wdrag
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February 2019 General Discussion and Observation Thread
wdrag replied to Stormlover74's topic in New York City Metro
Have posted the snowfall/qpf on the Feb 17-18 ops thread, if you're interested in a look back. Here also, i just want to post something... that has been excellently modeled I think beyond 10 days in advance by the GEFS especially (EPS was more tempered). That means by the 26th... a small part of Tennessee could have 15" of rain in February while a part of Kentucky 10". You can use this plus the 7 day QPF from WPC to be somewhat impressed. Light Red is 5+, purple 10+ the past two weeks. -
I just wanted to post what happened for the Sunday night-Monday Feb 17-18 event. NOHRSC image interp snowfall... very very good product! and the NWS multi platform QPF... I think the QPF was little less than modeled by all models n of I80 and that hurt us a little ne PA/nw NJ. Any questions...just ask. I'll be away until 5P today.
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A couple of ensemble probability posts for tomorrows event. Big QPF and asstd bigger snowfall peels east somewhere near I80. 00z/19 EPS further N than 0z6/19 GEFS. 03z/19 SREF not that promising for NYC but i suspect 2-3" before the change to sleet etc. This is what I used for one of my local friend posts this morning. These probabilities can temper enthusiasm but are good AI checks against hope. Let the reality check occur by 6P Wednesday.
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Wantage NJ. ZL- ended. 30.4 Treated pavement wet. Otherwise still icy. Images wouldn't load. Thats okay. Gotta run.
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Ditto here in Wantage NJ with freezing drizzle ongoing here at 645AM. 30.0F. This is definitely a problem on all untreated surfaces in far nw NJ.
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Wantage NJ 8 s High Point 0.1" ice pellets, T snow, and unknown glaze amount of less than 0.1" radial. 30.2F ZL- at 420AM.
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Wantage NJ 8 s High Point. Mostly IPW- at this time. 31.8./16.7 Possible last report til ~ 5am.
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Wantage NJ 8 s of High Point. SB ~716P/17. small flake so far. 33/12 and down from a high of 39. May post 1 or 2 more times before 9PM. A slightly better start in flake size compared to the snow-ice event of last Tuesday.
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Hi! Looks like a nice little event coming tonight into Monday, with some banding, especially se NYS-CT where all snow likely.
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OBS only thread winter event Feb 12-early 13 , 2019
wdrag replied to wdrag's topic in New York City Metro
My last: Thanks for those added obs the past two days. Here's the remainder of 0.1 estimated radial glaze this morning at 9A (melting). -
OBS only thread winter event Feb 12-early 13 , 2019
wdrag replied to wdrag's topic in New York City Metro
Wantage NJ - 8 S of High Point. Final 2.5". glaze on top. Still 28.4F at 4A. Thanks for joining this thread w your obs. Walt -
OBS only thread winter event Feb 12-early 13 , 2019
wdrag replied to wdrag's topic in New York City Metro
sorry for the delay. RH is relative humidity. Models are generally very good at forecasting deep layered high humidity precipitation, but are not so good with precip at layers of high humidity below ~3000 feet (example when a dry slot cleans out the high humidity above 3000 feet). In yesterdays case, With still very high humidity trapped below the inversion, and probably a temperature of nearly -8C somewhere in that layer, and just a bit of lift (with the secondary developing near the coast-there was convergence here), fine snow may have been produced because snow generally needs to be generated with ice nuclei in a saturated layer of ~ -8C or colder. Also, as a side bar...when precip is changed to rain by a warm layer aloft, it can refreeze to ice pellets (sleet), with a temperature of -6C below that above freezing layer, or to ice pellets by a deep layer of sub0C below the above freezing layer. Anyway, hopefully the first part of your message is answered and my reasoning is possibly not the only answer. -
OBS only thread winter event Feb 12-early 13 , 2019
wdrag replied to wdrag's topic in New York City Metro
Ditto on fine snow here in Wantage. 2.4 at 720P and 20.8F. the snow means that that there is possibly only a shallow saturated layer of rh with lift in the -8C range causing the fine snow. -
OBS only thread winter event Feb 12-early 13 , 2019
wdrag replied to wdrag's topic in New York City Metro
Doubtful above freezing. still 20.3 F here in Wantage at this time. -
Hi, The following are two graphics that I think are useful in determining snowfall potential. The first is the NWS ensemble probability for various amounts of snow and freezing rain. In this case, for a local briefing I used the prob for snow exceeding 4", issued prior to 4am this morning by the NWS. It ... and if you haven't seen or used this, its good stuff. It showed not that a great a chance for exceeding 4" along and s of I84. I also added a graphic for consideration: Anytime the NAM FOUS has 0 or +C at T5, it sleets or rains, barring excessive VV in the ideal dendritic growth zone (saturated -12 to 18C). Anyway, here's a 00z/12 look at the NAM 3KM T section for HPN. Note the modeled 0C aloft approaching HPN ~17z, when the sleet began mixing in. If the model changes with time, that needs to be considered. In this case, the warming aloft was pretty stout early on. I view both of these tools as helpful reality checks, especially NAM inside of 60 hours. Any questions? Later, Walt
