cells along the western portion of the front will probably be at least semi-discrete to start, but if storm mode trends toward more isolated, watch out.
  4. November 5th, 2017 Severe Weather Event

    Very large hail is a big concern and a moderate risk for hail would not surprise me. Even the slightly less unstable HRRRX shows a CAPE/shear parameter space that would support very efficient hail growth. Very uncommon for this time of year. Some soundings I pulled showed 700-500mb lapse rates steeper than 8 C/km.
  5. November 5th, 2017 Severe Weather Event

    Can't really disagree with SPC much here. Even if tornado potential may be limited, wind fields and mid-level lapse rates suggest large to very large hail will be possible, supporting the enhanced risk.
  6. November 5th, 2017 Severe Weather Event

    The front looks generally quasi-stationary through late afternoon, outside of areas to the W/SW of central Illinois. There does seem to be a rapid surge closer to 00z. The warm front and triple point areas seem to be the most intriguing with respect to severe potential. Storm motions suggest that cells could ride along an effective warm front, but low level lapse rates continue to be a glaring concern. The 3km NAM also merges cells into a QLCS by early afternoon. No major changes from earlier thinking that this looks like a spotty hail event with a few isolated tornadoes possible. Also concur that early day storms could be possible prior to midday, especially in vicinity of the warm front.
  7. November 5th, 2017 Severe Weather Event

    I'm not sure if 11/14/11 was mentioned, but that seems to be a reasonable analog that doesn't lie on one extreme end of the spectrum. That involved a weak frontal wave moving across central IL/IN within several hail reports and a few isolated tornadoes. The kinematic and thermodynamic fields look similar to the progs for Sunday, although I will go back to the capping inversion (looks a bit more pronounced this go-around), which may ultimately limit or prevent open warm sector storm development. Nonetheless, watch the warm front and triple points for a relatively higher tornado potential. Wind fields become more unidirectional near the cold front, but even there a narrow window for semi-discrete storms may exist. Of course, this is an evolving forecast and things may change, but I think the below maps show a reasonable "estimate" of what we may be looking at for Sunday. A more wound up solution than the consensus could result in a more significant event.
  8. November 5th, 2017 Severe Weather Event

    Have to wonder if the NAM is onto something, or simply wrong. The 12z RGEM is at least 100 miles farther north with the low (northern MO) and warm sector (to the IN/MI border). The upcoming Euro will be very telling. If it continues to lean toward the NAM, then the northern solutions would seem to be increasingly unlikely.
  9. November 5th, 2017 Severe Weather Event

    For what it's worth, not only does the 12z GFS remain north, but the SREF mean is also a bit slower and farther northwest. Some of it may be a resolution issue, but it appears to keep areas as far north as Chicago in the warm sector, given dew-points and 10m wind vectors: SREF severe probabilities are also maximized from central IL into western IN.
  10. November 5th, 2017 Severe Weather Event

    Another potential issue here appears to be lapse rates in the 0-3km layer. Yes, mid to upper level lapse rates look very favorable, but forecast soundings show an inversion in the 850-750mb layer across Indiana and surrounding areas Sunday afternoon. A modest capping inversion could be a net positive in terms of discrete nature of storms, however, if the cap is too substantial, there won't be surface-based convection. The KIND forecast soundings at 21z Sunday from both the GFS and NAM show a sizable cap and meager 0-3km lapse rates of less than 6 C/km. Even at 00z, the low level lapse rates remain marginal and suggest there may be a significant lack of surface-based convection in the warm sector. Soundings farther west and north show similar issues. The NAM's forecast cap is actually more substantial than the GFS. (18z 11/2) It's certainly not a typical November setup. Cool air aloft contributes to steep 700-500mb lapse rates (>7.5 C/km), however unseasonably warm air in the 800-750mb layer creates an environment with marginal boundary layer instability and resultant surface-based convective inhibition. The 16z ILX sounding on 11/17/13 sampled 7.6 C/km 0-3km lapse rates. The only other thing to note here is that the warm frontal zone may be more favorable for tornadogenesis this time around than it was on 11/17/13, when the warm front was all the way up to northern Lower Michigan and featured poor instability and marginal boundary layer moisture in comparison to this November's potential event. The issues about cloud-cover don't seem major either. Some clouds can actually work to keep LCLs down a bit and with relatively strong wind fields in place, kinematics become more important than thermodynamics. CAPEs were only around 1000 J/kg, generally, for 11/17/13. The environmental average mean MLCAPE for tornadoes in the Indiana area is only in the ballpark of 500-1000 J/kg. For what it's worth, CIPS does rank 11/17/13 in the top 10 (#9) for analog matches to Sunday, but only 3/15 (20%) of analogs show a tornado outbreak in the Ohio Valley/Midwest vicinity.
  11. Destabilize that boundary layer and don't be surprised if there's a spin up or two in western SNE. 700-500mb lapse rates are meh, but we've certainly seen worse. (~6 C/km)
  12. October 14 Severe Threat

    The environment will be supportive for tornadoes from northeastern MO into northern IL and possibly eastern IA, but the complication will be storm mode/convective evolution. Some convection allowing models suggest that a sustained, discrete cell or two may develop in northern IL (south of I-80) this afternoon and ride an instability gradient eastward. If convection can both initiate and sustain itself, this area would be primed for a tornado or two. Farther west and north, storm mode may be messy/clustered, along with less impressive instability. However, remnant outflow and/or a surface boundary would be focal points for locally enhanced low level shear, boosting the tornado threat. Edit to clarify northern IL portion. Areas in far northern IL should remain fairly stable in the boundary layer.
  13. Watch two areas this afternoon: 1. Far northeastern CO into SW NE. The environment appears unimpressive given a dearth of low level moisture (dews in the 40s), but shear is highly favorable to support rotating updrafts given sufficient buoyancy. Any cells that remain discrete/semi-discrete into SW NE may pose the greatest risk to produce very large hail and an isolated tornado. 2. West-central to NW KS. Stronger low-level flow resides here, along with much more favorable low level thermodynamic profiles. CAMs have more or less shown one robust updraft going up near what appears to be faint boundary in the vicinity of Leoti. If a sustained cell can form here, a long-lived supercell would seem possible, if not probable, continuing into north-central KS early this evening. The parameter space around 23-02z would easily support a tornado given boundary layer dews in the lower 60s, lowering LCLs (already lower than areas to the NW this afternoon) and a low-level jet strengthening to 40-50+ knots at 850mb.
  14. Major Hurricane Irma- STORM MODE

    Sandy's wind field exploded even larger along the East Coast.
  15. Major Hurricane Irma- STORM MODE

    Max wind gusts in mph around the time of landfall: