"Thank you for actually penning these books. They are a wonderful review of the concepts without the excessive (but necessary) amount of math behind them. I wish they had been recommended as supplements in both my undergrad and graduate years."
— Josh Tobias, 2017
"I have used Digital Atmosphere for quite sometime and consider it to be one of the most straightforward, comprehensive, and operationally useful programs on my server. I have found it to be invaluable for my day-to-day analyses and forecasting as well as my ongoing research. Tim is also extremely helpful and absolutely indispensable when it comes to locating scripts, the best datasets, and even professional contacts to help make any organization as productive as possible."
"The quality of your products is second to none."
— C. Brian Batey
"Thanks Tim for your quick response (we like that at FedEx) about our Professional Versions! As we're a 24/7 operation, we're look forward to augmenting our present weather system with Digital Atmosphere."
— Mel Bradley, FedEx Operations
"Wow. Your books are incredibly technical and useful. I consider myself a very amateur weather watcher and feel that I am already ahead of the curve. Thank you."
— Terry W. Taylor
"The NEXRAD support is truly awesome and easy to use - and the other feature just really tops it off. This is about my sixth email tonight - the other five being to other spotters in the area telling them they just have to download Digital Atmosphere and give it a serious going over."
— David Cashion
"I'm really looking forward to the next phase of Digital Atmosphere Workstation. I'm sure it will be as excellent as all your other products."
— Simon Keeling
Weather Consultancy Services, UK
"I run and manage a number of festival type events and Digital Atmosphere is able to produce charts that I can use for normal weather forecasting with a fair degree of accuracy and in particular wind speed and direction that is crucial to many of events."
— Robert Connolly, GI7IVX
"The archive data arrived today. WOW! What an amazing set of data! Thanks again for all the extras that you included as well!"
— Bryan Bollman, IA
"We do run GEMPAK and all the Unidata software also, but your package has numerous advantages, the biggest being Windows."
"I am very impressed with what you have done. I have already shown several people at work your site. I plan on talking to our MIC [Meteorologist In Charge] soon to see if we can get Digital Atmosphere in the office to complement/supplement AWIPS."
— Ken Simosko, NWS, Pocatello
"This new version is even better than the older version which was awesome! Your programming skills and met knowledge amaze me!"
— Chris Kincaid
To try out a fully working copy of WX-SIM (runs Atlanta, Georgia only) click here:
wxsimdem.exe (WX-SIM Version 12.6 Limited / 1.3 MB) (Windows Vista/XP/2000)
|The main screen for WX-SIM is the data entry screen. This is where you set up the "starting conditions" for the virtual atmosphere. You can adjust the time and date (solar positions are automatically handled), temperature, humidity, wind, pressure, cloud layers, and more. To automate this whole process you can use the WXSIMATE module to import data from your home weather station or via the Internet from the nearest observation site. In this example we'll take a look at the forecast for Atlanta.|
|The synoptic map for October 8, 2009 showed a warm front just south of Atlanta.
During the next 24 hours or so, therefore, we can expect unsettled weather, an increase in clouds, and
a slight warming trend.
NOTE: This graphic is NOT created with WXSIM and is only shown here for comparison purposes.
|WXSIMATE comes with WXSIM and is a much-recommended enhancement that automates much of the data entry. It connects with either your home weather station or the Internet, automatically populating all of the windows with conditions from the nearest observation site. It's also capable of downloading gridded model fields, statistical model output, and upper air conditions, making it almost essential for the serious WX-SIM user. If you have a home weather station, WXSIMATE does not connect directly to the station but looks through the logs generated by one of three weather station programs, which you must be running. These three programs are Davis Instruments WeatherLink, Brian Hamilton's Weather Display, or Virtual Weather Station.|
|The data import window in WXSIMATE shows you the results of any data that's been imported. Here we can see that one METAR observation close to our site has been found, along with a graph of NAM forecast output to help provide a first guess dataset for WX-SIM. Forecast model output from dynamic models run at NOAA/NCEP is important because it dictates the large-scale changes that will impact the station's forecast. WX-SIM uses this to refine and adjust its output.|
|The FOUS import panel lets us fine-tune the exact details of the forecast model data that we want to ingest. The cloud, precipitation, and wind data is particularly helpful since these represent parcels brought in from other areas which WX-SIM is not capable of forecasting for.|
|The Upper Air panel displays the latest radiosonde data along with the model output. All of the functions except for automated 1-Click are only available in the Professional version, but the panel allows adjustments to be made to help reach the exact sounding profile desired. Note that stability indices and cloud layers are automatically calculated and displayed.|
|Advection indicates air mass properties that will be brought in from elsewhere. While WX-SIM is capable of estimating changes without knowing such information, it can help make the forecast much more accurate. As seen here, WX-SIM can examine all of the data upwind and use it to figure out how the air mass will change over time (graph at lower right).|
|The interrupt screen is used to force manual changes in clouds, wind, and other parameters during the forecast period.
This is useful if, for example, you know when storms are likely to develop or exactly when a cold front will arrive.
You can even add in an expected eclipse and factor in the reduction in solar heating.
The interrupt planner takes advantage of free, automatically (through WXSIMATE) downloaded GFS data out to 180 hours. This now even includes use of GFS forecast data for advection after wind shifts that occur at any time during the forecast run. This means model data to support WXSIM is available worldwide, out to at least a week. Most people run forecasts between 4 and 7 days.
|The Output window shows the progression of the forecast computation, which
takes about 20 to 30 seconds on a fast Pentium, and produces an output of
the forecast in graphic and text format. The information is also exported
to CSV and TXT files (see below). The forecast here calls for slow warming
and cloudy weather, with drizzle arriving the next evening. In fact,
here is the forecast it generates:
Contrast it with the official NWS forecast shown here.
For those wondering, Atlanta reached 80 degrees this afternoon. WX-SIM correctly anticipated slightly warm temperatures, and that with just a bare minimum of setup and without any gridded model data for this particular run.
|Data is automatically exported in CSV and TXT format so you can view the information in Excel, ingest them into a database, or use custom scripts to display the forecast. Examples can be downloaded here: latest1daily.csv (daily), latest1.csv (15 min interval), and latest1.txt (text version with detailed summaries).|
|WRET is a separate program that allows you to view detailed displays of the WX-SIM output. It is included free with all copies of WX-SIM. With WRET you can mix and match different kinds of graphed fields and control the period of the display window.|
|The Great Sun Outage is an experiment we like to do with WX-SIM. Here we have taken real data but switched the sun off at 12 noon on Friday. This is represented by the drop in the light blue line on the graph As you can see, there is an immediate dropoff from the midday temperature of 80 degrees, and by midnight it's 58. The temperature fall during the weekend and the rest of the week is very gradual due to the high specific heat of the earth's surface and the lack of an insulating blanket of snow. A week later, it's in the 40s.|
|The Great Sun Outage displayed in WRET shows plots of temperature, dewpoint, and valley temperatures (valleys tending to accumulate cold air drainage at night). There is also a text plot showing the amount of solar radiation received in watt-hours per meter squared and inches of accumulated rain. The lower graph displays cloud cover, relative humidity, solar radiation, and thundershower activity. By clicking anywhere on the graph, a sounding for that time will pop up. Each of the weather parameters can be changed to something else using the options in WRET.|