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JAN 4th Coastal

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Due to popular demand, storm mode is gone.  You can weenie it up and post whatever.  don't care.  Enjoy.

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18z NAVGEM shifted the precip a little east but the low looks to be in about the same location and the 500 mb map looks similar. 

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With the caveat that I'm utterly unqualified to discuss synoptic met as a climo guy, just flipping between the Canadian and GFS on tropical tidbits, it looks like a lot of the precip field variation is caused by differences in handling the spacing between vorticity from the shortwave and that from the surface low. The Canadian draws them closer and the consolidation looks like it happens closer to our area, causing convection and a wider precip fieldgfs_z500_vort_us_11.thumb.png.b44a40f20d9957e516b481d09462fe63.pnggem_z500_vort_us_12.thumb.png.3abd26031b90e0a06b82c3dddbaf2c2d.png

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Picking up something that was brought up in a previous thread:  Tropical Tidbits now shows the high-res RGEM (HRDPS), which apparently went operational on December 14th.  In case you're wondering what that is, it's a version of the RGEM with 2.5 km resolution, as opposed to 10 km for the normal RGEM.  A brief summary is provided in the official note announcing its release, but the below sections are probably most relevant.  (The RDPS is the RGEM).

THE HRDPS ALSO SHOWED AN OVERALL POSITIVE GAIN OVER THE RDPS WITH
RESPECT TO UPPER AIR AND SURFACE OBECTIVE SCORES. THIS OPERATIONAL
DECLARATION IS FURTHER SUPPORTED BY THE WIDE SPREAD USE OF THIS
SYSTEM BY REGIONAL FORECASTERS ACROSS THE COUNTRY, AS INDICATED BY A
RECENT SURVEY CONDUCTED BY THE ANALYSIS AND PROGNOSTIC SECTION (A 
AND P) OF THE CMC.

PRODUCT AVAILABILITY
THE HRDPS-4.4.0 OUTPUT WILL NOW BE AVAILABLE MUCH SOONER THAN
BEFORE. WHEREAS THE AVAILABILITY OF OUTPUT FROM THE FOUR DAILY RUNS
OF THE EXPERIMENTAL HRDPS VARIED BY RUN, THE RAW OUTPUT WILL NOW BE
AVAILABLE FROM THE OPERATIONAL HRDPS BY T+4:20 FOR ALL RUNS, WHICH
IS ANYWHERE FROM 10 MINUTES TO 2 HOURS SOONER THAN BEFORE, DEPENDING
ON THE RUN.

A test version of the HRDPS has been available for a while, but we haven't used it much because it wasn't widely available and came out much later than the RGEM.  It looks like it's coming out more quickly now that it's operational.  I haven't noticed a major improvement in its performance over the RGEM for winter storms in our area, but it seems that it does tend to run a little drier, especially when the RGEM is too wet.  That's consistent with its verificiation scores: we should expect it to be (on average) drier than the RGEM with less of a cold bias.

In case you're wondering why only half the country is covered, it's more narrowly focused on Canada than the RGEM.  This is the region it covers.

N1HL6Cw.jpg

It will be fun to see how well it does with this storm.

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Lets see how things tick at 00z. Hopefully if they do go in the wrong direction its more than a tick and we can forget about this threat once and for all

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I don't know how many times in the past Andros Island has been mentioned in a snowstorm thread, but the NAM places the low just north of there at 18z. 

Melbourne Radar currently showing convection east of Fort Pierce FL, and other returns that look like flocks of birds scurrying around in the ever-shrinking warm sector.

Meanwhile mid-20s (F) dewpoints over the central Gulf of Mexico in a broad northeast flow that has pushed the arctic front past Veracruz and part way across the Yucatan.

This thing is going to go ballistic when those arctic winds make full contact with the Gulf Stream.

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Trough looks more negative around hr 45 for the 12k NAM

Edit: 12k NAM throws precip fairly far West, just East of DC. Not sure what to make of the 12k NAM run. 

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NAM looks worse to me, at least looking at 500 MB. Looks east and open. That may be all she wrote. I guess I'll check back tomorrow and see what happened overnight before tossing my towel on this one, but hopefully if we miss out, so does everyone else.

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1 minute ago, osfan24 said:

NAM looks worse to me, at least looking at 500 MB. Looks east and open. That may be all she wrote. I guess I'll check back tomorrow and see what happened overnight before tossing my towel on this one, but hopefully if we miss out, so does everyone else.

Nope, Norfolk gets clobbered pretty good.

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1 minute ago, osfan24 said:

NAM looks worse to me, at least looking at 500 MB. Looks east and open. That may be all she wrote. I guess I'll check back tomorrow and see what happened overnight before tossing my towel on this one, but hopefully if we miss out, so does everyone else.

everytime we hit a crossroads and we need a positive trend...the opposite happens

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Just now, DCAlexandria said:

Nope, Norfolk gets clobbered pretty good.

I meant the folks to our north. Norfolk can have their foot or whatever.

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LOL nam 3k has a 966 right off  Hatteras but snowshield hits a brick wall over Bob Chills house

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1 hour ago, Quasievil said:

Interesting where the HRDPS has the low by hour 48. Quite a bit further north then the 18Z GFS at the same timeframe.

2B978A37-0F72-4026-AFBD-C6F5B42E9436.png

I think it's just happens to be the lowest pressure within the scope of the model, so it's just a placeholder until the low comes into view.

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3knam at 500 looks like an overall better trough alignment to me . Lakes low is slightly further west this run allowing hieght rises to the east ne. A little better phase between the first 2 pieces and it would be able to make a better push north with that lakes low west this run...more changes coming I'm sure

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Just now, Ralph Wiggum said:
4 minutes ago, DCAlexandria said:
Nope, Norfolk gets clobbered pretty good.

And Boston.

Yeah I just saw Boston does get crushed at the end of the run. Ugh.

Not surprised about the NAM though, not that it's terrible, but when I saw the SREF's cut back drastically, I had a feeling the NAM would take a step back as well.

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1 minute ago, Ji said:

LOL nam 3k has a 966 right off  Hatteras but snowshield hits a brick wall over Bob Chills house

Nams remind me of the euro with the shield to the west of the low. Not identical of course but they both have the same bulge to the west. 

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