The weather app, along with a few other apps, were suprisingly missing from the iPad shown during Steve Jobs' keynote during the unveiling of the iPad. Regardless of what that means, developer Vimov isn't waiting around. Weather HD will be available at iPad launch, and it takes a very artistic approach to providing weather information.
It may be a novelty item, or it may fill a much needed gap in the iPad app offerings. The video of Weather HD displays simplistic weather reports with stunning visuals, and may appeal to people regardless of the weather app availablity.
Only April 3rd will answer these questions. Weather HD may have a market regardless.