Severe Weather Southeast Louisiana, April 4, 2011

[cyclogenesis]

April 2, 2011
this Saturday afternoon
550 PM CDT



Alright Gang ~~ Time for cyclogenesis to start rolling-out his PRELIMINARY thoughts on your big severe weather event up and coming for late Monday afternoon and Monday night, April 4, 2011. NOTICE--->> The SPECIFICS of this writing is applicable to SOUTHEAST LOUISIANA WEATHER ONLY!



I. Summary of the Bottom Line


First and foremost, let me say this: I believe this weather event will be "earmarked" with a HIGH WIND and DAMAGING wind potential, above all else, with secondary threats for HAIL, and then TORNADOES. Although, for c.y.a. reasons, I do believe your SPC will issue a Tornado Watch for all the area by late Monday afternoon, April 4th. This watch, followed by severe weather warnings, will commence from late Monday afternoon in to Monday night.



II. Initial Capping



I expect there to INITIALLY be a low-to-mid level capping inversion take shape EARLY Monday and early Monday afternoon. Anytime I see forecast 850 mb temps of 16 to 17° C and 700 mb forecast temps of 7 to 7.5° C, it offers the "smell" of cap to me. Surely enough, your GFS indicates 87 J/kg of conv. inhibition early Monday afternoon, and a cap strength of 2° C. Now, severe weather lovers, do not despair, as a cap is a good thing to have. It prevents "grungeola" piles of trash showers from developing too early and trashing over the atmosphere, (over-turning), and lets the HEAT of the day to BUILD over the region, to unleash in an explosive, yet nevertheless, pleasing ways for storm lovers to enjoy.


Look for this capping to be overcome by early evening as the cold front rapidly approaches, cooling aloft commences, and the stronger forcing / increasing wind speeds necessary for severe storms arrives at that time later on.



III. Model Inter-comparisons.



This was no easy, nor clear-cut solution to this Saturday morning's 12Z Saturday morning suite of models. We have an equal diversion of solutions on the short-wave troughs trajectory.


#1.) Your GFS is joined by the WRF and a little lesser extent the UKM in keeping a further NORTH track of the short-wave trough's path, passing NORTH of Southeast Louisiana.


#2.) Your ECMWF is joined by the NGP's, JMA, and to some extent the C-gem, although it's slower than the former 3 in this sentence.


I've seen this crap go on before between these models' differences, and the ECMWF has won-out in the past with a further South track, getting the severe weather potential more accurate.


However, I do respect the 500 mb patterns of the UKMET, and right now, it's about as close to a compromise between the GFS & ECMWF as there is, although it's tending to side just a little closer to GFS, but still offers a compromise between the 2.


I'm not ready to deduce & release a formal, structured writing to my weather e-mailing recipients, nor put on my website because of these VERY IMPORTANT model differences, that have consequences on the EXTENT of severe here.



IV. Justification for HIGH WIND & WIND DAMAGE threat



Whenever I see hodographs that tend toward straight-lined hodographs late in the afternoon, and winds veering at 850 mb to nearly westerly, out ahead of the front, this combined with HIGH Capes on the order of 1500 to 2000 J/kg and LI's of -5 to -7 and Showalters of -1.7 to -3, it indicates the magnitude of instability will just as equally as good as the last event we just completed, on the night of the 29th. Only this time, there will be MORE wind involved. Still, I'd prefer to see 0 - 6 km shears of better than the forecasted 30 to 36 kts.


This deep shear of 0-6 km forecast is more contingent upon the path & track of the short-wave trough. A further southward track will increase the belts of winds at all levels with a further south track, than a further North track.


I don't think there's going to be a whole lot of activity well in advance of the front due to this capping I mentioned above. By the time storms ignite, the winds in the lower levels of the troposphere will have already veered, decreasing the helicity, tending toward straight-lined hodographs, a uni-directional wind profile which will be MORE SUPPORTIVE of a SQUALL LINE formation. Some of you have come to know a squall line as a QLCS, which is short for Quasi-Linear Convective System, for those of you SPC worshippers. That's the language they use for a "squall line" Or LEWP's for "Line-echo Wave Pattern" So that's the lingo on that.


In fact, I think it may even be possible that a gust front will precede the squall line, whereby, just immediately AHEAD of the cold front the low-level winds will have already veered owing to a mesoscale gust front, which will come from the rain-cooled air, which will serve as a way of under-cutting the surface-based instability, and then the storm evolution becomes what I like to call, "outflow dominated" storms. This most often occurs with "anafronts". So I think that most of the storm activity will be confined right along the front, a little behind it, but NOT much ahead of the front in Southeast Louisiana.


Any further Southward track of the short-wave trough's positioning as the ECMWF, NGP's, JMA, and C-GEM models show, and we'll have a much less of a capping inversion to worry about, as there'll be greater height falls farther south, which implies colder-air advection, and a quick erosioning of the cap, along with increased belts of winds at all levels. This is why the forecast PATH & AMPLITUDE of this trough is EXTREMELY PIVOTAL in determining the EXTENT and SEVERITY of the severe weather this far South in Southeast Louisiana.


I do expect a Severe Weather Watch -- (likely a Tornado Watch) -- and several warnings to be issued in Southeast Louisiana starting late Monday afternoon to our North and spreading in to the rest of Southeast Louisiana during the early evening hours.


Because of the fast-moving nature of this cold front, these storms will be fast-racers, and not stick around and dump rainfall like that mini-MCS complex did on Tuesday night the 29th. So it's going to be in "in-and-out" kinda system -- not go on for a lengthy, 6 to 12 hours as the last one did. Also for that reason, the durations of heavy rainfall will be shorter -- much shorter than last time; this is why you're not seeing a whole lot of QPF in the models, because squall lines get in-and-out in a quick hurry. Blink; and you might miss it!


Okay, that's all for this edition.




-- cyclogenesis

[cyclogenesis]

April 3, 2011
this Sunday evening
606 PM CDT


Hey Gang ~~ I have placed a formal, structured writing on Monday's, 4/4/2011, severe weather event on to my website. This writing appearing on my website is applicable to Southeast Louisiana weather. You can read all the details by clicking-on the following website weblink appearing below:



http://cvamagic.tripod.com/







-- cyclogenesis

[BigB0882]

Thanks, just got your newsletter and was happy to know we may have some exciting weather to watch tomorrow. Keep up the great work!

[cyclogenesis]

BigB0882 ~~ Yes, sir! Bree Smith in the BTR market dropped me a line and suggested I give Twitter a try. I signed-up for it, got established, but after poking around with it, and getting familiar with it, I think it's really for folks who have a HIGH visibility profile, like members of the media. I don't think it works so well with general members of the public.


For now, I'll just stick with these 2 forum boards -- this one and the other one I'm more active on. And, to a much lesser extent, Facebook.


People who really care about the weather visit "weather forum boards" in my opinion; not participate on Facebook or Twitter for that kind of stuff.



-- cyclogenesis

[cyclogenesis]

335 AM CDT
Monday, April 4, 2011


I'm counting on an increasingly upper divergent regime to make it all come together with the dynamics later today and this evening, with the quickly-approaching, right-entrance region of the jet. Values have more than doubled since the last model run, and that's worth noting! The squall line will have some cyclical ups & downs, thru its journey. Get in to the area too early and it'll fight with a cap and get moisture hungry. Get in to the area too late, and the CAPE levels decrease. Needs to be timed just right. 00Z WRF shows the cap breaking very close to around 5 PM. Current thinking is that it'll be timed to as close as it needs to be, just shortly after max heating of the day, for it to pop.


My weather writing I made yesterday evening 553 PM still appears to be on track for Southeast Louisiana for late today and this evening, Monday, April 4, 2011.


The weather writing can be found at: http://cvamagic.tripod.com/






-- cyclogenesis

[MGC]

Looks to be a pretty potent squall line this morning approaching the Shreveport area. Here on the Mississippi Coast, low level moisture has really picked up since last evening. Pretty good south wind here this morning. Low deck of clouds which are racing north.....MGC

[BigB0882]

Man, that was quite some wind we had here in Baton Rouge. It has been windy all day and still is but the squall just brought some big punches with it. I heard the rain hitting our back door and I knew that meant major wind because we have a porch with a cover so the rain was getting pushed way in to the door. Not good at guessing wind speeds but I would say 40 mph gusts? Have to watch the news tonight to see what they clocked.

[cyclogenesis]

I tell you what, Gang! I *NAILED* this weather forecast to the WALL!!! The timing, the severe weather, the type of severe weather...


Here's just a short snippet of what happened in the New Orleans area, this early Monday evening:


61 mph PEAK WIND gust, (severe high wind gust criteria), measured at the New Orleans International Airport in Kenner.


59 mph PEAK WIND gust, measured at the New Orleans Lakefront Airport in New Orleans East.


Numerous severe thunderstorm warnings & Tornado watches all along the Gulf coastal states here!


What a tremendous rush it was!!




-- cyclogenesis

[cyclogenesis]

April 4, 2011
this Monday night
940 PM CDT



**** Lots of HIGH wind damage actually did occur and were reported in Southeast Louisiana and the New Orleans area from Monday evening's storms, on April 4th ****



I. Introduction.


Well, it didn't last long, and didn't put down a whole lot of rain, but there sure was LOTS of HIGH WIND DAMAGE reports, & another BIG round of verifiable Severe Weather that had occurred in Southeast Louisiana early Monday evening & Monday night, April 4th, just as I predicted it would happen, 24-hours in advance in my writing to you.



II. A Preliminary Early Look


A preliminary look at earlier this evening's storm reports show the following:

16 Verified reports, (at least), of severe weather in Southeast Louisiana, (HIGH WIND DAMAGE) either in the form of downed trees, downed power lines, roofs blown off, fences knocked down & even measured severe wind gusts. Additional reports of severe weather also occurred in coastal & Southern Mississippi as well. Note that, the 921 PM LSR issuance was merely a correction of the times of the storm reports and not additional reports

Parishes reporting the severe weather reports included St. Charles Parish, St. John Parish, Tangipahoa parish, Jefferson Parish, St. Tammany Parish, Washington Parish, St. James Parish, Livingston Parish, East Baton Rouge Parish, and Point Coupee parishes. Wowsie! That's a lot of parishes sustaining high wind damage reports

Understand that, this is likley NOT the last of all the severe weather reports. I expect a trickle of more reports will come in tomorrow I expect.



III. Watches issued


There were 2 Tornado Watches issued for Southeast Louisiana on Monday afternoon & again on Monday night, April 4, 2011.



IV. Warnings issued.


Many severe weather warnings were issued by your National Weather Service field office in Slidell.


The first warning was issued at 431 PM, and the last warning was issued at 849 PM, right in the time frame I was expecting the severe weather to come in my original writing to you!


In total there were:

14 Severe Thunderstorm Warnings issued

8 Tornado warnings issued

PEAK Wind gust of 61 mph at New Orleans International Airport was measured at 721 PM

PEAK Wind gust of 59 mph at New Orleans Lakefront Airport, measured at 744 PM on Monday evening, April 4th

Rainfall amounts in New Orleans were generally light with only 1/4" to 1/2" occuring at the KMSY & KNEW airports, (as of 9 PM's report, though the final rainfall reports have not come in yet, as of the time of this writing)


In other news....


In other news, I'm sad to announce that I have discontinued my subscription to the ECMWF model, effective today, Monday, April 4th. It was just getting to be too expensive to maitain that subscription for just that one and only model. Our severe weather season will be coming to a close soon, anyways, near the mid-part of April, too, so no longer going to spring the money for it anymore.


In the event we get a serious threat from a tropical storm or hurricane during the heart of hurricane season, I will once again subscribe to the model data.





-- cyclogenesis

[BigB0882]

A lot of people are still without power here in Baton Rouge. We got really lucky. Most people I know are still without power or had their power come back on rather recently. It is kind of funny because they are all scared of being all hot and sweaty but they clearly haven't set foot outside as it is in the lower 50's already.

[cyclogenesis]

A lot of people are still without power here in Baton Rouge. We got really lucky. Most people I know are still without power or had their power come back on rather recently. It is kind of funny because they are all scared of being all hot and sweaty but they clearly haven't set foot outside as it is in the lower 50's already.

BigB0882 ~~ It was a historic weather episode! 10's of thousands of people throughout Southeast Louisiana lost electricity.



On a personal note, so too, did cyclogenesis!! I was without electricity for 1 hour and 10 minutes last night.



This was certainly one of my very BEST forecasts of all time! Certainly worthy of a 4-star writing!


In all there were 33 confirmed Wind Damage and/or Severe HIGH WIND GUST reports scattered across 11 parishes of Southeast Louisiana!


This event joins in the series of events from the February 1, March 5, March 9, and March 29th, as another blockbuster severe weather outbreak of storms in Southeast Louisiana!


Southeast Louisiana, and particularly, New Orleans, is becoming a hot-spot mecca for severe weather occurrences this spring 2011!


It's about time!! It makes up for the past 2 consecutive lack-luster storm seasons we've had here in the past 2 years. This is truly the way God intended weather to be!




-- cyclogenesis

[LaPlaceFF]

0650 PM TORNADO 1 NNW GRAMERCY 30.07N 90.70W

04/04/2011 F0 ST. JAMES LA NWS STORM SURVEY



TOUCHDOWN OCCURRED NEAR INTERSECTION OF NORTH AIRLINE AVENUE ANDHIGHWAY 3125. THE TORNADO MOVED TO THE SOUTH-SOUTHEAST THROUGH A RESIDENTIAL NEIGHBOORHOOD WITH THE WORST DAMAGE OBSERVED ON ZILDORE AVENUE BETWEEN 6TH AND 7TH. CARPORT LIFTED OFF A HOMECAUSING SIGNIFICANT DAMAGE TO HOME. THE TORNADO CONTINUED TO THE SOUTH-SOUTHEAST CAUSING SIGNIFICANT TREE DAMAGE AND SOME MINOR TOMODERATE ROOF DAMAGE. TORNADO FINALLY LIFTED NEAR THE END OF EAST 2ND STREET. MAX ESTIMATED WINDS WERE 80 MPH.


This was by my house...

[Kennethb]

I think we easily had 60 mph gust. Interesting was that these winds came just behind the squall line. Biggest gusts since Gus. We were without power for 24 hours.

Another similarity to Gus was they had to close Highland Rd to clear trees and restore power lines. We had lines of cars coming down my street which paralells Highland Road. Except my road is a dead end. They get upset as they have to turnaround on a narrow driveway and find another way home.