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STORM MODE THREAD- January 22-23 Mid Atlantic Storm Thread #4 - No Banter

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Looking at the 6z RGEM and NAM-4K on Tropical Tidbits (with their fixed 10:1 ratio) and looks to be 3.5 to 4' jackpots there too, in line with the insane GFS. I recall Sterling indicated a 12:1 average ratio yesterday, which would bring their totals right to what GFS is showing.

 

All three models (GFS, RGEM, NAM-4K) now show the surface low retrograding over the mouth of the Chesapeake Bay.

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This 06z update shows pretty clearly the presence of a dry slot that wasn't shown in the 00z version. And while is shows a very strong 2nd round moving in, it also makes it clear how reliant DC is on deformation banding to really produce for HECT or else the overall snowfall projection is in jeopardy. To go from no indication of a dry slot for DC with the 00z data to now having a dry slot with the 06z data, I'll be anxious to see the 12z update.

DCA is around 2.4" QPF all snow on 06z RGEM:

attachicon.gifR9_RN_S9_SN_G9_PE_Z9_FR_METE_0000_Washington.png

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I have a serious question... Would there be a threat of storm surge inside the eastern tributaries of the bay? I just heard the marine forcast on the news and it sounds like several hours of prolonged easterly winds.

 

CBOFS is not predicting that; wind direction prevents water backing up into the bay:

 

http://tidesandcurrents.noaa.gov/ofs/ofs_animation.shtml?ofsregion=cb&subdomain=0&model_type=wl_forecast

 

For instance, Annapolis:

 

http://tidesandcurrents.noaa.gov/ofs/ofs_station.shtml?stname=Annapolis&ofs=cb&stnid=8575512&subdomain=0

 

And Baltimore:

 

http://tidesandcurrents.noaa.gov/ofs/ofs_station.shtml?stname=Baltimore&ofs=cb&stnid=8574680&subdomain=0

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Thanks! Ocmd has a period tomorrow morning where they go over five feet. Not sure if that is depelarture from the normal high tide or if that is just cumulative... But either way it could get serious down there nonetheless.

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From the WPC discussion:

 

WPC AMOUNTS UTILIZED WPC QPF WITH A THERMAL BLEND OF THE GFS AND
ECMWF...DISCOUNTING THE NAM AND SREF ESPECIALLY ACROSS THE
NORTHEAST ON DAY 2 AS NORTHERLY OUTLIERS. OVERALL FORECAST
CONFIDENCE WAS ABOVE AVERAGE...BOLSTERED BY FAIRLY GOOD AGREEMENT
BETWEEN THE GFS/ECMWF. CONFIDENCE WAS TEMPERED SOME BY THE 00Z
ECMWF...WHICH IS INDICATING A SIGNIFICANT DRY SLOT WHICH WOULD
HAMPER AMOUNTS ACROSS PORTIONS OF THE MID ATLANTIC ON SATURDAY.
IN ADDITION...STRONG FRONTOGENESIS IS EXPECTED TO PRODUCE A TIGHT
NORTHERN GRADIENT ACROSS THE NORTHERN MID ATLANTIC INTO SOUTHERN
NEW ENGLAND. WHILE THE NAM AND A NUMBER OF SREF MEMBERS ARE
LIKELY TOO FAR TO THE NORTH...A SLIGHT SHIFT IN THE LOW TRACK MAY
REQUIRE ADJUSTING THE NORTHERN EXTENT OF ACCUMULATING SNOWS.

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I am no expert but that sounds bad. It sounds to me like they are saying that it's gonna stop early here in the Washington DC area and than snow harder north of us. Geez!!!

 

They are saying their confidence of the 2 foot plus totals is tempered for the areas that might dryslot (which includes DC), they aren't saying what is or isn't going to happen definitively.  I think we'll be more confident about the placement of the dryslot when the 12z suite is complete and hopefully it'll look different than what the euro showed last night.

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I have a serious question... Would there be a threat of storm surge inside the eastern tributaries of the bay? I just heard the marine forcast on the news and it sounds like several hours of prolonged easterly winds.

From what I saw the jet sets up north of the bay, major flooding is more a concern in northern MD beaches, DE/NJ. My family has a back bay property in NJ that I think will flood near December 1992 levels. Fortunately the house itself is 7 feet off the ground.

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One comment that I don't believe is banter re : dry slot - most everyone knows but i will say again - to chase historic snowfall totals around here often means flirting with the dry slot. So that's what the danger is here - worth it to have a chance at something of a generational event.

Sent from my iPhone using Tapatalk

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This 06z update shows pretty clearly the presence of a dry slot that wasn't shown in the 00z version. And while is shows a very strong 2nd round moving in, it also makes it clear how reliant DC is on deformation banding to really produce for HECT or else the overall snowfall projection is in jeopardy. To go from no indication of a dry slot for DC with the 00z data to now having a dry slot with the 06z data, I'll be anxious to see the 12z update.

 

 

Yeah it doesn't look too bad though, the one panel at 12z Saturday looks a little dry.  Better than the Euro which ends all the heavy snow for us at 7am and never brings it back.

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For those of us in and around DC just waking up to the 6z GFS doubling down on its crazy 0Z run while the Euro is predicting literally half of those totals 12 hours before the storm begins, can someone summarize what the main differences are?  I understand the Euro has the dryslot reaching our area mid-day Saturday, but I assume it's more than just that?  Is it the placement of the low?  The amount of moisture in the entire storm overall?

 

I'm curious what we should be watching for on real-time radar and today which might given us a clue about which model's solution is coming true. 

 

(To be clear, I'm not complaining about "only" 1;8 inches of QPF. Just genuinely perplexed by how the top two models, which have been pretty well alligned on this storm for a week, would suddenly diverge at the 11th hour, and it would be fun to see which one ends up "winning")

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So basically Euro had 1.8+ liquid for DC - which would probably yield 20-24 inches.

Hi-res NAM at 6z just improved and shows 25 inches for DCA - up from 17-19 inches at 00z.

06z NAM is a hit: 24- 27 inches or so

06z RGEM supports 24-28 inches

06z GFS supports 40+ inches

00z Euro Para supports 24+ inches

So the forecast is pretty good for at least 20 inches in the DC area and then we wait on the dry slot. No slot and these totals increase... get in the dry slot and we get between 20-24 inches. Can't really complain about a storm bringing 20+ inches of snow to the area --- although I want no part of the dry slot of course. Hopefully it stays over by the coast. We'll know in 24 hours.

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Can somebody explain what happened with the Euro last night? I tried reading it but I finally bored with it and skipped over it.

Are its numbers accurate or not?

Numbers are accurate but the evolution was a bit ragged. I was skeptical. It's younger brother looks much cleaner. Similar to all other guidance.

You are going to get destroyed. Enjoy it.

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Heh, para euro says what dry slot. Uniform 2' right down 95 increasing westward. Nwva jack with 3" qpf.

i just heard the Para became the op 5 minutes ago

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For those of us in and around DC just waking up to the 6z GFS doubling down on its crazy 0Z run while the Euro is predicting literally half of those totals 12 hours before the storm begins, can someone summarize what the main differences are? I understand the Euro has the dryslot reaching our area mid-day Saturday, but I assume it's more than just that? Is it the placement of the low? The amount of moisture in the entire storm overall?

I'm curious what we should be watching for on real-time radar and today which might given us a clue about which model's solution is coming true.

(To be clear, I'm not complaining about "only" 1;8 inches of QPF. Just genuinely perplexed by how the top two models, which have been pretty well alligned on this storm for a week, would suddenly diverge at the 11th hour, and it would be fun to see which one ends up "winning")

06z GFS was really not all that different from 00z. It cut back a little bit but still very high QPF. It may have shifted the higher values a bit east as well.

Euro had issues overnight. I stayed up and there was one or two panels missing. It was a bit drier but it's common to see fluctuations in the global stock this close in. Hi Res guidance takes over at this range and so does radar, satellite and now casting.

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Heh, para euro says what dry slot. Uniform 2' right down 95 increasing westward. Nwva jack with 3" qpf.

Higher than the op map and has a 24" swath stretching from Charlottesville to Baltimore!

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FWIW 00z GFS Para pretty much showing the same thing it's shown for like 5 days in a  row.  2.5"+ area wide...3"+ favored areas.  

 

Looking at the evolution and slp/precip panels the solution makes complete sense. Doesn't have the ragged stuff with the deform like the op. I didn't like what the op was doing with the intense precip over the ocean near the triple point low. Para is nice and connected with the deform. We'll see which one is right in 36 hours. 

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Bob, that's 0z right?

Sent from my iPhone using Tapatalk

 

Yes. I didn't screw that up this time.  SLP placement nearly identical to the op. Just cleaner with the ccb/deform

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