Super Typhoon WutipAfter previously reaching Category 4 intensity on 23 February, Super Typhoon Wutip underwent an eyewall replacement cycle (MIMIC-TC) and emerged to reach Category 5 intensity at 06 UTC on 25 February 2019 (ADT | SATCON) — becoming the strongest (and only Category 5) February tropical cyclone on record for the Northwest Pacific basin (and also for the Northern Hemisphere). Rapid scan (2.5-minute) Himawari-8 “Clean” Infrared Window (10.4 µm) images (above) displayed a well-defined eye with an annular to axisymmetric eyewall structure; mesovortices could also be seen circulating within the eye. Of particular interest were the series of gravity waves propagating radially outward from the eye during the first few hours of the animation.
In addition, note the arc of cooling cloud tops south of the eye beginning around 1530 UTC. A comparison of Himawari-8 Infrared and Infrared-Water Vapor brightness temperature difference (BTD) images from the CIMSS Tropical Cyclones site (below) revealed increasing BTD values within that arc of colder clouds — an indication of convective overshooting tops that were likely penetrating into the stratosphere.Himawari-8 “Red” Visible (0.64 µm) images (below) provided a clearer view of the mesovortices within the eye. Satellite-derived deep-layer wind shear in the vicinity of Wutip was very light — in the range of 5-10 knots — surrounding the time period when Wutip peaked at Category 5 intensity at 06 UTC (below). Wutip continued to exhibit a well-defined poleward outflow channel (below), although mid-upper level outflow was good in all quadrants of the storm (which aided the intensification process). Although Ocean Heat Content was modest, Sea Surface Temperature values around 28ºC were favorable (below).