Sinlaku Intensifies to Category 5, threatens the Marianas and Guam
Typhoon Sinlaku (whom we introduced to you two days earlier when it was a mere tropical storm) has undergone steady and significant intensification and has now reached Category 5 status with estimated winds as high as 150 knots (170 mph). Satellite imagery of Sinlaku depicts it as a nearly perfectly symmetric eye with a tight and consistent circulation surrounding it. Here is the view from the Band 13 (10.4 micron) channel aboard Himawari-9, which provides the best geostationary view of the western Pacific Ocean.
The ATMS Band 18 (183 GHz) microwave imagery (courtesy of the CIMSS Tropical Cyclone page) shows a very similar story. Different microwave bands require different interpretations, but here the interpretation is relatively straightforward: the cold brightness temperatures of the eyewall and precipitation bands are easily contrasted against the warmth of the uniform ocean background.
By contrast, ATMS channel 8 (55 GHz) shows the warm temperature anomaly that is at the heart of a warm-core low like a strong tropical system. Since tropical cyclones are latent heat machines, their center is warmer than the surrounding areas. This is one trait that sets them apart from the baroclinic midlatitude systems that may look similar but have drastically different characteristics, including a cold central core.
The CIMSS Deep Multispectral INtensity of TCs estimator (D-MINT) automated estimation of cyclone intensity has been tracking this storm from the beginning, showing its steady increase from an invest all the way to a Category 5 storm. The Joint Typhoon Warning Center cites these values in estimating Sinlaku’s wind speed as part of its prognostic reasoning.
Recent forecasts have been pushing the track slightly northward and projecting a path over Saipan. Tropical storm conditions are still expected for Guam. One good note in the evolution of this system is that the Air Mass RGB seems to indicate that Sinlaku is moving into a region of drier day, which it may soon start ingesting and which could contribute to its weakening in the future. This dry air is discernible as the areas of orangish-brown against the greener colors of the more moist air.
