LiveBlog: July 26th Severe Weather
This liveblog will be updated with the most recent information at the bottom as the day goes on and severe weather develops.
8:45am
For the first time since the June 29th Derecho we have a Moderate Risk for severe weather here in Central Ohio. The risk is real and there's a potential for an event as destructive as the derecho, with high wind storms, hail, and more potential power outages.
The SPC has a large swath of Moderate Risk forecasted for today, from Ohio to New York City:
It's rare that we have such an explosive setup as we see today, where late summer heat and humidity clash at the perfect time of day with a convective force like a strong cold front. But today is perfect.
The Setup
All of Central Ohio is under a Heat Advisory, with temps reaching the mid 90's and dewpoints in the low 70's. You can feel it outside. Like the atmosphere just want to explode. But as I've written before, gasoline isn't dangerous unless you have a match. An approaching cold front diving down from the upper Great Lakes is the match today.
As the front approaches, strong southwesterly flow will bring in very hot and humid air, raising instabilities to extreme levels. The mid level CAPE will reach its peak right around the time the front approaches the area.
This afternoon's setup
Storms should initiate around 1pm this afternoon, and I imagine show up in a line from roughly south of Indianapolis to around Lima, OH. These storms should become linear rather quickly. Supercells will not be the norm, but rather the exception. However, IF there is a stray cell that develops ahead of the line, it will be severe, and it will have the potential to rotate.
A couple of models have this becoming a broken segment that will develop a secondary line behind the main line and sort of take a due easterly movement and effect the southern portion of our area. If that does develop, expect some decent rainfalls in those areas.
I'll update later as storms initiate...
11:12am
Adding to the fuel, our Heat Advisory has now been upgraded to an Excessive Heat Warning.
12:36pm
Our first MD of the day suggests initiation may occur further east and multiple lines may develop as well. This would certainly make for a major severe weather outbreak for the area:
As of 12:26pm
Some of the wording used in the discussion tells us that the atmosphere may be even more unstable than originally suspected...
"WITH SFC DEW POINTS COMMONLY 70S F...NET RESULT WILL BE PRECONVECTIVE MLCAPE STRENGTHENING TO 3500-5000 J/KG RANGE OVER BROAD SWATH OF WARM SECTOR"
The discussion also mentions a nearly unidirectional wind profile, so tornadoes are unlikely. However, because all of the other ingredients are there, it only takes the slightest shear to produce a weak tornado in this environment. Expect a watch to be issued soon, probably a Tornado Watch just to be safe.
1:33pm
Right on time, storm initiation to our north and west, and the Watch... although not a Tornado Watch, just the standard:
In effect until 10pm
This is a gigantic watch, and given the way the front is laid out it had to be.
The small cells that have developed ahead of the main area of forcing are pretty quick moving, somewhere between 40 and 50mph. Soon we should see an area behind these small cells begin to form a nice little squall line. And then the potential for yet another round behind that.
2:45pm
Round 1 is looking to be single cell storms. No line's formed yet...
6:15pm
Round one ended up turning in to a pretty impressive line as it moved through the Columbus area, setting off warnings and producing high winds and heavy rains.
What I don't have much confidence in is a significant round two. Storms developed behind the main line and are now speeding through southwestern Ohio, but the chance of any more developent, let alone severe development, seems pretty small.
This severe outbreak is over and it wasn't nearly as bad as it could have been.
Severe Weather Stats:
Severe Thunderstorm Watches: 7
Severe Thunderstorm Warnings: 11
Tornado Watches: 3
Tornado Warnings: 0
Flood Watches: 2
Flood Warnings: 1
Heat Advisories: 8
Excessive Heat Warnings: 6
Red Flag Warnings: 1
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Updated: 10:19 PM GMT on July 26, 2012
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Still Need Rain, More Storms Today
Yesterday's setup looked promising for some beneficial rains. All the ingredients were there for some slow moving, soaking thunderstorms. They began building off to our west and moving in. And then?
They just died off.
Yesterday's rain was scattered by definition definitely. Looking at the doppler rainfall estimates, Franklin County was literally surrounded by good rain. It just didn't happen here.
We Need The Rain
For most of the summer we have been running a deficit. While my rain gauge isn't always the most accurate, it has been pretty dead on this month, only recording 0.43" of rain.
Our dry conditions are confirmed by a couple of graphics. The first is from the Advanced Hydrologic Predicition Service, showing what percent of normal our rainfall has been over the past 30 days:
Here in Central Ohio we are roughly around 25%-50% of normal rainfall for the period. This even takes in to account any small amounts of rain we recieved yesterday.
This deficit has lead to the entire state being under a drought as shown from the latest Drought Index:
Currently over 98% of the state is considered in a moderate drought, including everyone in Central Ohio.
It's no wonder lawns are brown and crops are dying around here. We need the rain now more than ever.
Help Coming?
Again today thunderstorms are in the forecast. The front that was slowly sagging south yesterday should finally pick up steam and move in to our area. Already this morning a large area of rain and thunderstorms has developed over northern Indiana and Michigan. As this interracts with our still charged environment, more storms should fire, and hopefully a large area of slow moving rain congeals.
Already this morning small storms are developing out ahead of the main area of convection. Any of these storms should produce heavy rain, with PWAT's higher today, in the 1.8" to 1.9" range.
Decent instability and also decent shear, something we didn't have yesterday, may make these storms a little longer lasting than we saw before.
I'll update this afternoon if a Watch is issued.
Severe Weather Stats:
Severe Thunderstorm Watches: 6
Severe Thunderstorm Warnings: 10
Tornado Watches: 3
Tornado Warnings: 0
Flood Watches: 2
Flood Warnings: 1
Heat Advisories: 8
Excessive Heat Warnings: 5
Red Flag Warnings: 1
Severe Weather: July 18th, 2012
Finally! Something other than the heat to talk about. Wait... we're still talking about heat, too. Yesterday's high of 100° was the third of the season, and also prompted our 7th (and subsequently 8th) Heat Advisory of the season. All of that heat is being met by a sagging cold front this afternoon to prompt our 6th Severe Thunderstorm Watch of the season:
We're in an area of very hot, moist air, with temps in the mid 90's and dewpoints hanging at or a little above 70°. That alone wouldn't be much for afternoon storms, but a cold front in the northern-most part of the state is enough of an area of convergance for storms to pop this afternoon.
It was apparent early this morning that we may have a decently active day as small showers were able to develop in the area before sunrise. The radar hasn't been empty since then.
What to Expect
We could see very heavy rains, a little hail, and the potential for gusty downbursts with all of these storms. Individual cells aren't expected to move very fast, which will increase rainfall amounts and lessen the chance for major wind producing storms.
We need the rain. This is a good thing.
While we would ideally like a large, slow moving system to give us a long soaker, we don't see those much in the middle of the summer... so this is as good as we'll get for a while.
PWAT's are around 1.7, which is good enough. Much higher and we run the risk for flash flooding, so with those kinds of numbers we know the atmosphere is saturated enough to dump a good amount of liquid with each of these storms.
Supercells are unlikely this afternoon. Instead we should see individual cells develop and congeal in to larger storms.
It'll be nice to see some rain.
Heatwave Finally Ends
The heatwave that has been boiling a giant part of the country has finally ended, with the ridge being surpressed and cooler Canadian high pressure setting in.
The record heat event brought us 11 straight days above 90°, and two days at the end at or above 100° (officially there were more days, but I only had two days). The average temperature over those 11 days was 96.5°, which is just as oppressive as it sounds.
Friday's high was 100° and Saturday was the worst with 103°. That's a temperature I never want to see again. With dewpoints in the upper 60's Saturday felt like 111°.
65% of Ohio is under a moderate drought and a lot of it has to do with this recent heat wave.
I'm looking forward to writing about something other than hot weather!
Severe Weather Stats:
Severe Thunderstorm Watches: 5
Severe Thunderstorm Warnings: 10
Tornado Watches: 3
Tornado Warnings: 0
Flood Watches: 2
Flood Warnings: 1
Heat Advisories: 6
Excessive Heat Warnings: 5
Red Flag Warnings: 1
Ohio's Heatwave Gets Worse
Today was our sixth straight day of 90°+ heat and the streak isn't over yet. What appeared to be our sixth straight day of a Heat Advisory quickly became our second Excessive Heat Warning of the season, and the warning has been extended through Saturday. Wilmington is forecasting temperatures in the very upper 90's in to the weekend and dewpoints close to 70°. That could make for an outright oppressive next few days.
While it's uncomfortable for those of us with AC, the unfortunate ones are those who still don't have power from the June 29th Derecho. As of a couple hours ago more than 61,000 customers in Central Ohio alone are still without power. While I don't mind opening windows and dealing with heat when it's a little warm, 98° with no breeze is unthinkable.
But we're not the only ones dealing with this historical heat wave. So far it looks like ten states have Excessive Heat Warnings, making the term "excessive" more appropriate than ever:
Relief is coming eventually, with a trough forecasted to move in late this weekend. In the meantime any cool off will have to come in the form of an afternoon storm. For a while it looked like we were in a pattern where we would see a pulse of energy ride over top of the ridge every other day, with storms last Friday and Sunday.
What does it mean for storms to ride over top the ridge? Right now we have a large blocking high pressure in the nation's midsection that is the cause of this massive heatwave. This ridge is strong enough that all storm systems are being pushed in to Canada and then back down on the eastern side of the high, as is seen today with what little active weather we have:
Tomorrow is just about the last chance for any of this rain to reach us before the trough moves through on Sunday, so in the meantime... keep those AC's on.
Severe Weather Stats:
Severe Thunderstorm Watches: 4
Severe Thunderstorm Warnings: 9
Tornado Watches: 3
Tornado Warnings: 0
Flood Watches: 2
Flood Warnings: 1
Heat Advisories: 5
Excessive Heat Warnings: 5
Red Flag Warnings: 1
