OKpowdah

Moderator Meteorologist
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Everything posted by OKpowdah

  1. Following the recurvature of Typhoon Francisco, we get a huge jet amplification again in the West Pacific, and it looks like both the GFS and ECMWF want to develop an intense low in the poleward exit region by day 7-10. Could get kinda windy around the Aleutians to western Alaska.
  2. A lot of bust potential with temperatures early next week in Oklahoma with the frontal passage. We'll see how far southwest that airmass can penetrate, before getting shoved eastward. NWS forecast high for Norman on Tuesday is 70. MEX guidance is 59.
  3. We're watching another potential major Typhoon recurving in the West Pacific, passing close to Japan by day 4 (Tuesday night ET). The story begins though with just some simple extratropical cyclogenesis in the northern Sea of Japan and the amplification of downstream ridging. This ridge eventually breaks as it pinches another downstream disturbance, and then bridges with ridging over the eastern Pacific. The favored superposition of negative PV anomalies develops a very strong ridge on the west coast of North America toward Alaska. As Wipha recurves, distributing upper level latent heat and negative PV downstream, we see a huge WPac ridge form, and a rapid acceleration of the jet. On the poleward exit side of the jet, another extratropical system rapidly intensifies near the Aleutians. As the huge ridge breaks, all the cyclonic vorticity on the poleward side of the jet gets dumped into this system over the Aleutians, forming a pretty stable trough over the North Pacific. Day 5-9 (17th-21st): And so now we have the very distinct pattern of a large trough over the Aleutians and blocking ridge over western North America. As you might imagine, this could have some interesting implications over central and eastern North America, with a negative NAO in place over the north Atlantic. At the very least a period of below normal temperatures, and an opportunity for snow in the Midwest.
  4. Personally, I'm more interested in the prospects of an early season winter storm in the northern Plains. Always a challenge to get all the right factors together this early in the season though.
  5. Just throwing this around. Fooling around with different EOF interpretations of ENSO: Maybe some method to differentiate between east- and west-based events.
  6. The Quasi-Biennial Oscillation (QBO) is a cycle of zonal wind in the equatorial stratosphere with a period that varies between 24 and 30 months. This oscillation is a product of downward propagating alternating wind regimes. The current method of monitoring this oscillation is through an index, calculated by the zonal wind anomaly at 30hPa averaged along the equator. This method excludes information on the vertical structure of winds in the stratosphere, and presents the QBO as a one-dimensional temporal oscillation. Presented here is a new framework for monitoring the QBO. This framework incorporates both the oscillation in time and in space. The two leading principle components (PCs) of equatorial stratospheric zonal winds are calculated from NCEP/NCAR reanalysis monthly mean data. These PCs are then standardized and used as X and Y coordinates in a 2-dimensional phase space. A phase angle can then be calculated from the coordinates, forming a new index that is much more representative of the state of the stratosphere. The results show a very clear pattern of zonal wind and temperature regimes in the stratosphere. Furthermore, from each of these phases, there are physical connections to characteristics in the troposphere on a monthly to seasonal basis. These include the distribution of tropical cyclone activity, the El Niño / Southern Oscillation (ENSO), and the extratropical pattern. This new framework for monitoring the QBO is shown to be much more applicable to seasonal forecasting. Compare the EOF-constructed oscillation to a 52-month reanalysis segment
  7. The Quasi-Biennial Oscillation (QBO) is a cycle of zonal wind in the equatorial stratosphere with a period that varies between 24 and 30 months. This oscillation is a product of downward propagating alternating wind regimes. The current method of monitoring this oscillation is through an index, calculated by the zonal wind anomaly at 30hPa averaged along the equator. This method excludes information on the vertical structure of winds in the stratosphere, and presents the QBO as a one-dimensional temporal oscillation. Presented here is a new framework for monitoring the QBO. This framework incorporates both the oscillation in time and in space. The two leading principle components (PCs) of equatorial stratospheric zonal winds are calculated from NCEP/NCAR reanalysis monthly mean data. These PCs are then standardized and used as X and Y coordinates in a 2-dimensional phase space. A phase angle can then be calculated from the coordinates, forming a new index that is much more representative of the state of the stratosphere. The results show a very clear pattern of zonal wind and temperature regimes in the stratosphere. Furthermore, from each of these phases, there are physical connections to characteristics in the troposphere on a monthly to seasonal basis. These include the distribution of tropical cyclone activity, the El Niño / Southern Oscillation (ENSO), and the extratropical pattern. This new framework for monitoring the QBO is shown to be much more applicable to seasonal forecasting. Compare the EOF-constructed oscillation to a 52-month reanalysis segment
  8. Quick animation of the drought monitor in Oklahoma over the last year
  9. Compare the drought conditions to this time last year:
  10. Full EOFs using zonally averaged 10, 20, 30, 50, and 70mb level zonal wind.
  11. Awesome work Mike! The only thing I would alter is instead of looking at the wind as a function of longitude, average them zonally and look at a function of latitude, maybe 20S-20N. Anyway, cool stuff!
  12. Here's what the weight function looks like. Excuse the dark background: taken off a presentation I gave a few weeks ago. Here is the track trajectory plot. ... I really need to get around to coding the vectors as white lol just lazy on my part
  13. Velocity potential is generally symmetric about the equator with the maximum amplitude in the tropics. How the velocity potential varies with time (phase) is mostly a function of longitude. The tropics latitude band is thus the best representation of its variability. It is representative of conditions over the Atlantic because of its symmetry. 1) For each particular phase, I used a weighting function that actually incorporates months +/-40 degrees from the phase of interest, so there's some representation of the "season" around a particular phase. 2) Since this calculation incorporates a range of months, it's not necessarily supposed to be a gauge for a complete hurricane season. It's an indication of the "bias" of TC activity for a given month. I understand what you're saying though. Honestly, to tell you the truth, I don't care which is more active W/E, just that they are relative maxima. Not sure what you're asking, but the track density maps give an indication of predominant tracks fairly well. I have one with track trajectory vectors overlaid also. Just haven't gotten around to posting it. 1979-2012. For the TC activity by month, I used the months of the hurricane season. For the track density maps, I used all storms (ranged between 20 to 80 storms for each phase).
  14. Thanks for the overlay man. We got our first Gulf to SE coast rider of the year. So all phases were using data from 1979 to the present (satellite era, and available data for stratospheric winds). Each month in this period is then weighted based on it's actual calculated phase (i.e. for phase 60, a month with a phase of 52.6 has a higher weight than a month with a phase of 31.9). Each TC data point in HURDAT then gets two weights applied: the Barnes interpolation to a 1 deg grid, and the phase weight. I can tell you that there are 59 individual TCs that contribute some level of weight on the phase 60 map
  15. I'm still speechless and just trying to comprehend what happened on Friday. Terrible terrible day. Friday was an especially dangerous situation. Between the gridlock traffic, the road network, and the fact that the evolution of the meso was far from linear ... there were satellite vortices breaking off, dying, redeveloping all around the meso. And it all very quickly became rain wrapped. It was an incredibly dangerous day that turned tragic.
  16. Here is the TC density standardized anomaly. Can notice some distinct predominant track regimes by phase
  17. Just slapped this one together. It's TC density in the Atlantic from 1979 to the present (simply based on 6 hourly obs interpolated to a one degree grid using Barnes weighting). The first frame is all TCs ... the frames after that have each TC ob weighted by the particular MQI phase weight for that month. I plan to compare the phases more effectively by scaling them based on all TCs. And also weight by intensity .. All coming soon..
  18. Thanks man! Yeah the 330-60 phase is right around the easterly shear peaking in the lower stratosphere. Definitely stuff I want to explore more. Some signal there for sure.
  19. Same plot for OLR near the equator ... there is some signal of a relationship to ENSO that I'm trying to pull out. Tough to be confident because of the overlap in the QBO and ENSO frequency power spectra.
  20. Wanted to throw this plot up here also. This is upper level (.21 sigma) velocity potential by MQI phase and longitude. Very strong signal, and interestingly a longitudinal progression between phases 90 and 210. Also, notice that a divergent regime (albeit weak) moves into the Atlantic around phase 270 ... in theory would support some increase in tropical activity, and be at least some support for that max in the easterly phase of the QBO.
  21. Not sure if anyone has shared this yet, but I took this screenshot of the 0-3km EHI valid for the hour before the Moore tornado.
  22. I'm a little behind. Just got back into Norman, and just got internet back. Here's a good radar loop of the storm. Sorry if already posted http://i.minus.com/iluhrlDRbUSAQ.gif
  23. 12z GFS is actually pretty impressive with the threat middle of next week
  24. Yeah I mean, I'll be stoked to watch the first cold front that doesn't clear out the Gulf this season. But I think that at the very least, the snow cover may help establish the low level baroclinic zone further south such that as we get later into the spring, lows don't just take off to the northeast ... so we get the greater helicity and higher LI's with proximity to the surface low.