RAMM/CIRA 2nd Quarter Report
Tropical Cyclones (DeMaria, Zehr, Knaff, Dostalek, Mueller)
Updated code which converts GFS model data from grib format to a packed ASCII format was placed on a NESDIS computer. The packed ASCII format of the GFS data is used in subsequent programs for tropical cyclone research, and is one of the final steps in the transition of the experimental tropical cyclone genesis parameter to NESDIS operations.
A paper entitled “An Operational Statistical Typhoon Intensity Prediction Scheme for the Western North Pacific,” discussing the development and operational performance (July 2003-October 2004) of the Statistical Typhoon Intensity Prediction Scheme, has been accepted for publication by Weather and Forecasting.
The paper entitled “Further Improvements to the Statistical Hurricane Intensity Prediction Scheme” has been accepted for publication in Weather and Forecasting.
The final technical report discussing the development of a statistical-dynamical tropical cyclone intensity prediction tool for the JTWC Indian Ocean and Southern Hemisphere areas of responsibility was submitted to ONR. The pre-operational transition is complete and an evaluation is being performed at NRLMRY and JTWC. Transition to operations at JTWC is expected in spring 2005. As part of this project, a consensus/ensemble version that allows for the model to be evaluated using forecast fields from several models (GFS, NOGAPS, UKMET, etc.) is being developed. The premise is that the consensus of these forecasts for the season will be more skillful than that of any given member. Forecast information (example for SH15 is shown in Figure 1) is being sent via the internet to the Joint Typhoon Warning Center. This version of the product will be run at NRLMRY for the remainder of the season in an operational manner.
Figure 1: Intensity forecasts for SH15P (Meena), a rapidly developing tropical cyclone located near American Samoa, valid 4 February at 18 UTC. Shown are the STIPS based consensus members; AFWA (AFS1), GFS (GFS1), NOGAPS(NGS1), UKMET (UKS1), WBAR (WBS1) along with other intensity forecasts, including JTWC.
A paper entitled “ Effects of Environmental Vertical Wind Shear and Storm Motion on Tropical Cyclone Rainfall Asymmetries Deduced from TRMM” by M. Lonfat, S. Chen, J. Knaff, and F. Marks was revised and submitted Monthly Weather Review following the reviews from Journal of Atmospheric Science. The paper has been conditionally accepted for publication. The paper discusses the asymmetries of tropical cyclone rainfall with respect to motion and the 200 to 850 hPa vertical wind shear. Results show that the effects of storm motion and vertical wind shear combine to explain much of the storm-to-storm variability of rainfall asymmetries. It is hoped that the relationships will improve both forecasting and modeling of tropical cyclone related rainfall.
A talk discussing the possibilities of improving tropical cyclone wind speed probabilities was given at the DOD Tropical Cyclone Conference in February. The talk showed that the prospects for improving intensity forecasts in the JTWC area of responsibility are quite good based on results derived from several recent JHT sponsored projects (i.e. by using satellite data (IR and ocean heat content) as potential predictors). Using the Monte Carlo tropical cyclone wind speed probability code, the impacts of the anticipated improvements were assessed. These results suggest that by improving intensity forecasts alone results in an increased ability to warn based on wind speeds without increases in warning area, particularly beyond 48 hours. This is most important to the Navy who makes decisions to sortie ships well before 48 hours. Also found was that track improvements result in simply a decrease in warning area with no increase in the success of the forecasts.
A presentation discussing a satellite-only tropical cyclone wind analysis was given at the 59th Interdepartmental Hurricane Conference in Jacksonville, FL in March. The method uses a variational methodology to create a combined analysis of winds at flight level. The analysis makes use of an IR-based method developed at CIRA to estimate the near-core winds, surface winds from QuickSCAT, SSMI, AMSU-based non-linear balance winds at 850 and 700 mb, and Cloud drift winds below 500 mb. Figure 2 shows an example of this analysis for Hurricane Ivan on 9 September at 18 UTC. Work continues to fully automate the creation of such analyses for all tropical cyclones and to reduce these winds to the surface by next quarter. These analyses will be made available to operational centers for their assessment.
Figure 2: Flight-level (~700 mb) wind analysis, which utilizes IR-based winds, cloud drift winds, QuikSCAT and SSMI which were collected over a 12-h period and navigated to a storm relative framework at 18 UTC 9 September.
Loops of all 12 channels from Meteosat 2 nd Generation (MSG) for a tropical cyclone in the southwestern Indian Ocean (22 January 2005) were added to the GOES-R case study database. In addition, MODIS bands corresponding to GOES-R ABI channels were added. Imagery can be viewed at:
J. Knaff met with J. Cline (NWS, Pacific Region), B. Ward (NWS, Pacific Region), and G. Cruz-Miller (NWS, MIC, Guam) about the potential transition of tropical cyclone products to operations. Of particular interest was the tropical cyclone formation product, which currently runs in the GOES-East footprint, and the possibility of such a product being developed for the GOES-9 or MTSAT footprint to support areas of the Pacific Region where tropical cyclogenesis often occurs (e.g., Guam, and Micronesia). As a result of this meeting, J. Cline sent a request to J. Heil (NWS) to make this a priority item.
A manuscript entitled “ Objective Estimation of Tropical Cyclone Wind Structure from Infrared Satellite Data” by K. Mueller, M. DeMaria, J. Knaff and T. Vonder Haar was submitted to Monthly Weather Review. The paper details a method to create tropical cyclone inner core winds (r < 200km) from IR imagery. An example is shown in Figure 3.
Figure 3: Plot of IR derived Total Wind Field (left panels) and Aircraft Measured Total Wind Field (right panels) for 24 hours in the lifetime of Hurricane Ivan in 2004.
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