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Vendor Forecast Discussion

am19psu

By am19psu,
in Philadelphia Region

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ChescoWx

ChescoWx

Posted
Posted

JB's latest comment on the WB site regarding the GFS

 

"No I am not going to trash it. I dont believe it, but I am not going to simply dismiss it". He goes on to say he thinks that he has the right idea and believes that amounts are more likely to increased rather than taken down, but he says he will not laugh at it as the weather has a way of humbling him when he tries to spike the ball....he goes on to say the Canadian btw has been winning skill score battles in the longer term and this will certainly be a coup for it from earlier.

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ChescoWx

ChescoWx

Posted
Posted

Latest paraphrased evening post from JB

 

He likes what he has out but suspects in honing in tomorrow he will need to increase some amounts in the Midwest and mid Atlantic. He sees the heaviest snow of course in the mountains, but the center of this is as he has been saying will be south of New England and aimed at the snow hole in the mid Atlantic. He sees that alot of areas north of I-80 see less than 2".... and south of the PA TPK can see more than 10. He also talks a bit about rations. Where its in the upper 20s and its -8 at 850, the upward motion totals are a better indicator of snow amounts than 10 to 1. This is the old "magic" formula., total the 6 hour upward motion in Microbar/s and you get the amounts. If you have plus 15 and plus 5 , and its -8, you get near 20 inches. He says young forecasters have no idea what they heck this is about, but it was an empirical formula that old timers used to use. He says a 5 to 1 ratio is possible but only its snowing and 35 or 36.. but usually when it snows hard it comes down to 32 the same way that when it rains hard in a freezing rain situation temp rise to near freezing. He says the freezing process releases heat into the air..the energy to melt a snowflake taken out of the air has the opposite effect. That is why sometimes you will see it start to snow hard with a wet bulb above freezing and then like magic it will drop to freezing. Its not cold air coming down from above...but instead what happens in the melting process. Its almost as if there is some kind of defense mechanism the snow uses to maintain itself. He links to an article for a read on the release of heat into the air because of freezing he says "melting snowflakes will sacrifice themselves for the millions that follow"

 

http://theweatherprediction.com/habyhints2/468/

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Ellinwood

Ellinwood

Posted
Posted

JB's gonna bust so hard.

Perhaps it's the old dogs that need to spend more time learning about the behind-the-scenes computation and output of the models. That whole last post shows that he understands some of the physics and mechanics of the atmosphere, but he's (likely) drawing the wrong conclusions when it comes to actual snow on the ground.

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ChescoWx

ChescoWx

Posted
Posted

From Larry Cosgrove's letter tonight ( I do miss him from his days on PHL 17....I remember his blizzard of '96 reporting - hoping he makes it back to his hometown one of these days)

 

"Secondary cyclogenesis will occur Sunday evening near Wilmington NC, which will create a myriad of forecast problems. As the very cold 500MB low crosses middle Appalachia, thundersnow will break out with 1 - 2 inch per hour snowfall rates. The new low center over the Virginia Capes will track northeastward, phase with the cold pool and vorticity, and offer the chance at a crushing dollop of wet snow from northern Virginia into the Philadelphia PA and Atlantic City NJ metros (no accumulating snow is likely to fall north of the Interstate 78 corridor from Allentown PA into Newark NJ). This being March, the daylight hours will turn that snow over to rain, drizzle or sleet where vertical velocities slacken. But where elevation, UVV, cold 850MB temperatures and time of day conspire (think Front Royal VA to West Chester PA and 50 miles either side), someone could see 4 - 8 inches of wet snow"

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snowwors2

snowwors2

Posted
Posted

From Larry Cosgrove's letter tonight ( I do miss him from his days on PHL 17....I remember his blizzard of '96 reporting - hoping he makes it back to his hometown one of these days)

 

"Secondary cyclogenesis will occur Sunday evening near Wilmington NC, which will create a myriad of forecast problems. As the very cold 500MB low crosses middle Appalachia, thundersnow will break out with 1 - 2 inch per hour snowfall rates. The new low center over the Virginia Capes will track northeastward, phase with the cold pool and vorticity, and offer the chance at a crushing dollop of wet snow from northern Virginia into the Philadelphia PA and Atlantic City NJ metros (no accumulating snow is likely to fall north of the Interstate 78 corridor from Allentown PA into Newark NJ). This being March, the daylight hours will turn that snow over to rain, drizzle or sleet where vertical velocities slacken. But where elevation, UVV, cold 850MB temperatures and time of day conspire (think Front Royal VA to West Chester PA and 50 miles either side), someone could see 4 - 8 inches of wet snow"

AGREED..first to call the 2-3 feet in '96...back in those days I spoke with Larry (before, during and after) nearly every snowstorm..he was very accessible.  In '96 or so, he did a weather presentation to my son's class at glenside elementary...he was terrific...really great guy!!

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famartin

famartin

Posted
Posted

Latest paraphrased evening post from JB

 

He likes what he has out but suspects in honing in tomorrow he will need to increase some amounts in the Midwest and mid Atlantic. He sees the heaviest snow of course in the mountains, but the center of this is as he has been saying will be south of New England and aimed at the snow hole in the mid Atlantic. He sees that alot of areas north of I-80 see less than 2".... and south of the PA TPK can see more than 10. He also talks a bit about rations. Where its in the upper 20s and its -8 at 850, the upward motion totals are a better indicator of snow amounts than 10 to 1. This is the old "magic" formula., total the 6 hour upward motion in Microbar/s and you get the amounts. If you have plus 15 and plus 5 , and its -8, you get near 20 inches. He says young forecasters have no idea what they heck this is about, but it was an empirical formula that old timers used to use. He says a 5 to 1 ratio is possible but only its snowing and 35 or 36.. but usually when it snows hard it comes down to 32 the same way that when it rains hard in a freezing rain situation temp rise to near freezing. He says the freezing process releases heat into the air..the energy to melt a snowflake taken out of the air has the opposite effect. That is why sometimes you will see it start to snow hard with a wet bulb above freezing and then like magic it will drop to freezing. Its not cold air coming down from above...but instead what happens in the melting process. Its almost as if there is some kind of defense mechanism the snow uses to maintain itself. He links to an article for a read on the release of heat into the air because of freezing he says "melting snowflakes will sacrifice themselves for the millions that follow"

 

http://theweatherprediction.com/habyhints2/468/

 

That's just not scientifically accurate.  It might've been an "easy rule of thumb" for the days when model data was much more limited, but in today's world, when we can see progged temps through the atmosphere, its better to actually locate the intersection of upward motion and determine the temperature.  I.E., if its -8 at 850, your best lift is at 700 but its only -5 there... guess what, you aren't getting good ratios.

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ChescoWx

ChescoWx

Posted
Posted

420pm update from JB

 

He sees the core of the heaviest snow in the I70 corridor in the mid west but the worst part of this may be over NJ because of the wind that can develop. The big cities of southern New England should end up a miss, with PHL BWI. IAD beating NYC, but he says he likes the 4 inch line right over the CPK. He will have his new numbers at around 6pm on his site - he already told his commercial clients

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noctilucent

noctilucent

Posted
Posted

According to that map, DYL gets only 1"-2". I don't buy it. I'll stick to 4"-6" in that area and wouldn't be surprised to bust with even higher amounts there.

 

Actually DTs is the most reasonable map I have seen given results vs. predictions this winter, late March climatology and the timing of the storm.

 

Thus, I hereby facepalm you.....

 

:facepalm:

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ago4snow

ago4snow

Posted
Posted

I certainly respect your opinion. I would point out that the statement was made several hours ago with model data that was much more aggressive than what we have now.  I disagreed with the forecast and not with the ability of the forecaster. Otherwise, I would not like to turn this into the NY forum, where people spend more time criticizing each other than they do forecasting the weather. 

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