Tuesday February 28th, 2017

Disclaimer

The information contained herein is provided with the understanding that The Caribbean Institute for Meteorology and Hydrology (CIMH) makes no warranties, either expressed or implied, concerning the accuracy, completeness, reliability or suitability of the outputs from the mesoscale models. Precipitation amounts predicted by the models are at best estimates and may not represent actual measured totals. The information may be used freely with appropriate acknowledgement of its source, but shall not be modified in content and then presented as original material. CIMH is not a National Meteorological and Hydrological Service and, as a result, does not issue offical forecasts for the Caribbean Meteorological Organization (CMO) Member States. The products herein are provided to assist in the development of forecasts by trained meteorologists. CIMH reserves the right at anytime to modify or discontinue -temporarily or permanently- this product.

Summary of project

This site is intended to provide a high resolution numerical weather model output centered over Haiti. In addition, outputs from a hydrological model for specific watersheds in Haiti are made available. Outputs from the mesoscale numerical prediction model, Advance Research Weather Research and Forecasting Model (ARW), hereafter referred to as WRF, will be uploaded to this site twice daily (approximately at 0930UTC and 2130UTC). The WRF runs are initialized by data from the Global Forecast System (GFS) model run for the 0000Z and 1200Z. Visualizations are produced using the Open Grid Analysis and Display system (OpenGrADS). These visualizations present three (3) different forecast products as overlay images on top of a watershed delineation map for Haiti. Hazard index prediction outputs from the CASC2D model will also be uploaded to this site twice daily for selected watersheds. The Generic Mapping Tools (GMT) software and Ghostscript interperter were used as post-processing tools to create the visualizations. Coordinates for the location of critical infrastructure within the watersehds are presented as an overlay. Products provided represent the collaborative efforts of the Caribbean Institute for Meteorology and Hydrology (CIMH) and the Caribbean Catastrophe Risk Insurance Facility (CCRIF). Visualizations for the latest initialized data and the previous 12hrs will be available.

Summary of WRF

There are three (3) versions of the Weather Research and Forecasting model. The one used for these simulations is the ARW. The ARW is a portable state-of-the-art atmospheric simulation system which has been developed by that is portable and efficient on available parallel computing platforms. This version of WRF is suitable for use in a broad range of applications across scales ranging from meters to thousands of kilometers.

Resolution

Outputs are provided at a 4km spatial resolution.

Explanation of outputs

Three (3) products are available for viewing. These are:

(1) 48-hour aggregated accumulations following model initialization:

This product provides an hourly precipitation aggregate from model initialization. Hence, the final image provides an aggregated accumulation of the modeled precipitation for the 48-hour prediction period following initialization. This product can be used to support the identification of areas that may experience significant rainfall over the 48-hour prediction period.

(2) Disaggregated hourly accumulations for the model run:

This product displays hourly accumulations for the current 48-hour prediction period. This product supports prediction of intense rainfall events that can lead to flash flooding.

(3) 48-hour accumulation up to each output time:

This product provides the 48-hour aggregated accumulation up to each hour within the current 48-hour prediction period. Hence, at each display time, modeled precipitation for the previous 48 hours is aggregated. As a result, outputs from previous model runs are utilized in developing this product. This product supports identification of areas of persistent precipitation which can have significant implications on soil saturation levels thereby triggering flooding and land slides

Note that for the legend on the graphics, the disaggregate graphics indicate values from 0.5mm to 100mm or more, where as the other two kinds of outputs indicate values from 0.5mm to 250mm or more.

Summary of CASC2D

The CASCade 2 Dimensional (CASC2D) hydrological model was originally developed at the Colorado State University. It solves two dimensional flow routing and diffusive wave channel routing equations to estimate watershed runoff from a given rainfall input by using explicit finite difference techniques.It is also capable of keeping track of soil moisture conditions by applying the Green and Ampt infiltration scheme.

CASC2D has been incorporated as part of the open source GRASS GIS for hydrologic simulations as r.hydro.CASC2D. The version available in the GRASS GIS 5.4 package was used to produce the hazard index predictions in critical watersheds in Haiti.

Resolution

The SRTM 90-m digital elevation dataset is being used to provide the DEMs for the watersheds. The model outputs are at the same resolution

Explanation of outputs

48 hourly water depth prediction outputs are produced by the r.hydro.CASC2D GRASS GIS module for the selected watersheds. The hazard indices represent uncalibrated water depth outputs resulting from the disaggregated hourly accumulations inputs from the WRF model runs. This product provides indicative information as it relates to the expected inundation extents and the potential hazard level within the watershed. The UTM coordinate system has been used for the hydrological model outputs.