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RL3AO wrote:But it is a forecast. It's an ensemble surge model thats based on the NHC forecast track and historical error.
Thanks...I was confused by this previous post:
[quote = wxman57]Note that the storm surge map above is not a forecast, it's a probabilistic map. Let me explain. As an example, let's say you look at the map and for your area you see that the potential inundation is "greater than 6ft" (but less then 9ft). It does not mean that the forecast for your location is for a storm surge causing 6-9ft of inundation. It means that the surge (inundation) for your location has only a 10% chance of being higher than 6-9ft. Conversely, there's a 90% chance that the surge will be 6-9ft or lower.[/quote]
Well forecast isn't the best word. It is a model that makes hundreds of different runs and outputs the probability (in this case the 10% exceedance) as inundation. It's going to be a very very powerful tool that was very much needed in the past.
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mitchell wrote:You can't represent the surge threat using a deterministic track over LiDAR topography. In most cases, such a plot is guaranteed to be wrong.if they live in a location where they could get inundated by 6-9 ft. of storm surge, then they need to prepare for the possibility of such a surge, even though there's a fair chance the surge will turn out to be less than that.
I agree with all of what you say, and think there is potential for confusion for exactly the reasons you say above: two different types of storm surge forecasts going on (deterministic and worst case), showing different outcomes, both likely to be wrong. In my observation this creates both frustration, and cynicism.
No deterministic storm surge forecasts will be issued. All surge forecasts will be probabilistic. The probabilistic inundation maps will depict a reasonable worst-case scenario (not the absolute worst-case). Such a surge could happen at a location, depending upon the precise storm track and size/intensity at landfall.
wxman57 wrote:No deterministic storm surge forecasts will be issued. All surge forecasts will be probabilistic. The probabilistic inundation maps will depict a reasonable worst-case scenario (not the absolute worst-case). Such a surge could happen at a location, depending upon the precise storm track and size/intensity at landfall.
Understood. and my point was that I can see the potential confusion between the NWS probabilistic maps, and other local (non-NWS) forecast applications products (such as the University of Delaware Coastal Flood Monitoring System I linked to above) which ARE deterministic surge forecasts out to 48 hours draped over LiDAR topography, and are widely used by residents and local emergency managers in communities along the Delaware coast.