The 2011 Atlantic hurricane season officially began today. The first five named storms - should they form - will be Arlene, Bret, Cindy, Don, and Emily.
The start of the season prompted several forecast groups to release updated forecasts for the season while two disturbances with some potential to grow into tropical storms have already developed.
Active tropical disturbances
One disturbance, about 200 miles east of Jacksonville and on a path to strike the northern Florida peninsula, is given a 30 percent odds of developing into a tropical storm by the National Hurricane Center. Conditions are favorable for some further development; however, the system has limited time left over water. By tonight, it will come ashore with heavy rains and wind gusts to 25-35 mph.
The disturbance’s evolution is fairly remarkable as it initiated as an area of thunderstorms over Michigan last night. It was then steered by the clockwise circulation around the periphery of the large high pressure system (sometimes referred to as a “ring of fire” due to the associated convection) over the eastern U.S. into the Atlantic ocean and then south/southwestward toward Florida. The satellite loop showing the disturbance’s journey is impressive and worth a view.
After this system crosses Florida, the system will emerge in the Gulf of Mexico where there is some chance it redevelops. Jeff Masters at Wunderground writes: “Sea surface temperatures in the Gulf are about 27°C (81°F), 0.5 - 1.0°C above average, and it is possible that 93L could gain enough strength to become Tropical Depression One as it crosses the Gulf.”
Masters also noted the presence of a second disturbance between Central America and Jamaica which could spin up into a tropical low:
“All of the computer models predict that an area of low pressure will form in this region by Thursday, and this low will have the potential to develop into a tropical depression late this week or early next week. A surge of moisture accompanying a tropical wave currently south of Hispaniola may aid development when the wave arrives in the Western Caribbean on Thursday. Water temperatures in the Central Caribbean are about 1°C above average, 29°C, which is plenty warm enough to support development of a tropical storm.”
Updated hurricane season forecasts
With the start of hurricane season, AccuWeather and CSU have tweaked their seasonal outlooks, but - as it turns out - not revised the number of projected storms and hurricanes from earlier this spring.
AccuWeather, which is forecasting 15 named storms, 8 hurricanes and 4 major hurricanes, highlighted areas of concern in its revised outlook:
This year, the early season threat area will be the western Gulf of Mexico and the southern portion of the Caribbean. Within this zone, the higher concern for landfalls will be along the Texas and Louisiana coastlines.
As for the mid-to-late season zones, the eastern Gulf and Caribbean will be the focus. The higher concern areas will be the Florida Peninsula to the Carolinas.
CSU continues to predict 16 named storms, 9 hurricanes, and five major hurricanes. Unlike its April forecasts - which have shown limited forecast skill, CSU’s June forecasts from 1999-2009 demonstrated a skill 19% - 30% higher than a no-skill climatology according to a NOAA study (h/t Jeff Masters).
Florida State issues hurricane season forecast
Scientists at COAPS have just released their third annual Atlantic hurricane season forecast. This year’s forecast calls for a 70% probability of 14-20 named storms and 8-10 hurricanes. The mean forecast is for 17 named storms, 9 hurricanes, and an accumulated cyclone energy (ACE; a measure of the strength and duration of storms) of 163. These numbers are above the 1995-2010 average of 14 named storms and 8 hurricanes, and are related to warm tropical North Atlantic sea surface temperatures, a weakening of La Niña conditions, and the ongoing positive phase of the Atlantic Multi-decadal Oscillation.
No major hurricane has hit U.S. coast since Wilma in 2005. Consider us jinxed.
No major #hurricane has made landfall in the U.S. since Wilma '05. There has NOT been a 6-year stretch in historical records!