Napril Fools? Pattern and Model Discussion . . .

[OceanStWx]

2 minutes ago, Damage In Tolland said:

Lol. I knew that would get you .. your office is good.. ours .. leaves a bit to be desired 

There are some legit concerns that with the external pressures for decision support, that forecasts are becoming more reliant on black box procedures and tools to populate the grids you see online.

Probably fine for a quiet weather day, but days like yesterday and today that can get you into trouble fast. Like bad 2 m temps, or PoP that's way too high in the dry slot, etc.

[OceanStWx]

1 minute ago, Sugarloaf1989 said:

Nobody had this amount of sleet forecast, not the NWS, Crapuweather or WU. Also, everyone I saw had the temperature climbing above freezing when it went the other way once the precipitation started.

That was my point to Kevin (though this office had plenty of sleet in the forecast ). There were plenty of people who ran close to model 2 m temps, which were always going to be woeful. 

Another issue was that models had a hard time with the depth of the cold air vs the warm nose aloft, so without manual intervention almost any weather tool that had +3 temps aloft would spit out FZRA vs. PL. That's why it's up the human forecaster to recognize that's not what we want and change it.

[Sugarloaf1989]

Four frozen weather events in the first three weeks of April is simply amazing. I wonder if today was some sort of town record for late season plowing.

[Cold Miser]

26 minutes ago, OceanStWx said:

Clown.

But, I do think we have an issue sometimes with putting in the grids what we expect to happen. Most everyone expected the cold air to take forever to get scoured out, yet some forecasters still relied on model guidance to derive their temp grids. Yeah, we have thousands of grid points to edit but if you even use a fraction of the GFS with its faux mixed layer near the surface your 2 m temps are going to be way off with an inversion like this.

 

[Cold Miser]

6 minutes ago, Sugarloaf1989 said:

Four frozen weather events in the first three weeks of April is simply amazing. I wonder if today was some sort of town record for late season plowing.

Total cold, rain April misery right now.  It would be unreal if we received another event before the end of the month.

[ORH_wxman]

7 minutes ago, OceanStWx said:

That was my point to Kevin (though this office had plenty of sleet in the forecast ). There were plenty of people who ran close to model 2 m temps, which were always going to be woeful. 

Another issue was that models had a hard time with the depth of the cold air vs the warm nose aloft, so without manual intervention almost any weather tool that had +3 temps aloft would spit out FZRA vs. PL. That's why it's up the human forecaster to recognize that's not what we want and change it.

Once you get like a 1500-1800 foot layer below freezing...esp when the max cold layer is like -8C...almost impossible to get pure ZR. But the model guidance tends to revert to the old rule of thumb that anything over 3C in the warm layer is usually freezing rain since usually underneath that is hard to get deep and prolific cold. But this time the easier rules failed since the inversion was so extreme.

[Sugarloaf1989]

4 minutes ago, Cold Miser said:

Total cold, rain April misery right now.  It would be unreal if we received another event before the end of the month.

I agree, sleet covered landscape here and now a heavy 38F rain.

 

[HIPPYVALLEY]

This might be the latest I've ever run the snow blower.  1.5" of sleet and still coming down.  30F 

[HIPPYVALLEY]

Roads are a disaster, no plows. 

[OceanStWx]

9 minutes ago, ORH_wxman said:

Once you get like a 1500-1800 foot layer below freezing...esp when the max cold layer is like -8C...almost impossible to get pure ZR. But the model guidance tends to revert to the old rule of thumb that anything over 3C in the warm layer is usually freezing rain since usually underneath that is hard to get deep and prolific cold. But this time the easier rules failed since the inversion was so extreme.

We're developing new methods to produce weather grids at the NWS, but going is slow when other fires have to be put out. Currently the code is broken, so it wasn't particularly helpful yesterday.

One method is to introduce a probably of refreezing to sleet when the cold layer approaches and eclipses 2500 ft in depth. Another, along similar lines, is to measure the area of the warm layer and the cold layer and let that dictate ptype. 

[STILL N OF PIKE]

2 minutes ago, HIPPYVALLEY said:

This might be the latest I've ever run the snow blower.  1.5" of sleet and still coming down.  30F 

CAD ftw

[CapturedNature]

18 minutes ago, Sugarloaf1989 said:

Four frozen weather events in the first three weeks of April is simply amazing. I wonder if today was some sort of town record for late season plowing.

What did you have on 4/28/1987?  There was several inches from that event across the area.  I think the difference though is that this more ice than snow.

[Sugarloaf1989]

3 minutes ago, MetHerb said:

What did you have on 4/28/1987?  There was several inches from that event across the area.  I think the difference though is that this more ice than snow.

I was living in NYC at that point in time.

[wxeyeNH]

44 minutes ago, dendrite said:

lol...legit snowing again. More snow than yesterday.

It's snowing in Concord?   Im up to 30.8F with light ZR

[ORH_wxman]

19 minutes ago, OceanStWx said:

We're developing new methods to produce weather grids at the NWS, but going is slow when other fires have to be put out. Currently the code is broken, so it wasn't particularly helpful yesterday.

One method is to introduce a probably of refreezing to sleet when the cold layer approaches and eclipses 2500 ft in depth. Another, along similar lines, is to measure the area of the warm layer and the cold layer and let that dictate ptype. 

Yeah its tough because the depth of the cold layer necessary to refreeze can be dictated by the minimum temp in the cold layer...a 2000-2500 foot cold layer of -1C to -3C below a thick +8C warm layer prob isn't refreezing into sleet pellets (this is actually the profile we roughly had in the 2008 ice storm)...but if you now insert about 1000 or 1500 feet worth of -6C to -8C air in that cold layer, the story changes. You can prob refreeze stuff pretty easy at -8C with a cold layer less than 2000 feet.

Some of the old school papers I used to read really liked using -6C in the cold layer as a differentiator. If you could get to -6C in the cold layer, you were almost always observing sleet provided the depth of the sub-freezing layer was a minimum of ~500 meters.

[dendrite]

5 minutes ago, wxeyeNH said:

It's snowing in Concord?   Im up to 30.8F with light ZR

I have Patriots day off...it was snowing at home. Probably low level salt nuclei stuff. It wasn't great growth or anything...but it wasn't tiny snow grains either.

[Sugarloaf1989]

Snowing at MRG and the Sugarbush Valley per webcams. It is very light snow.

 

[dendrite]

At first glance, the lalaland NAM looks pasty up here for Thursday.

[wxeyeNH]

1 minute ago, dendrite said:

I have Patriots day off...it was snowing at home. Probably low level salt nuclei stuff. It wasn't great growth or anything...but it wasn't tiny snow grains either.

31.1F  light sleet here.   Wind is howling and we actually have clouds of blowing sleet across the fields.  Trees have almost 1/4" of ice too and I need it to get above 32F quick or might have some power issues with this wind.

The field has the 1" of sleet and freezing rain.  Im guessing some real good runoff in my gully area that runs into the pond when the heavy stuff gets here.  Deer were trying to dig through the sleet layer last night to get to grass.

[MarkO]

Had some flakes mix in earlier, but predominantly -zr. Hit my maximum temp last night at midnight at 27.6F, lowest temp was around 23 but it was mid day'ish. 

31.0/27

[NorEastermass128]

13 minutes ago, dendrite said:

At first glance, the lalaland NAM looks pasty up here for Thursday.

We winter. 

[#NoPoles]

47 degrees. Jeezus those poor marathon runners

[bmj16725]

37 F here with torrential rain - just had some lightning as well.

[dendrite]

31.7F

Light freezing rain showers mixed with snow grains and occasional pellets.

[powderfreak]

This has been a crazy couple days.  They've plowed our road now several times over the past 48 hours.

Full winter and I think the mountain closed with the deepest top-to-bottom snowpack I've seen in a decade here.  Not just up high but feet of depth to the base.

[OceanStWx]

29 minutes ago, ORH_wxman said:

Yeah its tough because the depth of the cold layer necessary to refreeze can be dictated by the minimum temp in the cold layer...a 2000-2500 foot cold layer of -1C to -3C below a thick +8C warm layer prob isn't refreezing into sleet pellets (this is actually the profile we roughly had in the 2008 ice storm)...but if you now insert about 1000 or 1500 feet worth of -6C to -8C air in that cold layer, the story changes. You can prob refreeze stuff pretty easy at -8C with a cold layer less than 2000 feet.

Some of the old school papers I used to read really liked using -6C in the cold layer as a differentiator. If you could get to -6C in the cold layer, you were almost always observing sleet provided the depth of the sub-freezing layer was a minimum of ~500 meters.

That's the problem with most NWS ptype tools. Now it's easy for me to say, because I don't code them up.

There are some that do the old thickness rules, but the majority use a top down approach that focuses solely on the warm layer. Many of those are designed with the middle of the country in mind, where cold air is often very shallow and doesn't dictate ptype as much as temps aloft. But we had legit 1000-1500 m deep cold layers on our last few soundings. 

[RUNNAWAYICEBERG]

FFW at work. In full spring mode now.

[Sugarloaf1989]

Warm air starting to flow in here, up to 41F with upper 40's on the coast.

[ORH_wxman]

2 minutes ago, OceanStWx said:

That's the problem with most NWS ptype tools. Now it's easy for me to say, because I don't code them up.

There are some that do the old thickness rules, but the majority use a top down approach that focuses solely on the warm layer. Many of those are designed with the middle of the country in mind, where cold air is often very shallow and doesn't dictate ptype as much as temps aloft. But we had legit 1000-1500 m deep cold layers on our last few soundings. 

Yeah, our CAD on a regional level is probably the strongest of anywhere in the country due to the geography/topography...so it builds up into the lower mid-levels pretty frequently. That can make those ptype rules based on the Midwest and plains misleading. I have given presentations on icing in New England and I often tell everyone that you have to throw out the old "valleys are the last to see ZR change to rain" rules that others areas of the country are so used to. That New England has the elevation icing events because our soundings so frequently will have normal cooling lapse rates up to about 2000 feet in many of our events. Not all of them of course, but I'd say in an overwhelming majority of them the icing is actually more intense at elevations between 1000-2000 feet than lower down. Then you can apply this observation to sleet events too...we can get sleet events with warm layers much warmer than the popular +3C cutoff due to our deeper cold inversions. It really is not an easy place to forecast mixed, transition, or icing events if you are not already quite familiar with the local climo and how the topography affects it...as you said, the models fail so often in diagnosing the ptypes in our region because they can't resolve the CAD in both magnitude and depth...almost always underestimating both.

[dendrite]

32F and pouring sleet.