Thursday, 21 July 2016

Record heat (93F) in Gulf of Mexico

Record Hot Atlantic Basin to Fuel Brutish 2016 Hurricanes?

20 July, 2016
Last week, Gulf of Mexico sea surface temperatures off Tampa Bay were outrageously hot. On July 10, the ocean temperature measure hit 93 degrees Fahrenheit (34 Celsius). By the 11th, temperatures had warmed still more. And by the 12th, ocean surfaces had hit a sweltering 95 F (35 C).
Tampa bay water temperatures
(NOAA shows extreme sea surface temperatures at Old Port in Tampa, FL. Hat tip toMichael Lowry.)

It’s rare that you ever see ocean waters anywhere on Earth become so hot. And when you do, it’s often in places like the Red Sea or the Persian Gulf — not the Gulf of Mexico. But in the new world driven to increasingly extreme warmth by human fossil fuel emissions, the potential heat bleeding off of ocean surfaces has jumped by quite a bit.
And it’s not just true with Tampa Bay. According to Michael Lowry, a hurricane specialist at The Weather Channel, the whole of the Gulf of Mexico recorded its hottest average daily July sea surface temperature at 86.3 F (30.1 C).
Atlantic Basin Sees Record July Heat

The record ocean heat extends still further. National Hurricane Center storm specialist Eric Blake earlier today noted that the entire Atlantic Basin west of longitude 60° W is the hottest it’s ever been during any hurricane season, including the record storm year that was 2005. In other words, a huge zone of ocean stretching from the far eastern edge of the Caribbean, encompassing all of the Gulf of Mexico and running up the entire eastern seaboard of the US and on to just east of Bermuda is now seeing the hottest July ocean temperatures ever experienced in our modern records.

Record Hot Atlantic Basin Sea Surface Temperatures
(Sea surface temperatures hit record ranges for the western North Atlantic during recent days. CDAS image via Eric Blake.)

Overall ocean surface temperatures range from 0.5 to 1 C above average for the Caribbean, 0.5 to 2.5 C above average for the Gulf of Mexico and 1 to 6 C above average for the coastal US Atlantic. These temperatures compare to an already hotter-than-normal 1981-to-2010 average, so departures from the 20th-century average would be even greater.
Record Ocean Heat to Strengthen 2016 Atlantic Hurricanes?

Hot ocean temperatures are fuel for the powerful storms we call hurricanes. But it’s not the only ingredient. Low-pressure formation at the surface, a lift in the atmosphere, high pressure aloft, widely available moisture, and a lack of wind shear are all atmospheric assists that aid in storm formation. So far during July, a dearth of these other factors has resulted in no storms as of yet for the month.
2016, however, has already seen four named tropical storms — including the odd winter Hurricane Alex and three tropical storms which spun up during June. And given the extreme ocean surface heat in the Northwestern Atlantic, some agencies are beginning to call for the potential for more and possibly powerful storms on the way.

According to The Weather Network:
The main driving elements for hurricane formation in the Atlantic are the SST values present in the Atlantic itself, the predicted wind shear conditions in the region, and the SST pattern found in the Pacific related to the timing of the transition from El Niño to La Niña in the equatorial Pacific Ocean. Model predictions anticipate that the second part of this 2016 season will be more active as La Niña intensifies in the Pacific and becomes one of the main drivers of activity for the Atlantic.
As a result of the combined extreme Atlantic Basin heat and the predicted emergence of La Niña conditions in the equatorial Pacific, some hurricane monitors are upping the number of storms predicted for 2016. Colorado State is now forecasting 15 named storms as opposed to its earlier 13. However, its prediction for the number of major hurricanes has remained the same at two, with one affecting the US.

Predicted tropical wave
(Models predict what appears to be a very healthy tropical wave emerging off the west coast of Africa by July 28. If a tropical cyclone results that tracks into record warm western Atlantic waters, peak storm intensity near the US could be quite extreme. Hat tip tometeorologist Ryan Maue for the ECMWF infrared forecast capture.)

However, predicted warm-water formation in the Pacific off Mexico could dampen Atlantic storms by pushing in more dry air and developing a higher degree of wind shear than is typical during a La Niña year. In addition, large African dust flows currently over the tropical Atlantic also may tend to suppress storm formation.
Given the ambiguous conditions noted above, the situation still appears to be a bit of a crapshoot. That said, those extreme sea surface temperatures near the US will likely continue to ramp up through August. And that’s a situation that creates a potential where storms approaching the US rapidly intensify as they hit those record-hot waters. Overall, it’s a pretty dicey environment for forecasters and one that has been wagged in no small amount by conditions related to human-forced warming.

Hat tip to DT Lange

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