wkd Posted March 5, 2015 Share Posted March 5, 2015 0Z rgem Link to comment Share on other sites More sharing options...
famartin Posted March 5, 2015 Author Share Posted March 5, 2015 0Z RGEM and NAM Link to comment Share on other sites More sharing options...
Ralph Wiggum Posted March 5, 2015 Share Posted March 5, 2015 Latest RUC increases totals in SE PA. Strong banding signal. http://ruc.noaa.gov/RUC/jsloopLocalDiskDateDomainZip.cgi?dsKeys=ruc_jet:&runTime=2015030501&plotName=1hsnw_sfc&fcstInc=60&numFcsts=25&model=ruc&ptitle=RUC Model Fields&maxFcstLen=24&fcstStrLen=-1&resizePlot=1&domain=full Link to comment Share on other sites More sharing options...
Coltsfan1217 Posted March 5, 2015 Share Posted March 5, 2015 Latest RUC increases totals in SE PA. Strong banding signal. I swear your two favorite models are the CRAS and RUC Link to comment Share on other sites More sharing options...
Ralph Wiggum Posted March 5, 2015 Share Posted March 5, 2015 Latest HRRR is a SEPA pasting: Link to comment Share on other sites More sharing options...
Darksideblugrss Posted March 5, 2015 Share Posted March 5, 2015 Latest RUC increases totals in SE PA. Strong banding signal. http://ruc.noaa.gov/RUC/jsloopLocalDiskDateDomainZip.cgi?dsKeys=ruc_jet:&runTime=2015030501&plotName=1hsnw_sfc&fcstInc=60&numFcsts=25&model=ruc&ptitle=RUC Model Fields&maxFcstLen=24&fcstStrLen=-1&resizePlot=1&domain=full If that ends up to be true we will have one crazy day of obs tomorrow Link to comment Share on other sites More sharing options...
Animal Posted March 5, 2015 Share Posted March 5, 2015 Latest HRRR is a SEPA pasting: Looks decent up north in my area Link to comment Share on other sites More sharing options...
famartin Posted March 5, 2015 Author Share Posted March 5, 2015 GFS is solid. About 0.60" as snow at TTN. Seems we've reached near-universal agreement. Link to comment Share on other sites More sharing options...
hazwoper Posted March 5, 2015 Share Posted March 5, 2015 GFS is solid. About 0.60" as snow at TTN. Seems we've reached near-universal agreement. Crazy! Still sitting at 37.7 with all this moderate rain, but yet we still have quite a bit of QPF after changeover. Amazing these late winter storms can be with the moisture feed. Link to comment Share on other sites More sharing options...
RU848789 Posted March 5, 2015 Share Posted March 5, 2015 Actually, if the last 5000 feet are at 33 and its saturated, it will be rain at the surface. 5000 feet is a long way for a snowflake and you actually have liquid water droplets at much lower temps than freezing. If its above freezing and saturated, its not hard to melt the flakes as it runs into all those little droplets. However, melting takes energy from the atmosphere, so gradually, assuming no advection, the continued melting of snowflakes would slowly cool the column from 5000 feet on down to the surface to 32, at which point it would snow. The whole "transporting cold air down" is actually mainly based on the heat absorbed from melting snowflakes. I see what you're saying about flakes at 33F and 5000 feet of saturated column with liquid droplets present - in that case, yeah, the flakes should melt, but as you said that requires heat from the atmosphere, which would eventually cool the column and allow the snowflakes to make it to the ground. I guess I was thinking more of what happens when the snowfall generation rate in the dendriditc nucleation and growth region, 10-15K feet up at -12 to -18C (let's say -15C, on average, or 5F) is very high, due to intense vertical velocities bringing relatively warm/moist air up from below. I would think that a very heavy snowfall rate of flakes that are all 5F or so could provide enough momentum to truly drag some of the local cold air down with them through the column, such that maybe only a fraction of the snowflakes would ever reach the melting point and melt while falling through the last few thousand feet at 33F, resulting in snow reaching the ground, especially if the column isn't saturated (not all of the snowflakes are going to melt/evaporate to saturate the column). Also, as an aside, I'm sure you or others have done this calculation, but it surprises me a little bit that 5F snowflakes falling through a 33F column for ~5000 feet, even if saturated, would result in all of the flakes melting. I guess I would have thought that the limited time to traverse those 5000 feet (curious to know what that flake velocity is, so one could calculate the residence time of a flake in that 33F column) would not be enough to allow both the warming up of the snowflake from 5F to 32F and then the melting of the flake at 32F. especially since the latter requires a fair amount of heat for the phase change. Maybe this is not a good comparison, but I think about how long it takes to melt snow on the ground at 33F. Link to comment Share on other sites More sharing options...
famartin Posted March 5, 2015 Author Share Posted March 5, 2015 I see what you're saying about flakes at 33F and 5000 feet of saturated column with liquid droplets present - in that case, yeah, the flakes should melt, but as you said that requires heat from the atmosphere, which would eventually cool the column and allow the snowflakes to make it to the ground. I guess I was thinking more of what happens when the snowfall generation rate in the dendriditc nucleation and growth region, 10-15K feet up at -12 to -18C (let's say -15C, on average, or 5F) is very high, due to intense vertical velocities bringing relatively warm/moist air up from below. I would think that a very heavy snowfall rate of flakes that are all 5F or so could provide enough momentum to truly drag some of the local cold air down with them through the column, such that maybe only a fraction of the snowflakes would ever reach the melting point and melt while falling through the last few thousand feet at 33F, resulting in snow reaching the ground, especially if the column isn't saturated (not all of the snowflakes are going to melt/evaporate to saturate the column). Also, as an aside, I'm sure you or others have done this calculation, but it surprises me a little bit that 5F snowflakes falling through a 33F column for ~5000 feet, even if saturated, would result in all of the flakes melting. I guess I would have thought that the limited time to traverse those 5000 feet (curious to know what that flake velocity is, so one could calculate the residence time of a flake in that 33F column) would not be enough to allow both the warming up of the snowflake from 5F to 32F and then the melting of the flake at 32F. especially since the latter requires a fair amount of heat for the phase change. Maybe this is not a good comparison, but I think about how long it takes to melt snow on the ground at 33F. Maximum fall speed of snowflakes is about 6 feet per second. For them to traverse 5000 feet, it would take about 14 minutes. Many snowflakes fall at slower speeds, with some falling at only 1 foot per second. Obviously, it depends on the flake's geometry. In any case, 14 minutes is plenty of time for melting. Consider that when falling through saturated air, both heat from air and from droplets they strike are absorbed by the flakes. So, at least at first, melting would be fairly quick. Of course, if the rate is heavy and advection is minimal, it wouldn't take long for the column to cool enough for snow to reach the ground. Link to comment Share on other sites More sharing options...
KamuSnow Posted March 5, 2015 Share Posted March 5, 2015 Maximum fall speed of snowflakes is about 6 feet per second. For them to traverse 5000 feet, it would take about 14 minutes. Many snowflakes fall at slower speeds, with some falling at only 1 foot per second. Obviously, it depends on the flake's geometry. In any case, 14 minutes is plenty of time for melting. Consider that when falling through saturated air, both heat from air and from droplets they strike are absorbed by the flakes. So, at least at first, melting would be fairly quick. Of course, if the rate is heavy and advection is minimal, it wouldn't take long for the column to cool enough for snow to reach the ground. Interesting comparison regarding the maximum speed at which a snowflakes falls - 5000 feet in 14 minutes is about 4 mph which is (for me) 2nd gear walking speed. Funny to think that a snowflake falls at the speed at which we walk. Hmmm... Link to comment Share on other sites More sharing options...
RU848789 Posted March 5, 2015 Share Posted March 5, 2015 Maximum fall speed of snowflakes is about 6 feet per second. For them to traverse 5000 feet, it would take about 14 minutes. Many snowflakes fall at slower speeds, with some falling at only 1 foot per second. Obviously, it depends on the flake's geometry. In any case, 14 minutes is plenty of time for melting. Consider that when falling through saturated air, both heat from air and from droplets they strike are absorbed by the flakes. So, at least at first, melting would be fairly quick. Of course, if the rate is heavy and advection is minimal, it wouldn't take long for the column to cool enough for snow to reach the ground. Cool stuff - thanks for indulging me. Didn't think the max speed would be that low - is that due to a higher coefficient of friction factor based on shape, as opposed to a rain drop (more surface area in contact with the air for a snowflake), which I presume would fall faster? Knew I should've majored in meteorology instead of chem eng'g, lol - might finally be time for some formal education at dear old RU, since I'm only 10 minutes away - I'm guessing I'd be the oldest one there... Link to comment Share on other sites More sharing options...
famartin Posted March 5, 2015 Author Share Posted March 5, 2015 Cool stuff - thanks for indulging me. Didn't think the max speed would be that low - is that due to a higher coefficient of friction factor based on shape, as opposed to a rain drop (more surface area in contact with the air for a snowflake), which I presume would fall faster? Knew I should've majored in meteorology instead of chem eng'g, lol - might finally be time for some formal education at dear old RU, since I'm only 10 minutes away - I'm guessing I'd be the oldest one there... Yes. Hey, the more RU met grads, the merrier Link to comment Share on other sites More sharing options...
famartin Posted March 5, 2015 Author Share Posted March 5, 2015 Last GFS and GGEM runs before the snow: Link to comment Share on other sites More sharing options...
Treckasec Posted March 5, 2015 Share Posted March 5, 2015 New Snow Total map. Link to comment Share on other sites More sharing options...
KamuSnow Posted March 5, 2015 Share Posted March 5, 2015 Would be nice if we could get that high off the coast to stand still and just let this long band train over us for another 24 hours or so, lol. Link to comment Share on other sites More sharing options...
Mitchell Gaines Posted March 5, 2015 Share Posted March 5, 2015 Here's my AFD, very busy so not much posting today. NOW IS IN PROGRESS ACROSS THE REGION WITH AREAS ACROSS SOUTHEASTNJ AND THE SOUTHERN DELMARVA CHANGING FROM SLEET AND RAIN TO SNOWIN THE NEXT FEW HOURS. THE BACK EDGE OF THE SNOW IS APPROACHINGTHE NORTHWEST PARTS OF THE REGION. CAA WILL CONTINUE TO PUSH INTOTHE REGION BEHIND A COLD FRONT WITH A CONTINUING STREAM OFOVERRUNNING MOISTURE. TEMPERATURES WILL CONTINUE TO DROP TODAYACROSS THE AREA AND ONLY A FEW ADJUSTMENTS WERE MADE WITH THE 9:30AM UPDATE. PRECIPITATION SHOULD END VERY SLOWLY FROM NORTH TOSOUTH THIS AFTERNOON. WIND GUSTS AROUND 20 MPH HAVE ALSO BEENREPORTED IN SPOTS AND THESE WERE INCREASED WITH THE 9:30 AMUPDATE.ONTO SNOW AMOUNTS IN THE ADVISORY AREA A FEW INCHES HAVE ALREADYFALLEN WITH THE POTENTIAL FOR SOME ADDITIONAL ACCUMULATION WITHTOTALS STILL LOOKING TO AVERAGE UNDER WARNING CRITERIA.FURTHER SOUTH TOWARD THE PHILADELPHIA METRO AREA MODERATE TOHEAVY SNOW BANDS HAVE SETUP ACROSS THIS REGION WITH REPORTS OF 1TO AS MUCH AS 2 INCHES PER HOUR FOR SHORT INTERVALS. THE RAP ANDHRRR BOTH INDICATE THAT THESE MESOSCALE BANDS WILL BE SOMEWHATPROGRESSIVE BUT CONTINUE THROUGHOUT THE DAY TODAY. THESE BANDS ARECAUSED BY SIGNIFICANT FRONTGENETICAL FORCING AND AMPLE ISENTROPICLIFT. STORM TOTALS OF 6-8 INCHES STILL LOOK ON TRACK ATTM. ALSOPLEASE REFER TO MCD 124 FROM THE SPC AND THE SPS WE HAVE INEFFECT.IN THE DELMARVA AND SOUTHEAST NJ, THE 9:30 AM UPDATE SLOWS THECHANGEOVER AN HOUR OR SO. HOWEVER STILL DO NOT THINK THIS WILL CUTINTO TOTALS EXTENSIVELY ATTM. THIS IS DUE TO THE SAME MESOSCALEBANDING SIGNATURES SINKING FURTHER SOUTH FOR THE AFTERNOON HOURS.THIS IS PICKED UP WELL BY THE RAP, HRRR AND 06Z 800-600 MBFRONTGENETICAL FORCING ON THE 06Z NAM FROM EARLIER TODAY.SNOWFALL MAY ALSO FALL AROUND AN INCH FOR A TIME THIS AFTERNOONLEADING TO 4-8 INCHES OF SNOW BY EVENING.ROAD CONDITIONS WILL CONTINUE TO DETERIORATE TODAY WITH THE SNOW,ALLOW EXTRA TIME IF YOU HAVE TO TRAVEL. Link to comment Share on other sites More sharing options...
Bluescat1 Posted March 5, 2015 Share Posted March 5, 2015 Good AFD Mitch! Link to comment Share on other sites More sharing options...
Redmorninglight Posted March 5, 2015 Share Posted March 5, 2015 Good AFD. Puts our minds at ease some. Link to comment Share on other sites More sharing options...
famartin Posted March 5, 2015 Author Share Posted March 5, 2015 Shoulda just kept my original 5-10 for this one. I downgraded to 4-8 yesterday. 7.4 verifies both but it fit into the first forecast better. Link to comment Share on other sites More sharing options...
Harbourton Posted March 6, 2015 Share Posted March 6, 2015 Shoulda just kept my original 5-10 for this one. I downgraded to 4-8 yesterday. 7.4 verifies both but it fit into the first forecast better. May not have reached double digits in a single storm this year, but at least we had our biggest snowfall albeit in March. Final total 7 3/4 inches. Did not watch models, and radar today just watched the snow come down during the daylight which was rare this year. As Wederman said I hope the full moon comes out tonight. It will be spectacular. Link to comment Share on other sites More sharing options...
baseball0618 Posted March 6, 2015 Share Posted March 6, 2015 Should we revisit the hysteria over the 6Z GFS & 12Z NAM run on 3/4 and learn from the experience of taking the wait and see approach before we start all of the bridge jumping? Always a good idea for anyone to go back and look at each event to see what did or didn't go wrong. I am sure the good mets do this regularly in order to perfect their craft. Link to comment Share on other sites More sharing options...
Recommended Posts
Archived
This topic is now archived and is closed to further replies.