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Earlier radar observations from the San Juan WSR-88D showed a concentric eyewall, and observations from an Air Force Hurricane Hunter aircraft showed a secondary wind maximum over the northwest quadrant. These phenomena may be associated with some weakening, but since the central pressure hasn't risen much the intensity is held at 160 kt at this time. Moreover, the concentric eyewall has become less apparent in recent radar imagery. Considerable lightning activity has been noted in the eyewall of Irma, which
research has shown to sometimes be a harbinger of weakening. Notwithstanding, low vertical wind shear and warm waters along the forecast track of Irma should allow it to remain a very powerful hurricane during the next several days.

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