Mike Hollingshead
Yes and no, I think. The last half makes sense, but calling convection itself convective feedback wasn't making sense to me. You guys know more then me, so feel free to correct me here.
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Yes and no, I think. The last half makes sense, but calling convection itself convective feedback wasn't making sense to me. You guys know more then me, so feel free to correct me here.Mike Hollingshead
Robert, some great observations indeed. I don't think they pertain to the chase ops from 18z through and past 0z though. Is the precip suffering or is the 500 vorticity? The 500 vorticity. It's likely this little wave won't even happen and we wont' have to worry about anything....LOL. Nice to read from knowledgeable people on here. Thanks,
MIke
Stuart Robinson
EF5
Sure - but I am confused with the real world Obs...
DP's of mid 40's in the GOM right now from bouy obs - I need to see these shot up first ...
http://www.hpc.ncep.noaa.gov/sfc/namscsfcwbg.gif
above URL will update ...
Stuart Robinson
EF5
In fact WV loops shows very dry air spilling off TX - we need to see this change..
http://www.rap.ucar.edu/weather/satellite/...lt_big&itype=wvMike Hollingshead
Yeah that has been the topic for more then a week. We are all confused as to how this is supposed to happen. It's odd how confused the models are not. Run after run after run shows sfc TDs around or above 60 by Friday. And we've pointed out already how shallow this will likely be. I think one calls this talk, HOPE. Hope the models understand how this will happen. If nothing else we'll waste some shear and get an early bust out of the way.
Robert Dewey
EF5
Convective feedback is a very in depth subject, and is very complex, since it deals with model physics and dynamics.
After looking at the 18Z model data a bit more, and trying to trace individual lows...I think I see what is happening. It appears as though the "suspect" is in the 850MB level...It appears as though a piece of the 850MB low at 12Z THU breaks off and heads southeast into northern CO/NE...It then encounters slight lee side enhancement, making it a bit more defined by about 6Z/12Z FRI, with incresing vertical velocities. The low continues to track east into the very unstable air of IA/MO...Sparking the development of a MCS...which then basically creates a domino effect...The MCS increases the vertical velocity, and QPF explodes as a result of convection firing (which would be correct if the scenario played out).
So in actuallity...This scenario is possible, but very unlikely since all of the above factors must fall into place at the right time. And since the main "suspect" forms around 12Z THU...Any areas along its path would be subject to total model error, at least from the 18Z run. However; All is not lost for the southern IA/northern MO region! The 12Z ETA still looks like it could pose a decent severe weather threat across the region, with LI down to -10C (though I should be taking the 67F Td with a grain of salt, but thats a whole new can of worms)!!...
Ok, I think I'm gonna take a little break now...LOL
Robert
Jared Mysko
EF2
This system is getting more, and more fun to watch as comes closer to reality. I wonder if there is a chance that severe weather may affect more northern areas than Iowa, say SD or Minnisota? If it is at all close to me, I may take a trip south and see how far I get, lol.
can't wait for my first chase of the year,
Jared
Amos Magliocco
EF5
I could post this to any of the forecast day threads but maybe its most pertinent to Friday first, at least. Scanning through the forecast discussions last night, I found one from OUN early Wednesday morning that reported an ETA six hour dewpoint forecast for a buoy point in the Gulf which was 6 degrees too high. Yesterday's Day 2 mentioned over ambitious dewpoints and again today: "LOW LEVEL MOISTURE RETURN TO VICINITY OF BOUNDARY ONCE AGAIN APPEARS TO BE OVERDONE IN ALL THE OPERATIONAL GUIDANCE."
Likewise the Day 3 this morning mentions the greater availability of moisture in the southern plains and the resultant tornado threat.
I'm not saying there won't be storms tomorrow, just that many forecasters think these moisture progs for far northern points are over the top. It's interesting and strange how the ETA and GFS have fallen into the same trap, nearly identical with the robust return.
Amos Magliocco
EF5
Here are some links for people to conduct their own examination of the model initialization. The first is GOM buoy data:
http://www.ndbc.noaa.gov/Maps/WestGulf.shtml
Of particular interest (and this is the buoy cited in the OUN AFD from Wednesday morning, I think) is Station 42002, which described as its location: "W GULF 240 nm South-Southeast of Sabine, TX." As best I can approximate, this is about where this morning's 12Z ETA analysis (0 hour) shows a pool of 65F dewpoints. Yet at 14Z (nine minutes ago), the buoy reported a dewpoint of 51F.
Closer to shore, the readings are better, but ETA 12Z analysis still overplays them by four or five degrees.
For whatever reason, the model is grossly overestimating dewpoints in the western Gulf.
Robert Dewey
EF5
Looking at the RUC 12HR forecast for 00Z FRI...It looks much more realistic - http://www.rap.ucar.edu/weather/model/ruc1...hr_sfc_dewp.gif, than the ETA 12HR forecast valid for 00Z FRI - http://www.rap.ucar.edu/weather/model/eta1...hr_sfc_dewp.gif.
The 12Z ETA valid for 00Z FRI has mid 50's dewpoints all the way into northeastn KS, while the RUC has low 40's at the same time and area!
The reason I am using the RUC, is because it had very good initialization on Td's, whereas the ETA was overdone.
Robert
Robert Dewey
EF5
I wonder if the moisture problem in the ETA will cause other problems...Seems like excess moisture (yesterdays 12Z ETA valid for ~00Z SAT showed a 67.5F Td about 25mi south of DSM!), would cause problems with precipitation. Since excess moisture leads to excess instability, the model would likely produce convection/precipitation where it should not (i.e. an MCS at 06Z SAT over northwest IA into northeastern WI - http://www.rap.ucar.edu/weather/model/eta4...hr_sfc_prcp.gif). Unless I see some serious moisture return in the next 12-18HR, like the ETA projects, then I have serious doubts.
RobertMike Hollingshead
http://www.ndbc.noaa.gov/station_page.phtm...l?station=42020
http://www.ndbc.noaa.gov/station_page.phtm...l?station=42045
It is nice to see the difference one day can make. Two western gulf buoys.
Joel Wright
EF5
Moisture is obviously overdone by seemingly all the models. (I think mid 50Td's will be the best Iowa can do tomorrow). But the strength of the dynamics alone should be enough for scattered elevated storms to fire. I still think marginally severe hail will be the main threat. Like I said earlier these elevated type cells produce some incredible lightning so that'll at least make things interesting..
Robert Dewey
EF5
Expect that area of low 60's/mid 60's Td's to continue to overspread the GOM, and hopefully advect northward...
BTW...I checked out your new website...You got some great hi-res pics on there.
RobertCraig Maire II
Dewpoints
I live in Washburn Iowa and am hoping for some good storms (any storms!) this weekend! I've noticed the dewpoints have started rising, (crawling upwards!lol) dewpoints yesterday were in the upper teens to upper 20s while there in the lower to mid 40s in portions of southern and southwest Iowa and the mid to upper 30s in my area, hopefully we can see them rise to atleast +55F by Friday night!!
CraigSimilar threads
