Evaluation of official tropical cyclone landfall forecast issued by India Meteorological Department

Abstract

India Meteorological Department (IMD) introduced the objective tropical cyclone (TC) track forecast valid for next 24 hrs over the North Indian Ocean (NIO) in 2003. It further extended the validity period up to 72 hrs in 2009. Here an attempt is made to evaluate the TC landfall forecast issued by IMD during 2003-2013 (11 years) by calculating the landfall point forecast error (LPE) and landfall time forecast error (LTE). The average LPE is about 67, 95, and 124 km and LTE is about 4, 7, and 2 hrs, respectively for 24, 48, and 72-hr forecasts over the NIO as a whole during 2009-2013. The accuracy of TC landfall forecast has been analysed with respect to basin of formation (Bay of Bengal, Arabian Sea, and NIO as a whole), specific regions of landfall, season of formation (pre-monsoon and post-monsoon seasons), intensity of TCs (cyclonic storm (CS), and severe cyclonic storm (SCS) or higher intensities) at the time of initiation of forecast and type of track of TCs (climatological/straight moving and recurving/looping type). The LPE is less over the BOB than over the AS for all forecast lengths up to 72 hrs. Similarly, the LPE is less during the post-monsoon season than during pre-monsoon season. The LPEs are less for climatologically moving/straight moving TCs than for the recurving/looping TCs. The LPE over the NIO has decreased at the rate of about 14.5 km/year during 2003-2013 for 24-hr forecasts. The LTE does not show any significant improvement for 24-hr forecast during the same period. There is significant decrease in LPE and LTE during 2009-2013 compared to 2003-2008 due to the modernisation programme of IMD. The 24-hr LPE and LTE have decreased from 157.5 to 66.5 km and 7.8 to 4.1 hrs, respectively. However, there is still scope for further reduction in 48 and 72-hr forecast errors over the NIO to about 50 and 100 km respectively based on the latest technology including aircraft reconnaissance, deployment of buoys, and assimilation of more observational data from satellite and Doppler weather radars, etc., in the numerical weather prediction (NWP) models during the next five years.

Comparative evaluation of the skill of a global circulation model and a limited area model in simulating tropical cyclones in the north Indian Ocean

“…Similar conclusions also hold for simulations with a 48 hr lead ( Figure S2). These results are in agreement with previous evaluation studies over the NIO basin (Mohapatra et al, 2015). The smaller error over the BOB may be attributed to the fact that the open sea area, which is a data sparse region, is relatively less in the case of the BOB compared with the Arabian Sea.…”

“…The smaller error over the BOB may be attributed to the fact that the open sea area, which is a data sparse region, is relatively less in the case of the BOB compared with the Arabian Sea. While there is a dense observatory network along the coast surrounding the BOB due to dense coastal observatories and cyclone detection radars, the coastal area surrounding the Arabian Sea does not have such a network (Mohapatra et al, 2015). However, the flows simulated by the GCM are more organized around the observed location than those simulated by the LAM (Figure S2).…”

Elliptical Structures of Gravity Waves Produced by Typhoon Soudelor in 2015 near Taiwan

“…In addition, the TC timing was fairly good, with errors <3 h (distance errors <55 km) ahead of time from 7 August 06:00 UTC. Indeed, timing and distance errors remained a challenging task prior to landfall especially beyond the 48-h integration period [56][57][58]. Satellite images clearly captured the TC asymmetry and the ERC from 5 August to 7 August.…”

Coastal zone management in India − present status and future needs

“…The prediction of cyclone tracks and landfall, 24 h before the event, has been improved to 140 km and 70 km, respectively (Mohapatra et al 2013(Mohapatra et al , 2015. The assimilation of OSCAT data improved the location of the center and track predictions (Prasad et al 2013).…”

“…During the last 10 years, loss of lives has been minimized because of the availability of accurate and timely information on track, landfall point, velocity of wind, storm surge, etc. (Mohapatra et al 2013(Mohapatra et al , 2015, the suitable response and actions of the government and the trust of local people in the forecast and government. The tsunami warning center has performed very well (Kumar et al 2012a) and there has been no false warning during the last 10 years.…”