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Fiona makes landfall in Nova Scotia

By Scott Bachmeier •

GOES-16 Mid-level Water Vapor (6.9 µm) images [click to play animated GIF | MP4]

Hurricane Fiona transitioned to a strong post-tropical cyclone just prior to making landfall in Nova Scotia, Canada around 0700 UTC on 24 September 2022 — 1-minute Mesoscale Domain Sector GOES-16 (GOES-East) Mid-level Water Vapor (6.9 µm) images (above) showed the storm during the 0200-1800 UTC period. This anomalously-deep cyclone may have set a new Canadian record (931 hPa) for minimum mean sea level pressure (surface analyses). The highest surface wind gust was 97 knots / 112 mph / 179 km/h at mesonet site Arisaig (along the northeastern coast of mainland Nova Scotia), with a peak wind gust of 90 knots / 104 mph / 167 km/h at METAR site Grand Etang CWGQ (just off the west coast of Cape Breton Island) shortly before 0800 UTC. A preliminary storm summary issued by Environment Canada is available here.

One feature of interest was a region of lee waves generated by strong easterly boundary layer winds interacting with the Highlands terrain in the northern portion of Cape Breton Island — these waves spread westward across parts of the Gulf of Saint Lawrence (below).

Comparison of GOES-16 Water Vapor image at 0700 UTC and topography [click to enlarge]

Sentinel-1A Synthetic Aperture Radar (SAR) water surface winds at 1015 UTC (below) captured lighter winds of 20 knots or less (brighter shades of violet) within the post-tropical cyclone’s eye as it was emerging northwestward from Cape Breton Island — along with an arc of strong winds within the storm’s eastern semicircle, where speeds of 100 knots or higher (shades of red) were seen. Off the north coast of Cape Breton Island, the peak wind gust at St. Paul Island (CWEF) just prior to 1000 UTC was 85 knots — and SAR winds at 1015 UTC in the vicinity of CWEF were in the 75-80 knot range.

Sentinel-1A Synthetic Aperture Radar (SAR) winds at 1015 UTC [click to enlarge]

The animation of GOES-16 airmass RGB, below, shows the evolution of Fiona and its interaction with a Potential Vorticity Maximum (orange/red in the RGB).

GOES-16 airmass RGB, 0000 UTC 21 September – 0000 UTC 25 September

Perhaps you are skeptical that the Orange/Red signature in the Airmass RGB is a Potential Vorticity Signature. Consider the animation below, downloaded from the TropicalTidbits website and showing 00 – 30 hour GFS model output from the run initialized at 0000 UTC on 23 September. A rich source of cyclonic potential vorticity air (in orange) wraps around Fiona as it moves north. Similar behavior is apparent in the Airmass RGB animation above. This cross section (also from the excellent Tropical Tidbits site) of the model data (24 h into the forecast run) also shows a classic stratospheric intrusion structure.

330 K Potential Vorticity color-shaded in PV Units at 6-h time-steps, 0000 UTC on 23 September 2022 through 0600 UTC on 24 September 2022 (Click to enlarge)

This collection of training videos from ECCC includes one from Chris Fogarty (scroll down at that website) that includes an in-depth post-storm analyses of the landfall.

Categories: GOES-16, Other Satellites, SAR, Tropical cyclones