ClicheVortex2014 Posted December 21, 2015 Share Posted December 21, 2015 ...um... what? Really, they have a higher risk then us! I understand it. Climatology argues against having severe weather this time of year. While there's obviously a severe threat per the models, they're just taking the safe route... as is SPC and Dr. Forbes. I'm surprised IWX mentioned supercells. The risk for it is real, but talking about it this early is pretty ballsy IMO Edit: ILN didn't mention severe weather either 1000 J/kg SBCAPE in southern Michigan at 3z in late December. Is the 4km off its rocker? nam4kmCGP_con_sbcape_057.gif I vote yes Link to comment Share on other sites More sharing options...
Stebo Posted December 21, 2015 Share Posted December 21, 2015 1000 J/kg SBCAPE in southern Michigan at 3z in late December. Is the 4km off its rocker? nam4kmCGP_con_sbcape_057.gif Most likely, though if there was ever a chance for that to verify with as strong of a moisture advection regime this would be it. Do I think 1000 J/kg+ is possible, probably not, but 500-750 J/kg isn't unrealistic. Link to comment Share on other sites More sharing options...
Hoosier Posted December 21, 2015 Share Posted December 21, 2015 I understand it. Climatology argues against having severe weather this time of year. While there's obviously a severe threat per the models, they're just taking the safe route... as is SPC and Dr. Forbes. I'm surprised IWX mentioned supercells. The risk for it is real, but talking about it this early is pretty ballsy IMO Edit: ILN didn't mention severe weather either I vote yes IND could've discussed the pros and cons of the setup. Even the Michigan offices (GRR and DTX) said something about it. Link to comment Share on other sites More sharing options...
HillsdaleMIWeather Posted December 21, 2015 Author Share Posted December 21, 2015 HAHAHAH, YEAH RIGHT Link to comment Share on other sites More sharing options...
Stebo Posted December 21, 2015 Share Posted December 21, 2015 HAHAHAH, YEAH RIGHT Good analysis... Link to comment Share on other sites More sharing options...
andyhb Posted December 21, 2015 Share Posted December 21, 2015 HAHAHAH, YEAH RIGHT Can you please do more than these one liners and spamming of maps? This is getting ridiculous. Link to comment Share on other sites More sharing options...
Stebo Posted December 21, 2015 Share Posted December 21, 2015 Just to dive deeper into the 4km, it isn't really that unrealistic when you think about it. The only difference is in the dew points, instead of 57-58 it is 60-61. I mean if it was showing something stupid like 63+ then yeah I would immediately discount it. Hell the point sounding below has a 59 dew point with 1000+ J/kg: The main thing is the cold air aloft driving the instability and I don't suspect that to change too much between now and then Link to comment Share on other sites More sharing options...
ClicheVortex2014 Posted December 21, 2015 Share Posted December 21, 2015 Most likely, though if there was ever a chance for that to verify with as strong of a moisture advection regime this would be it. Do I think 1000 J/kg+ is possible, probably not, but 500-750 J/kg isn't unrealistic. Absolutely. And 500-750 is certainly enough for at least a decent shot at severe weather. I'm not sure what cool season event has featured that range of CAPE in our subforum. I'm thinking 10/26/10... but the wind profile was a completely different beast. IND could've discussed the pros and cons of the setup. Even the Michigan offices (GRR and DTX) said something about it. Agreed Link to comment Share on other sites More sharing options...
Hoosier Posted December 21, 2015 Share Posted December 21, 2015 Just to dive deeper into the 4km, it isn't really that unrealistic when you think about it. The only difference is in the dew points, instead of 57-58 it is 60-61. I mean if it was showing something stupid like 63+ then yeah I would immediately discount it. Hell the point sounding below has a 59 dew point with 1000+ J/kg: The main thing is the cold air aloft driving the instability and I don't suspect that to change too much between now and then Ah, I was wondering if maybe it was more lapse rate driven as the modeled temps/dews didn't look too crazy. 700-500 mb of 7.0 C/km in a severe weather setup is pretty darn good at this time of year. Other models are a bit less but do show the pocket of steeper lapse rates swinging toward southern MI on Wednesday evening. Link to comment Share on other sites More sharing options...
Stebo Posted December 21, 2015 Share Posted December 21, 2015 Ah, I was wondering if maybe it was more lapse rate driven as the modeled temps/dews didn't look too crazy. 700-500 mb of 7.0 C/km in a severe weather setup is pretty darn good at this time of year. Other models are a bit less but do show the pocket of steeper lapse rates swinging toward southern MI on Wednesday evening. Yeah, and with the strong wind field and no MCS blowing up to steal moisture, the road is open for moisture to continue to scream northward through the evening. Link to comment Share on other sites More sharing options...
HillsdaleMIWeather Posted December 21, 2015 Author Share Posted December 21, 2015 18Z GFS had an uptick on the Supercell composites Link to comment Share on other sites More sharing options...
Thundersnow12 Posted December 21, 2015 Share Posted December 21, 2015 Good analysis... Someone want to explain why he hasn't been 5 posted yet? This brings nothing. At least state why you say that. Back on topic.. The 18z 4km max UD tracks were pretty ominous in IL and IN, strengthening between 0-3z Link to comment Share on other sites More sharing options...
IllinoisWedges Posted December 21, 2015 Share Posted December 21, 2015 LOT's AFD just came out. They also mentioned the potential for low topped supercells if we can get some CAPE. LOT's statement: "SO A CONDITIONAL THREAT OF GUSTY WINDS/POSSIBLY LOW-TOPPED SUPERCELLS SEEMS LIKE IT COULD EXIST...AND NOTSURPRISINGLY SOME OF THE CIPS ANALOGS FOR SUCH A DEEP LOW TO OURWEST THIS TIME OF YEAR INDICATE SOME POTENTIAL FOR STRONGERSTORMS." Link to comment Share on other sites More sharing options...
Central Illinois Posted December 21, 2015 Share Posted December 21, 2015 18Z GFS had an uptick on the Supercell composites The GFS is available and free to everyone so we can see it.... LOT's AFD just came out. They also mentioned the potential for low topped supercells if we can get some CAPE. LOT's statement: "SO A CONDITIONAL THREAT OF GUSTY WINDS/POSSIBLY LOW-TOPPED SUPERCELLS SEEMS LIKE IT COULD EXIST...AND NOT SURPRISINGLY SOME OF THE CIPS ANALOGS FOR SUCH A DEEP LOW TO OUR WEST THIS TIME OF YEAR INDICATE SOME POTENTIAL FOR STRONGER STORMS." ILX basically said the same thing mentioned Several clusters of thunderstorms possibly severe also mentions if we can get breaks in cloud cover then the potential would go up Link to comment Share on other sites More sharing options...
ClicheVortex2014 Posted December 21, 2015 Share Posted December 21, 2015 One of my weakest points of severe weather forecasting is determining storm mode. This time of the year, I just assume that it's going to be linear... because it usually is. I see the talk of low-topped supercells, and I see the models output; it looks like the dominant storm mode is semi-discrete to discrete. But is there any reason to doubt this? Events where storm mode isn't an issue are quite rare... probably even more rare for a December event... just not sure if this is really expected to be one of those events. Link to comment Share on other sites More sharing options...
Hoosier Posted December 21, 2015 Share Posted December 21, 2015 One of my weakest points of severe weather forecasting is determining storm mode. This time of the year, I just assume that it's going to be linear... because it usually is. I see the talk of low-topped supercells, and I see the models output; it looks like the dominant storm mode is semi-discrete to discrete. But is there any reason to doubt this? Events where storm mode isn't an issue are quite rare... probably even more rare for a December event... just not sure if this is really expected to be one of those events. Storm mode is often difficult...sometimes it's pretty obvious that you will have a solid window of supercells and then the question is when it transitions toward more of a linear mode. Looking at shear vectors in relation to initiating boundaries helps. I check VV plots as well. One thing that bothers me a bit about this setup in terms of a better tornado threat in our region is the lack of directional shear. Looking at forecast soundings across the region, there's really not a whole lot. There's some in the lowest km so I guess that counts for something, and we see a lot of setups with that kind of wind profile so I guess it's not really anything new. Mid/upper level flow is pretty meridional (better farther south). Surface low will be deepening throughout the day so perhaps the surface winds can stay a little more backed than progged but we'll see. Link to comment Share on other sites More sharing options...
MattPetrulli Posted December 21, 2015 Share Posted December 21, 2015 So I got my question on Weather Underground tonight. Asked if violent tornadoes are possible on Wednesday and Greg Forbes replied "Yes, violent, long tracked tornadoes are possible Wednesday." I like to ask for opinions from other meteorologists. All of that aside, 18z GFS is still holding on to a tornado outbreak on Wednesday. Soundings are better than 12z GFS. Link to comment Share on other sites More sharing options...
ClicheVortex2014 Posted December 21, 2015 Share Posted December 21, 2015 Storm mode is often difficult...sometimes it's pretty obvious that you will have a solid window of supercells and then the question is when it transitions toward more of a linear mode. Looking at shear vectors in relation to initiating boundaries helps. I check VV plots as well. One thing that bothers me a bit about this setup in terms of a better tornado threat in our region is the lack of directional shear. Looking at forecast soundings across the region, there's really not a whole lot. There's some in the lowest km so I guess that counts for something, and we see a lot of setups with that kind of wind profile so I guess it's not really anything new. Mid/upper level flow is pretty meridional (better farther south). Surface low will be deepening throughout the day so perhaps the surface winds can stay a little more backed than progged but we'll see. Thanks. I watched Rich Thompson's tornado forecasting workshop... I only remember a couple factors to help determine storm mode. One's how the upper flow matches the position of the cold front. If the flow is parallel to the front, there'll be a tendency for linear storm mode. Looking at the 18z NAM for 24/00z, it looks like that'll be the case. Since the models are showing that kind of storm mode, I have to assume that frontal convergence must be weak... or they're just underestimating it and will see a linear storm mode. That's worrisome. But down south, it looks like the upper flow will nearly be perpendicular to the front. That seems to be just another factor in favor for nastiness down there. So I got my question on Weather Underground tonight. Asked if violent tornadoes are possible on Wednesday and Greg Forbes replied "Yes, violent, long tracked tornadoes are possible Wednesday." I like to ask for opinions from other meteorologists. All of that aside, 18z GFS is still holding on to a tornado outbreak on Wednesday. Soundings are better than 12z GFS. I'm surprised by Dr. Forbes' response... not because I disagree, but he's usually more conservative than that Link to comment Share on other sites More sharing options...
Stebo Posted December 21, 2015 Share Posted December 21, 2015 Storm mode is often difficult...sometimes it's pretty obvious that you will have a solid window of supercells and then the question is when it transitions toward more of a linear mode. Looking at shear vectors in relation to initiating boundaries helps. I check VV plots as well. One thing that bothers me a bit about this setup in terms of a better tornado threat in our region is the lack of directional shear. Looking at forecast soundings across the region, there's really not a whole lot. There's some in the lowest km so I guess that counts for something, and we see a lot of setups with that kind of wind profile so I guess it's not really anything new. Mid/upper level flow is pretty meridional (better farther south). Surface low will be deepening throughout the day so perhaps the surface winds can stay a little more backed than progged but we'll see. GFS and NAM tend to not pick up on the low level wind response to a deepening low pressure. One would imagine the winds would be a bit more southerly maybe even south southeasterly once the low really ramps up. To be honest though what it is showing now is fine, so we have a margin of error in this case. So I got my question on Weather Underground tonight. Asked if violent tornadoes are possible on Wednesday and Greg Forbes replied "Yes, violent, long tracked tornadoes are possible Wednesday." I like to ask for opinions from other meteorologists. All of that aside, 18z GFS is still holding on to a tornado outbreak on Wednesday. Soundings are better than 12z GFS. I would agree with him, but the potential would be better south, not to say up here doesn't have a conditional potential of stronger tornadoes as well. Link to comment Share on other sites More sharing options...
MattPetrulli Posted December 21, 2015 Share Posted December 21, 2015 Thanks. I watched Rich Thompson's tornado forecasting workshop... I only remember a couple factors to help determine storm mode. One's how the upper flow matches the position of the cold front. If the flow is parallel to the front, there'll be a tendency for linear storm mode. Looking at the 18z NAM for 24/00z, it looks like that'll be the case. Since the models are showing that kind of storm mode, I have to assume that frontal convergence must be weak... or they're just underestimating it and will see a linear storm mode. That's worrisome. But down south, it looks like the upper flow will nearly be perpendicular to the front. That seems to be just another factor in favor for nastiness down there. I'm surprised by Dr. Forbes' response... not because I disagree, but he's usually more conservative than that GFS and NAM tend to not pick up on the low level wind response to a deepening low pressure. One would imagine the winds would be a bit more southerly maybe even south southeasterly once the low really ramps up. To be honest though what it is showing now is fine, so we have a margin of error in this case. I would agree with him, but the potential would be better south, not to say up here doesn't have a conditional potential of stronger tornadoes as well. Yeah he's usually quite conservative on forecasts like this. I agree, if violent tornadoes were to happen, I'd go with LA to Southern MS, maybe one in Alabama too. Storm mode looks to be at least semi-discrete based on NAM-NAM 4K. Some supercells could go on for a while into the evening before either becoming linear or just weakening. Link to comment Share on other sites More sharing options...
Hoosier Posted December 21, 2015 Share Posted December 21, 2015 The parameters down south are sick...definitely enough for strong/violent tornadoes, at least on paper. Link to comment Share on other sites More sharing options...
andyhb Posted December 22, 2015 Share Posted December 22, 2015 The parameters down south are sick...definitely enough for strong/violent tornadoes, at least on paper. Just waiting for CUmet to chime in. Link to comment Share on other sites More sharing options...
Stebo Posted December 22, 2015 Share Posted December 22, 2015 DTX thoughts: ATTENTION LATE WEDNESDAY INTO PREDAWN THURSDAY MORNING TURNS TOSEVERE POTENTIAL AS LOW PRESSURE LIFTS TOWARD THE STRAITS ANDATTENDANT LLJ OF 60KTS ENCROACHES FROM THE WEST. SE MICHIGAN WILLREMAIN WELL-REMOVED FROM THE STRONGEST FORCING, BUT THE THREAT FORSHOWERS/ISOLATED TSTORMS WILL EXIST THROUGH WEDNESDAY NIGHT AS T/TDSRISE TO AROUND 58/54 DEGREES IMMEDIATELY IN ADVANCE OF THE FRONT -QUITE IMPRESSIVE FOR OVERNIGHT DURING LATE DECEMBER. SEASONABLY HIGH0-6KM BULK SHEAR IN EXCESS OF 80KTS / SRH > 250 M2/S2 / MUCAPE > 300J/KG WILL PRESENT AN INSTANCE OF SEVERE POTENTIAL IN AN EXTREMESHEAR/VERY MARGINAL CAPE SCENARIO. SEVERE WIND GUSTS OR MARGINALPOTENTIAL FOR ISOLATED WEAK TORNADOES MAY EXIST WITHIN STRONGERSHOWERS. THOUGH THE THREAT WILL BE MARGINAL, POTENTIAL WARRANTSMONITORING. FOR NOW, WILL MAKE AN INTRODUCTORY MENTION IN THE HWOFOR WIND GUSTS TO 50 MPH WED NIGHT AS UNCERTAINTY IS HIGH ATTM. Only the GFS is showing a T/Td similar to that and even it is a touch higher. They are going pretty bold with that T/Td so if we do realize higher T/Td like the NAM12/NAM4/Euro are showing we will really be in business I think. Link to comment Share on other sites More sharing options...
Indystorm Posted December 22, 2015 Share Posted December 22, 2015 IND has now issued an HWO and now says that spotter activation may be needed on Wed. I am going to be watching this event and the progged Sun/Mon event very closely as I'm sure many of you will as well. Link to comment Share on other sites More sharing options...
Stebo Posted December 22, 2015 Share Posted December 22, 2015 Just to give you an idea of the aerial coverage the 4km NAM has: Link to comment Share on other sites More sharing options...
MattPetrulli Posted December 22, 2015 Share Posted December 22, 2015 Just to give you an idea of the aerial coverage the 4km NAM has: Still has some semi discrete storms on there at least. Link to comment Share on other sites More sharing options...
Indystorm Posted December 22, 2015 Share Posted December 22, 2015 "...some semi discrete storms?" I think that 4K map Stebo posted is quite concerning and it doesn't even show MS/AL. Link to comment Share on other sites More sharing options...
MattPetrulli Posted December 22, 2015 Share Posted December 22, 2015 "...some semi discrete storms?" I think that 4K map Stebo posted is quite concerning and it doesn't even show MS/AL. I meant IL and IN. Link to comment Share on other sites More sharing options...
PGM Posted December 22, 2015 Share Posted December 22, 2015 Any ideas on what the SPC is thinking for tomorrow's Day 2 outlook? Will we see an upgrade to enhanced or moderate for MS, AR, TN? Sent from my XT1563 using Tapatalk Link to comment Share on other sites More sharing options...
HillsdaleMIWeather Posted December 22, 2015 Author Share Posted December 22, 2015 Any ideas on what the SPC is thinking for tomorrow's Day 2 outlook? Will we see an upgrade to enhanced or moderate for MS, AR, TN? Sent from my XT1563 We haven't seen a 15 to 45% jump in awhile, so I bet they will go Enhanced while saying "UPGRADE TO MODERATE MAY BE NEEDED" Link to comment Share on other sites More sharing options...
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