Hawaii Weather/Climate Modeling Ohana

The MM5 Pages

MM5 Hawaiian Forecast Manual

Introduction

The forecasts on this web site are based on computer runs using the MM5 mesoscale model.  The MM5 is probably the most popular mesoscale weather model and is used in research worldwide. It was developed at the National Center of Atmospheric Research in Boulder Colorado, and at Penn State University.  It is an evolving model, with a new version appearing every year or few years. The MM5 is state of the art using the most up to date meteorological research for the model's formulation and set up.  The Hawaiian forecast uses the most recent version as of 08/2002.  For more information on MM5 refer to the MM5 home page or to the below paper:
 

http://www.mmm.ucar.edu/mm5/mm5-home.html

One Kilometer Numerical Weather Forecasting to assist Telescope Operations.doc One Kilometer Numerical Weather Forecasting to assist Telescope Operations.ps

 

The Domains

6 different domains are used in the Hawaiian forecast.  Each domain covers a specified area that is run at particular horizontal and vertical resolutions within MM5.

1) The outer domain (fig 1) has a 27 km horizontal resolution.  It is the largest domain, a 4860 by 4860 km square centered on the Hawaiian Islands.  This domain is designed to simulate the larger scale features that affect the islands, for example frontal passages, and tropical disturbances.

Figure 1:  27 km resolution domain, temperature plot

 
2) Within the outer domain is a 9 km resolution domain that covers the region surrounding the near vicinity of the Hawaiian Islands (fig 2).
 

Figure 2:  9 km resolution domain low cloud plot

 
3) There are then four 3 km resolution domains over a)Kauai and Nihau, b)Oahu, c)Molokai, Lanai, Kahoolawe, and Maui (fig 3) d)The Big Island.
 

Figure 3:  3 km resolution Maui domain, wind strength and direction

 
4) Finally at present a 1km resolution domain over the Haleakala region on Maui.
 

Figure 4:  1 km resolution Haleakala domain, low cloud plot

Website structure

The MM5 home page first allows the user to select one of the 6 domains to view.  The viewer than has the option of looking at 1 of 7 fields (8 if looking at the summit). The web page gives general information pertaining to the current picture. It also allows the viewer to click through the images one by one (backwards and forwards), user a list to go to a specific time, or let the browser animate the images in 1 hour increments. This uses JavaScript, if the viewers browser can not see the page, than he may click on the non-JavaScript option to view the pages in format that is viewable by all browsers.  
 

The Fields

a)Temperature (see fig 1): This field provides the temperature (in Degrees Farhenheit) at the lowest sigma level (.995). Sigma of .995 conforms to an Elevation of 36 meters (118 ft) above sea level and 3076 meters (10089 ft) at the Haleakala summit.  

b)Wind (see fig 3): in meters per second.  The wind speed in knots is approximately twice the value (1.94 knots per m/s and 2.237 mph per m/s). Sigma of .995 conforms to an Elevation of 36 meters (118 ft) above sea level and 3076 meters (10089 ft) at the Haleakala summit. 

c),d),e) Low (see fig 2), middle, and high clouds:  The representation of clouds in MM5 is sensitive to many factors.  Different cloud and microphysics schemes are used for different studies and each scheme makes different assumptions.  For the Hawaiian forecast (9 and 27 km) we use the Grell cloud scheme with the Reisner mixed phase cloud microphysics scheme.  For the 3km and 1km resolution domains only the Reisner microphysics scheme is used (no cumulus parameterization). 

Clouds are plotted on sigma levels.  Sigma coordinates are terrain following coordinates as shown in fig 4.  For this reason the low, middle, and high layers are dependent on the elevation of the surface.  For the complex topography of the Hawaiian Islands it is important to note that over the mountains the clouds in the low level field will only be low relative to the surface, that may be as high as 4000 meters. 

The clouds are defined by the cloud water mixing ratio.  For the low cloud field, clouds(grey shading) are plotted at mixing ratios greater than 0.15 g/kg. For the middle and high clouds the grey shading is for mixing ratios greater than 0.125 g/kg.
 

Figure 4:  Sigma coordinates over mountainous terrain

 
f)Relative Humidity: This plot has relative humidity (with respect to water) at the surface in %.

g)Rainfall: This plot has the accumulated model rainfall over the past hour before the specified time.  The rainfall is in mm (1 in = 25.4 mm).
 

Haleakala Domain

Within the 3km resolution domain covering the island of Maui, a 1km resolution domain is nested over the Haleakala volcano region.  The summit observatories are providing observational surface data for 6 stations within the region at the locations shown on fig 5.  These observations will be assimilated into the forecast thereby hopefully improving the accuracy of the model in this region.  This is particularly important given the high resolution of the domain. 
 

 
This domain is designed to provide the observatories with primarily cloud cover data as well as the other meteorological conditions.  Establishing cloud cover in such a high resolution domain may be a difficult task given the complex daily cycle and topography.  We hope to be able to validate the model results by using the observations for Haleakala.
 

West Pacific Domains

We have the ability to provide MM5 forecasts for specific islands in the west Pacific.  These islands include Guam, Pohnpei, American Samoa, and Eniwetok.  The resolution of domain around each island would most likely be 3km.  The island domains would then be nested in a 9 km, 27km, and finally a 81 km resolution domain covering the West Pacific region.