Tuesday, February 09, 2016

Hurricane Patricia's 215 mph Winds: A Warning Shot Across Our Bow


By: Jeff Masters , 5:12 PM GMT on February 08, 2016

The Eastern Pacific's Hurricane Patricia--rated the strongest hurricane ever recorded in the Western Hemisphere with 200 mph sustained winds on October 23, 2015--was actually much stronger, with 215 mph winds, said the National Hurricane Center (NHC) last week, after completing a detailed post-season review. An Air Force hurricane hunter aircraft measured a surface wind of 209 mph in Patricia at 0600 UTC October 23 using a Stepped-Frequency Microwave Radiometer (SFMR); this was the highest surface wind ever measured in a tropical cyclone, worldwide, since the technology was introduced in the mid-1980s. A 207 mph surface wind was measured by the SFMR instrument on a NOAA hurricane hunter aircraft during an eyewall penetration about twelve hours later, at 1732 UTC. In between those two times, there were no measurements by the Hurricane Hunters, but satellite imagery showed that the hurricane improved in organization up until about 1200 UTC, with the eye warming and the eyewall cloud tops cooling. NHC thus assigned Patricia a peak intensity of 215 mph winds with a central pressure of 872 mb at that time. Hurricane Patricia's 215 mph winds officially tie it with the Northwest Pacific's Super Typhoon Nancy of 1961 for strongest winds of any tropical cyclone in world history, and Patricia's lowest pressure of 872 mb makes it the second most intense tropical cyclone in world history, behind the 870 mb measured in the Northwest Pacific's Super Typhoon Tip of 1979 (Tip's top sustained winds of "only" 190 mph were not as high as Patricia's, since Tip was a large, sprawling storm that did not have a tiny concentrated area of extreme eyewall winds.) Note that that the maximum sustained winds estimated in typhoons like Nancy during the 1940s to 1960s are considered by hurricane experts to be too strong; a re-analysis of Super Typhoon Nancy would likely find that its winds were considerably slower than 215 mph. I regard Patricia as unmatched for the strongest winds of any tropical cyclone in recorded history. It is possible that previous hurricanes where hurricane hunter flights were not available, such as the Category 5 1935 Labor Day hurricane that devastated the Florida Keys, had peak winds on par with Patricia, though.

In the 24-hour period ending at 2 am EDT (06 UTC) October 23, 2015, Patricia's central pressure dropped an astonishing 95 mb, to 886 mb, and the winds increased by 120 mph, to 205 mph, making Patricia the fastest-intensifying hurricane (by winds) and second-fastest intensifying hurricane (by pressure) ever observed in the Western Hemisphere.


Another remarkable record: a NOAA reconnaissance aircraft flying through the eye at 17:33 UTC October 23, several hours after the time of estimated peak intensity, measured a maximum 700-mb temperature of 32.2°C (90°F). This is the warmest 700-mb eye temperature ever measured in a tropical cyclone world-wide.


Hurricane Patricia's remarkable intensification was made possible by very light wind shear and record warm ocean waters. During its rapid intensification phase, Patricia tracked over a large expanse of anomalously warm waters with sea surface temperatures (SSTs) of 30.5°-31°C (87°-88°F). These were the highest SSTs ever observed over this region in mid-October.


Several of NHC's forecasts for Patricia had intensity errors through 48 hours that were the highest on record since NHC took over warning responsibility in the eastern North Pacific basin in 1988: up to 120 mph off, beating the record 115 mph error for a forecast made in Hurricane Linda of 1997. None of the intensity models anticipated the degree to which Patricia would intensify, nor how quickly it would occur, and the official intensity forecasts for Patricia from NHC severely underestimated the rapid intensification that occurred and failed to explicitly show rapid intensification until it was actually occurring. It should be noted, however, that a key model used to make intensity forecasts--the SHIPS Rapid Intensity (RI) guidance--was temporarily unavailable before Patricia’s rapid intensification began due to missing satellite inputs. Having these data in real time would likely have resulted in better intensity forecasts than those that were made.


Consider, now, if the bad intensity forecasts for Hurricane Patricia had been made for a Hurricane Patricia clone that had ended up making landfall in a heavily populated area such as Miami, Galveston/Houston, Tampa, or New Orleans, but without the hurricane weakening dramatically at landfall. A 15-mile diameter area of 215 mph winds--EF5 tornado speeds--would have caused near-total destruction. Since the storm would have been significantly under-warned for, a full evacuation might not have been completed, resulting in one of the deadliest hurricane tragedies in human history. The ten-year drought in major hurricane landfalls in the U.S. is going to end someday, and an onslaught of major hurricanes like we experienced in 2004 - 2005--seven landfalls by major hurricanes in two years--could happen again. As I discussed in my 2013 post, Hurricanes and Climate Change: Huge Dangers, Huge Unknowns, the consensus among hurricane experts is that climate change is likely to bring an increase in the number of high-end hurricanes like Patricia. Now that ocean temperatures are considerably warmer than they were a few decades ago, the maximum potential intensity a hurricane can reach is higher, and we should expect to see a few Patricias sprinkled among the inevitable phalanxes of major hurricanes that will assault our shores in the coming decades.


Progress is being made in improving hurricane intensity forecasts, thanks to the 10-year Hurricane Forecast Improvement Project (HFIP), which aims to reduce hurricane track and intensity errors by 50% by 2019. Unless some dramatic breakthroughs in intensity forecasting occur in the next three years, though, we are going to fall short of that goal. But if we really want to crack the intensity forecast puzzle, we should be spending far more on hurricane research than we do


Will we wait again to see unprecedented mayhem like during Katrina in 2005 and Sandy in 2012 before responding to the need to spend more money on better hurricane forecasts? Consider Patricia a shot across our bow--we have been warned (again.) It is up to us to respond.
Unfortunately, it is safe to assume that we will ignore the warning until it's too late.

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