Jump to content
  • Member Statistics

    17,502
    Total Members
    7,904
    Most Online
    Weathernoob335
    Newest Member
    Weathernoob335
    Joined

General Severe Weather Discussion 2018


weatherwiz
 Share

Recommended Posts

5 minutes ago, Typhoon Tip said:

12z NAM blasts interior SNE like a p-wave off a h-bomb with some sort of what looks like derecho activity late Monday afternoon... 

But, like I was ruminating in the other thread, this situation (and unsure if the NAM is handling appropriately) may be too capped.  Big heat domes tend to come with a CIN layer below the EML ... I am noticing that NAM is subtly lower with heights in the transient eastern ridge than prior runs, and that may just erode enough of that to unlid what proooobably would amount to some pretty high SB CAPE.   If that happened, it would be explosive as an understatement - 

Yeah I didn't mention Monday but Monday looks real interesting as well. Models do show some s/w energy moving through as the ulvl ridge breaks down. This also allows for some strengthening westerlies to move overhead. As far as the capping is concerned the lid strength index values were right around -5 or so which would indicate that capping wouldn't be a concern...I guess that could make sense with height falls aloft?...usually with capping issues we see heights rising. 

I wouldn't rule out MCS regeneration across our region either with perhaps some activity developing along the OFB as it propagates into western sections. 

Link to comment
Share on other sites

9 minutes ago, weatherwiz said:

Yeah I didn't mention Monday but Monday looks real interesting as well. Models do show some s/w energy moving through as the ulvl ridge breaks down. This also allows for some strengthening westerlies to move overhead. As far as the capping is concerned the lid strength index values were right around -5 or so which would indicate that capping wouldn't be a concern...I guess that could make sense with height falls aloft?...usually with capping issues we see heights rising. 

I wouldn't rule out MCS regeneration across our region either with perhaps some activity developing along the OFB as it propagates into western sections. 

well ... that's based on modeling, right?    ... those algorithms producing said index(es) are based upon modeled input - what if the models are wrong?   ... 

I mean, big heat "tends" to come along with cap/CIN... That factor suppresses wide-spread CU genesis and hence, unabated sun and big heat can then transpire; the two circumstances thus tend to come together.  

There's obviously the temporal concern with moving parts.  If we CIN through say...2 pm, and temps bomb to 97 with DPS of 60+, then ... your -5 stuff moves over top, that could be the source for Monday afternoon shenanigans...   But, we're talking about the modeled inputs behaving ...combined with experience of course.  

The Euro 'looks' too be more of the CIN heat synopsis though 

 

Link to comment
Share on other sites

8 minutes ago, Cyclone-68 said:

Is there an EML in the region when this happens? 

Haven't seen the soundings but most likely ... the source/origin of the air mass is ejected out of the SW high country and that's typically EML. 

 If any CIN recedes and exposes the high heat and DP below to an elevated mixed layer, that's an intriguing scenario to say the least...

Link to comment
Share on other sites

38 minutes ago, Typhoon Tip said:

well ... that's based on modeling, right?    ... those algorithms producing said index(es) are based upon modeled input - what if the models are wrong?   ... 

I mean, big heat "tends" to come along with cap/CIN... That factor suppresses wide-spread CU genesis and hence, unabated sun and big heat can then transpire; the two circumstances thus tend to come together.  

There's obviously the temporal concern with moving parts.  If we CIN through say...2 pm, and temps bomb to 97 with DPS of 60+, then ... your -5 stuff moves over top, that could be the source for Monday afternoon shenanigans...   But, we're talking about the modeled inputs behaving ...combined with experience of course.  

The Euro 'looks' too be more of the CIN heat synopsis though 

 

You're certainly right with that perspective. I went ahead and looked at H7 temperatures and those would certainly suggest capping. When you have H7 temps approaching +10 around these parts that's pretty strong. 

What I was thinking was this didn't necessarily have that textbook look of nig heat into our region...we weren't under the dome of the high pressure (almost right on the crest) and the source of the hottest llvl air was just to our SW and it was the flow transporting some of this into our area. But look at H7 ridging and positioning we do get those high H7 temps in.

As far as EML goes the pattern actually looks pretty damn good for advection of an EML plume or EML air into our region. There is just one problem...there is no (or little source region lol). What screws things over I think is that initial trough which digs into the western US this weekend and (while flattening) progresses towards the central US and it screws with the EML environment 

 

Link to comment
Share on other sites

3 hours ago, weatherwiz said:

Some pretty impressive looking hodos tomorrow. Lapse rates and better forcing being a bit late hurt things but from C Ny into western SNE there will be some really good storms 

SPC really down on the threat per new Day 1

 

  ...Northeast...

   Weak mid-level height falls are expected to spread across
   southeastern Canada into New England during the day1 period ahead of
   a notable short-wave trough. Latest model guidance suggests a plume
   of high PW, approaching 2", will spread across southern ON/QC ahead
   of a surface front that should approach the international border by
   late afternoon. Extensive frontal convection will be noted along the
   boundary as it surges southeast toward upstate NY/New England.
   Forecast soundings ahead of the wind shift suggest some
   boundary-layer heating will occur but 3-6km lapse rates will remain
   quite weak with values likely remaining on the order of 5.5 C/km. As
   a result, poor mid-level lapse rates will negate meaningful hail
   production and damaging winds should be the primary risk with
   convection as it spreads southeast into this region. Have maintained
   15% severe probs across stronger-forced regions of the Northeast
   with lower probs west along the trailing boundary. This activity
   will likely spread into southern New England into parts of the
   northern Middle Atlantic during the evening hours.
Link to comment
Share on other sites

Wasn’t completely impressed with the 12z soundings from ALB and OKX but I was shocked to see that the H7-H5 lapse rates were 7...though they are weakening during the day. Shear isn’t terrible and still some directional shear in lowest few km. 

There will be a few decent storms around the region today. 

Link to comment
Share on other sites

SPC - "...A band of relatively fast mid-level winds extends across the Great Lakes region and into the northeast states this morning. A surface cold front will sweep southeastward across the northeast US this afternoon and evening, with multiple lines/clusters of thunderstorms expected along and ahead of the front. Early visible satellite imagery over this region shows the potential for substantial daytime heating, with afternoon highs well into the 80s or even lower 90s F. This will yield steep low level lapse rates and MLCAPE values over 1000 J/kg. While storm mode and low/mid level winds appear favorable for a more organized severe wind event, poor mid-level lapse rates appear to be a limiting factor. Storms should spread across much of New England through mid-evening and eventually move offshore and weaken after dark..."

1 .. not sure I agree with the early visible sat trends. "Clearly" (nyuk nyuk) we are being plagued by periodic summit plume exhaust down wind of elevations... This will negate some - how much, we'll see

2 .. I've noticed over the years that MLR is perhaps most important in our region of the CONUS. The reasons for that are complex... for one, EMLs tend to be homogenized by previous day's convective processing before those air masses arrive - that sort of defaults our region, statistically, to relying upon other parameters.  MLR being one of them...  It will be interesting to see if milked EML and MLR being poor are limiting factors yet again.. 

3 ... no one has mentioned this, buut... sometimes these types of fronts have a preceding trough that formulates in the daytime heating...  This causes winds to back west and veer ahead, and that causes a "dry-line" ...that may 86 things if that happens, because when that happens... the theta-e can be prematurely swept out to sea.    

 

Link to comment
Share on other sites

I see a couple positives for today besides the triple H weather:

The NAM forecast 40-50 kt jet streak forecast to move across the northern and central parts of New England today.

And the forecast northwesterlies aloft, tending towards right movers from 290 degrees. That way inflow from the SW is still a pretty large hodograph.

Link to comment
Share on other sites

Satellite shows some early ballooners on the N side of Lake Ontario... I'd watch these cells in their rapid progression/growth in the flow.  They are moving into an area less abated to heating by the same gunk we have here, back east.   Anyway, could see that organizing into an outflow event perhaps with the wind fields... 

What is the convective temp btw ? 

Link to comment
Share on other sites

 Mesoscale Discussion 0779
   NWS Storm Prediction Center Norman OK
   1119 AM CDT Mon Jun 18 2018

   Areas affected...western into northern NY...VT and NH

   Concerning...Severe potential...Watch possible 

   Valid 181619Z - 181815Z

   Probability of Watch Issuance...60 percent

   SUMMARY...Isolated strong thunderstorms primarily capable of 40-55
   mph gusts and wind damage are possible.  A localized risk yielding
   pockets of 55-60 mph may accompany the most intense downdrafts.

   DISCUSSION...Subjective surface analysis places a cold front over
   Lake Huron and extending through Ontario into Quebec.  Ahead of the
   front, the boundary layer is warming through the 80s into the lower
   90s degrees F late this morning into the early afternoon.  Rich
   low-level moisture with lower 70s surface dewpoints reside over much
   of NY with upper 60s in VT/NH.  WSR-88D VAD trends at Burlington, VT
   and Buffalo, NY show mid-level westerly flow beginning to increase
   across the Lower Great Lakes.  Additional strengthening in primarily
   westerly low- to mid-level flow is expected through the early
   evening.

   The 12Z Buffalo, NY RAOB sampled a very poor 700-500 mb lapse rate
   (4.5 degrees C/km) with little improvement expected as the upstream
   air mass farther west near Detroit moves eastward into the lower
   Great Lakes later today.  Nonetheless, strong surface heating has
   steepened 0-2 km lapse rates and up to 1500 J/kg MLCAPE is now
   analyzed in western NY and around 500 J/kg in northern VT/NH.  A
   skinny CAPE profile as a product of the poor mid- to upper-level
   lapse rates will tend to limit momentum transfer from those layers
   to the surface in the form of intense gusts.  As a result, strong
   gusts are mainly expected with the more vigorous multicell cores and
   localized wind damage.

   ..Smith/Weiss.. 06/18/2018

   ...Please see www.spc.noaa.gov for graphic product...

   ATTN...WFO...GYX...BTV...ALY...BGM...BUF...
Link to comment
Share on other sites

Here's a question I've always had but never found an answer. On bufkit in the hodograph section, on the bottom left of the hodograph there is an output for Cape and Helicity...does anyone know what level the Cape is measured in? is it surfaced-based (I'm guessing it is not sfc-based output) mixed-layer, or most-unstable? If i had to guess I would guess mixed-layer. I even tried playing with the llc values on the right to see if that would adjust Cape values but it only does so with helicity 

Link to comment
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now
 Share

  • Recently Browsing   0 members

    • No registered users viewing this page.
×
×
  • Create New...