Hurricane Cristina Hits Cat 4; Little Change to Arabian Sea Tropical Cyclone Nanauk

Hurricane Cristina walled off the dry air surrounding it and put on an impressive round of rapid intensification overnight, topping out as powerful Category 4 hurricane with 150 mph winds and a central pressure estimated at 935 mb at 11 am EDT Thursday. Cristina is the second hurricane this year to reach major hurricane strength in the Eastern Pacific, setting a record for the earliest date of formation for the season's second major hurricane. The previous record was a full thirteen days later in the season: June 25, 2010, when Hurricane Darby reached Category 3 strength. The other major hurricane this year in the Eastern Pacific was Hurricane Amanda, which peaked as a top-end Category 4 hurricane with 155 mph winds at 15 UTC (10 am EST) May 25, becoming the strongest May hurricane ever recorded in the Eastern Pacific. This year is also the first time there have been two Category 4 hurricanes before July 1 in the Eastern Pacific. Prior to Cristina, the earliest second Category 4 hurricane was Hurricane Elida in 1984, which reached that threshold on July 1. Reliable records for the basin go back to 1966.


Figure 1. Cristina near peak strength at 12:16 pm EDT June 12, 2014.

The usual formation date for the second hurricane of the Eastern Pacific season is July 14, so we are over a month ahead of usual for hurricanes in 2014. The 1981 - 2010 averages for the Eastern Pacific hurricane season are 15 named storms, 8 hurricanes, and 4 major hurricanes, so we've already had half the usual number of major hurricanes for an entire season, with the typical August 24 peak of the season nearly two and a half months away. This year is shaping up to be an El Niño year, and El Niño conditions typically increase the sea surface temperatures and decrease the vertical wind shear over the tropical Eastern Pacific, favoring the development of more and stronger tropical cyclones.


Figure 2. True-color MODIS image from the Aqua satellite of Hurricane Cristina at 21 UTC Wednesday, June 11, 2014. At the time, Cristina was a Category 1 storm with 80 mph winds. Image credit: NASA.

Satellite loops show that Cristina has an impressive eye surrounded by an eyewall with very cold cloud tops. The eyewall is thinner on the northwest side of the eye, suggesting that wind shear of about 5 - 10 knots due to upper level winds out of the northwest is affecting the storm. There is still time for Cristina to potentially intensify into a Category 5 storm today, but increasing wind shear combined with decreasing sea surface temperatures will begin to weaken the storm on Friday and into the weekend. Cristina is headed away from Mexico, and no watches or warnings will be required.

Little change to Arabian Sea's Tropical Cyclone Nanauk
Tropical Cyclone Nanauk continues steaming westwards across the Arabian Sea at 11 mph towards Oman. Nanauk is over some of the warmest ocean waters on the planet, 31 - 32°C (88 - 90°F), but has changed little in strength over the past two days, due to high wind shear of 25 - 30 knots, which is disrupting the circulation. Nanauk is expected to continue moving west-northwest towards Oman Thursday, but both the European and GFS models now predict that Nanauk will dissipate in the next two days. High wind shear associated with the advancing Southwest Monsoon is predicted to increase over Nanauk, allowing very dry air over the Middle East to penetrate deep into the storm's core and disrupt it. This would be very good news for Oman, which has suffered a number of deadly and costly tropical cyclone landfalls since 2002.


Figure 3. True-color MODIS image from the Aqua satellite of Tropical Cyclone Nanauk (65 mph sustained winds) over the Arabian Sea taken at approximately 6:30 am EDT June 12, 2014. The coast of Oman can be seen at the left side of the image. Image credit: NASA.

Tropical cyclones rare in Oman
Tropical cyclones are quite rare in Oman, but have hit the nation unusually often in the past few years. According to NOAA's Historical Hurricane Tracks database, only five have hit Oman at tropical storm strength or higher since accurate satellite data began in 1990, with three of those landfalls occurring since 2007:

Nov. 2, 2011: 40 mph tropical storm, Keila (14 killed)
June 4, 2010: 75 mph Category 1 hurricane, Tropical Cyclone Phet (24 killed)
June 6, 2007: 75 mph Category 1 hurricane, Tropical Cyclone Gonu (50 killed)
May 10, 2002: 40 mph tropical storm, the 2002 Oman cyclone (9 killed)
October 3, 1992: 45 mph tropical storm

Earlier historical landfall records indicated that the deadliest cyclone to affect Oman was a Category 1 storm that hit on June 13, 1977, killing 105 people.

Tropical Cyclones Gonu of 2007: Oman's Costliest Natural Disaster
The most expensive natural disaster in Oman's history was Tropical Cyclone Gonu, which hit the eastern tip of Oman as a Category 1 storm on June 6, 2007. Gonu is the first Category 4 or higher storm recorded in the Arabian Sea since the satellite era began in 1970. The Joint Typhoon Warning Center (JTWC) estimated Gonu's peak sustained winds at 165 mph, the strongest winds of any tropical cyclone they have ever rated in the northern Indian Ocean (second place: the 160 mph winds of the 1991 Bangladesh cyclone that killed 138,000 people.) Fortunately, dry air and wind shear knocked Gonu down to Category 1 strength before landfall, but the storm still killed 50 people and did $4.2 billion in damage (2007 USD) in Oman, with flash flooding causing most of the deaths and destruction. Gonu dropped heavy rainfall of up to 610 mm (24 inches) on Oman's east coast, which is six times higher than the annual rainfall in Oman of 100 mm (about 4".) In Iran, the cyclone caused 28 deaths and $216 million in damage (2007 USD).


Video 1. The Story About Cyclone Gonu video shows remarkable footage of why so many people died in Oman: they went out into the flood waters in their cars.

Quiet in the Atlantic
There are no tropical cyclone threat areas in the Atlantic to discuss today, and none of the reliable models for forecasting tropical cyclone genesis is predicting development over the coming five days. The GFS model continues to predict that about 6 - 9 days from now the upper level winds over the Western Caribbean will relax and low-level moisture will build, potentially allowing a tropical disturbance with heavy rains to develop there. However, the European model keeps the wind shear high over the Western Caribbean early next week, so any development in the region remains in doubt.

Jeff Masters