Nearly Flawless Forecast for Historic Hurricane Helene Due to Lessons Learned from Michael
Intensity Forecast Slightly Underestimated
Very Strong Track Forecast
The track forecast for historic Hurricane Helene was absolutely immaculate from First Call issued on Tuesday and was unchanged with the issuance of Final Call on Thursday.
The forecast rationale that all of the guidance, including the National Hurricane Center were underestimating how quickly a hurricane as powerful and vertically stacked as Helene would begin to feel the influence of the incoming trough and veer somewhat to the east.
The intensity forecast, while accurate overall, was not flawless.
Landfall Intensity Underestimated
The evolution of the intensity forecast was exceptionally accurate, as First Call explicitly articulated that the system would not undergo any rapid intensification until after dawn on Thursday and instead only intensify gradually through Wednesday night, which its precisely what took place.
The system was somewhat disrupted when it skirted the northeastern most tip of the Yucatan, as anticipated and then began to rapidly intensify after dawn on Thursday. Final Call
"In fact, poleward ventilation of Helene may be enhanced as a result of the approaching trough's initial interaction with the system in addition to what is obviously likely to be a very moist airmass in the mid levels of the atmosphere".
This unique type on interaction with the trough was correctly identified as the type that allows for significant intensification right to the coast.
This is very analogous to the the type of scenario that was misdiagnosed by Eastern Mass Weather with respect to Hurricane Michael in October of 2018.
Although the forecast was certainly superior to the one with respect to Michael, which called for significant weakening, Helene even intensified slightly more aggressively than anticipated Thursday into Thursday evening. This was on display via numerous very vidid lightening strikes within the eyewall throughout the night on final approach to the coast.
It ultimately made landfall with 140 mph maximum sustained winds instead of the forecast for 125 mph at 11:10pm EDT instead of the forecast 12:00am EDT.
FINAL GRADE: A