Bobnekaro's Analysis of Hurricane Eta

NHC Intensity: 130 knots (150 mph), 923 mb

My Intensity: 130 knots (150 mph), 921 mb

Analysis:

I have the peak intensity of Hurricane Eta at 130 knots (150 mph). Contrary to many weather enthusiasts, I am convinced Eta did not reach Category 5 intensity. Here is why:


 * The maximum 700mb flight-level wind observed by the recon aircraft was only 137 knots, which, using a standard 90% reduction, equals ~123.3 knots. That is WELL SHORT of the Category 5 threshold of 137 knots.
 * The maximum SFMR reading was 135 knots, which was marked as suspect with high rain rates. The SFMR instrument may have a high bias at these intensities regardless.
 * Considering the 135 knot SFMR as reliable (it my not be), blending the two supports an intensity of 129.15 knots - very close to the operational NHC intensity of 130 knots.
 * I don't think Eta peaked BEFORE recon arrived late on November 2, since Eta was still deepening during the flight.
 * During the flight, the recon aircraft noted the start of an eyewall replacement cycle, later confirmed in radar data with concentric eyewalls appearing around 03z November 3.
 * Raw T#s began to fall immediately after recon left, and by 06z, the CDO had warmed somewhat and the satellite presentation degraded. Therefore, it seems unlikely Eta strengthened significantly after the recon mission left. I have lowered the pressure slightly to 921 mb, assuming some very slight deepening occurred after the plane left.
 * Although recon did not sample every quadrant, Eta was not moving particularly quickly, which likely means there was no significant difference in the maximum wind speed in the NW quadrant, which would be the right-front quadrant in Eta's case.
 * By 11:30z November 3, recon found Eta much weaker, and the pressure had risen to the mid-930s mb with Eta having weakened to the low-mid Category 4 range.
 * Dvorak estimates were NOT in solid agreement on Category 5 intensity either. TAFB peaked at T7.0 (140 knots), while SAB peaked at T6.5 (127 knots), and SATCON supported an intensity of around 130 knots. Contrary to popular belief, I don't think Eta would be analyzed at more than a low-end Category 5 without reconnaissance data.

I think it is extremely unlikely NHC upgrades Eta to Category 5, despite the outstanding satellite presentation.