Ian Posted September 20, 2011 Share Posted September 20, 2011 I think this next event is probably worthy of its own thread. multiple models have multiple inches fo rain over the coming period, and hpc/lwx Long term /Thursday through Monday/... unsettled weather pattern will persist into the long-term period as the upper low becomes cutoff from the westerlies over the Midwest/Great Lakes regions through early next week. A cold front will slowly approach Thursday before moving through on Friday. Persistent southerly flow ahead of the low and associated cold front will maintain tropical moisture feed up the eastern Seaboard. Have increased probability of precipitation to likely through Friday night. While guidance is in reasonable agreement regarding the expected synoptic pattern late this week...there are considerable differences each day on the mesoscale level. These differences will determine the coverage and amount of rainfall. With the middle-Atlantic region being situated in the right-entrance region of a strengthening upper-jet streak and precipitable waters between 1.5-2 inches...there is increasing concern for the potential of heavy rainfall across portions of the County Warning Area Thursday and Friday as the cold front moves through. However...uncertainty of threat will remain high until the mesoscale players can be determined. The cold front is expected to stall somewhere along the eastern Seaboard this weekend. The exact placement of the boundary will determine if the axis of heavy precipitation along the front will impact eastern portions of the County Warning Area or remain east of the area. Nonetheless...have increased probability of precipitation this weekend into early next week with models coming into better agreement of the cutoff low remaining over the Midwest. Southerly flow ahead of the low will continue to supply moisture from the Atlantic and Gulf. Link to comment Share on other sites More sharing options...
Ellinwood Posted September 20, 2011 Share Posted September 20, 2011 Was considering making a thread like this... could we add the severe potential to the thread? I can make a separate thread if need be, but it seems redundant. EDIT: Thanks The potential for widespread 1-3"+ totals is definitely there as the upper-level disturbance sits over the Midwest and Tennessee Valley regions from the 22nd-26th before pushing east on the 27th (though the models could be too quick with kicking it out). Of course, not good news for the rain-soaked areas of the Mid-Atlantic and Northeast... rainfall totals since June 1st: As for severe... I won't hold my breath, but with the upper-low nearby we could see a few days of severe in the region... especially as the vort. max starts to move eastward after stalling out. Dynamics will be rather impressive as it kicks out, so instability will be less of a concern. Biggest doubts right now are coming from the clouds and rain that are progged to keep the region more stable, with weaker lapse rates through most of the event. Link to comment Share on other sites More sharing options...
usedtobe Posted September 20, 2011 Share Posted September 20, 2011 The problem is that it is no over by the end of that graphic especially for New England. The closing off of an upper low to our southwest and development of a slow moving surface low coupled with a stationary front across New England means there probably will be lots of rain with more flooding especially to our north. That doesn't rule us out but from PA into New England I'd be really concerned. Link to comment Share on other sites More sharing options...
WxUSAF Posted September 20, 2011 Share Posted September 20, 2011 12" of rain for September or bust. Link to comment Share on other sites More sharing options...
Ian Posted September 20, 2011 Author Share Posted September 20, 2011 cool map mark. good points wes. Link to comment Share on other sites More sharing options...
Bob Chill Posted September 20, 2011 Share Posted September 20, 2011 What is the wettest sept on record for the airports? If this rain threat verifies, I would have to assume that areas near the Chesapeake will set all time monthly rainfall records. Link to comment Share on other sites More sharing options...
Ian Posted September 20, 2011 Author Share Posted September 20, 2011 What is the wettest sept on record for the airports? If this rain threat verifies, I would have to assume that areas near the Chesapeake will set all time monthly rainfall records. Sept 1934 (17.45) at DC http://www.americanw...e-aug-sep-2011/ We've got a way to go for that.. tho I did see similarities to the pattern on a brief look (maybe ~10 days later in 1934). Might have to take a closer look. Not sure on other airports off the top of my head. Link to comment Share on other sites More sharing options...
usedtobe Posted September 20, 2011 Share Posted September 20, 2011 cool map mark. good points wes. The event for the period shown on the HPC maps looks like a synoptic type rainfall event but at 156 hrs the look is almost like a winter time event though it does looks somewhat like the grumm composite for a frontal event except that the PW anomalies look weaker. Link to comment Share on other sites More sharing options...
WVclimo Posted September 20, 2011 Share Posted September 20, 2011 Sept 1934 (17.45) at DC http://www.americanw...e-aug-sep-2011/ We've got a way to go for that.. tho I did see similarities to the pattern on a brief look (maybe ~10 days later in 1934). Might have to take a closer look. Not sure on other airports off the top of my head. BWI: 1934 (12.41") IAD: 1975 (11.26") That 1975-76 analog is popping up too often in a lot of comparisons. That was the year a 9" snowfall in March brought Martinsburg's season total to 9.4" Link to comment Share on other sites More sharing options...
Bob Chill Posted September 20, 2011 Share Posted September 20, 2011 That 1975-76 analog is popping up too often in a lot of comparisons. That was the year a 9" snowfall in March brought Martinsburg's season total to 9.4" Yea, the 74-75 year came up in all my simpleton research. Second year Nina's have not been kind to the MA so the odds of a less than exciting winter are definitely higher than a good winter around these parts. HM's thread on the main board is excellent though. Kinda gives us hope that we might get in on enough action to at least be a decent winter. Link to comment Share on other sites More sharing options...
Bob Chill Posted September 20, 2011 Share Posted September 20, 2011 Sept 1934 (17.45) at DC http://www.americanw...e-aug-sep-2011/ We've got a way to go for that.. tho I did see similarities to the pattern on a brief look (maybe ~10 days later in 1934). Might have to take a closer look. Not sure on other airports off the top of my head. Wow. 17.45 is a huge month. Almost 50% of annual climo precip in a single month is going to be really hard to beat. Link to comment Share on other sites More sharing options...
Ian Posted September 20, 2011 Author Share Posted September 20, 2011 I've had hits on the 1930s quite a bit throughout the year. I guess it makes more sense to base off ENSO phase but finding 2nd yr ninas gives you a really small sample to work off of. I don't get long range enough I suppose. Link to comment Share on other sites More sharing options...
Bob Chill Posted September 20, 2011 Share Posted September 20, 2011 LR is tough beause of the variables. I think the criticism a lot of people give out about LR forecasts isn't fair. IMO- LR forecasting is more a presentation of statistical odds than it is a hard and fast forecast. People are so quick to say "BUST BUST BUST" but most forecasts explain exactly why the "odds" of x and y happening is favored and not saying x and y is going to happen. I agree about 2nd year Nina. Small sample and ENSO doesn't tell the whole story. If it did then last year would be beyond explanation. What analog years in the 30's do you like? Link to comment Share on other sites More sharing options...
Ian Posted September 20, 2011 Author Share Posted September 20, 2011 LR is tough beause of the variables. I think the criticism a lot of people give out about LR forecasts isn't fair. IMO- LR forecasting is more a presentation of statistical odds than it is a hard and fast forecast. People are so quick to say "BUST BUST BUST" but most forecasts explain exactly why the "odds" of x and y happening is favored and not saying x and y is going to happen. I agree about 2nd year Nina. Small sample and ENSO doesn't tell the whole story. If it did then last year would be beyond explanation. What analog years in the 30's do you like? None in particular I guess--I've just seen it show up throughout the summer etc in various fashions. Perhaps the major drought out west is part of it. I keep thinking about honing in on a methodology for some sort of seasonal framework but I never have the time to do so. I am much more a fan of the short range as a whole. Though after parsing through lots of climo stuff the last yr or so I've begun to get a bit more interested. Link to comment Share on other sites More sharing options...
PrinceFrederickWx Posted September 20, 2011 Share Posted September 20, 2011 One other stat I'd like to add: Baltimore/BWI has never had two back-to-back months of double-digit rainfall totals. We're less than a half inch away from that happening. And to think I complained about a "precip hole" over Baltimore earlier this year. Link to comment Share on other sites More sharing options...
Bob Chill Posted September 20, 2011 Share Posted September 20, 2011 None in particular I guess--I've just seen it show up throughout the summer etc in various fashions. Perhaps the major drought out west is part of it. I keep thinking about honing in on a methodology for some sort of seasonal framework but I never have the time to do so. I am much more a fan of the short range as a whole. Though after parsing through lots of climo stuff the last yr or so I've begun to get a bit more interested. It is interesting seeing similarities with analog years and not concentrating on ENSO as a baseline. I'll poke around with the 30's and look at some of the indexes like NAO and EPO. I have a hard time with pre 1950 stuff because I don't know how accurate the indexes are. Link to comment Share on other sites More sharing options...
H2O Posted September 21, 2011 Share Posted September 21, 2011 this morning disco. still calling for friday to be the rainer, .SHORT TERM /THURSDAY THROUGH FRIDAY/...UPPER LOW DROPS SOUTH FROM CANADA INTO THE UPPER MIDWEST ON THURSDAY INTO FRIDAY. CWA WILL BE CAUGHT IN A MOIST SOUTHWEST FLOW ALOFT...WITH SOUTHERLY FLOW AT THE SURFACE. MODELS ALSO FORECAST A FRONTAL BOUNDARY PUSHING EAST INTO THE MID ATLANTIC BY FRIDAY /PERHAPS WITH AN AREA OF LOW PRESSURE ALONG THE BOUNDARY OVER THE CHESAPEAKE BAY REGION/. PLUME OF HIGH PRECIPITABLE WATER AIR IS FORECAST TO TRANSPORT NORTH INTO THE MID ATLANTIC...WITH VALUES AOA 1.50 INCHES EAST OF THE BLUE RIDGE BY FRIDAY /PERHAPS CLOSER TO 2 INCHES NEAR THE BAY/. MULTIPLE SHORTWAVES/VORTS ARE EXPECTED TO AFFECT THE AREA DURING THIS TIME. THEREFORE...HAVE CHANCE AND LIKELY POPS FOR SHOWERS IN THE FORECAST DURING THIS TIME. RAINFALL...ESPECIALLY FRIDAY...HAS THE POTENTIAL TO BE LOCALLY HEAVY. WITH LOTS OF CLOUDS...INSTABILITY MAY BE HELD DOWN SOME. BUT WITH HIGH MOISTURE AND PERHAPS OCCASIONAL BREAKS IN THE CLOUDS... THERE MAY ALSO BE A CHANCE OF THUNDERSTORMS ESPECIALLY ACROSS THE EASTERN PORTION OF THE CWA Link to comment Share on other sites More sharing options...
aldie 22 Posted September 21, 2011 Share Posted September 21, 2011 Boy the NAM sure is wet Link to comment Share on other sites More sharing options...
yoda Posted September 21, 2011 Share Posted September 21, 2011 Boy the NAM sure is wet Link to comment Share on other sites More sharing options...
WxUSAF Posted September 21, 2011 Share Posted September 21, 2011 12z NAM is not so wet. Link to comment Share on other sites More sharing options...
forkyfork Posted September 21, 2011 Share Posted September 21, 2011 12z NAM is not so wet. it has a warm core system coming up the coast, but too far east for most of us... there's a lot of spread in the sref members, though Link to comment Share on other sites More sharing options...
WxUSAF Posted September 21, 2011 Share Posted September 21, 2011 it has a warm core system coming up the coast, but too far east for most of us... there's a lot of spread in the sref members, though From the very limited model output I've seen in the last couple days, it does seem that there's some wobbling between a broader moderate rain event for the entire Mid-Atlantic and a heavy rain event for the immediate coastline with a sharp precip gradient and then just light rain for those of us west of the Chesapeake. Link to comment Share on other sites More sharing options...
mitchnick Posted September 21, 2011 Share Posted September 21, 2011 From the very limited model output I've seen in the last couple days, it does seem that there's some wobbling between a broader moderate rain event for the entire Mid-Atlantic and a heavy rain event for the immediate coastline with a sharp precip gradient and then just light rain for those of us west of the Chesapeake. a trend we don't want to hold or get established for the winter Link to comment Share on other sites More sharing options...
WxUSAF Posted September 21, 2011 Share Posted September 21, 2011 12z GFS is nothing special. Keeps heavy precip along the coast. Light-mod rains for most of us. Link to comment Share on other sites More sharing options...
North Balti Zen Posted September 21, 2011 Share Posted September 21, 2011 12z GFS is nothing special. Keeps heavy precip along the coast. Light-mod rains for most of us. To echo mitch...winter pattern! Link to comment Share on other sites More sharing options...
forkyfork Posted September 21, 2011 Share Posted September 21, 2011 12z GFS is nothing special. Keeps heavy precip along the coast. Light-mod rains for most of us. the meso models want to bring a low up from the SE coast while the gfs doesn't have much of anything the rgem would be a soaker Link to comment Share on other sites More sharing options...
WxUSAF Posted September 21, 2011 Share Posted September 21, 2011 the meso models want to bring a low up from the SE coast while the gfs doesn't have much of anything the rgem would be a soaker Looking forward to a winter lacking any model consensus 36-48 hours out from an event. Link to comment Share on other sites More sharing options...
Bob Chill Posted September 21, 2011 Share Posted September 21, 2011 Looking forward to a winter lacking any model consensus 36-48 hours out from an event. As long as one model shows a snow solution I'll hug it. Link to comment Share on other sites More sharing options...
nj2va Posted September 21, 2011 Share Posted September 21, 2011 As long as one model shows a snow solution I'll hug it. This. I know tihngs look bad when I start touting NOGAPS in the winter. Link to comment Share on other sites More sharing options...
forkyfork Posted September 21, 2011 Share Posted September 21, 2011 the 12z euro has the heavy axis west of the 00z run Link to comment Share on other sites More sharing options...
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