Re: Florence Pics (Wednesday morning)
Posted by Chris in Tampa on 9/5/2018, 8:33 pm
We have readings over land, including weather balloons that weather services release across the country to determine the conditions in the upper levels. But in the ocean, we don't have that. We have to rely on satellites only. Without direct observation in the upper levels over the ocean, it's always going to be a less reliable forecast, especially since the storm is in the middle of the ocean. That's why NOAA has a high altitude jet that samples around the storm when it is closer to land. It drops dropsondes that measure data on the way down to the ocean's surface. Really expensive supercomputers are great at crunching numbers, but at some point it's about the data.

But I don't think 10 days out any model will ever be able to forecast where a storm is going to go with any great reliability. Too many variables to consider. I guess that's where ensembles come in. Are they in agreement or not long term.

Global Ensemble Forecast System (GEFS):
https://www.tropicaltidbits.com/analysis/models/?model=gfs-ens&region=atl&pkg=lowlocs
About: https://www.ncdc.noaa.gov/data-access/model-data/model-datasets/global-ensemble-forecast-system-gefs

If you change various things, does the path change? In that model imagery above you can see the center point of the storm forecast for each ensemble member. If they all go to the same place, that means more confidence.

"The GEFS attempts to quantify the amount of uncertainty in a forecast by generating an ensemble of multiple forecasts, each minutely different, or perturbed, from the original observations."

If they go all over the place, there is less confidence. Over the ocean you have less data. So if you see that a small change to the initial conditions has a big impact, meaning the ensemble members go all over the place, that means it's really important that you get those initial conditions right. But over the ocean, without recon, with just satellite data basically, it's going to be harder to get those initial conditions right than closer to land.

You can see the ensemble members of the GFS are around Bermuda but the further you get out from that, it really gets uncertain.

Beyond 7 days, and even with a lot of storms beyond 5 days, I just don't know how much better those forecasts will get. Even that far out you're going to have times where models, or even an NHC forecast, that are just really wrong. (That's why I don't like the idea of the NHC ever making public 7 day forecasts)
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Florence Pics (Wednesday morning) - Target, 9/5/2018, 7:39 am
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