Government of Sultanate of Oman Public Authority of Civil Aviation Directorate General of Meteorology. National Report To

Transcription

1 Government of Sultanate of Oman Public Authority of Civil Aviation Directorate General of Meteorology National Report To Panel on Tropical Cyclones in the Bay of Bengal And Arabian Sea 45 th Session, Muscat, Sultanate of Oman Sep 2018

2 Annual Report on Activities in Meteorology In the Sultanate of Oman During the year Meteorological Events 1.1. Tropical Cyclone Mekunu May 2018: Mekunu was Category-1 tropical cyclone, as classified by the Oman Directorate General of Meteorology (DGMET), that made landfall south of Oman over coast of Dhofar Governorate, on 25 May 2018, 2000 UTC. The cyclone brought more than 500 mm of rainfall over Dhofar in three days; five folds more than the annual average of 83 mm. Salalah plain is a low-lying area surrounded by mountains and sea which make it vulnerable to flash flooding. However, the damage was limited, and casualties reported were four which is historically low in the region for a Category-1 tropical cyclone. International organisations, including Word Meteorological Organization ascribe this to the early warning given by DGMET and the continuous flow of accurate guiding information to the decision makers and civil defence. This information led to the proper preparedness of various governmental organisation and for the public to take early precautions. Moreover, the improved infrastructure in the recent years namely, the flash flood protection dams reduced the impact of flash flooding on the cities and towns of in Dhofar. Sahalnoot Dam, in particular, protected Salalah city from the scenario of 10 May 2002 Cyclonic Storm ARB 01, when a flash flooding swept across the city causing widespread damage in the communication, transportation and electrical grid infrastructure. The last extreme tropical case directly affected Oman before Mekunu was tropical storm Kila that made landfall over Dhofar on the 1 November 2011 and also cased substantial damages. The system started as low pressure in the south-western region of the Arabian Sea on the 20 May 2018 as an area of deep convection. Figure 1 shows the best track chart of Mekunu from 21 May 1100 UTC to May UTC and Figure 2 shows the wind and pressure histories in that track. Initially, Mekunu moved westward for almost 24 hours while it was a tropical depression. It veered then northwards on 22 May 0600 UTC after it was classified as deep depression and continued in this direction until it has dissipated inland over Dhofar Governorate. On 22 May 1200 UTC DGMET classified the system as a tropical storm and got the name Mekunu from the WMO Regional Specialised Meteorological Centre-Tropical Cyclones, India (RSMC) later that day. Twenty-four hours later, Mekunu was classified as a Category-1 tropical cyclone by DGMET. The system intensified further in the following three days up to tropical cyclone of Category-2 with maximum 10-minutes sustained wind of 85 to 90 kt on 25 May UTC; a few hours before making landfall as Cateogry-1 at around 2000 UTC on 25 May; 25 km southwest Salalah city. Mekunu rapidly weakened by land interaction and continental dry air mass intrusion. The system gradually dissipated over the Empty Quarter desert on May. The movement average speed was 11.5 km/h since it was classified as a tropical storm to its landfall. 2

3 Figure 1 : Mekunu best track drawn using the issued reports and warnings by the Oman National Multi-Hazard Early Warning Centre form 21 May UTC to 26 May 2018, 1800 UTC. Figure 2 : The maximum wind (blue) and lowest pressure (red) histories along the best track of Mekunu s path. The data was gathered from DGMET reports and Multi-platform Tropical Cyclone Wind Analysis (CIRA, 2018). The mean sea level pressure was calculated using an equation by Brown et al., (2006). 3

4 Figure 3 : Rainfall accumulation at DGMET weather stations during Mekunu impact, May. Figure 4 : Rainfall accumulation by Water Resources rain gauges during Mekunu impact, May. 4

5 Figure 5 : 10-minutes sustained wind speed over Dhofar Governorate during the landfall of Mekunu on 25 May, 2000 UTC Tropical Storm Sagar (16 21 May 2018) : Tropical Storm Sagar started as a low pressure system which formed over southwest Arabian Sea on the morning of 14 th May During next day, it became a well-marked low pressure area over the same region. Due to favorable environmental conditions for tropical cyclones, it developed into a depression over Gulf of Aden. On the evening of 16 th of May 2018, the system started to move west-northwestwards and gradually intensified into a deep depression. During the morning of 17 th of May 2018, it became a tropical storm called Sagar which was located over Gulf of Aden. Thereafter, on 9 th of May 2018, it moved west-southwestwards and crossed Somalian coast as a tropical storm with maximum sustained wind speed of km/h and gusting of 90 km/h. Moving further west-southwestwards, it started to weaken and became a deep depression during the mid-night of 19 th of May, and later to a depression on the early morning of 20 th. After making a complete landfall over Ethiopia and Somalia during the morning of 20 th of May 2018, the system declined to a well-marked low pressure. High and medium level clouds associated with the system affected parts of the south coast of Oman. The sea condition was moderate to rough and the maximum wave height reached 2.5 m. The forecasting Center of Oman issued a bulletin to inform the public about the system. The bulletin contains a clear clarification that there would be no direct impact from this system over the Sultanate. 5

6 Observed track of tropical storm Sagar (16-20 May, 2018) 2. Meteorological Facilities 2.1. Upper Air Observation The Sultanate of Oman operates two upper air-observing stations located at Muscat (41256) and Salalah (41316). Both these are equipped with Vaisala s Digicora GPS wind finding system. The radiosonde used is Vaisala RS41 equipment. One flight is launched from each of these stations in a day Ship Weather Reports Weather Reports from Ships are received through GTS Wave Measurements Three wave radar measurement station was installed offshore of Oman Sea and Arabian Sea in 6 locations another 3 wave radars are planned to be installed. 10 tide gauges were installed disrupted offshore Oman Sea and Arabian Sea as part of Tsunami Network Synoptic Land Stations There are a total of 74 meteorological stations out of which 23 are listed in the WMO s Regional Basic Synoptic Network (RBSN) including 2 radiosonde stations, 12 Regional Basic Climatological Network (RBCN) stations out of which 3 listed in Global Climate Observing System Surface Network Doppler Weather Radars Four Dual Polarization S-Band Doppler Weather Radar have been commissioned and one more is expected to be commissioned soon. The Radars are supplied by Selex Gematroniks. 6

7 2.6. Telecommunication All the meteorological stations operated by the Directorate General of Meteorology (DGMET) are connected to the MSS computer located at the National forecasting and Early Warning Center at Muscat International Airport by a reliable telephone links (dial-up Telephone lines and GSM Network). The MSS is connected to the RTH Jeddah by a dedicated link at 64 kbps based on TCP/IP protocol. In addition a 16 Mbps Internet leased line has been established as well as for transmitting and receiving meteorological data with different meteorological centers such as New Delhi and Abu Dhabi Satellite reception The Department installed Satellite ground receiving station for intercepting High Resolution images from Polar Orbiting satellites operated by NOAA, EUMETSAT and China as well as from geostationary satellites operated by EUMETSAT Oman Center of Excellence (COE) The 13 th EUMETSAT Satellite Application Course was successfully organized and conducted at Oman Centre of Excellence (COE) for training satellite meteorology during March Data Visualization The Directorate General of Meteorology (DGMET) is using a visual weather application for visualizing all meteorological data in most standard formats including data in GRIB1, GRIB2 and BUFR format coded data. It has proved to be a useful and powerful tool for visualization, analyzing and forecasting the weather Data Processing System Global Numerical Weather Prediction NWP products are received via Internet, GTS, DWD Sat. We receive products from meteorological centers including ECMWF, NOAA, UK met office and German Weather Service (DWD). Current processing capabilities consist of a PC Cluster of 80 nodes and 4 spare nodes with total of 168 processors. 2x Intel Xeon 2.3 GHz Hexacore is used for each node. This make a total of 960 processing core. All nodes are connected via very fast Interconnection network using 108-ports Infiniband (Mellanox ConnectX 3, QDR 40GBit). Local Oman Regional Model ORM was established with the kind cooperation of National Weather Service of Germany DWD since

8 A- DGMET run an operational version of COSMO model (Consortium for Smallscale Modeling). COSMO is a non-hydrostatic limited-area numerical weather prediction. It runs on 7x7 km resolution and covers the area between 30.0E, 7.0N (lower left corner) to 78.0E, 35.25N (upper right corner). There are 769x453 grid points and 50 vertical layers. The model is running on 64 nodes from the PC Cluster. It produces up to 120-h forecast at 00 and 12 UTC. And 2.8km model resolution covering Oman and adjacent areas. COSMO was introduced to enhance the accuracy of predicting local rainfall over Hajar Mountains and adjoining area during summer. Figure.1 shows the domain covered by COSMO_07 model. B- WRF Weather Research and Forecast model is successfully running with two resolutions; parent domain of 7 km and nested domain of 3.5 km. The parent domain covers approximately similar to COSMO_07 domain as shown in figure below, while the nested one cover Oman area. This model runs to give the forecasters more confidence in their decision by comparing different Regional models. C- A WAM based wave model was established with the kind cooperation of HZG of Germany, which covers the Arabian Sea, gulf of Oman and Arabian Gulf. WAM model run of 14km resolution and nested into 3.5km resolution. 8

9 D- With the kind cooperation and assistance from NOAA a Hurricane Weather Research Forecast (HWRF) Model was installed during June 2013 at the Oman National Meteorological Service. This Model is run with three resolutions, 27, 9 and 3 km. The 3km moving nest covers the event domain and tracking the tropical cyclone movement. It is used to forecast Track, Intensity and Direction of Movement for Storms and Cyclones over the Arabian Sea and Bay of Bengal. E- Seasonal forecast of TCs model has been implemented in Met-office since It forecasts the probability of TC activity occurrence for the next few months. Its method is based on relating TC activity and monthly SST configurations over the NIO. F- Early Warning System was established since Part of the system responsibility deals with Tropical Cyclone events. In TC event, EW runs different models in addition of the above models. For example, IHC Swan real time to check wave status, IIT Storm Surge Model and IHC H2D real time for the storm surge status. G- Flash Flood Guidance (OMANFFG): The FFG system was successfully installed and benign in operation since 2017, It is Immediate prediction of areas likely to be exposed to flash floods using rainfall readings available from weather stations, satellite, weather radars and numerical predictions. H- Storm Surge: DGMET currently runs Storm Surge Model based on the vertically integrated model which was developed by Prof. S. K. Dube (IIT). Storm Surge Model is a program that simulates surge, current and wind stress for specific track data. The track data includes longitude, latitude, time step pressure drop and radius of maximum wind Verification Package The Directorate General of Meteorology managed successfully to develop in-house its own verification package. The developed system verifies the continuous weather parameters such as T_2m, TD_2m and for the categorical weather parameters such as Total precipitation, PMSL, Wind Speed and Direction. The system generates different statistical scores such as Bias, Root Mean Squared Error (RMSE) and absolute error. In Addition to generating a Time-Series Plots, Min, Max, Median Box Plots and Scatter Plots. An Automated Verification Package still in process. Now the package produces Monthly verification, initial and daily verification Aeronautical Services In order to meet ICAO recommended practices and to fulfill the requirements for Aviation the Directorate General of Meteorology (DGMET) installed a SADIS workstation as early as In addition all the SADIS data and products are also received thru a secured FTP Server from UK as a back-up. A new service was established for the provision of en-route flight folders for all Airlines operating in the Sultanate to be accessed on our web portal. 9

10 3. Training/Research The 7th WMO Center of Excellence in Oman has conducted the 13 th session of satellite application course (SAC) for Middle East countries in cooperation with Eumetsat. The research section has accomplished many researches and studies of the some weather events and systems that affect Oman and the region of Arabian Peninsula. Also, study section has implemented a new website contain the virtual laboratory, met calendar and some important meteorological information. Other important Workshops, Seminars, Researches and Training Courses attended by the Met personnel during the year 2018 are as follows:- Workshop/Seminar/Training/Research Course Country No. of Persons EWS - On Job Training Indonesia 7 EUMETSAT Satellite Application Course Oman 6 International Summer School on Applications with the newest Multi-spectral Environmental Satellites Italy 1 ---END--- 10