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Numerical Weather Prediction Activities

As a pioneer among Numerical Weather Prediction (NWP) centers, JMA has continued the active development of a suite of numerical weather prediction (NWP) systems since the commencement of operational numerical prediction in 1959. In its role as one of the world's most advanced NWP centers, JMA today outputs a variety of NWP products to support National Meteorological and Hydrological Services (NMHSs) in the provision of effective and efficient services.

Numerical Weather Prediction Models and related Application

JMA currently operates the following NWP models:
  1. The Global Spectral Model (GSM) for daily forecasts, tropical cyclone information and one-week forecasts up to 11 days ahead covering the entire globe
  2. The Meso-Scale Model (MSM) for weather warnings/advisories, very short-range forecasts of precipitation and aviation forecasts covering Japan and its surrounding areas, providing 39-hour forecasts every 3 hours
  3. The Local Forecast Model (LFM) for aviation forecasts, weather warnings/advisories and very short-range forecasts of precipitation covering Japan and its surrounding areas, providing 9-hour forecasts every hour
  4. The Global Ensemble Prediction System (GEPS) based on a low-resolution version of the GSM for tropical cyclone information, one-week forecasts, early warning information on extreme weather and one-month forecasts
  5. An ensemble prediction system based on an atmosphere-ocean coupled model for three-month forecasts, warm-season outlooks, cold-season outlooks and El Niño outlooks
  6. Other NWP models for specific targets such as ocean waves and sea ice extents

JMA also uses NWP models in relation to atmospheric environmental issues, as exemplified by its work as a Regional Spcialized Meteorological Center (RSMC) under the framework of WMO's Emergency Response Activities (ERA) programme for environmental emergency response activities in Asia. The Center provides NMHSs with outlooks on the diffusion and deposition of hazardous materials based on JMA's Atmospheric Transport Model in the event of the accidental release of such materials from nuclear facilities.

GSM       MSM and LFM
Domains and topography of JMA's NWP models

Specifications of JMA's NWP models
Global Spectral Model (GSM) Meso-Scale Model (MSM) Local Forecast Model (LFM) Global Ensemble Prediction System (GEPS) Seasonal Ensemble Prediction System
Purposes Daily forecasts, Tropical cyclone information
One-week forecasts
Weather warnings/advisories,
Very short-range forecasts of precipitation
Aviation forecasts
Tropical cyclone information One-week forecasts Early warning information on extreme weather One-month forecasts Three-month forecasts,
Warm-season outlooks,
Cold-season outlooks
El Niño outlooks
Forecast domain Globe Japan and its surrounding areas Globe
Grid size and/or number of grids 0.1875 deg. (TL959) 5 km/
817 x 661
2 km/
1,581 x 1,301
0.375 deg. (TL479) 0.5625 deg. (TL319) Atmosphere
1.125 deg. (TL159)

0.3-0.5 x 1.0 deg.
Vertical levels/Top 100/0.01 hPa 76/
21.8 km
20.2 km
100/0.01 hPa Atmosphere
60/0.1 hPa

52 layers and a bottom boundary layer
Forecast range (Initial time)/number of ensemble members 84 hours (00, 06, 18 UTC)
264 hours (12 UTC)
39 hours (00, 03, 06, 09, 12, 15, 18, 21 UTC) 9 hours (hourly) 5.5 days (00, 06, 12, 18 UTC)*

27 members
11 days (00, 12 UTC)

27 members
18 days (00, 12 UTC; twice a week)

13 members
34 days (00, 12 UTC; twice a week)

13 members
210 days (00 UTC; once a month)

51 members in all
Initial condition 4D-Var Analysis 4D-Var Analysis 3D-Var Analysis Global analysis with ensemble perturbations
* Forecasts from initial times at 06 and 18 UTC are operated when any of the following conditions is satisfied at the initial times: (i) A tropical cyclone (TC) of tropical storm (TS**) intensity or higher is present in the RSMC Tokyo-Typhoon Center’s area of responsibility (0°–60°N, 100°E–180°). (ii) A TC is expected to reach TS intensity or higher in the area within the next 24 hours. (iii) A TC of TS intensity or higher is expected to move into the area within the next 24 hours. ** A TS is defined as a TC with maximum sustained wind speeds of 34 knots or more and less than 48 knots.
More about JMA's Numerical Weather Prediction

Major Progress in NWP Systems

Global Spectral Model and Ensemble Prediction Systems

In 2007, horizontal resolution was improved from 55 to 20 km for the Global Spectral Model (GSM) and from 110 to 55 km for the One-week Ensemble Prediction System. At the same time, the number of vertical layers was increased from 40 to 60 for both models. In 2008, the Typhoon Ensemble Prediction System was put into operation. In 2013, the range of the forecast run at 12 UTC was extended from 216 to 264 hours for both the GSM and the One-week Ensemble Prediction System.
In 2014, JMA improved the horizontal resolution of the One-week Ensemble Prediction System from 55 to 40 km, and also increased the operation frequency and the number of ensemble members per day. It further improved the GSM by increasing the number of vertical layers from 60 to 100, raising its top level from 0.1 to 0.01 hPa and revising the physical processes involved. In addition, the Typhoon Ensemble Prediction System was improved by increasing the horizontal resolution from 55 to 40 km and the number of ensemble members from 11 to 25. The details of improvements implemented in 2014 are summarized in the Joint WMO Technical Progress Report on the Global Data Processing and Forecasting System and Numerical Weather Prediction Research Activities for 2014.

Meso-Scale Model

In 2009, JMA's Nonhydrostatic model-based Variational Analysis Data Assimilation (JNoVA) 4D-Var replaced Hydrostatic 4D-Var as the operational meso-scale data assimilation system. In 2013, the forecast domain was enlarged and the forecast period was extended to 39 hours for all eight daily operations (one every three hours).

Local Forecast Model

In 2012, JMA began operating the Local Forecast Model (LFM) with a horizontal resolution of 2 km for eastern Japan every three hours with a particular focus on creating nine-hour predictions for timely provision of fine-grid forecasts to support aeronautical operation, especially in the vicinity of Tokyo International Airport (Haneda). In 2013, the LFM was modified to cover the whole of Japan and to run every hour for more sophisticated meteorological forecasts to further support disaster risk reduction and safer flights over the nation.

Seasonal Ensemble Prediction System

In 2015, JMA updated its Seasonal Ensemble Prediction System. Changes included enhancement of the horizontal and vertical resolutions of the atmospheric model from 180 to 110 km and from 40 to 60 levels with the top level moved from 0.4 to 0.1 hPa, expansion of the target area to the whole globe in the oceanic model, and introduction of a sea-ice model.