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GOES-R – Risk Reduction – Tropical Cyclones

Tropical Cyclones

This project investigates the use of GOES-R proxy data to improve tropical cyclone analysis and forecasting, specifically the improvement of forecasts of intensity forecasts and tropical cyclone formation. It is known that the tropical cyclone intensity forecast skill still lags that of track forecasting. A major source of intensity forecasting errors comes from storms that rapidly intensify and are poorly anticipated by current techniques. Rapid intensity changes are also a major concern because of their potential impact during coastal evacuation and disaster mitigation planning. TC genesis/formation forecasting capabilities are very limited; with probabilistic forecasts that are measurably better than only climatological forecast. Satellite data has been important to the modest improvements in tropical cyclone formation forecasting over the last decade, but there are many possibilities to improve such forecasts. In this work we use GOES-R proxy imagery and lighting data to explore the potential improvements in tropical cyclone intensity and formation forecasting that is possible with the next generation of GOES satellites.

Specific tasks include: i) Expand GOES-R proxy datasets, ii) Evaluate impact on forecast algorithms, and iii) Begin real time web site to demonstrate experimental GOES-R products

Expand GOES-R proxy datasets

Simulated ABI channels 7 through 16 were created for seven hurricane cases by using the MSG data collected during the 2006-2008 Hurricane Seasons and the AWG algorithms. These cases are Gordon (2006), Helene (2006), Dean (2007), Karen (2007), Bertha (2008), Ike (2008) and Omar (2008). The 10 channels of storm centered, 500×500 pixel imagery have 3km resolution (i.e., MSG resolution). This imagery allow for the development and evaluation of future ABI-based products, some of which were presented at the Interdepartmental Hurricane Conference in March. Figure 1 shows an example of this imagery for Hurricane Ike (2008).

Simulated storm centered ABI imagery over Hurricane Ike (2008) on 4 September 2008 at 18 UTC. The enhancement table is the same for all images and the color bar at the bottom of the images provides information about the corresponding temperatures in degrees Celsius.

Work also continued on expanding the proxy lightning dataset. The 2008 World Wide Lightning Locator Network (WWLLN) was obtained from University of Washington and added to the re-processed 2005-2007 dataset. In addition, the WWLLN processing code has been adapted to include the data from the eastern Pacific so the lightning relationships can be compared with those from the Atlantic.

Evaluate impact on forecast algorithms

Preliminary examination of the WWLLN lightning density data along with environmental conditions has shown that there are two distinct regimes associated with increased lightning density. Regime 1 is characterized by large values of vertical wind shear and asymmetric convection is most commonly associated with tropical cyclones that are transitioning to extra-tropical cyclones. Regime 2 is characterized by low wind shear, and symmetric convection and intensification. This second regime may be useful for better anticipating tropical cyclone intensification events. Figure 2 shows the Regime 2 radial composites of lightning density for those tropical cyclones that underwent rapid intensification ( >30 kt/day; red) and those that did not (blue). Results suggest that if variations of vertical wind shear are accounted for the radial distribution of lightning density, more lightning occurring within 1000 km, may indicate a greater likelihood of future rapid intensification. The strongest signal appears near the cyclone’s core (within 100 km) and in the typical rainband region 200-500 km.

Regime 2 (i.e., low vertical wind shear) composites of lightning density as a function of radius for those rapidly intensifying cases (RI Cases; Red) and those storms that did not undergo rapid intensification (Non-RI; Blue). A more detailed description of this preliminary study can be found in DeMaria and DeMaria (2009) [ ]

Begin real time web site to demonstrate experimental GOES-R products

Scripts have been developed to create real-time simulated ABI imagery (channel 7-16) from MSG channels and a local server has been used to enable local sharing of the simulated ABI imagery. Using these data, along with real-time tropical cyclone information, plans are underway to automatically create and archive storm centered proxy in real-time during the 2009 hurricane season.

Coordination with NHC has begun to establish a real-time GOES-R demonstration system that will enable NHC forecasters to view and use ABI proxy – based products and simulated imagery. Scripts have already been written that will create ABI proxy imagery using MSG data and the existing NHC IT infrastructure. Real-time versions of the lightning-based experimental intensity forecast algorithms described above are also planned. Based on initial discussions with NHC, both the ABI and lightning applications will be tested in real time starting with the 2010 hurricane season through the GOES-R Proving Ground. An example of a three color Air Mass product that uses the GOES-R proxy data is shown below with hourly lightning from WWLLN overlaid is shown in Figure 3.

An example of a three color (red, green, blue) composite image product that depicts different air masses using a combination of Simulated ABI channels with hourly WWLLN data overlaid. The tropical air masses are characterized by high tropopause (low ozone) and appear greenish. Lower tropopause air masses are characterized by bluish colors.

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