Time series rainfall doesn't add up to map totals

  • I've noticed that for both NAM and ECMWF forecasts the time series details dont always add up to the total displayed on the map for the selected duration. Does anyone know why there is a discrepancy here and if one value could be considered most accurate?

    See examples below. Map views are for either a 24 hour or 48 hour duration


  • Moderator

    For me seems OK

    There is no 48 hrs duration

    You must count the accumulation from model's reference time.

  • Hi @Gkikas-LGPZ - Thanks for responding. In most forecasts I check I do mostly see consistency as you do, but even the numbers in your time series add up to 14.0 mm, not 14.5 mm. I think you're suggesting that the model's reference time may be earlier than what is displayed in the time series, and therefore is greater as it's counting precip that is not displayed?

    The model time is 2020-03-27 12:00 Zulu time/UTC, which converted to the local region is 7:00 AM CDT (-5). I'm assuming that the time series converts to the local time zone, so it shouldn't be referenced from a time prior to the converted time series. If the time series is also in UTC it still wouldn't be referencing values off the table so long as its only summing from the reference time.

    The NAM model (North American only) does report a 48 hour duration.

  • Sailor Moderator

    Both of you are probably right. I understand that Rain accumulation map figures are from reference time of the model run. In the Meteogram if you show UTC time (in Settings select Display all time in UTC) you see missing hours from the run start in North America. Here in Europe we are closer to UTC and there are less discrepancies. It's just an assumption, I’ve not checked everywhere.


Log in to reply

Windyty, S.E. - all rights reserved. Powered by excellent NodeBB
NodeBB & contributors, OSM & contributors, HERE maps
Terms and Conditions     Privacy Policy