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<front>
<journal-meta>
<journal-id journal-id-type="publisher">ESSDD</journal-id>
<journal-title-group>
<journal-title>Earth System Science Data Discussions</journal-title>
<abbrev-journal-title abbrev-type="publisher">ESSDD</abbrev-journal-title>
<abbrev-journal-title abbrev-type="nlm-ta">Earth Syst. Sci. Data Discuss.</abbrev-journal-title>
</journal-title-group>
<publisher><publisher-name></publisher-name>
<publisher-loc>Göttingen, Germany</publisher-loc>
</publisher>
</journal-meta>
<article-meta>
<article-id pub-id-type="doi">10.5194/essd-2026-792</article-id>
<title-group>
<article-title>TailWeather: from tail to extremes, a global climatological dataset for machine-learning weather forecasting</article-title>
</title-group>
<contrib-group><contrib contrib-type="author" xlink:type="simple"><name name-style="western"><surname>Liu</surname>
<given-names>Zhi-Song</given-names>
<ext-link>https://orcid.org/0000-0003-4507-3097</ext-link>
</name>
<xref ref-type="aff" rid="aff1">
<sup>1</sup>
</xref>
<xref ref-type="aff" rid="aff2">
<sup>2</sup>
</xref>
</contrib>
<contrib contrib-type="author" xlink:type="simple"><name name-style="western"><surname>Boy</surname>
<given-names>Michael</given-names>
</name>
<xref ref-type="aff" rid="aff1">
<sup>1</sup>
</xref>
<xref ref-type="aff" rid="aff2">
<sup>2</sup>
</xref>
<xref ref-type="aff" rid="aff3">
<sup>3</sup>
</xref>
</contrib>
<contrib contrib-type="author" xlink:type="simple"><name name-style="western"><surname>Makkonen</surname>
<given-names>Risto</given-names>
</name>
<xref ref-type="aff" rid="aff4">
<sup>4</sup>
</xref>
</contrib>
</contrib-group><aff id="aff1">
<label>1</label>
<addr-line>Department of Computational Engineering, LUT University, Finland</addr-line>
</aff>
<aff id="aff2">
<label>2</label>
<addr-line>Atmospheric Modelling Center, Lahti (AMC-Lahti), Finland</addr-line>
</aff>
<aff id="aff3">
<label>3</label>
<addr-line>Institute for Atmospheric and Earth System Research (INAR), University of Helsinki, Finland</addr-line>
</aff>
<aff id="aff4">
<label>4</label>
<addr-line>Finnish Meteorological Institute (FMI), Finland</addr-line>
</aff>
<pub-date pub-type="epub">
<day>16</day>
<month>10</month>
<year>2026</year>
</pub-date>
<volume>2026</volume>
<fpage>1</fpage>
<lpage>29</lpage>
<permissions>
<copyright-statement>Copyright: &#x000a9; 2026 Zhi-Song Liu et al.</copyright-statement>
<copyright-year>2026</copyright-year>
<license license-type="open-access">
<license-p>This work is licensed under the Creative Commons Attribution 4.0 International License. To view a copy of this licence, visit <ext-link ext-link-type="uri"  xlink:href="https://creativecommons.org/licenses/by/4.0/">https://creativecommons.org/licenses/by/4.0/</ext-link></license-p>
</license>
</permissions>
<self-uri xlink:href="https://essd.copernicus.org/preprints/essd-2026-792/">This article is available from https://essd.copernicus.org/preprints/essd-2026-792/</self-uri>
<self-uri xlink:href="https://essd.copernicus.org/preprints/essd-2026-792/essd-2026-792.pdf">The full text article is available as a PDF file from https://essd.copernicus.org/preprints/essd-2026-792/essd-2026-792.pdf</self-uri>
<abstract>
<p>Weather forecasting models are usually judged by their average skill, yet average skill says little about the rare conditions that matter most. Testing forecasts on those conditions requires a target defined consistently everywhere. Disaster catalogs record harm, but they are sparse and shaped by reporting; climatological tails can be defined everywhere, but rarity does not imply harm. We present TailWeather, a global, land-only, 0.25&amp;deg; dataset of climatological tail events derived from ERA5, covering 1981&amp;ndash;2022 and early January 2023. It labels heatwaves, cold waves, heavy precipitation, and extreme wind daily, and meteorological drought monthly. Every label carries an ordinal severity tier and an intensity score relative to the local 1991&amp;ndash;2020 climate, so users can move thresholds, within the score&amp;rsquo;s resolution, without recomputing the climatology. Compared with the EM-DAT disaster catalog, stricter tails are more strongly enriched in recorded impacts for all five hazards, by 1.6 (extreme wind) to 9.3 times (heatwave) at the best-balanced threshold. Yet 80.1 % of the world&amp;rsquo;s land population lives where the catalog is too sparse to test this link locally for at least one hazard. In forecast examples, leading AI systems that predict 2 m temperature to within about 1 K at day 1 reach a critical success index below 0.5 on heatwave tails, and their tail skill is lowest for extreme wind. TailWeather offers a reusable physical target for studying and evaluating weather extremes, one that complements rather than replaces disaster catalogs. The dataset is available at &lt;a href=&quot;https://doi.org/10.57967/hf/10661&quot; target=&quot;_blank&quot; rel=&quot;noopener&quot;&gt;https://doi.org/10.57967/hf/10661&lt;/a&gt;.</p>
</abstract>
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