The Saffir-Simpson Hurricane Wind Scale is undergoing a minor modification for 2012 in order to resolve awkwardness associated with conversions among the various units used for wind speed in advisory products. The change broadens the Category 4 wind speed range by one mile per hour (mph) at each end of the range, yielding a new range of 130-156 mph. This change does not alter the category assignments of any storms in the historical record, nor will it change the category assignments for future storms. The reasoning behind this change and a tabulation of the old and new scales is available here (PDF). The new summary table is shown below:
| Category | Winds | Summary |
|---|---|---|
| 1 | 74-95 mph 64-82 kt 119-153 km/h | Very dangerous winds will produce some damage |
| 2 | 96-110 mph 83-95 kt 154-177 km/h | Extremely dangerous winds will cause extensive damage |
| 3 | 111-129 mph 96-112 kt 178-208 km/h | Devastating damage will occur |
| 4 | 130-156 mph 113-136 kt 209-251 km/h | Catastrophic damage will occur |
| 5 | 157 mph or higher 137 kt or higher 252 km/h or higher | Catastrophic damage will occur |
More Information
- About the Saffir-Simpson Hurricane Wind Scale (PDF)
- Saffir-Simpson Hurricane Wind Scale Extended Table (PDF)
When will Florida's Drought End?
The short answer is no time soon. However, things are looking better in terms of the global weather pattern that has been causing our years-long drought and we might see some relief by the end of May -- only 8-10 weeks from now.
La Niña, the cooling of the equatorial Pacific waters off the coast of South America that has dramatically affected our weather for most of the past two years, is almost gone. Sea surface temperatures (SSTs) over the tropical Eastern Pacific in the area 5°N - 5°S, 120°W - 170°W, also called the "Niña 3.4 region," have warmed rapidly over the past month. They are now slightly warmer than the -0.5°C threshold to be considered La Niña conditions. This is the first time since early August that La Niña conditions have not been present.
It is likely that SSTs will continue to warm during March and April, and NOAA's Climate Prediction Center is predicting that they will declare an official end to La Niña sometime between March and April. A moderate to strong La Niña began in the summer of 2010, weakened briefly during May - July 2011 to neutral status, then re-intensified to a borderline weak/moderate La Niña from August 2011 - January 2012.
Above: Comparison of the sea surface temperature departure from average from January 4 and February 22, 2012, over the tropical Eastern Pacific. During January, a large region of the ocean was more than 0.5°C cooler than average, meaning a La Niña event was present. Beginning in mid-February, waters warmed rapidly from east to west along the Equator, signaling and end to the La Niña event. Image credit: NOAA.
The forecast: neutral or El Niño conditions by fall
The period March - May is the typical time of year that El Niño or La Niña events end, and it is common for the opposite phenomena to take hold by fall. Since 1950, there have been twelve La Niña events that ended during the first half of the year; during six of those years (50%), an El Niño event formed in time for the August - September - October peak of hurricane season.
The official forecast from Columbia University's IRI and NOAA's Climate Prediction Center calls for a 31 - 32% chance of an El Niño event during the 2012 Atlantic hurricane season. El Niño conditions tend to suppress Atlantic hurricane activity by creating high levels of wind shear that tends to tear hurricanes apart. Given the relatively high chance of an El Niño event this fall, plus ocean temperatures over the tropical Atlantic that are cooler than we saw in 2011 and 2010, it is unlikely we'll have an Atlantic hurricane season as active as the ones in 2010 and 2011 (nineteen named storms both years, third busiest seasons on record). The demise of La Niña also means that global temperatures should begin to approach record warm levels by the end of the year. The cool waters of a La Niña event keep global temperatures cooler than average.
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