DerekZ Posted April 15, 2011 Share Posted April 15, 2011 The timeframe from Saturday evening through Sunday morning could be an interesting one in the Delaware Valley so I thought it would be worthwhile to start a thread on it. COASTAL FLOODING We are approaching a Full Moon, and the baseline tides this weekend are already expected to be the highest of the year so far. Persistent east to southeast winds today and tomorrow will cause departures several feet above normal. Mt. Holly's AFD has recognized the possibility of coastal flooding for several days. A Coastal Flood Watch is already out for portions of the LWX WFO. Of particular concern is the Delaware Bay Operational Forecast System , which shows levels exceeding 10 feet above mean lower low water (MLLW) on the Delaware River at Philadelphia at high tide on Sunday morning at 1:00 a.m. This would approach Major Flooding and would be an uncommon occurrence, as 10' above MLLW was last reached in the December 1992 storm. I am not sure of the track record of this product and Mt. Holly seems to expect minor to moderate flooding. Departures of 2.5' would be required to reach 10' above MLLW FLASH FLOODING The 12z NAM shows over an inch of rain throughout the Delaware Valley in the 3 hours ending Sunday at 6z. This amount of rain looks like it falls just short of Flash Flood Guidance for the area, but it will be close and that amount of rain in a short time will undoubtedly cause issues at least in poor drainage locations. Flooding of larger rivers is not expected at this time. Link to comment Share on other sites More sharing options...
IsentropicLift Posted April 15, 2011 Share Posted April 15, 2011 I posted this in the NYC forum but it holds serve for alot of people in this area as well... New WRF has over 2" of rain falling in about 6 hours, especially over northern NJ. That would exceed flash flood guidance big time. Resized to 82% (was 1024 x 819) - Click image to enlarge Link to comment Share on other sites More sharing options...
Thunder Road Posted April 15, 2011 Share Posted April 15, 2011 PNE gets 2.07" on the 12z NAM, 1.12" in 3 hours. Maybe we can finally get some thunderstorms to make our ol' buddy Lee happy Link to comment Share on other sites More sharing options...
LMolineuxLM1 Posted April 15, 2011 Share Posted April 15, 2011 PNE gets 2.07" on the 12z NAM, 1.12" in 3 hours. Maybe we can finally get some thunderstorms to make our ol' buddy Lee happy Who wants a surprise? Link to comment Share on other sites More sharing options...
Billabong Posted April 15, 2011 Share Posted April 15, 2011 PNE gets 2.07" on the 12z NAM, 1.12" in 3 hours. Maybe we can finally get some thunderstorms to make our ol' buddy Lee happy Onshore flow can be a killer. But who knows, I guess we'll have to see how strong the easterly component gets tomorrow. Maybe we can squeeze out a rumble of thunder or two, especially further south. Link to comment Share on other sites More sharing options...
DerekZ Posted April 15, 2011 Author Share Posted April 15, 2011 Wind Advisory now in effect for Philadelphia area from noon to midnight on Saturday, with sustained winds from 20 to 35 mph with gusts to 45 mph. Coastal Flood Watch also in effect for high tide around 1 a.m. on Sunday, with moderate flooding possible. Link to comment Share on other sites More sharing options...
tombo82685 Posted April 15, 2011 Share Posted April 15, 2011 PNE gets 2.07" on the 12z NAM, 1.12" in 3 hours. Maybe we can finally get some thunderstorms to make our ol' buddy Lee happy most of the models show very limited convective precip. Link to comment Share on other sites More sharing options...
DerekZ Posted April 15, 2011 Author Share Posted April 15, 2011 Mt. Holly website is still having issues as graphics and AFD aren't updating. Found AFD at another source (Iowa State) AFD Highlights (another excellent discussion, by the way): - No flood watch issued at this time. Nuisance flooding appears most likely - Widespread amounts of 2"+ during the event would be necessary for any serious concerns, and that doesn't appear likely right now - In terms of coastal flooding, event is expected to be similar to 12/1/10 which resulted in departures of 2' in Delaware Bay and Delaware River. That would result in moderate flooding for the overnight Saturday high tide. Other notes: 18z NAM came in wetter with over 2" of rain at PHL in 6-8 hours Link to comment Share on other sites More sharing options...
tombo82685 Posted April 15, 2011 Share Posted April 15, 2011 it gonna pour Link to comment Share on other sites More sharing options...
LMolineuxLM1 Posted April 15, 2011 Share Posted April 15, 2011 Who wants a surprise? So does anyone want a surprise? Link to comment Share on other sites More sharing options...
PAPPG Posted April 15, 2011 Share Posted April 15, 2011 Big pressure gradient= lots of wind Pressure now very high at 30.31 Link to comment Share on other sites More sharing options...
phlwx Posted April 16, 2011 Share Posted April 16, 2011 Yawn...another heavy rain/wind with some possible embedded thunder event. Wake me up when we get an actual severe event. BTW, the NAM's been a bit too juicy lately on precip...GFS is a bit less nasty and probably more in line with reality. 1-2" more realistic. Link to comment Share on other sites More sharing options...
NaoPos Posted April 16, 2011 Share Posted April 16, 2011 Nam continues to be a deluge.. 1.5" + Link to comment Share on other sites More sharing options...
Voyager Posted April 16, 2011 Share Posted April 16, 2011 This is why I've been complaining about the rain lately. I took the photo out the driver's side window of my tri-axle truck. Even after 2 dry days, the area where I load looks like this. I took it Friday afternoon where I get my coal. If I have to get out of the truck for any reason, I am ankle deep in mud. Link to comment Share on other sites More sharing options...
phlwx Posted April 16, 2011 Share Posted April 16, 2011 FWIW, here's the GFS (time sensitive link) http://www.meteo.psu.edu/~gadomski/AVNEAST_0z/f27.gif GFS is a bit "tamer" on precip...I'm more inclined to lean that way. Link to comment Share on other sites More sharing options...
phlwx Posted April 16, 2011 Share Posted April 16, 2011 A low pressure wave will track along the front today. Anywhere south of that low wave is where thunderstorms will probably have a chance of going severe. If the GFS is right the chances are Philly south. Heaviest rains will probably be along/north of the low wave. Link to comment Share on other sites More sharing options...
RedSky Posted April 16, 2011 Share Posted April 16, 2011 feels like snow out, starting to rain a nippy 43F Link to comment Share on other sites More sharing options...
iceman56 Posted April 16, 2011 Share Posted April 16, 2011 45.5 with light to occasionally moderate rain in NW Chester Co. .08" so far Link to comment Share on other sites More sharing options...
Rtd208 Posted April 16, 2011 Share Posted April 16, 2011 Post your storm obs here. Link to comment Share on other sites More sharing options...
phlwx Posted April 16, 2011 Share Posted April 16, 2011 Tornado watches down by DC until 9 PM Link to comment Share on other sites More sharing options...
NaoPos Posted April 16, 2011 Share Posted April 16, 2011 i knwo its not our area.. but downtown raleigh is under a tor emergency with a huge hook ehco/debris ball on radar heading straight downtown.. if you guys wanna check it out, the SE and mid atl blogs have it covered.. Link to comment Share on other sites More sharing options...
Bilas Posted April 16, 2011 Share Posted April 16, 2011 i knwo its not our area.. but downtown raleigh is under a tor emergency with a huge hook ehco/debris ball on radar heading straight downtown.. if you guys wanna check it out, the SE and mid atl blogs have it covered.. Wow that's scary looking! Link to comment Share on other sites More sharing options...
Quakertown needs snow Posted April 16, 2011 Share Posted April 16, 2011 Link to comment Share on other sites More sharing options...
blinkers88 Posted April 16, 2011 Share Posted April 16, 2011 Tornado Watch issued :0 Link to comment Share on other sites More sharing options...
NaoPos Posted April 16, 2011 Share Posted April 16, 2011 http://www.spc.noaa.gov/products/watch/ Link to comment Share on other sites More sharing options...
am19psu Posted April 16, 2011 Share Posted April 16, 2011 Doubt we'll see much verify, but new tornado watch issued for the western area. DISCUSSION...STRONG PRESSURE FALLS OCCURRING OVER ERN PA/NJ ARE INDICATIVE OF INTENSE LOW-LEVEL WAA AND THE NEWD PROGRESSION OF SURFACE LOW CURRENTLY ANALYZED OVER WRN VA /N OF ROA/. WHILE AMBIENT AIR MASS IS EXPECTED TO REMAIN ONLY MARGINALLY UNSTABLE...THE PRESENCE OF STRONG LARGE-SCALE FORCING FOR ASCENT AND EXTREME VERTICAL SHEAR INDICATE A RISK FOR BOWING AND/OR SUPERCELL STRUCTURES CAPABLE OF DAMAGING WIND GUSTS AND A COUPLE TORNADOES. Link to comment Share on other sites More sharing options...
NaoPos Posted April 16, 2011 Share Posted April 16, 2011 SEL2 URGENT - IMMEDIATE BROADCAST REQUESTED TORNADO WATCH NUMBER 152 NWS STORM PREDICTION CENTER NORMAN OK 440 PM EDT SAT APR 16 2011 THE NWS STORM PREDICTION CENTER HAS ISSUED A TORNADO WATCH FOR PORTIONS OF DELAWARE EASTERN MARYLAND SOUTHWEST NEW JERSEY SOUTHERN PENNSYLVANIA COASTAL WATERS EFFECTIVE THIS SATURDAY AFTERNOON AND EVENING FROM 440 PM UNTIL 1100 PM EDT. TORNADOES...HAIL TO 0.5 INCH IN DIAMETER...THUNDERSTORM WIND GUSTS TO 70 MPH...AND DANGEROUS LIGHTNING ARE POSSIBLE IN THESE AREAS. THE TORNADO WATCH AREA IS APPROXIMATELY ALONG AND 35 STATUTE MILES NORTH AND SOUTH OF A LINE FROM 30 MILES WEST OF ALTOONA PENNSYLVANIA TO 55 MILES EAST OF HARRISBURG PENNSYLVANIA. FOR A COMPLETE DEPICTION OF THE WATCH SEE THE ASSOCIATED WATCH OUTLINE UPDATE (WOUS64 KWNS WOU2). REMEMBER...A TORNADO WATCH MEANS CONDITIONS ARE FAVORABLE FOR TORNADOES AND SEVERE THUNDERSTORMS IN AND CLOSE TO THE WATCH AREA. PERSONS IN THESE AREAS SHOULD BE ON THE LOOKOUT FOR THREATENING WEATHER CONDITIONS AND LISTEN FOR LATER STATEMENTS AND POSSIBLE WARNINGS. OTHER WATCH INFORMATION...CONTINUE...WW 150...WW 151... DISCUSSION...STRONG PRESSURE FALLS OCCURRING OVER ERN PA/NJ ARE INDICATIVE OF INTENSE LOW-LEVEL WAA AND THE NEWD PROGRESSION OF SURFACE LOW CURRENTLY ANALYZED OVER WRN VA /N OF ROA/. WHILE AMBIENT AIR MASS IS EXPECTED TO REMAIN ONLY MARGINALLY UNSTABLE...THE PRESENCE OF STRONG LARGE-SCALE FORCING FOR ASCENT AND EXTREME VERTICAL SHEAR INDICATE A RISK FOR BOWING AND/OR SUPERCELL STRUCTURES CAPABLE OF DAMAGING WIND GUSTS AND A COUPLE TORNADOES. AVIATION...TORNADOES AND A FEW SEVERE THUNDERSTORMS WITH HAIL SURFACE AND ALOFT TO 0.5 INCH. EXTREME TURBULENCE AND SURFACE WIND GUSTS TO 60 KNOTS. A FEW CUMULONIMBI WITH MAXIMUM TOPS TO 300. MEAN STORM MOTION VECTOR 20045. Link to comment Share on other sites More sharing options...
wederwarrior Posted April 16, 2011 Share Posted April 16, 2011 Big rumbles and driving rain Temp: 47 92 tornadi spawned yesterday from this front Link to comment Share on other sites More sharing options...
PAPPG Posted April 16, 2011 Share Posted April 16, 2011 54t/52d Good flash/rumble 10 minutes ago. Up to .61 rain. Max rate only .78/hr Wind gusting to 30mph, now shifting SE from E Link to comment Share on other sites More sharing options...
Thunder Road Posted April 16, 2011 Share Posted April 16, 2011 54.6° 0.57" of rain, max gust to 18 mph so far Link to comment Share on other sites More sharing options...
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