Hurricane Paula sets a rapid intensification record

Hurricane warnings are flying along the coast of Mexico's Yucatan Peninsula for Hurricane Paula, the 16th named storm and 9th hurricane of this very active 2010 Atlantic hurricane season. Paula intensified remarkably quickly, setting a modern record for the fastest intensification from the issuance of the first advisory to hurricane strength. The first advisory for Paula was issued at 5pm EDT yesterday, and Paula strengthened into a hurricane just twelve hours later, at 5am EDT this morning. Since reliable record keeping of intensification rates of Atlantic hurricanes began in 1970, when regular satellite coverage became available, no storm has ever intensified into a hurricane that quickly. Hurricane Humberto of 2007 held the previous record for fastest intensification from first advisory issued to hurricane strength--18 hours. However, there is one caveat to keep in mind. The final Atlantic hurricane data base (HURDAT) stores points every six hours--at 00, 06, 12, and 18 UTC. It is likely that Paula will be recognized as having been a tropical depression at 12 UTC (8am EDT) or 18Z (2pm EDT) yesterday, 3 - 9 hours before the first advisory was issued. Even though Paula met the criteria for being named a tropical depression yesterday morning, NHC elected not to do so, since it was unclear whether or not passage over land would disrupt the nascent tropical depression (a new tropical depression must demonstrate some staying power before it will get recognized, typically.) In the final HURDAT data base, it may turn out that Paula will be recognized as intensifying from first advisory to a hurricane in eighteen hours, tying Humberto's record. There have been six storms that accomplished the feat in 24 hours.


Figure 1. Microwave image of Paula taken at 6:35am EDT 10/12/10 shows that Paula is a small hurricane, with heavy rains confined to a small area near the center. Though the images are not radar images, one can think of these images as similar to having a radar in space that can provide images of where heavy rain is occurring. Image credit: Navy Research Lab, Monterey.

Fortunately for Mexico, Paula has not been able to maintain its rapid intensification rate. Satellite intensity estimates show that Paula has leveled off in intensity this morning. Microwave satellite images (Figure 1) and traditional satellite imagery reveal that Paula is small hurricane with a limited amount of heavy thunderstorms. Water vapor satellite loops indicate that the atmosphere in the Western Caribbean is moist enough to support further development, but moderate wind shear of 15 knots due to strong upper-level winds out of the south are hampering Paula's intensification. Radar from Belize and Cancun shows that Paula's outer spiral bands are still well offshore. The next hurricane hunter mission is scheduled for 2pm EDT this afternoon; there has been no airplane in the storm since about 4am this morning.


Figure 2. Total accumulated rainfall for the 5.25 day period beginning at 2am EDT today, October 12, 2010, as predicted by the 2am EDT runs of the HWRF model (top) and GFDL model (bottom.) The HWRF model predicts Paula will stay trapped in the Western Caribbean, causing very high rainfall totals. Image credit: Morris Bender, NOAA/GFDL.

Forecast for Paula
Tropical storm force winds of 39+ mph extend out from Paula's center about 60 miles to the north, and are forecast to expand to 100 miles by early Wednesday morning. Paula's current northwest motion of 10 mph means that tropical storm force winds should reach the coast of Mexico near Cozumel between 8pm - 2am local time tonight. A good way to visualize this is to use our wundermap with the "hurricane" layer turned on, and click on the "forecast" and "wind radius" boxes. Hurricane force winds extend out just ten miles from the center, so only a very small region of coast will receive Paula's strongest winds. The 5am EDT wind probability product from NHC predicts a 91% chance that Cozumel will receive tropical storm force winds, and a 31% chance of getting hurricane force winds of 74+ mph. The main threat from the storm will be heavy rain, particularly over western Cuba and the northeastern tip of Mexico's Yucatan Peninsula, if Paula stalls as expected and wanders in the region for many days. Rainfall forecasts from the HWRF and GFDL models (Figure 2) suggest that Paula will be capable of dumping more than a foot of rain in isolated regions over the next five days. The latest SHIPS model forecast calls for wind shear to rise to the high range, 20 - 25 knots, tonight through the end of the week. This high shear, combined with the dry atmosphere to the north of Paula, should keep the hurricane from becoming a major hurricane. NHC is giving Paula just a 6% chance of becoming a major hurricane. The shear and dry air may even weaken the storm below hurricane strength later this week, as suggested by most of the intensity forecast models. Paula is a small storm, so is fairly vulnerable to shear and dry air.

There is considerable doubt about the future path of Paula. Steering currents in the Western Caribbean will collapse on Wednesday, potentially allowing Paula to wander in the region for many days, as predicted by the GFS and HWRF models. It is also possible that Paula will push far enough inland over Mexico's Yucatan Peninsula that the storm will dissipate. Finally, if Paula grows large enough and strong enough, it could get caught up a strong trough of low pressure predicted to traverse the U.S. this week (and spawn a Nor'easter for New England this weekend.) In this scenario, offered by the GFDL model, Paula would make a sharp turn to the east-northeast, hit western Cuba, bring tropical storm-force finds to the Florida Keys on Friday, then move into the Bahama Islands by Saturday morning. NHC is making the reasonable forecast of sticking with what the majority of models are saying, but residents of South Florida, Central Cuba, and the Bahamas should be prepared for Paula to come their way as a strong tropical storm.

"Hurricane Haven" airing this afternoon
My live Internet radio show, "Hurricane Haven", will be airing again today at 4pm EDT. The call in number is 415-983-2634, or you can post a question to broadcast@wunderground.com. Be sure to include "Hurricane Haven question" in the subject line.

Today's show will be about 30 minutes, and you can tune in at http://www.wunderground.com/wxradio/wubroadcast.h tml. The show will be recorded and stored as a podcast.

Jeff Masters