snow. Posted December 9, 2013 Share Posted December 9, 2013 I think we had tried to get to the bottom of this a couple of days ago -- the raw ECMWF output has a categorical yes/no for a series of p-types -- if for a given timestep, if snow=yes, he's sums up the liquid equivalent and applies a 10:1 ratio -- this causes some issues because just because the categorical p-type is snow at say 18z doesn't mean that it was snow for the entire 6-hour time step for the output -- that's simply how to end up getting more snow even if the thermal profiles don't support it -- it's either sloppiness on Maue's part or he's limited by temporal sampling of the ECMWF output, which in that case renders most ECMWF snow maps worthless when you have thermal profiles that may not support snow over the entire 6-hour binning of QPF. Thanks for the explanation Link to comment Share on other sites More sharing options...
HM Posted December 9, 2013 Share Posted December 9, 2013 Wouldn't that scenario reduce totals for the D.C. metro? Obviously, these maps are not the way to diagnose these vertical circulations (2d at some stagnant time). A cross section would be more preferable. I don't think this is a classic case where some big band in NW areas robs the southern areas of their expected synoptic-scale aided snowfall. Plus, everything will move eastward anyway. I think the regular causes of lift that come through in the morning should still bring the area snow. Link to comment Share on other sites More sharing options...
Bob Chill Posted December 9, 2013 Share Posted December 9, 2013 I only use euro snow maps as a guide for orientation and maximas. They are very error prone in a marginal airmass. I suppose they would be accurate in near perfect column but we don't do that well around here. It's not a hard exercise to figure out temp profile with various panels and add in how much precip falls. The only grey area is a changeover of some sort within a 6 hr panel. Just extrapolate and guess a little. Snow maps for the public was a terrible invention imo. Link to comment Share on other sites More sharing options...
chris87 Posted December 9, 2013 Share Posted December 9, 2013 Thanks for the explanation it's frustrating because there is no reason why all model output couldn't provide sub-time step information about how much of each p-type the model produces during an output period. Link to comment Share on other sites More sharing options...
Ian Posted December 9, 2013 Share Posted December 9, 2013 I forecast totally off snow maps which is why I am usually wrong. Link to comment Share on other sites More sharing options...
mitchnick Posted December 9, 2013 Share Posted December 9, 2013 you mets are starting to make this hard for us weenies can't we just stick with colorful snow maps and pictures in books? j/k keep it up! Link to comment Share on other sites More sharing options...
snow. Posted December 9, 2013 Share Posted December 9, 2013 so for DCA QPF we have the following 12z spread GFS - 0.62" NAM - 0.47" Euro - roughly 0.25" I'd think 0.35" is a reasonable expectation which would probably give DC proper a 3-4" storm (in terms of contouring a broad brush forecast map), and DCA around 2.7" or something like that knowing how they measure...at least gets DCA its first 2" event since 2011 If I were putting out a map for DC proper, I'd probably lean toward 2-4" rather than 3-5" at least right now As far as the 0z euro...I don't expect it to suddenly become a moisture bomb..it isn't what the euro does..it doesnt swing like that..it is probably locked into a blend of last night and today's runs...maybe it bumps up a little... Link to comment Share on other sites More sharing options...
BTRWx Posted December 9, 2013 Share Posted December 9, 2013 Obviously, these maps are not the way to diagnose these vertical circulations (2d at some stagnant time). A cross section would be more preferable. I don't think this is a classic case where some big band in NW areas robs the southern areas of their expected synoptic-scale aided snowfall. Plus, everything will move eastward anyway. I think the regular causes of lift that come through in the morning should still bring the area snow. Thanks for the clarification. We have experienced that exact NW band cutoff scenario too many times, so it's all too familiar. It usually seems to me that an axis similar to the image frequently seems to position itself over that same area and trek to the NE rarely reaching further south and east, but hoping this one is different. Link to comment Share on other sites More sharing options...
snowdude Posted December 9, 2013 Share Posted December 9, 2013 Here's my map! Link to comment Share on other sites More sharing options...
snow. Posted December 9, 2013 Share Posted December 9, 2013 Here's my map! image.jpg nice map..good to be cautious...The GFS/NAM pump out over .5" of liquid for us,....I think you may be a bit too conservative for DC, but still well done Link to comment Share on other sites More sharing options...
HM Posted December 9, 2013 Share Posted December 9, 2013 Someone asked earlier about thunder...if it is going to happen, it is going to be N VA into the NW suburbs of DC where all the elements come together (see my attached image from GFS 12z of stability, moisture, frontogen, EPV). The soundings here also look supportive. Link to comment Share on other sites More sharing options...
gymengineer Posted December 9, 2013 Share Posted December 9, 2013 so for DCA QPF we have the following 12z spread GFS - 0.62" NAM - 0.47" Euro - roughly 0.25" I'd think 0.35" is a reasonable expectation which would probably give DC proper a 3-4" storm (in terms of contouring a broad brush forecast map), and DCA around 2.7" or something like that knowing how they measure...at least gets DCA its first 2" event since 2011 If I were putting out a map for DC proper, I'd probably lean toward 2-4" rather than 3-5" at least right now As far as the 0z euro...I don't expect it to suddenly become a moisture bomb..it isn't what the euro does..it doesnt swing like that..it is probably locked into a blend of last night and today's runs...maybe it bumps up a little... I like Wes' range of 2-5". It covers your thoughts well too... Link to comment Share on other sites More sharing options...
snowdude Posted December 9, 2013 Share Posted December 9, 2013 nice map..good to be cautious...The GFS/NAM pump out over .5" of liquid for us,....I think you may be a bit too conservative for DC, but still well done Thanks! I was too "scared" to go higher. Lmao. This is the first snow map Ive ever made for tv Link to comment Share on other sites More sharing options...
Sparky Posted December 9, 2013 Share Posted December 9, 2013 Here's my map! image.jpg I think you have the Carroll Co. part right. I am thinking 4-6" for Westminster and really all of Carroll. Link to comment Share on other sites More sharing options...
stormtracker Posted December 9, 2013 Author Share Posted December 9, 2013 15z SREFS Link to comment Share on other sites More sharing options...
Interstate Posted December 9, 2013 Share Posted December 9, 2013 I forecast totally off snow maps which is why I am usually wrong. You would have been pretty much spot on with Sunday's storm Link to comment Share on other sites More sharing options...
mitchnick Posted December 9, 2013 Share Posted December 9, 2013 15z SREFS I don't like this trend especially considering last night's precip ended up south and east Link to comment Share on other sites More sharing options...
yoda Posted December 9, 2013 Share Posted December 9, 2013 CTP (State College) went 2-5 in the WWA they just issued for their zones (including the ones on the Mason-Dixon line) Link to comment Share on other sites More sharing options...
DCAlexandria Posted December 9, 2013 Share Posted December 9, 2013 SREF has a sligth SE Bias Link to comment Share on other sites More sharing options...
yoda Posted December 9, 2013 Share Posted December 9, 2013 I don't like this trend especially considering last night's precip ended up south and east Thats cause Randy didnt post the right one... this is the one he should have posted The 0.5 line touches DCA Link to comment Share on other sites More sharing options...
Joe Vanni Posted December 9, 2013 Share Posted December 9, 2013 I don't like this trend especially considering last night's precip ended up south and east Hey Mitch, I think you're misreading it; I thought the same. That line that's touching DC is the 0.5 inch line, not 0.25. It's actually broader with the 0.25 inch line and now has brought on the .5 inch which 9z didn't have. Link to comment Share on other sites More sharing options...
stormtracker Posted December 9, 2013 Author Share Posted December 9, 2013 I don't like this trend especially considering last night's precip ended up south and east It's fine dude. It's better than 9z Link to comment Share on other sites More sharing options...
Eskimo Joe Posted December 9, 2013 Share Posted December 9, 2013 New event. Winter Weather Advisory from 12/10/2013 3:00 AM to 2:00 PM EST for Montgomery County, Carroll County. More information. Link to comment Share on other sites More sharing options...
stormtracker Posted December 9, 2013 Author Share Posted December 9, 2013 DCZ001-MDZ003>007-009>011-013-014-VAZ027>031-039-040-042-051>054-501-502-WVZ052-053-100330-/O.UPG.KLWX.WS.A.0009.131210T1000Z-131210T1800Z//O.NEW.KLWX.WW.Y.0035.131210T0800Z-131210T1900Z/DISTRICT OF COLUMBIA-WASHINGTON-FREDERICK MD-CARROLL-NORTHERN BALTIMORE-HARFORD-MONTGOMERY-HOWARD-SOUTHERN BALTIMORE-PRINCE GEORGES-ANNE ARUNDEL-SHENANDOAH-FREDERICK VA-PAGE-WARREN-CLARKE-MADISON-RAPPAHANNOCK-LOUDOUN-CULPEPER-PRINCE WILLIAM/MANASSAS/MANASSAS PARK-FAIRFAX-ARLINGTON/FALLS CHURCH/ALEXANDRIA-NORTHERN FAUQUIER-SOUTHERN FAUQUIER-BERKELEY-JEFFERSON-INCLUDING THE CITIES OF...WASHINGTON...HAGERSTOWN...FREDERICK...WESTMINSTER...GAITHERSBURG...COLUMBIA...BALTIMORE...ANNAPOLIS...WINCHESTER...FRONT ROYAL...LEESBURG...CULPEPER...MANASSAS...MANASSAS PARK...FAIRFAX...ALEXANDRIA...FALLS CHURCH...WARRENTON...MARTINSBURG...CHARLES TOWN229 PM EST MON DEC 9 2013...WINTER WEATHER ADVISORY IN EFFECT FROM 3 AM TO 2 PM ESTTUESDAY...THE NATIONAL WEATHER SERVICE IN BALTIMORE MD/WASHINGTON HASISSUED A WINTER WEATHER ADVISORY FOR SNOW... WHICH IS IN EFFECTFROM 3 AM TO 2 PM EST TUESDAY. THE WINTER STORM WATCH IS NOLONGER IN EFFECT.* PRECIPITATION TYPE...SNOW...HEAVY AT TIMES. THE PRECIPITATIONMAY START AS A PERIOD OF SLEET...ESPECIALLY SOUTH OF INTERSTATE66 IN VIRGINIA AND EAST OF INTERSTATE 95.* ACCUMULATIONS...3 TO 5 INCHES.* TIMING...NEAR DAWN TUESDAY THROUGH EARLY TUESDAY AFTERNOON...INCLUDING THE TUESDAY MORNING RUSH HOUR.* TEMPERATURES...UPPER 20S TO LOWER 30S.* WINDS...NORTHWEST 5 TO 10 MPH.* IMPACTS...HAZARDOUS TRAVEL CONDITIONS ARE EXPECTED FROM HEAVYSNOW. THE SNOW WILL IMPACT THE MORNING RUSH TUESDAY WITH THEPOTENTIAL FOR ACCUMULATION RATES OF 1-2 INCHES PER HOUR.PRECAUTIONARY/PREPAREDNESS ACTIONS... Link to comment Share on other sites More sharing options...
stormtracker Posted December 9, 2013 Author Share Posted December 9, 2013 That was the shortest watch ever. Link to comment Share on other sites More sharing options...
Scarlet Pimpernel Posted December 9, 2013 Share Posted December 9, 2013 Hey Mitch, I think you're misreading it; I thought the same. That line that's touching DC is the 0.5 inch line, not 0.25. It's actually broader with the 0.25 inch line and now has brought on the .5 inch which 9z didn't have. Was just going to say about the same thing. It is hard to see because the "0.25" label kind of obscures things; you kind of have to count the lines because of that. The 0.50" line actually goes a bit northwest DC proper, so the immediate DC area is easily encompassed in that contour. And yes, there was no 0.50" line in the 09Z SREF. Link to comment Share on other sites More sharing options...
mitchnick Posted December 9, 2013 Share Posted December 9, 2013 Hey Mitch, I think you're misreading it; I thought the same. That line that's touching DC is the 0.5 inch line, not 0.25. It's actually broader with the 0.25 inch line and now has brought on the .5 inch which 9z didn't have. yep, too fast on the trigger Link to comment Share on other sites More sharing options...
Don Cherry's Jacket Posted December 9, 2013 Share Posted December 9, 2013 That was the shortest watch ever. Did they retract it? Link to comment Share on other sites More sharing options...
Terpeast Posted December 9, 2013 Share Posted December 9, 2013 Did they retract it? They changed it to a WWA. Someone will probably get warning criteria snow, but don't know where exactly the banding is going to set up. Link to comment Share on other sites More sharing options...
stormtracker Posted December 9, 2013 Author Share Posted December 9, 2013 Did they retract it? Went to a WWA...i posted it Link to comment Share on other sites More sharing options...
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