The calendar still reads Meteorological Winter, and the Atlantic Basin remains as busy as expected. Early last week, the threat for a hurricane-force low in the Western Atlantic was well-advertised. The NWS Ocean Prediction Center (OPC) North Atlantic 96-Hour Surface Forecast issued at 1529 UTC 17 February predicted a 965 mb hurricane-force low due south of Newfoundland at 1200 UTC 21 February 2025. This forecast ended up being extremely accurate, with the 1200 UTC 21 February 2025 Atlantic Surface Analysis by NWS OPC indeed showing that same pressure, 965 mb, for a hurricane-force low due south of Newfoundland.
GOES-East Full Disk Air Mass RGB imagery showcased the rapid intensification of the extratropical cyclone from ~0150 to ~1510 UTC 21 February 2025. During this time period, the pressure in the system dropped from roughly 987 mb at the 0000 UTC 21 February Surface Analysis to 965 mb at the 1200 UTC 21 Feburary 2025 Surface Analysis. In the video, you’ll notice dark oranges and reds envelope the circulation, as high levels of potential vorticity (PV) aid the cyclogenesis. A banded area of clouds also develops on the south side of the circulation towards the end of the animation, a feature that can develop once the low pressure develops very strong, hurricane-force winds. The 1200 UTC 21 February 2025 NWS OPC Atlantic Surface Analysis, overlaid on the GOES-East Air Mass RGB imagery provides a look at the system’s structure, with the low pressure center tucked back from the triple point along an occluded front, within the area of high-PV air.
A composite of Metop-B and Metop-C/ASCAT passes from ~1224 to ~1500 UTC 21 February 2025 showed the wind field for the extratropical cyclone south of Newfoundland. While the intense storm (>48 kts, orange and brown colors) and hurricane-force (>64 kts, red color) are mainly limited to the system’s southern quadrant, gales (>34 kts, yellow colors) extend far to the south, all the way to near Bermuda.
A Senintel-3a/SRAL altimeter pass at 1330 UTC 21 February 2025 observed Significant Wave Heights up to 6.9 meters, or in excess of 22 feet, well to the southeast of the low pressure center. NWS OPC Wind/Wave Analysis at 1200 UTC 21 February 2025 suggested Significant Wave Heights (average height of the highest 1/3 of wave heights) closer to the center were even higher, in excess of 29 feet.
Over 24 hours later, the extratropical cyclone still remained a powerful hurricane-force low. The OceanSat-3/OSCAT scatterometer observed hurricane-force winds in the system’s southern quadrant at ~1518 UTC 22 February 2025. In the western quadrant, there were a few erroneous wind observations, noted by a stark difference in wind speed and direction from the background wind field. OSCAT is a Ku-band scatterometer, operating at a shorter wavelength than the C-band ASCAT scatterometer, making it more sensitive to rain contamination and the corresponding sea surface roughness, leading to incorrect wind speed and direction values. OSCAT-3 has been deployed in AWIPS to select regional NWS field offices, and is expected to be incorporated into OPC’s AWIPS workstations over the next couple of weeks.
NWS OPC waters remain busy, with two more hurricane-force lows predicted over the next four days, with one in the Pacific, and the other in the Atlantic.
