June 15, 2020 Tropical Update
Global tropics are quiet. Sharpiegate report drops
10% chance = snore
The National Hurricane Center is watching an area of showers for further development but only 10% over the next 48-hours. This is in the general orbit of a strong upper-level or cut-off low centered over the Carolinas which is providing some very cool mid-June air as far south as Atlanta. Earlier today, thunderstorms in North Georgia dropped significant hail of quarter size indicating the cooler, mid-level air.
Now on to Sharpiegate from last hurricane season with Dorian. Rather than retread worn ground on the topic, I’d like to point your attention to a few issues of scientific interest about the proper use of hurricane forecast “cone” maps.
Timing of the forecast: as you note on this forecast advisory made 5 pm Aug 18, 2019 the 120-hour point location of Dorian is over central Florida. NHC provides 5-day forecasts to the public but internally with consultation and conjunction with WPC, 7-day positions are generated: where does this storm track continue on to Days 6 and 7? Models at the time highlighted the potential of a Gulf of Mexico reemergence and I was concerned enough about the possibility to Tweet. Mind you this is when the storm is near Puerto Rico so still a long way off from affecting the United States.
We know in hindsight that the storm stalled in the western Bahamas and spared the Florida coastline but only after many more forecasts and days observing Dorian.
Was Alabama ever threatened? Of course. A 7-day track in the Gulf would provide at least tropical storm force winds inland but perhaps treacherous or even a disastrous landfall around Mobile. But, eventually we KNEW that Alabama was not going to be where major impacts would occur instead with a focus on Florida and then Georgia as Dorian headed north along the FL east coast.
The forecast cone means nothing physically. It is not based upon the current weather model forecasts but instead the statistical error of forecasts made by humans at the NHC over the previous 5-years. 66% of the forecast positions made by NHC exist within the cone but obviously that means many times the track position can and will occur well outside of it. I would favor “dynamic cones” but that is just too complicated for public messaging.
When Trump Tweeted out that Alabama was under threat, his information was stale. This happens when the storm track is shifting with every forecast or a major change is made. That is also partly the reason the El Faro sank during Hurricane Joaquin: outdated hurricane forecasts from a vendor. Link to story.
Thus, it is incumbent upon folks on social media or the President of the United States to always provide the most up-to-date information if you are going to serve as a fountainhead of such information. You can only amplify and disseminate valid products. Otherwise, you get the disconnect between NWS Birmingham and the White House.
The politics with Sharpiegate are also interesting but I won’t get into that today. News broke this afternoon about a government accountability report that faulted NOAA acting-admin Neil Jacobs for violating some process standards on scientific integrity and ethics. My Tweet thread is here:
In summary, we should make it a practice to look at the 7-day forecast since NHC has been creating those products internally for a while and get used to making and owning longer term forecasts. There is significant value to a client in having a good 7-day forecast. 10-days might be pushing it but there is also much to be learned by looking at model bias and trends.