Tornadoes kill 3 in Michigan...

More tornadoes hit the U.S. on Thursday and early Friday morning, causing damage and injuries in Michigan, Indiana, Kentucky, and Florida. A 29-year old man was killed in Kalkasaka County, Michigan, when a tornado destroyed his home. Two other people were killed in Williamston, Michigan, after a tornado destroyed their lakefront home. In Nappanee, Indiana, five people were injured and 20 homes destroyed by a tornado at 10:30 pm. At least eight people were injured in western Kentucky from a series of tornadoes that raked the area, and a tornado hit downtown Pensacola, Florida, flipping cars and damaging the town's main shopping mall. A tornado that hit near Paris, Missouri, killing two people just after midnight on Thursday, was rated as an EF-2 storm with top winds of 135 mph.

The storm system that spawned this week's severe weather has moved over the Eastern U.S., and there is a chance of severe weather today from Florida northwards to New England, according to the latest severe weather outlook from the Storm Prediction Center. Only isloated tornadoes are likely today, as the atmosphere is not nearly as unstable as it was Wednesday and Thursday.

"Medicane" (Medepression?) hits Spain
A tropical storm-like system swept over the island of Majorca in the Mediterranean on Wednesday, triggering flooding that killed two people. The storm then made landfall on the Mediterranean coast of Spain yesterday morning near the city of Murcia. The satellite presentation of the storm at landfall (Figure 1) showed well-formed spiral bands and a cloud-free center. Murcia, Spain reported sustained winds of 30 mph, gusting to 45 mph, at 14 GMT Thursday. A personal weather station in Santa Pola recorded sustained winds of 40 mph, gusting to 45 mph, and 0.68 inches of rain during passage of the storm. We have a number of other personal weather stations in the region, but none reported higher winds, or a pressure lower than 1013 mb. Radar from the Spanish Instituto Nacional de Meteorologia (Figure 2) showed some well-organized banding. The UKMET model did not indicate the storm had a warm core, so this was likely not a true tropical depression. Sea surface temperatures were about 23° C (about 1° C warmer than normal) under the storm, which is quite a bit colder than the 26.5° C usually associated with tropical storm formation. The satellite presentation suggests that the storm was probably generating a shallow warm core near the surface, and was getting some of its energy from release of latent heat--the same energy source that powers tropical cyclones. Yesterday's "Medepression" was probably a hybrid tropical/extratropical storm, and was predominantly non-tropical.


Figure 1. Satellite image from NOAA-17 polar orbiting satellite at 10:37 GMT 10/18/07. Image credit: U.S. Navy.


Figure 2. Radar image at 6:20 GMT for the Mediterranean coast of Spain. Image credit: Spanish Instituto Nacional de Meteorologia (INM).

Warm-cored hybrid storms have been reported in the Mediterranean Sea before, and there is a large body of scientific literature published on the subject (see below). These storms can become quite severe and cause considerable damage. However, there is no system in place to name these storms, and the National Hurricane Center is not responsible for issuing warnings in the Mediterranean Sea. There are quite a few "Medicanes" in past years that would have earned names as subtropical storms had NHC been responsible for warnings in the Mediterranean Sea. There is concern that global warming may raise sea surface temperatures enough in the Mediterannean later this century to allow full-fledged hurricanes to form and threaten the densely populated cities that dot the coast.

Some of the scientific literature discussing hybrid storms in the Mediterrean Sea:

Emmanuel, K., 2005, "Genesis and maintenance of Mediterranean hurricanes", Adv. Geosci., 2, 217-220.

Lagouvardos K., V. Kotroni, S. Nickovic, D. Jovic, and G. Kallos, 1999: "Observations and model simulations of a winter sub-synoptic vortex over the Central Mediterranean", Meteorol. Appl., 6, 371-383.

Mayengon, R., 1984, "Warm core cyclones in the Mediterranean", Mariners Weather Log, 28: 6?9.

Pytharoulis, I., G.C. Craig and S. P. Ballard, 2000, "The hurricane-like Mediterranean cyclone of January 1995", Meteorol. Appl., 7, 261-279.

Rasmussen, E. A., and Turner J., 2003: Polar Lows, Cambridge Press. 214-219

Rasmussen, E. & Zick, C., 1987, "A subsynoptic vortex over the Mediterranean with some resemblance to polar lows", Tellus, 39A: 408-425.

Reale, O., and R. Atlas, 2001, "Tropical Cyclone-Like Vortices in the Extratropics: Observational Evidence and Synoptic Analysis", Weather and Forecasting, 16, No. 1, pp. 7-34.

Reale, O. ,1998, "Dynamics and classification of two sub-synoptic scale "Hurricane-like" vortices over the Mediterranean Sea", Annales Geophysicae Part II: Hydrology, Oceans & Atmosphere (Supplement II to Volume 16), EGS, C634.

How to search for strongest winds from a storm
A good way to search for the strongest winds from a storm in our personal weather station data is to load a google map for the region of interest:

http://www.wunderground.com/stationmaps/gmap.asp? zip=00000&wmo=08360

Then, click on the station plot for stations of interest. The history page will then pop up, allowing one to see plots and tabular data for today beginning at midnight local time for the station. Airport weather data and conditions from U.S. buoys are also available on the same google map. Use the search box at upper right to change the location the map is centered on.

Tropical update
The tropical Atlantic is quiet today. The GFS model is predicting formation of a tropical cyclone on Tuesday about 800 miles east of the Lesser Antilles Islands. None of the other models are going along with this forecast. If there are no major developments to report this weekend, I may not update this blog until Monday.

Jeff Masters