Regarding pinhole eyes
Posted by Chris in Tampa on 10/1/2016, 7:41 pm
Not sure if there is a real definition, but below you can see that eyes this small are indeed rare.



Paper (PDF), Pinhole Eyes in Tropical Cyclones:
https://ams.confex.com/ams/pdfpapers/138273.pdf



"Figure 1. Histogram depicting the number of eye diameter estimates made by AR [aircraft reconnaissance], stratified by the size of the estimate and binned in 1 n mi increments."



"This project primarily relied on three different
datasets: the extended best track (EBT, Demuth et al.
2006), the aircraft reconnaissance data from the
National Hurricane Center fix files, and the
environmental parameters compiled for the Statistical
Hurricane Intensity Prediction Scheme (SHIPS, DeMaria
et al. 2005). The EBT adds operational estimates of
various TC size parameters to the traditional location
and intensity information retained in the best track
dataset. The EBT includes this information every six
hours for all named storms in the years 1988-2006. The
aircraft reconnaissance (AR) data in the fix files includes
information about intensity, location, and various TC
parameters, including size estimates, during AR
missions over the period 1989-2006. The SHIPS
dataset includes information on TC environment, in six
hour increments, over the period 1982-2006.
To examine the characteristics of TCs with pinhole
eyes, a threshold for the designation of a pinhole eye
needed to be chosen. To choose the threshold the AR
eye diameter estimates were used. The AR included
2076 eye diameter estimates, as shown in Figure 1.

These estimates occurred in 99 different TCs over the
18-year period. We chose to define pinhole eyes as the
smallest 10% of all AR eye diameter estimates. To deal
with the peaks at 5 n mi increments, the threshold for
pinhole eyes was defined as those eye diameters less
than 10 n mi, which includes less than 10% of the total
eye diameter estimates."
90
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1930z Vortex: XTRP 940mb, C6 Eye Closed - CX, 10/1/2016, 4:27 pm
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