Further improvement in the JMA/GSM SHIPS by using GSMaP

The Japan Meteorological Agency (JMA) plans to operationalize the Statistical Hurricane Intensity Prediction Scheme (SHIPS) for improving tropical cyclone (TC) intensity forecasts as well as strengthening TC-related services as the Regional Specialized Meteorological Centre (RSMC). To achieve this, with great support of SHIPS developers in the US, the Meteorological Research Institute of JMA has transported SHIPS code with some modification so that the SHIPS can run from outputs of the JMA Global Spectral Model (JMA/GSM) and can forecast central pressure as well as maximum sustained wind up to 5 days ahead.

To further improve the skill of the SHIPS, we are trying to incorporate new predictors derived from the Global Satellite Mapping of Precipitation (GSMaP) data, a microwave satellite-derived rainfall product, into the SHIPS regression equation. We decided to use the GSMaP because GSMaP_NOW, a quasi-realtime version of the GSMaP, is currently provided at 30-min intervals with almost no latency, which makes it possible to use microwave satellite-derived rainfall information in the SHIPS. As a first step, we incorporated the following three new predictors associated with a TC at an initial time; i) axisymmetricity (AXIS), ii) horizontal scale of rainfall area (the outer radius of azimuthal mean rainfall with 3 mm per hour, 3EDG) and iii) the radius of maximum rainfall (RMAX). The AXIS contributes largely to intensification in the first half of the forecast when TC structure is more axisymmetric. The 3EDG contributes to weakening up to 30-hr forecasts and contributes to intensification after that when its value is above the average. The RMAX contributes to weakening in the second half when its value is above the average. The accuracy of the SHIPS with the GSMaP was improved by at most 8.6 % mainly in the first half of the forecast. We will work further on the improvement to operationalize the SHIPS with the GSMaP.