June 2012 General Discussion

[A-L-E-K]

Feels like were only had a 6-8 degree diurnal swing yesterday with the lake cooling during the day and UHI/lake warming at night

[Chicago WX]

52 for the low at the LAF.

Gonna be a long while until it feels that nice again.

[Thundersnow12]

LOT regarding storm chances thursday night

SEVERAL MODELS CONTINUE TO ATTEMPT TO DEVELOP CONVECTION ALONG THE

FRONT INTO FAR NORTHERN IL BY 00Z FRI DESPITE VERY WARM MID-LEVEL

TEMPS...AND RELATIVELY DRY SURFACE AND BOUNDARY LAYER CONDITIONS.

FORECAST SOUNDINGS DO INDICATE EROSION OF CAP VERY LATE IN THE

DAY/EVENING ACROSS THE NORTHERN PART OF THE CWA AND THUS HAVE

MAINTAINED SLGT CHANCE POPS BY THURSDAY EVENING. 4000 J/KG MLCAPE

AND 0-6 KM BULK SHEAR INCREASING TO 40-50 KTS WOULD SUPPORT THE

POTENTIAL FOR SEVERE STORMS IF SOMETHING CAN BREAK THROUGH THE

CAP...AND SPC HAS OUTLOOKED NORTHERN 2/3 OF CWA FOR 5 PERCENT SEVERE

RISK.

[A-L-E-K]

LOT regarding storm chances thursday night

SEVERAL MODELS CONTINUE TO ATTEMPT TO DEVELOP CONVECTION ALONG THE

FRONT INTO FAR NORTHERN IL BY 00Z FRI DESPITE VERY WARM MID-LEVEL

TEMPS...AND RELATIVELY DRY SURFACE AND BOUNDARY LAYER CONDITIONS.

FORECAST SOUNDINGS DO INDICATE EROSION OF CAP VERY LATE IN THE

DAY/EVENING ACROSS THE NORTHERN PART OF THE CWA AND THUS HAVE

MAINTAINED SLGT CHANCE POPS BY THURSDAY EVENING. 4000 J/KG MLCAPE

AND 0-6 KM BULK SHEAR INCREASING TO 40-50 KTS WOULD SUPPORT THE

POTENTIAL FOR SEVERE STORMS IF SOMETHING CAN BREAK THROUGH THE

CAP...AND SPC HAS OUTLOOKED NORTHERN 2/3 OF CWA FOR 5 PERCENT SEVERE

RISK.

I'm doing my best to stay positive and ignore the recent history of thermonuclear caps holding strong...it's been so boring for so long and i'd really love to see this front get active.

[LizardMafia]

52 for the low at the LAF.

Gonna be a long while until it feels that nice again.

Went to get in the car to come to work this morning, I was like wow this feels great!

Going to be awhile before we get temps that chilly again..

[michsnowfreak]

What a BEAUTIFUL summer day out there today. After most of SE MI outside the heat island starting the day in the 40s (DTW was 53F) we are now clear blue sky and 75F. Why oh why cant it be like this ALL summer?

[Chicago WX]

It'd be nice if I could buy into what the 12z GFS is selling for rain/storm chances on Friday. Does us no good down here, but southern WI, northern IL, on through northern IN make out decently.

[A-L-E-K]

GFS continues to be in convect anywhere and often mode

[Geos]

Bottomed out at 50° this morning, which really chilled the house temp off to the mid 60s. 12z GFS is generous with the moisture for northern IL & IN later on...

[A-L-E-K]

12z GFS is generous with the moisture for northern IL & IN later on...

The GFS has DPs near 80 with a super rich theta-E airmass in place pooling along the boundary...it's really hard to imagine that being even remotely close to reality without a good gulf connection and with an on going drought. It's somewhat reassuring that the NAM and nearly all SREF members are active albeit lighter across the same area.

[Thundersnow12]

The GFS has DPs near 80 with a super rich theta-E airmass in place pooling along the boundary...it's really hard to imagine that being even remotely close to reality without a good gulf connection and with an on going drought. It's somewhat reassuring that the NAM and nearly all SREF members are active albeit lighter across the same area.

this time of year we usually see this and in an impressive way but its been so dry around here to believe it.

That 12z run though is what we need around here, lights up the whole E-W frontal boundary after 0z Thursday evening and continues for 24hours training along that boundary.

Yeah this is crazy

[A-L-E-K]

this time of year we usually see this and in an impressive way but its been so dry around here to believe it.

That 12z run though is what we need around here, lights up the whole E-W frontal boundary after 0z Thursday evening and continues for 24hours training along that boundary.

Given a more favorable moisture source and lack of drought I'd be all in for a likely training MCS event...I'm sure DVN will throw us another bone this afternoon

[daddylonglegs]

Isn't the GFS always wrong with dewpoints? As in its always way too high?

Low 70Fs here today...clouds keeping temps under control. Love this wx.

[Chicago WX]

Given a more favorable moisture source and lack of drought I'd be all in for a likely training MCS event...I'm sure DVN will throw us another bone this afternoon

Well, it's gotta rain at some point. I mean not to be simplistic or stupid, but if we used the drought thing as an inhibitor...rainfall would've been done 100's of years ago. But I get what you're saying...

[A-L-E-K]

Well, it's gotta rain at some point. I mean not to be simplistic or stupid, but if we used the drought thing as an inhibitor...rainfall would've been done 100's of years ago. But I get what you're saying...

Another question for you, I have been under the impression (very possibly incorrect) that most models incorporate seasonal plant transpiration rates into low level moisture progs...if so, do they also factor in dry conditions. I guess this would be an even bigger issue in a month when the crops are much further along.

you're probably right though, the drought talk is probably overplayed.

[Chicago WX]

Another question for you, I have been under the impression (very possibly incorrect) that most models incorporate seasonal plant transpiration rates into low level moisture progs...if so, do they also factor in dry conditions. I guess this would be an even bigger issue in a month when the crops are much further along.

you're probably right though, the drought talk is probably overplayed.

Not sure to be honest. Probably a good question for the poster dtk who I believe works, or knows of the processes in the modeling branch. Climo is certainly inputed and if you look at MOS or model progs, for example, dewpoint tendencies and the like are clear (i.e. LAF usually has higher predicted dewpoint temps than the other stations in Indiana). Though of course, that's not an answer to your question.

[Geos]

The crops definitely play a role in adding moisture to the air and that helps raise the dewpoints. Just look at the lows region wide that have been in the upper 40s to mid 50s this month. If we were just entering a dry streak with the crops further along, I think the dewpoint forecast would be close to be right, but I think they are over blown for later this week by 5° or so. Was just thinking would higher dewpoints aloft be able to over come the dry ground conditions? More elevated convection as a result?

[hm8]

You can easily see how hot dry spells like these can become feedback cycles with the dryness affecting plants transpiration , which in turn affects the low level moisture and reduces rain chances, which hurts the plants...

[Thundersnow12]

Just looking at current 18z dew points over the plains compared to the models right now the GFS is actually pretty close picking up on the max areas in ND/SD and KS/OK with dews between 72-75. The RAP is a good ways off in the southern plains.

[Powerball]

Saying the drought begets drought is just as simplistic as saying snowpack begets snowpack (CAD) in the winter.

[RobertSul]

Wow. 12z NAM shows widespread 3000+ CAPE in Southeastern Michigan, with a bullseye of what looks like 70kt+ shear over Detroit at hour 60. Looks like a decently strong cap, though.

[A-L-E-K]

Just looking at current 18z dew points over the plains compared to the models right now the GFS is actually pretty close picking up on the max areas in ND/SD and KS/OK with dews between 72-75. The RAP is a good ways off in the southern plains.

I guess that's nice to hear...12z Euro far from exciting but at least breaks out light returns this run compared to the dry 0z run.

[Geos]

Thundersnow ~ What model was Skilling showing on air with the 2"+ rain amounts over the region in the next 7 days?

[A-L-E-K]

Thundersnow ~ What model was Skilling showing on air with the 2"+ rain amounts over the region in the next 7 days?

sounds like the GFS

[turtlehurricane]

48 °F for a low in Madison, of course I totally missed it since the low occurs at 5 am this time of year. Not looking forward to the heat wave since things feel plenty warm outside and it's only in the upper 70s.

Today is 1 minute and 6 seconds shorter than the solstice at least, solar noon sun angle 0.2° lower too. C'mon winter.

[Hoar_Frost]

The crops definitely play a role in adding moisture to the air and that helps raise the dewpoints. Just look at the lows region wide that have been in the upper 40s to mid 50s this month. If we were just entering a dry streak with the crops further along, I think the dewpoint forecast would be close to be right, but I think they are over blown for later this week by 5° or so. Was just thinking would higher dewpoints aloft be able to over come the dry ground conditions? More elevated convection as a result?

Yes, but with at least two important caveats. First, if we ignore the ground-based sources of moisture (from evapotranspiration: soil, vegetation, etc.), which we will since the ground surface is pretty parched at this time in most areas, the moisture at any level above that must be advected (i.e., moved horizontally by the flow at whatever level above the ground) from somewhere else. In the centre of the country, the Gulf of Mexico is a key source of moisture. Second, the depth of moisture through the vertical column is important for convection. If moisture can be advected aloft, that is favorable for cloud formation and possibly precipitation if all other ingredients are in line (lift (from a front, for instance), steep enough lapse rates). But, if there is too deep a layer of dry air, such as near the ground, a situation could arise of precipitation attempting to fall through that layer and evaporating before it reaches the ground.

So, with respect to Thursday's situation, some things are worth thinking about. We will assume that the front is close enough to northern Illinois -- providing a source of lift that could break the cap, and suggesting that the thermal ridge (warmest temperatures aloft -- like 30C at 850 mb) is south of the area, which would, in turn, suggest steepened lapse rates (that is, greater instability) and a less stout cap. First, the cap must be broken, and the foregoing lends some support to a scenario of that occurring. Moisture -- and the quality of that moisture through the column -- is the remaining ingredient to be considered. Ground-based moisture is anemic. So, there is a strong reliance on advecting that moisture from somewhere else. The Gulf is closed off. Drought has developed to our south, west, and east. Would moisture exist sufficiently through the entire column? Some of the models, especially the GFS, suggest that moisture will be more than sufficient and, in fact, at extreme levels (80-degree sfc dewpoints, 2" PWAT values). If the cap broke -- will it? -- and the moisture were that extreme -- can it be? -- the result of a juicy MCS is reasonable. But, there are a lot of question marks, and I'd be very cautious about banking on widespread, plentiful rain on Thursday evening.

[Hoar_Frost]

Thundersnow ~ What model was Skilling showing on air with the 2"+ rain amounts over the region in the next 7 days?

Agreed with Alek -- looked like the GFS.

[A-L-E-K]

Thanks for that post Hoar-Frost

New day 3 from HPC says they're buying into overnight MCS potential

A ZONAL PATTERN WILL ESTABLISH ITSELF ACROSS THE NRN

U.S....ALLOWING WEAK VORT ENERGY TO TRAVERSE THE NRN SIDE OF THE

ROBUST MID LVL SUBTROPICAL RIDGE DOMINATING THE WX OVER THE SRN

TIER OF THE NATION. THIS ENERGY WILL BE INTERACTING WITH A COLD

FRONT THAT WILL BE SETTLING DOWN OVER THE MIDWEST AND STRETCHING

DOWNWIND GRADUALLY ACROSS THE OH VLY AND INTO THE MID-ATL BY THE

END OF THE PERIOD. RELATIVELY HIGH PWATS POOLED ALONG THE

BNDRY...ESP OVER THE N CNTRL PLAINS AND MIDWEST...ALONG WITH

PLENTY OF SFC-BASED INSTABILITY SHOULD HELP SUPPORT SEVERAL

CLUSTERS OF RELATIVELY ORGANIZED SHWRS/TSTMS. THE GREATEST THREAT

SHOULD BE THURS NIGHT AND FRI WITH THE 12Z GFS SHOWING BETTER

THERMODYNAMICS AND LOW LVL JET SUPPORT...WHICH BASED ON THE LARGE

SCALE SYNOPTIC PATTERN SEEMS REASONABLE. WIDESPREAD HVY RAINFALL

IS NOT EXPECTED ATTM GIVEN LARGER SCALE CONCERNS ABOUT A MID LVL

CAPPING INVERSION AND THE GENERAL LACK OF STG FORCING ALOFT WHICH

COULD HELP ERODE THIS CAP. SO...THE MAIN CONVECTIVE THREAT WILL BE

ASSOCD WITH INDIVIDUAL VORT IMPULSE ROUNDING THE TOP OF THE RIDGE.

[Thundersnow12]

Thundersnow ~ What model was Skilling showing on air with the 2"+ rain amounts over the region in the next 7 days?

I have no idea, haven't watched in awhile. Probably the GFS like Alek says. He does like to look at the SREF a lot though.

[Geos]

Nice explanation Hoar_Frost! My call would be for scattered thunderstorms with narrow corridors of rainfall. Will probably chip away at the dry conditions, instead of a widespread event. Keeping my fingers crossed for tropical remnants to come up with way later in the season.

---

73° currently with an east wind.

-- Thundersnow, thought you might be still interning at WGN.