tornadojay Posted January 19, 2011 Share Posted January 19, 2011 What is causing this storm to shift further south? It is not like we have a big -NAO or -AO to force the storm track to the south. The PNA is positive and the NAO is near neutral. I don't get it. Ant... I think part of the problem is what the depiction is in the Western Atlantic.. the flow is too much oriented from a west to east fashion and it is a swift flow at that... also, the shortwave impacting us is propogating from west to east because there is equal amounts of energy on both the front and back side of the trof. Without a good advection of vorticity into only the base of the trof at a time frame before it reaches us, we cannot force it to be negatively tilted.. as such, this has consequences with the heightfield out ahead of it and cannot force the system to go on a more northerly trajectory. Link to comment Share on other sites More sharing options...
Rainshadow Posted January 19, 2011 Share Posted January 19, 2011 not when Rainshadow posted verification scores, shows how overdone NAM qpf has been this winter. The wet bias is more pronounced farther out in forecast time and also at amounts reaching/exceeding the .50" threshold. The 00z and 12z nam runs are more of it coming closer to the sref mean and model consensus than that's it for this one, what's next? Link to comment Share on other sites More sharing options...
ag3 Posted January 19, 2011 Share Posted January 19, 2011 I do realize that the chance of reaching warning criteria snowfall is not the best at the moment (6") up north but 0.5" QPF with high ratios could still be realized up north. Any chance of watches for the far north later today? The chance of higher amounts are for eastern and north eastern areas. LI and SNE have a better chance at more QPF then areas to the west and north. Link to comment Share on other sites More sharing options...
RUNNAWAYICEBERG Posted January 19, 2011 Share Posted January 19, 2011 The wet bias is more pronounced farther out in forecast time and also at amounts reaching/exceeding the .50" threshold. The 00z and 12z nam runs are more of it coming closer to the sref mean and model consensus than that's it for this one, what's next? understood...thanks for correcting. Link to comment Share on other sites More sharing options...
IsentropicLift Posted January 19, 2011 Share Posted January 19, 2011 The chance of higher amounts are for eastern and north eastern areas. LI and SNE have a better chance at more QPF then areas to the west and north. I'm aware of where the best chance of higher QPF is as I'm more than capable of reading a model run. My question was pointed at rainshadow since I know he works for the NWS (Mt. Holly). Therefore the northereastern sections of the Mt. Holly CWA is my concern. Link to comment Share on other sites More sharing options...
Rainshadow Posted January 19, 2011 Share Posted January 19, 2011 I'm aware of where the best chance of higher QPF is as I'm more than capable of reading a model run. My question was pointed at rainshadow since I know he works for the NWS (Mt. Holly). Therefore the northereastern sections of the Mt. Holly CWA is my concern. I'm not on the public forecast desk today, just took a quick look at bufkit soundings off the latest nam, the omega is OK in the snow growth area, but not the stuff 15-20:1 ratios are made of. I can't access a terminal to see the fgen banding potential with it, but just glancing at the other mass fields, I wouldn't think it would be that robust. But that's just the nam, have to see what the gfs and euro do as well. Gotta get back to November, so if you have any other questions, please pm me, I'll try to answer them later. Link to comment Share on other sites More sharing options...
isnice Posted January 19, 2011 Share Posted January 19, 2011 12z NAM text for NYC crew: NYC: .30" - temps in the upper 20's LGA: .30" - temps in the upper 20's JFK: .29" - temps from 30-31.5 EWR: .33" - temps in the upper 20's With those temps in the city area, ratios will not be that high. I would go with 9-11 to 1 ratios or 2.5"-3.5" This is one of the widest misconceptions on this board. Surface temps DO NOT reflect snow ratios; temperatures in the dendrite snow growth regions do (around 600mb). In the NAM's case, ratios would be much higher than 9:1, and even 11:1. More likely 14:1. I haven't seen the NAM soundings but just looking at temps at 850mb, I can tell ratios would be rather high. With that said, I believe the truth lies with an 00z GFS, Euro, and 6z NAM blend. Many are bashing the NAM for its most recent debacle in QPF output. What most are neglecting to acknowledge is the fact that the dynamics of this storm are much different. Every model has a difficult time forecasting lare scale cyclogenic events. These effects are more pronounced on mesoscale models because that's what they're made for. Overrunning events that do not blow up over our area are not the same at all. I'm sure the verification rates for the NAM's QPF output are much higher for overrunning events than for any cyclogenic, unstable event. We are converging on a consensus. It seems as though the latest trends have been to hold pieces of the southern stream energy back before the northern stream arrives. Although I see no mechanism for this, it is plausible. The Euro may be overdoing this, as was suggested by BI earlier in the thread when commenting on latest water vapor imagery. I haven't seen the most recent imagery, but I would imagine that the Euro and its ensembles are still too far southwest. Most global models agree on a moderate event. In fact, all do except the Euro. All this to say, don't discount the 12z NAM, or the 6z NAM for that matter. Both are very viable solutions and not spitting out ridiculous QPF results. This is easier for the models to handle. Let them do it. Link to comment Share on other sites More sharing options...
famartin Posted January 19, 2011 Share Posted January 19, 2011 in before the NAM flip flops at 12z again Link to comment Share on other sites More sharing options...
famartin Posted January 19, 2011 Share Posted January 19, 2011 An excellent forecast. Mt Holly AFD calling for 3-5" for Friday: .SHORT TERM /TONIGHT THROUGH FRIDAY/... -- Changed Discussion --HIGH PRESSURE WILL BUILD IN TONIGHT AND THURSDAY WITH MOSTLY FAIR WEATHER AND SEASONABLE TEMPERATURES. THE NEXT LOW PRESSURE SYSTEM WILL DEEPEN AS IT MOVES ACROSS THE OHIO VALLEY AND MIDDLE ATLANTIC THURSDAY NIGHT AND FRIDAY. A SHIELD OF SNOW WILL SPREAD OVER THE AREA WITH ACCUMULATIONS EXPECTED. PRESENTLY 3 TO 5 INCHES OF SNOW LOOKS ON TARGET FOR MOST AREAS. ACCUMS COULD BE LESS ACROSS THE DELMARVA...BUT IT IS STILL TOO EARLY TO GET TOO FANCY WITH THE ACCUMS AND TRACK OF THE SYSTEM YET. THE DEEPENING LOW MOVES OFF TO THE NE FRI AFTERNOON AND A STRONG WRLY FLOW OF COLD AIR WILL ARRIVE ACROSS THE AREA. THIS COLD AIR WILL BE AROUND FOR THE WEEKEND.-- End Changed Discussion -- http://forecast.weat...1&highlight=off Upton has similar wording, talking about advisory to perhaps warning level snowfalls... .SHORT TERM /6 PM THIS EVENING THROUGH FRIDAY/... -- Changed Discussion --SHEARED OUT TROUGH AXIS CROSSES EAST OF THE REGION TONIGHT...WITH CANADIAN HIGH PRESSURE BUILDING TOWARDS THE REGION TONIGHT AND THEN OVER THE REGION ON THURSDAY. GUSTY CAA WNW FLOW TONIGHT WITH LOW-LEVEL DRYING AND CLEARING SKIES IN WAKE OF TROUGH AXIS. TEMPS EXPECTED TO FALL INTO THE MID/UPPER TEENS ACROSS INTERIOR...AND LOWER TO MID 20S COAST. THEN FOCUS WILL BE ON PAC AND NORTHERN STREAM ENERGY OVER THE CENTRAL PLAIN ON THURS...WITH MODELS/ENSEMBLES COMING INTO FAIRLY GOOD AGREEMENT WITH TROUGHING DIGGING INTO THE DEEP SOUTH BY THURS EVENING AND THEN NEGATIVELY TILTING UP THROUGH THE NORTHEAST ON FRIDAY. SOME SUBTLE DIFFERENCES IN PHASING/TIMING/STRENGTH WHICH ARE AFFECTING LOW PRESSURE EVOLUTION...BUT OVERALL IDEA IS THE SAME. AT THE SURFACE...RESULTANT BROAD LOW PRESSURE DEVELOPING FROM THE GULF TO THE TENNESSEE VALLEY LATE THURSDAY...LOOKS TO TRACK TO THE MID ATLANTIC COAST BY FRIDAY MORNING...WITH AN INTENSIFYING COASTAL LOW TRACKING NE TO THE VICINITY OF THE 40/70 BENCHMARK BY FRIDAY AFTERNOON. THE ABOVE MENTIONED UNCERTAINTY SHOWS ITSELF IN DIFFERENCES IN EXACT DETAILS OF THE LOW AMONG MODEL GUIDANCE...PARTICULARLY WITH TRACK AND INTENSITY. THE COMMON DENOMINATORS ARE THAT THIS WILL BE AN ALL SNOW EVENT WITH A TRACK SE OF THE AREA AND WITH POLAR HIGH LOCKED OVER CENTRAL US/SOUTHERN CANADIAN PLAINS INTO ONTARIO/QUEBEC...AND IT IS A QUICK HITTING SYSTEM. THE POTENTIAL FOR AN ACCUMULATING SNOWFALL IS HIGH...BUT AMOUNTS ARE STILL IN QUESTION. AN ADVISORY LEVEL SNOW WOULD BE EXPECTED WITH A TRACK SE OF THE 40/70 BENCHMARK AND LOW END WARNING SNOW WITH A TRACK INSIDE. MODELS VARY AMONG THESE SOLUTIONS. CLIMATOLOGY ON THESE QUICK MOVING SYSTEMS PUT THIS AT HIGH CONFIDENCE ON AN ADVISORY LEVEL EVENT WITH A LOW END THREAT FOR WARNING LEVEL SNOWS. STILL TOO EARLY FOR ANY WATCHES OR ADVISORIES...BUT MONITOR SUBSEQUENT FORECASTS AS THE DETAILS SHOULD CLEAR UP. WILL ADDRESS IN HWO. TEMPS DURING THIS PERIOD WILL RUN ABOUT 5 TO 7 DEGREES BELOW SEASONABLE...GENERALLY HIGH IN THE MID 20S INTERIOR TO UPPER 20S/LOWER 30S CITY/COAST. LOWS IN THE MID/UPPER TEENS INTERIOR AND LOWER/MID 20S CITY/COAST.-- End Changed Discussion -- http://forecast.weat...1&highlight=off Link to comment Share on other sites More sharing options...
famartin Posted January 19, 2011 Share Posted January 19, 2011 Still liking my 3-6 "gun to the head" call from yesterday Link to comment Share on other sites More sharing options...
MJO812 Posted January 19, 2011 Share Posted January 19, 2011 12z RGEM Link to comment Share on other sites More sharing options...
weatherweather Posted January 19, 2011 Share Posted January 19, 2011 rgem 998 low right off the coast near acy Link to comment Share on other sites More sharing options...
famartin Posted January 19, 2011 Share Posted January 19, 2011 12z GFS looks like its rolling the NCEP site is down again? There seemed to be problems getting the 12Z NAM graphics on the web earlier, but they seem to all be there now. Link to comment Share on other sites More sharing options...
ag3 Posted January 19, 2011 Share Posted January 19, 2011 RGEM would probably be over .50" of precip if it ran past 48 hours. Link to comment Share on other sites More sharing options...
tornadojay Posted January 19, 2011 Share Posted January 19, 2011 I guess I can do a bit of PBP. It's at hour 45 and there is a very weak broad low pressure with light QPF over the entire region Link to comment Share on other sites More sharing options...
Snowtrain Posted January 19, 2011 Share Posted January 19, 2011 12z GFS is rolling...any mets want to take the PBP? for what it's worth at hr 36 less amplified further east same movement compared to the changes in the recent NAM run. I woudl think it will be weaker and further south and east of previous run Link to comment Share on other sites More sharing options...
tornadojay Posted January 19, 2011 Share Posted January 19, 2011 at 48, there is a broad 1004 mb low pressure off the delmarva coast... continued light QPF Link to comment Share on other sites More sharing options...
Parsley Posted January 19, 2011 Share Posted January 19, 2011 RGEM gives eastern PA 5mm-10mm by 12z. I'd guessimate another 2.5mm-5mm (at most) after 12z based on the RH fields at 12z. That's 7.5mm-15mm total or roughly 0.30"-0.60" QPF (for what its worth). Link to comment Share on other sites More sharing options...
tornadojay Posted January 19, 2011 Share Posted January 19, 2011 ... and at 51, 1000 mb low pressure just south of the benchmark... looking at a zoomed in northeast view of the QPF, it looks like a 2-4 inch snowfall. Link to comment Share on other sites More sharing options...
tornadojay Posted January 19, 2011 Share Posted January 19, 2011 that's pretty much the story with this particular storm. I'll try to give some details on how the later time frames look and see if anything interesting pops up on the horizon. Link to comment Share on other sites More sharing options...
Riptide Posted January 19, 2011 Share Posted January 19, 2011 at 48, there is a broad 1004 mb low pressure off the delmarva coast... continued light QPF On a positive note, p-type issues are diminishing for coastal locations. Link to comment Share on other sites More sharing options...
famartin Posted January 19, 2011 Share Posted January 19, 2011 Yeah, seems like the consensus of the 12z models is a 2-4" storm throughout the area, and hope for up to 6" Disregard that, I was looking at 6Z :doh: Link to comment Share on other sites More sharing options...
NJwinter23 Posted January 19, 2011 Share Posted January 19, 2011 12z gfs does not phase the enrgy Link to comment Share on other sites More sharing options...
famartin Posted January 19, 2011 Share Posted January 19, 2011 Approximate real QPF from the 12Z GFS: NYC 0.23" PHL 0.26" Link to comment Share on other sites More sharing options...
Noreaster07 Posted January 19, 2011 Share Posted January 19, 2011 Snow ratios probabilities based on NAM and GFS runs from 6z (this process is slow to update) KRDG NAM 9:1-15:1 33% / >15:1 62% GFS 9:1-15:1 22% / >15:1 75% KABE NAM 9:1- 15:1 34% / > 15:1 60% GFS 9:1-15:1 21% / > 15:1 77% KPHL NAM 9:1- 15:1 39% / > 15:1 53% GFS 9:1-15:1 23% / > 15:1 73% KTTN NAM 9:1- 15:1 36% / > 15:1 57% GFS 9:1- 15:1 23% / >15:1 73% KLGA NAM 9:1-15:1 37% / > 15:1 55% GFS 9:1-15:1 25% / > 15:1 70% KEWR NAM 9:1-15:1 36% / > 15:1 58% GFS 9:1-15:1 25% / > 15:1 71% Link to comment Share on other sites More sharing options...
IsentropicLift Posted January 19, 2011 Share Posted January 19, 2011 What is going on with the 12z GFS? I thought it was out to hr 90 on the NCEP site and then when I refreshed the page its only out to hr 72? Link to comment Share on other sites More sharing options...
IsentropicLift Posted January 19, 2011 Share Posted January 19, 2011 Sounds like HPC thinks the NAM QPF was underdone? 12Z NAM EVALUATION ANY INITIALIZATION ERRORS WITH THE NAM DO NOT APPEAR TO SIGNIFICANTLY IMPACT ITS SOLUTION. ...CLIPPER DEVELOPING INTO NORTHEAST SHRTWV TROF WITH MID-ATLC NEW ENG COASTAL SFC LOW ... NAM HAS TRENDED FASTER AND SHARPER WITH THE DEVELOPING TROF ESPECIALLY EARLY IN THE PD. THIS CORRESPONDS TO A FASTER/STRONGER LOW DEVELOPMENT... BUT QPF TO NEW ENG DOES NOT SEEM TO BE SIGNIFICANTLY DIFFERENT THAN 00Z CYCLE. THE LOW TRACK SEEN IN THE NAM IS ON THE EAST SIDE OF THE SPREAD. Link to comment Share on other sites More sharing options...
Billabong Posted January 19, 2011 Share Posted January 19, 2011 What is going on with the 12z GFS? I thought it was out to hr 90 on the NCEP site and then when I refreshed the page its only out to hr 72? I got it out to 150 on NCEP. Link to comment Share on other sites More sharing options...
tornadojay Posted January 19, 2011 Share Posted January 19, 2011 I am in a conference call meeting, so it's tough for me to post, but the GFS is trying to consolidate a system for next week, however, it is having difficulty figuring out where to develop the low so it's somewhat sheared out... again... the western atlantic doesn't look that healthy at this point Link to comment Share on other sites More sharing options...
tornadojay Posted January 19, 2011 Share Posted January 19, 2011 at 168, it does produce moderate QPF over Philly and light QPF over NYC Link to comment Share on other sites More sharing options...
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