Inquiry Regarding Irregular Hourly Timestamps in IBTrACS v04r01

[Mincheol Moon]

I am currently working with the latest version of the IBTrACS dataset (v04r01.nc), analyzing tropical cyclone activity from 1958 to 2023. While examining the time variable for individual tropical cyclones, I noticed that the timestamps are not always aligned with the standard synoptic hours (i.e., 00, 03, 06, 09, 12, 15, 18, 21 UTC). In several cases, I encountered irregular hours such as 01, 05, 07, 11, 16, 19, 20, or 23 UTC.

I would like to ask:

1. Is this variation in hourly timestamps expected in v04r01?

2. Do these non-standard hours originate from specific input sources (e.g., regional centers or best track datasets)?

3. For consistent analysis, would you recommend adjusting or interpolating these timestamps to the nearest synoptic time (e.g., 6-hourly bins), or should they be preserved as-is?

Your guidance would be greatly appreciated in helping ensure proper treatment of temporal information for tropical cyclone analysis.

Thank you very much for your time and support.

[Jennifer Gahtan - NOAA Federal]

1. As in previous versions of IBTrACS, data are interpolated to 3-hourly timesteps (most reported at 6 hourly), but irregular hours provided by agencies are also kept.

2. IBTrACS includes non-standard hours as they are provided from their original source. Some agencies often provide extra timesteps around landfall and times when a storm has a higher impact (e.g. Helene 2024) though this will vary.

3. IBTrACS already provides data interpolated to the 3-hourly times, so no further adjustment of non-standard time data should be needed on your part. As for whether to include these non-standard timesteps in your analysis, I think it depends on your use case.

Also note that you can determine if data are interpolated or from the original source at each timestep by using the iflag variable.

Best,

Jennifer

--
You received this message because you are subscribed to the Google Groups "IBTrACS Q&A" group.
To unsubscribe from this group and stop receiving emails from it, send an email to ibtracs-qa+...@googlegroups.com.
To view this discussion visit https://groups.google.com/d/msgid/ibtracs-qa/45da71d4-9f9a-43b5-aa88-c098e334f7fen%40googlegroups.com.

--

Jennifer Gahtan, Ph.D.

Physical Scientist
CSSD
NOAA's National Centers for Environmental Information (NCEI)
151 Patton Ave. Asheville, NC 28801