Oil continues impacting Louisiana coast; storms for Caribbean and SE U.S. waters?

Light southeast to east winds are expected to blow over the northern Gulf of Mexico today through Sunday, resulting in potential oiling of Louisiana shorelines from the mouth of the Mississippi River westward 150 miles, according to the latest trajectory forecasts from NOAA. Clouds over the Gulf of Mexico have cleared, and we should get a good view late this afternoon on how far south the oil spill has penetrated into the Loop Current. Statements from NOAA and Synthetic Aperture Radar (SAR) satellite data imply that most of the oil that was pulled southwards to the northern boundary of the Loop Current is now caught in a counter-clockwise rotating eddy just to the north of the Loop Current. Some oil has escaped this eddy and is on its way south towards the Florida Keys. This tongue of oil consists of "numerous light sheens with some emulsified patties and streams," according to NOAA. I wish they'd provide more information about what the sensitivity of various ecosystems may be to oil at these concentrations. It would also be good to have more information about what the concentration of the toxic dispersants are in the surface waters of the spill, but I expect no one knows. The oil will grow more dilute as it travels the 500 miles to the Florida Keys. My present expectation is that the oil entering the Loop Current this week will cause only minor problems in the Keys next week. However, there is a lot of uncertainty about what the oil may do to the fragile Keys ecosystem. SAR imagery from last night and this morning continue to show a large plume of oil being drawn southeastward from the oil spill location into the northern boundary of the Loop Current. With winds expected to remain light over the coming week, I expect oil will continue to be drawn southwards into the Loop Current and the counter-clockwise rotating eddy just to its north. Much of the oil caught in this eddy may circulate around the eddy in 3 or so days, and potentially enter the Loop Current early next week. As I discussed in my post Wednesday, the Loop Current is very unstable right now, and is moving chaotically 10+ miles in a single day, making prediction difficult.


Figure 1. Synthetic Aperture Radar (SAR) image of the oil spill taken at 7:56am EDT May 20, 2010, by the Canadian Space Agency’s (CSA) RadarSat-1 satellite. Image credit: Center for Southeastern Tropical Advanced Remote Sensing, University of Miami Rosenstiel School of Marine and Atmospheric Science. SAR images have a resolution of 8 - 50 meters, and can be taken through clouds and precipitation.


Figure 2. Latest oil trajectory forecast from NOAA for this Saturday.

Oil spill resources
My post Wednesday with answers to some of the common questions I get about the spill
My post on the Southwest Florida "Forbidden Zone" where surface oil will rarely go
My post on what oil might do to a hurricane
NOAA trajectory forecasts
Deepwater Horizon Unified Command web site
Oil Spill Academic Task Force
University of South Florida Ocean Circulation Group oil spill forecasts
ROFFS Deepwater Horizon page
Surface current forecasts from NOAA's HYCOM model
HYCOM ocean current forecasts from LSU

Potential serious rainfall threat to Haiti next week
Long-range forecasts from the NOGAPS model, and to a lesser extent, the ECMWF and GFS models, continue to predict an increase in moisture and decrease in wind shear over the Western Caribbean 4 - 6 days from now, leading to development of a tropical disturbance with heavy rains in the Western Caribbean early next week. A strong subtropical jet stream over the southern Gulf of Mexico will steer the disturbance to the north and east, and the potential exists for heavy rains of 3 - 6 inches to affect eastern Cuba, Jamaica, Haiti, and the Dominican Republic in the Tuesday - Thursday time frame next week. It is possible that a tropical depression could form from this tropical disturbance, though most of the models indicate that high levels of wind shear will make this improbable.

Southeast U.S. coastal storm next week could become subtropical
A region of cloudiness and showers just east of the Bahama Islands will develop into a strong extratropical storm over the weekend. This storm is expected to move slowly northwestward towards the Southeast U.S. coast Sunday and Monday, and could bring 20 - 30 mph winds and heavy rain to the coast of North Carolina by Tuesday. While the storm will initially form in a region of high wind shear and be entirely extratropical, it will move into a region of lower wind shear in a gap between the polar jet stream to the north and the subtropical jet stream to its south early next week. At that time, the low will be positioned near the warm waters of the Gulf Stream, and will have the opportunity to develop a shallow warm core and transition to a subtropical storm. The models are divided on whether the storm will eventually make landfall on the Southeast U.S. coast 6 - 7 days from now, and it is too early to offer odds on this occurring. The counter-clockwise flow of air around this low will probably lead to northeasterly winds over the oil spill region Monday through Wednesday, keeping oil away from the coasts of Alabama and the Florida Panhandle, but pushing oil westwards towards Texas. Wunderblogger Weather456 has a more detailed discussion of the potential development of this system in his blog this morning.

Tornadoes and large hail pound Oklahoma
A significant severe weather outbreak occurred last night over Oklahoma and surrounding states, with 25 tornado reports, 8 reports of damaging winds, and 23 hail reports. Severe weather wunderblogger Dr. Rob Carver has the details in his wunderblog this morning. The Vortex2 field project had a perfect opportunity to intercept these tornadoes, since they were slow moving and occurred over relatively unpopulated regions. The University of Michigan students writing our Vortex2 featured blog will have an update when their schedule allows.


Figure 3. Baseball-sized hail pounds a suburban Oklahoma City swimming pool, making huge splashes, in this remarkable video. The action gets really intense about 90 seconds into the video.

I'll be back with a new post Friday.

Jeff Masters