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Amazing SPC storm report map (4/4/2011)


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Every year we see more and more spotters reporting which is also something to consider. It doesn't take away from the event, but I also wouldn't necessarily rate how impressive an event is, simply from spotter reports.

Good point. We may have to start weighting geographic coverage and number of high-end reports more heavily than we did in the past.

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Nice write up from AccuWx...

http://www.accuweather.com/blogs/news/story/48009/mondays-severe-weather-the-lar.asp

"In speaking with Meteorologist Greg Carbin of the Storm Prediction Center, he said that "if you add in the filters from a year ago on the preliminary data from Monday, you end up with approximately 850 severe weather reports." Only two other events have been observed with more than 850 severe weather reports. Those events occurred on May 30, 2004 and April 2, 2006.

Carbin said, "If you take the numbers literally in terms of overall severe weather reports with the time/space filtering, April 4, 2011 would fall into third place."

He also stated, "As far as wind reports, it appears that, even with filtering, this most recent event

may have the greatest number of severe wind reports in a single 24-hour period on record.""

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What will be interesting is how many reports can be confirmed in each local area. And how many total tornadoes actually touched down, will it be more or less? One thing for sure this was very dangerous event. I wonder how people in the area dealt with this, did they mind the warnings or did they go about the day. ( well on guy in ky did) We can learn alot from this day.

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I think the SPC busted. They needed a high risk from Baton Rouge to DC to Jacksonville. I have never seen an SPC map with this many reports. I think the most I saw was 850. Back before 2008 or 2009, the 0.75" and 0.88" hail reports were counted, but they are not counted now. These types of reports were numerous, so any particular strong severe weather day may have had 10 to 30 of these reports. Some days had many more than 30 of these smaller hail reports. Overall, it is harder to get a high number of reports on any particular day in 2010 and 2011.

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Of course of all the reports and fanfare I eneded up in the one spot in NC that was gapped by severe wx. We had the line come through but in a weakned state where I was. It picked up again to my east. :(.

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Of course of all the reports and fanfare I eneded up in the one spot in NC that was gapped by severe wx. We had the line come through but in a weakned state where I was. It picked up again to my east. :(.

Jeremy, looking at the SPC map, I think this was another north of I-40/west of I-85 event! It's like the winter of 2009/2010 all over again. lmaosmiley.gif

laugh.gif

eyewallscrewzone.png

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I think the SPC busted. They needed a high risk from Baton Rouge to DC to Jacksonville. I have never seen an SPC map with this many reports. I think the most I saw was 850. Back before 2008 or 2009, the 0.75" and 0.88" hail reports were counted, but they are not counted now. These types of reports were numerous, so any particular strong severe weather day may have had 10 to 30 of these reports. Some days had many more than 30 of these smaller hail reports. Overall, it is harder to get a high number of reports on any particular day in 2010 and 2011.

I think a high risk (for wind probabilities, not tor) would have been justified, although the geographical area you outlined seems a bit excessive. Maybe a high risk where the 20Z moderate was, with the new moderate between the slight and the high.

At the same time tho, it was a tough forecast to make. The deep veering winds (SSE at the sfc, W at 500), and extremely cold/dry air aloft typical of a high risk supercell environment were just lacking. And yes, serial derechos warrant high risks too, but it's very hard to forecast whether or not the squall line will stay intense or just become heavy rain and lightning, with little downward momentum transport... especially late in the evening and close to the Appalachians!

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That was a beast of a squall line and showed no signs of weakening. One section would briefly weaken and cells to the south would intensify. I was worried about my plant in Richmond, KY, but fortunatly that portion of the line weakened just as the cells were becoming tornadic to the west of Nashville.

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I think the SPC busted. They needed a high risk from Baton Rouge to DC to Jacksonville. I have never seen an SPC map with this many reports. I think the most I saw was 850. Back before 2008 or 2009, the 0.75" and 0.88" hail reports were counted, but they are not counted now. These types of reports were numerous, so any particular strong severe weather day may have had 10 to 30 of these reports. Some days had many more than 30 of these smaller hail reports. Overall, it is harder to get a high number of reports on any particular day in 2010 and 2011.

It was an impressive event for some.... I still think with more storm spotters now than ever and I think some of the reports were also very close together. Combined with quite a few of the Storm Reports being very minor I think the map is more overdone than what actually happened. I was in NW Georgia centered around many of these reports and it just was not that bad of an event. It was mainly outflow driven event by the time it got my way and I did not find it impressive.

Maybe it's just me who feels this way.... If some of you guys are as unimpressed as me I'd love to hear it.

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It was an impressive event for some.... I still think with more storm spotters now than ever and I think some of the reports were also very close together. Combined with quite a few of the Storm Reports being very minor I think the map is more overdone than what actually happened. I was in NW Georgia centered around many of these reports and it just was not that bad of an event. It was mainly outflow driven event by the time it got my way and I did not find it impressive.

Maybe it's just me who feels this way...

No, I'm with you, not based on my personal experience, but

1) the fact we're comparing apples and oranges since the reports are no longer filtered as they used to be

2) using point observations of an inherently continuous phenomenon (wind) gives very little information

Let's take a swath of land with an area of 25 square miles; in theory if that entire area experienced wind worthy of reporting, the number of points that would be reported is...infinite.

The wind point reports probably have some relationship with the actual distribution of report-worthy wind, but that relationship is unknown and affected by a host of non-scientific factors: the time of day, population density, human perception, etc. I'm sure it was a great event, but the actual number of reports is not something to use other than as a very coarse, zeroth order, overview.

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The set-up for next week (Sunday April 10-Monday April 11) is similar in that a pool of cold air aloft translates east across the Plains Sunday and into the Miss. Valley Monday. It's not nearly as dynamic as the April 4 set-up, but there is the warm surge ahead of a clear cold front and a strong low heading to the Great Lakes. I'd go with Indy to St. Louis to Little Rock area on Sunday, Pittsburgh to Nashville on Monday.

** Side note: I have NOT looked at SPCs extended outlook maps yet. I'd bet if I see this and it's not a crazy idea, they probably show something. I guess I should go check :)

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Going to be interesting to see what we do this weekend. This event set a high bar.

yes but like I posted things have to come together just right..with storms starting just after 12z and stay severe into the afternoon and all night...if they hold off until afternoon simply not enough time to get huge like this

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on this page it shows 999 reports for the 4th and 1347 for the month

I wonder if the filters are still active here

edit: maybe not it shows 330 reports for the 3rd and when you click the day link it shows 330 on the map. (there should be some reports close to each other on the 3rd too) When you click the day link for the 4th it shows 1471, so perhaps there is only enogh room for 3 digits in the column hence the 999(but then the months total is too low and it has 4 digits) so who knows

http://www.spc.noaa....al_summary.html

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The fact of the matter is that you really can't compare events in the past to modern events based on the number of storm reports. In and around 1980 storm reports started coming in a a much larger rate and that rate has continued to grow with each year. Today's 1000 report event may have been 100 prior to 1980.

http://journals.ametsoc.org/doi/pdf/10.1175/WAF866.1

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