Amped Posted October 26, 2012 Share Posted October 26, 2012 In layman's terms from a long time frustrated amature forecaster, here is my perspective on Sandies storm surge potential: "If Sandy Tracks 10 miles south of NYC, then they get a 20ft storm surge! However if Sandy Tracks 10 miles north of NYC, then they get a 0 ft storm surge!" This maybe an exaggeration, but it's close enough to reality. It was a similar scenario in Houston with Ike in 2008. With any land falling hurricane semiwarmcore system land-falling there is very little distance between the offshore and the onshore winds, hence a sharp gradient between a large surge and nothing or even a blowout tide. So my first question/concern: Is the margin for error really this low. WIll NYC at least get a 6" storm surge if it goes 10 miles to their north? Now Lets say thiis forecasting nightmare senario actually happens. 24 hrs out, models are showing an ambiguous track for NYC. This is a tough one to communicate to the public. You almost have to admit that they are preparing for the worst because you have absolutely no idea. On one hand you need to error on the side of caution. On the other hand a potential bust that would blow March 2001 out of the water is not good for the NWS's reputation or anyone else in the meteorological community. That brings me to my second question, does NWS have a plan to communicate this kind of huge uncertainty to the public, Or is it all up to TV mets and Twitter mets? Link to comment Share on other sites More sharing options...
aslkahuna Posted October 26, 2012 Share Posted October 26, 2012 NWS will do the best they can but rest assured the media will hash it all up. So it's up to the knowledgable people to pass the information to their firends and neighbors as best they can. Steve Link to comment Share on other sites More sharing options...
Roger Smith Posted October 26, 2012 Share Posted October 26, 2012 I don't think that the gradient in storm surge would be quite that dramatic, especially given the interconnected bodies of water around Long Island and the Hudson estuary. Your point is well taken but I would imagine that the zero storm surge would be located more like 50-100 miles away from the landfall point to the south or southwest depending on what part of the coast. Also the maximum storm surges will tend to be more like 50-150 miles east or northeast of the track of low pressure with a gradual decline to about 70% of that maximum along the track then sharper declines. So not quite an all or nothing situation. This is based on a few very deep non-tropical lows that created large storm surges in the UK / Holland and eastern Canada (not the same storms of course). Hurricane storm surges tend to peak closer to the centers or forward eyewall, but assuming transition has at least begun by landfall, that should spread the max out further to the right of the track, and different tidal ranges come into play so that an inlet with a bigger natural range will amplify the surge locally. If you are concerned about Queens or Jamaica in this regard, though, I think you're right to assume that a landfall anywhere east of JFK will probably mean no major problems in NYC while anywhere south of ACY might be far enough away to mitigate, so ACY to JFK landfalls would be worst in general and I would think Asbury Park or Sandy Hook would be peak for NYC surge. Long Island Sound on the other hand would receive a surge and funnel it west dependent more on wind field than landfall. Link to comment Share on other sites More sharing options...
Amped Posted October 27, 2012 Author Share Posted October 27, 2012 I don't think that the gradient in storm surge would be quite that dramatic, especially given the interconnected bodies of water around Long Island and the Hudson estuary. Your point is well taken but I would imagine that the zero storm surge would be located more like 50-100 miles away from the landfall point to the south or southwest depending on what part of the coast. Also the maximum storm surges will tend to be more like 50-150 miles east or northeast of the track of low pressure with a gradual decline to about 70% of that maximum along the track then sharper declines. So not quite an all or nothing situation. This is based on a few very deep non-tropical lows that created large storm surges in the UK / Holland and eastern Canada (not the same storms of course). Hurricane storm surges tend to peak closer to the centers or forward eyewall, but assuming transition has at least begun by landfall, that should spread the max out further to the right of the track, and different tidal ranges come into play so that an inlet with a bigger natural range will amplify the surge locally. If you are concerned about Queens or Jamaica in this regard, though, I think you're right to assume that a landfall anywhere east of JFK will probably mean no major problems in NYC while anywhere south of ACY might be far enough away to mitigate, so ACY to JFK landfalls would be worst in general and I would think Asbury Park or Sandy Hook would be peak for NYC surge. Long Island Sound on the other hand would receive a surge and funnel it west dependent more on wind field than landfall. This looks like the senario unfolding. A track due west into ACY and slong the MAson dixon would be horrible for the long Iland Sound. The flow has less curvature as you move away from the center hence a deeper fetch of ESE winds for a longer period of time. A track into southern Delaware would be devastating for anyone along the coast of NJ CT NY and SNE would still get slammed pretty food. NYC will get little surge if it tracks over or north of them, wind trajectories just wont make it onshore for any extended period of time. In other words the gradient is probably larger then 10 miles. But models are now closing in on N Central Jersey, I assume you still agree this is a forecasting nightmare!! Link to comment Share on other sites More sharing options...
Amped Posted October 27, 2012 Author Share Posted October 27, 2012 Looks like my worse case forecasting nightmare scenario verified spot on. At least I got one thing right about this storms. I hope forecasters have thought about how they will handle this. My final call. Bust, Storm tracks over southern CT and continues wnw to Buffalo. I just wouldn't bet my life savings on it. Edit: Forecast from the Amped Weather Service: We put getting the forecast right more often then not ahead of your personal saftey! Link to comment Share on other sites More sharing options...
Geos Posted October 27, 2012 Share Posted October 27, 2012 Thought this would be a good thread to post a few bathymetry maps of coastal New Jersey and Long Island. Storm surge will likely be the worst where the slope of the continental shelf is the most gradual and areas where the coastline shape acts to funnel water in. _ New York Harbor, Raritan Bay, and any estuary that open to towards the incoming wind direction would the most at risk for surge. I noticed a few places where the ocean floor slope is really gradual is off Atlantic City and just north of there, then up towards Barnegat Light area. Likely the Great South Bay between LI and it's southern barrier islands would see substantial water rises. Link to comment Share on other sites More sharing options...
Amped Posted October 28, 2012 Author Share Posted October 28, 2012 Thought this would be a good thread to post a few bathymetry maps of coastal New Jersey and Long Island. Storm surge will likely be the worst where the slope of the continental shelf is the most gradual and areas where the coastline shape acts to funnel water in. _ New York Harbor, Raritan Bay, and any estuary that open to towards the incoming wind direction would the most at risk for surge. I noticed a few places where the ocean floor slope is really gradual is off Atlantic City and just north of there, then up towards Barnegat Light area. Likely the Great South Bay between LI and it's southern barrier islands would see substantial water rises. No nobody reads my threads. I made it anyway so I can go over some of the odd details of this that people overlook, and also to get myself mentally prepared for a bust. I know it sounds funny but with every potential major storm comes the potential for a major bust. Also NHC says some things like "The exact landfall point doesn't matter" For wind that is going to be true but for storm surge, that couldn't be further from the truth. Yeah it doesn't matter if it's 100 or 200 miles south of you but weather it's south or north of you makes all the difference in the world. I also hoped people would respond but it appears nobody is up for this forecasting challenge. Just evacuate everyone and don't try to pinpoint. Link to comment Share on other sites More sharing options...
Geos Posted October 28, 2012 Share Posted October 28, 2012 No nobody reads my threads. I made it anyway so I can go over some of the odd details of this that people overlook, and also to get myself mentally prepared for a bust. I know it sounds funny but with every potential major storm comes the potential for a major bust. Also NHC says some things like "The exact landfall point doesn't matter" For wind that is going to be true but for storm surge, that couldn't be further from the truth. Yeah it doesn't matter if it's 100 or 200 miles south of you but weather it's south or north of you makes all the difference in the world. I also hoped people would respond but it appears nobody is up for this forecasting challenge. Just evacuate everyone and don't try to pinpoint. I'm interested in the storm as a whole, but especially the storm surge and what the wave action might do to the coast! There is no doubt that certain areas will suffer more than others from storm surge alone within the forecasted 4-8 foot surge area. I would more concerned with 4-8 feet of water washing on to the land then a 70kt wind! Sandy is likely to do some rearranging with the barrier islands tomorrow night - Wednesday. Link to comment Share on other sites More sharing options...
thewxmann Posted October 28, 2012 Share Posted October 28, 2012 To answer the title, no. The winds will be onshore hours before landfall, even if you're south of the landfall location. Around and after landfall, that's when the winds will turn offshore and the storm surge threat ends. Before then though, can't count out the surge threat. Link to comment Share on other sites More sharing options...
wxmeddler Posted October 28, 2012 Share Posted October 28, 2012 I posted this to twitter today: Link to comment Share on other sites More sharing options...
CoastalWx Posted October 28, 2012 Share Posted October 28, 2012 I can understand why Cantore was criticizing the whole NYC surge debacle. Bloomberg took a big gamble. Link to comment Share on other sites More sharing options...
Amped Posted October 28, 2012 Author Share Posted October 28, 2012 To answer the title, no. The winds will be onshore hours before landfall, even if you're south of the landfall location. Around and after landfall, that's when the winds will turn offshore and the storm surge threat ends. Before then though, can't count out the surge threat. Well now it's looking the GFS has locked down On central NJ ant sinks south to Hagerstown after landfall. 3 runs in a row in the same spot and other model agreement gives me some confidence. Looking a lot more likely they get a big hit, but there is still not a lot of error margin. Oh and now Deleware Bay is uncertain. It's always going to be someone. Link to comment Share on other sites More sharing options...
Geos Posted October 28, 2012 Share Posted October 28, 2012 Here's the link the Battery Water Level Gauge. http://water.weather.gov/ahps2/hydrograph.php?wfo=okx&gage=batn6 Area wide gauges: http://water.weather.gov/ahps2/index.php?wfo=phi Link to the USGS gauging stations database: http://waterwatch.usgs.gov/?m=real&r=nj&w=map Link to comment Share on other sites More sharing options...
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