May 2024 Weather Discussion

[tron777]

I'll have more here shortly... on my lunch break now and outside of the "Iron Curtain" I will be able to make better posts for the next hour. NAM will be coming out here shortly too so let's see what it looks like for later today.

[tron777]

Despite the date being wrong on this video, BG is LIVE right now. (As of this post)

[tpweather]

Many of the models are having trouble with what is going on at the surface so must do some extra work lol.

[tron777]

12Z Operational NAM has rain today but I don't see anything intense until this evening and that's when it has those scattered supercells impacting the Tri-state, The 3KM NAM or the Hi-res NAM is much more like the HRRR that I talked about earlier which is I think the way to go.

Here is the sounding near CVG from the 12Z HRRR valid at 5pm.

hrrr_2024050712_009_39.08--84.71.png

The 12Z 3KM NAM valid for the same location and time period.

nam4km_2024050712_009_39.23--84.58.png

[tron777]

Now that we have looked at some data, and this is what Tim was eluding too, is that can we believe it? What is actually happening in real time right now? Weak CAPE is already trying to build into the Tri-state despite the cloud cover. The airmass is very juicy and will continue to get juicer as time goes on. Per the latest visible sat.... we may see a peak or two of sun right out ahead of the first time to our West. Once it passes, there is a nice area of clear skies back over Western ILL getting into Central ILL so IMO the instability factor will be there later today. Dews are already at 66 at CVG per the 10am reading so upper 60s for dewpoints later today is certainly doable. LCL's are low so the cloud bases are low in other words which is what you want for supercell t-storm development, esp to get these things to rotate. Bulk shear over ILL is at 40 knots in the Eastern part of the state to 70 knots back towards St. Louis. So we have plenty of wind energy off to the West once this first line passes. Lapse rates could use some work. I'd like to see 7.0C or higher for large hail and for good storm organization. Currently, 7.0 to 7.5C exists over Western ILL and 6 to 6.5C over Eastern ILL getting into far Western IN. Helicity or spin in the atmosphere looks good in the 250-300 range over Central ILL. Supercell Comp index is decent from Paducah, KY and points SW. VTP or violent tornado parameter is building in that same zone I just mentioned. So all in all.... things to me should unfold as the data is showing IMO. We will need to watch the SPC mesopage along with the radar picture hour by hour to see how things evolve as the day wears on. Speaking of the current radar picture, none of that is currently severe, nor it is expected to be at this point in time as it approaches I-65 currently.

[tpweather]

Great Post Les and we are on the same page and Brian talked about what we are seeing at the moment and how he had to readjust his forecast somewhat with new information. I agree about the models and the hrrr is good for the short term because it updates every hour and like this morning the line of storms weaken but not so much on the southern end and that is where the warm front is located. So great video by Brian and all on the same page.

[Closet Meteorologist]

12Z Operational NAM has rain today but I don't see anything intense until this evening and that's when it has those scattered supercells impacting the Tri-state, The 3KM NAM or the Hi-res NAM is much more like the HRRR that I talked about earlier which is I think the way to go.

Here is the sounding near CVG from the 12Z HRRR valid at 5pm.


hrrr_2024050712_009_39.08--84.71.png


The 12Z 3KM NAM valid for the same location and time period.


nam4km_2024050712_009_39.23--84.58.png

Someone tell me how to read this!

[tron777]

Great Post Les and we are on the same page and Brian talked about what we are seeing at the moment and how he had to readjust his forecast somewhat with new information. I agree about the models and the hrrr is good for the short term because it updates every hour and like this morning the line of storms weaken but not so much on the southern end and that is where the warm front is located. So great video by Brian and all on the same page.

Definitely Tim... we are lock n step with this event for today. We'll just have to see if we need to adjust our thinking (good or bad) as time goes on.

[tron777]

12Z Operational NAM has rain today but I don't see anything intense until this evening and that's when it has those scattered supercells impacting the Tri-state, The 3KM NAM or the Hi-res NAM is much more like the HRRR that I talked about earlier which is I think the way to go.

Here is the sounding near CVG from the 12Z HRRR valid at 5pm.


hrrr_2024050712_009_39.08--84.71.png


The 12Z 3KM NAM valid for the same location and time period.


nam4km_2024050712_009_39.23--84.58.png

Someone tell me how to read this!

I wish I had the time to answer this and to write up something but my lunch break is about up. Here is a good link though that should explain a lot of it on how to read a Skew T diagram (or sounding).


https://www.weather.gov/source/zhu/ZHU_ ... tinfo.html

[tron777]

Hot off the presses from the boys:

.NEAR TERM /UNTIL 6 PM THIS EVENING/...
Morning update trended the forecast towards HRRR/RAP blended
into current forecast. This seemed on track for T/Td and
accounted for line of storms crossing the CWA this morning, with
a break behind it. While placement and occurrence of storms in
the airmass this afternoon/evening remains in question, the
model blend noted above looked to capture probability of
rain/storms if not relatively well then well within reason.

Weak showers running nw-se that tail off over Warren County have
a warm frontal appearance. The airmass difference here is an
uptick in dewpoints behind it.

Parameters of significant shear and instability remain in place
this afternoon for severe weather. This is an all-mode severe
weather threat with damaging winds, large hail, isolated
flooding, and tornados. Tornado parameters per SPC and some AI
forecasts have the entire CWA with a potential of significant
tornados >EF2. The AI enhances a more narrow corridor running
sw-ne through Cincy metro area, curving northward into Dayton
metro area.

[BookNerdCarp]

From NWS

[10:30 AM] You have questions, we have answers. We want to share a few key points with you regarding the setup for today:
- Will the early afternoon storms affect the evening storms? Not much. Although we are expecting some early afternoon storms, with greatest coverage near the Ohio River, this shouldn't have much impact on the instability that develops this evening because that more unstable environment will be advecting (or moving into) the area opposed to strictly redeveloping with sunshine. Clouds will have little to no impact on storm severity. Rapid destabilization is expected late afternoon into early evening.

- Will storms decrease in intensity after dark? No. The sunset will have little to no impact on the environment as there won't be much cooling or stabilization into the early nighttime hours. So just because the sun is setting does NOT necessarily mean the severe threat will decrease or end earlier. In fact, the greatest severe risk will likely continue in the several hour period AFTER sunset. We are still expecting the severe threat to wane beyond midnight.

- Will the severe outlook be updated or upgraded? We are in constant communication with SPC regarding updates and adjustments needed to any/all severe outlooks. That being said, it is important to NOT focus squarely on your specific category or color. There is a chance for severe weather area-wide late afternoon through the evening, including after dark.

- Will you be doing extra balloon launches today? Yes, one at 21z with the standard one at 00z also expected.

[tpweather]

I agree with the NWS as the llj with be gaining strength in the evening and many times you see this gaining in the 3-6a period but like yesterday in the plains the jet is gaining earlier so the severe threat that normally loses some intensity will still be strong.

[tpweather]

Looks like the storms are moving rather quickly so in the next hour or so expect a southwest to northeast band of showers and thundershowers to work its way in the area. Quick moving and though you can expect some heavy rain and thunder and lightning nothing looks severe plus the amount of time its raining should not cause much in the way of flooding expect the normal streets that have a harder time with runoff.

[tron777]

Great posts Tim and Matt... thank you Sir for sharing that info from ILN. Very informative and it looks like they are on the same page as we are. 72 / 67 as of 12pm at CVG.

[tpweather]

Already seeing the dew points go up in southeast Missouri and southwest Kentucky so more fuel will be added later today plus if after this first round goes by and we see a good deal of sun the stakes go up.

[BookNerdCarp]

Could be a bumpy ride tonight..

[MVWxObserver]

Currently 70 here in G'ville with a DP of 63.

[tpweather]

Theme of the spring as seeing some hail mixed in with the rain

[tron777]

...A STRONG THUNDERSTORM WILL IMPACT PORTIONS OF NORTHERN BRACKEN...
CENTRAL CAMPBELL...NORTHEASTERN PENDLETON...CLERMONT AND NORTHWESTERN
BROWN COUNTIES THROUGH 130 PM EDT...

At 101 PM EDT, a strong thunderstorm was located over New Richmond,
moving northeast at 45 mph.

HAZARD...Wind gusts up to 45 mph and pea size hail.

SOURCE...Radar indicated.

IMPACT...Gusty winds could knock down tree limbs and blow around
unsecured objects. Hail may cause minor damage to
vegetation.

Locations impacted include...
Amelia, Mount Orab, Bethel, New Richmond, Williamsburg, Batavia,
Felicity, Withamsville, Owensville, Goshen, Newtonsville,
Fayetteville, Mentor, Moscow, St. Martin, California, Chilo,
Chasetown, Saltair, and Nicholsville.

[tron777]

No changes to the 12:30pm SPC Day 1 convective outlook. PWATS are currently at 1.7" right over us so heavy rainfall is likely with this first batch as it moves thru. Sub severe wind and hail is also possible but this is nothing to be honest as to what could happen later as we've been talking about today. Seeing some partial clearing behind this first wave over Central IN and Western KY. CAPE Values are quickly rising and responding to our West. DCAPE values of 900-1000 J/KG are over ILL and that will be heading in our direction soon. Lapse rates are outstanding now (very steep) over ILL and bulk shear is in the 60-70 knot range. Helicity values of 200 are also off to the West. Supercell Comp and VTP looks pretty ominous down to our SW over West KY, West TN, SE MO, AR, etc. Derecho comp is between 6-10 in that same region. For hail, it looks very good for very large hail to occur in that same general area. So once that type of airmass gets advected into our region late this afternoon and evening, then we will be under the gun for supercells along with a line of storms later this evening. All severe hazards are absolutely still on the table folks.

CVG gusted to 41 mph as of 1pm when the line went thru there.

[tron777]

The action has arrived here in Mason with that first round. Booming thunder, heavy rain and very dark skies atm.

[tpweather]

Heavy rain has taken over

[pickles]

12Z Operational NAM has rain today but I don't see anything intense until this evening and that's when it has those scattered supercells impacting the Tri-state, The 3KM NAM or the Hi-res NAM is much more like the HRRR that I talked about earlier which is I think the way to go.

Here is the sounding near CVG from the 12Z HRRR valid at 5pm.


hrrr_2024050712_009_39.08--84.71.png


The 12Z 3KM NAM valid for the same location and time period.


nam4km_2024050712_009_39.23--84.58.png

Someone tell me how to read this!

I wish I had the time to answer this and to write up something but my lunch break is about up. Here is a good link though that should explain a lot of it on how to read a Skew T diagram (or sounding).


https://www.weather.gov/source/zhu/ZHU_ ... tinfo.html

Wow! Thanks for this, Les!

[tron777]

Wow! Thanks for this, Les!

You're welcome! I wish I had more time to post. Gosh do I miss working from home!

[tron777]

It looks like the first TOR watch of the event is going to be issued soon to our NW. This is for Eastern ILL and Northern and Western IN:

https://www.spc.noaa.gov/products/md/md0676.html