Europe braces for destructive weekend winter storm

A large but disorganized extratropical storm located over the middle-Atlantic Ocean is expected to move rapidly eastwards towards Spain over the next two days. As the storm approaches Spain on Friday, it is expected to tap into a cold polar airmass to its north and rapidly intensify into a meteorological "bomb"--a mighty winter cyclone with hurricane force winds. Though sea surface temperatures off the coast of Spain are about 1°C below average, the waters of 12 - 16°C will provide plenty of moisture and energy to the powerful storm, which may end up rivaling last year's Winter Storm Klaus in intensity. Klaus, which hit northern Spain and southwest France January 23 - 25, was Earth's most costly natural disaster of 2009, causing $5.1 billion in damage and killing 26. Klaus peaked in intensity at 967 mb, and brought wind gusts of 120 mph (193 km/hr) to Formiguères, France, 125 mph (200 km/hr) to Portbou, Spain, and 134 mph (216 km/hr) to Port d'Envalira, Andorra.


Figure 1. Visible satellite image of the Atlantic at 8am EST Wednesday, February 24, 2010. A developing extratropical cyclone over the middle Atlantic threatens to bring hurricane-force wind gusts to Spain and Portugal on Saturday. Meanwhile, a snowstorm over the New England is dumping heavy snows there. Image credit: NASA GSFC GOES project.

This Saturday's storm is expected to follow a track very similar to Klaus, reaching maximum intensity at 18 GMT Saturday as it passes just north of Spain and Portugal (Figure 2). If the storm tracks near or over the northwest corner of Spain as most of the models are predicting, the cyclone's powerful cold front will likely bring sustained winds of 50 - 60 mph with damaging hurricane-force wind gusts and flooding rains to northern Spain and Portugal. The latest 06Z (1am EST) run of the GFS model predicts that this weekend's storm will bottom out at a pressure of 968 mb, about the same minimum pressure achieved by last year's destructive Winter Storm Klaus (967 mb). The latest 06Z run of the Navy NOGAPS model is more aggressive, deepening the storm into a 948 mb monster that misses Spain by several hundred miles, but comes ashore over Ireland Sunday morning with a pressure of 956 mb. This is a central pressure typically found in Category 2 hurricanes! (Note, though, that extratropical systems generally do not generate winds as strong as a hurricane with a similar central pressure, since extratropical storms do not form an eyewall with extreme winds like a hurricane does). The NOGAPS is currently an outlier, though, and the other models such as the ECMWF, Canadian, and UKMET do not foresee the storm getting that intense. Even so, this weekend's storm has the potential to be a multi-billion dollar weather disaster for Europe.




Figure 2. Forecast from the 1am EST 2/24/10 run of the GFS model for 18 GMT Saturday for mean sea level pressure and 6-hour precipitation (top) and surface winds (bottom). The GFS is predicting that Saturday's storm will peak in intensity at this time with a pressure below 968 mb. Sustained winds of 70 - 75 mph (yellow green colors in bottom plot) are expected just offshore of Portugal. Images generated using our wundermap for Spain with the "model" layer turned on.

The winter storm-fest continues for the U.S.
This winter's relentless winter storm-fest over the U.S. continues this week, with a powerful cyclone over the Northeast U.S. expected to bring 2 - 3 feet of snow to the mountains of New Hampshire and Vermont. The storm is wrapping in too much warm air to bring heavy snow to the major cities along the coast, where most of the precipitation will fall as rain. Next Tuesday, a powerful low pressure system is expected to bring heavy rains to Florida, with the possibility of snow falling in northern Georgia and surrounding regions.

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My next post will be Thursday or Friday.

Jeff Masters