US Extreme Weather and Climate Change Dashboard

NCEI Regional Snowfall Index, annual major-storm count. Unit: Category 3+ (major) storms per year.

Category 3+ (major storms, n_major_plus) is used rather than the raw storm count, which likely conflates a real signal with growth in the observing network over time — see the Methodology page.

Source: NCEI Regional Snowfall Index (RSI)

Computing trend…

Station-level physical snowfall extreme (mean days per year a station's snowfall crosses the station's 90th-percentile threshold), a direct complement to RSI's per-storm regional impact scoring above. Unit: heavy-snow days per station.

Per-station 90th percentile of measurable-snow-day (1mm+) amounts, over the station's full available record -- adapted from the ETCCDI/CLIMDEX R95p "very wet days" convention (Zhang et al. 2011), not a fixed absolute threshold, so a naturally snowy station and a marginal-snow station are each judged against their own climate. Restricted to HCN stations with 100+ measurable-snow-day observations and 20+ years of record (a data-driven snowy-climate floor, not a geographic cutoff), a fixed reference network so a rising station count can't inflate this series. 2011-2014 are excluded from this series (not just muted) due to a real, verified COOP manual-snowfall-reporting collapse in those years. See the Methodology page.

Source: NOAA GHCN-Daily, HCN reference stations (snowy-climate subset)

Computing trend…

Direct central-pressure intensity of storms in this catalog affecting the US East Coast / western Atlantic. This catalog is now known to be pre-filtered toward already-significant/rapidly-deepening cyclones (see note) -- read this as the severity of storms significant enough to appear in it, not a representative sample of all East Coast ETCs. Unit: hPa (lower = more intense).

This catalog's filename flags it as a 'select' file: reconstructing bomb-cyclone status from the raw tracks finds 64% of all Northern-Hemisphere-wide storms in it qualify as bomb cyclones (1+ Bergeron), versus ~7% in a genuinely unfiltered NARR-based climatology (Fritzen, Lang & Gensini 2021, J. Appl. Meteor. Climatol. 60(9)), which also found no significant East Coast bomb-cyclone trend. A bomb-cyclone frequency panel is not shown for that reason. Pressure and wind (this panel and the one below) measure the severity of whatever storms this pre-filtered catalog retained, not a frequency -- but still describe this catalog's population, not literally every East Coast storm. No detected change over 1979-2021 (Mann-Kendall p=0.965).

Source: CEDA extratropical cyclone track catalog (Gray et al. 2024)

Computing trend…

Peak near-surface wind of storms in this catalog affecting the US East Coast / western Atlantic -- the metric most directly comparable to NCA5's Northeast-chapter 'increasing max wind speed since 1940' nor'easter finding. This catalog is now known to be pre-filtered toward already-significant/rapidly-deepening cyclones (see note), so read this as the severity of storms significant enough to appear in it, not a representative sample of all East Coast ETCs. Unit: m/s.

This catalog's filename flags it as a 'select' file: reconstructing bomb-cyclone status from the raw tracks finds 64% of all Northern-Hemisphere-wide storms in it qualify as bomb cyclones (1+ Bergeron), versus ~7% in a genuinely unfiltered NARR-based climatology (Fritzen, Lang & Gensini 2021, J. Appl. Meteor. Climatol. 60(9)). A detected increase over 1979-2021 -- the metric most directly comparable to NCA5's Northeast-chapter nor'easter wind-speed finding -- though this record only reaches back to 1979, so it cannot confirm or refute NCA5's longer, since-1940 claim, and describes only the pre-filtered population this catalog retained.

Source: CEDA extratropical cyclone track catalog (Gray et al. 2024)

Computing trend…