TropicalUpdate.com - Guide to Dvorak Classification of Satellite Images

TropicalUpdate.com
Guide to Dvorak Classification of Satellite Images

For current products follow this link: Current SAB Satellite Estimates
Research papers and additional links at the bottom of this page.

(T-Numbers/CI Numbers)

Sat Image T-Number Description

CI = 0.5 Curved cloud lines define a cloud system center within
a deep cloud layer.

CI = 1.5 This stage should appear 24 hours later. System begins to
exhibit a curved appearance in satellite images.

CI = 2.5 Minimal tropical storm status is reached when curved band
spirals halfway around the center.

CI = 3.5 Strong tropical storm status...reaches hurricane status at
CI=4.0, once cloud band completely circles the center.

CI = 4.5 Eye usually becomes visible at CI=4.5.

CI = 5.5 Once eye is observed, increased CI numbers are based on
several factors, including temperature contrast between the center
and surrounding cloud tops...smoothness of the central dense
overcast, increase in eye definition, and the embedding of the eye
within the CDO.

The above images were created using a graphic editing program, and are not inclusive of all cases.
A full table of Dvorak Satellite Numbers and corresponding pressure/wind estimates are available
from the Satellite Analysis Branch by clicking HERE.

Additional Dvorak Resources

The Dvorak Technique Through Time - Dr Jack Beven, TPC/NHC (Streaming Presentation Available)
The Dvorak Technique Through Time - PDF Paper from Dr Beven
The Objective Dvorak Technique - University of Wisconsin Research
Dvorak CI Estimates versus Best Track Data When RECON Present 1997-2003 - PDF AMS Paper

Sat Image	T-Number	Description
	CI = 0.5	Curved cloud lines define a cloud system center within a deep cloud layer.
	CI = 1.5	This stage should appear 24 hours later. System begins to exhibit a curved appearance in satellite images.
	CI = 2.5	Minimal tropical storm status is reached when curved band spirals halfway around the center.
	CI = 3.5	Strong tropical storm status...reaches hurricane status at CI=4.0, once cloud band completely circles the center.
	CI = 4.5	Eye usually becomes visible at CI=4.5.
	CI = 5.5	Once eye is observed, increased CI numbers are based on several factors, including temperature contrast between the center and surrounding cloud tops...smoothness of the central dense overcast, increase in eye definition, and the embedding of the eye within the CDO.