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T-Storm/Squall Line Threat II 3/1


dmillz25

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4 hours ago, IrishRob17 said:

To be fair, using the definition of a microburst it really couldn't be the same one.  That said, this is the first I'm hearing of microburst involved with Saturdays storms around here.  It appeared to me that everything was straight line winds.  When I had the microburst in September of 2014 there was a classic debris pattern of trees, fences, etc (even a cornfield) blown outward from the center in about a one mile diameter.  As for a gas grill, for me at least, I've found that a concrete block on the shelf underneath next to the tank has worked well as an anchor over the years.

Here is some good reading. http://www.srh.noaa.gov/jetstream/derechos/derecho_bowecho.html

 

A section from the above link.

As long as there are new thunderstorm cells forming on the gust front as it advances, replacing the older dissipating cells, the cold pool and rear inflow air will continue. Also, all along the leading edge of the bow echo, thunderstorms may be producing downbursts and microbursts.

About one half (46%) of bow echoes begin as unorganized thunderstorms; 30% form from squall lines, and about one-quarter (24%) from supercell thunderstorms.

If the bow echo (or series of bow echoes) progresses more than 250 miles (400 kilometers) with widespread wind gusts 58 mph (93 km/h) or greater, then the bow echo is classified as a derecho.

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I share the same hidden concerns as the SPC right now with regards to expanding the ENH risk to the NE. IF we have too much steady precip with lingering cloud cover in the AM and early afternoon hours, I think that expectations should be tempered. Though, if we get actual convection that can lay down some boundaries along with some clearing to raise the instability to levels we were seeing on the NAM last night, then I think the upper-end potential may be realized with some larger hail, isolated tornadoes, and damaging wind. 

 

Point is, this is going to be very heavily based on nowcasting so I don't want to hear bust calls before the event is underway. 

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4 minutes ago, Superstorm93 said:

I share the same hidden concerns as the SPC right now with regards to expanding the ENH risk to the NE. IF we have too much steady precip with lingering cloud cover in the AM and early afternoon hours, I think that expectations should be tempered. Though, if we get actual convection that can lay down some boundaries along with some clearing to raise the instability to levels we were seeing on the NAM last night, then I think the upper-end potential may be realized with some larger hail, isolated tornadoes, and damaging wind. 

 

Point is, this is going to be very heavily based on nowcasting so I don't want to hear bust calls before the event is underway. 

I've noticed that the models have slowed down the progression of the warm front, so their is a risk that we don't get warm sectored in time.

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Another decrease in SBCAPE on the 18z NAM. Yesterday we were looking at 1250-2000 j/kg of SBCAPE and now it's more along the lines of 500-750 j/kg. 

I'm not sure what the issue is, as the model still has the area around 70 degrees with dew points into the 60's. And it looks like we should be dry for most of the day, as the morning activity is now more focused South of the area.

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10 minutes ago, Tatamy said:

Looks like we are getting an early start to today's events.  I am getting lightning and thunder now with the approach of the first area of rain.  The lightning is associated with the 40 dbz echos near Allentown, PA.

Good amount of elevated instability with this activity.

mucp.gif?1488376065247

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4 minutes ago, NJwx85 said:

HRRR drops over an inch of rain along the track of the heaviest band.

I saw that. You can see the intensity of the rainfall increasing as it moves into the area of better instability aloft.

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4 minutes ago, bluewave said:

It looks like this first batch got further north than the HRRR was showing a few hours ago with stronger WAA further north than forecast. 

Well that's a good sign considering that the HRRR is really far South with the afternoon activity.

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43 minutes ago, bluewave said:

Some heavy downpours with this first batch of convection as it moves into an area of elevated instability and steep midlevel lapse rates. 

 

WUNIDS_map.gif

 

 

That's right over my other home in Carbon County (just north of where it says Lehighton.)

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