Jeff Masters just out...

Hurricane Rina is now a Category 2 storm, headed slowly west-northwest at 3 mph towards Mexico's Yucatan Peninsula. The most recent hurricane hunter mission was at 4:32 am EDT this morning, and the next aircraft is not due into the storm until this afternoon, so we'll have to rely on satellite estimates of the storm's strength until then. Recent satellite intensity estimates suggest Rina has leveled off in intensity, with no change in strength since the last hurricane hunter mission. A murky, cloud-filled eye is visible on visible satellite loops right now. Rina also has an impressive upper-level outflow channel to the north, and very intense thunderstorms with cold clouds tops that extend up to the stratosphere. Wind shear is a moderate 15 - 20 knots due to strong upper-level winds out of the south, and these winds are injecting dry air into Rina's south side, inhibiting heavy thunderstorm development there. Water temperatures are very warm, 29 - 30°C, and these warm waters extend to great depth. Rina has brought sporadic heavy rain squalls to the Cayman Islands; George Town on Grand Cayman has received 4.76" of rain over the past three days from Rina, as of 9 am EDT this morning.

Forecast for Rina
The hurricane hunters found Rina's eyewall had a gap in it during their 4:32 am EDT eye penetration this morning, probably caused by the moderate wind shear the storm has experienced over the past day. It is unlikely that Rina will be able to "bomb" and undergo rapid intensification unless it can close off this gap in the eyewall. Wind shear is not expected to increase until Wednesday night, so Rina still has a day and a half to continue its intensification process. Given the storm's inability to close off its eyewall so far, I expect that a Category 3 storm is the strongest that we will see. On Wednesday night, Rina will encounter a dry airmass with high wind shear that lies over the extreme northwestern Caribbean. These conditions should weaken the hurricane, but Rina could still be a major hurricane if it makes landfall in the Yucatan Peninsula on Thursday.

A trough of low pressure is predicted to pass to the north of Rina late this week, which should turn Rina more to the northwest by Thursday and northeast on Friday. However, it is uncertain if Rina will be strong enough to fully "feel" the steering influence of this through and be swept to the east-northeast into Southwest Florida and the Florida Keys. If Rina makes landfall in the Yucatan Peninsula and weakens significantly, the storm will likely be too weak to get caught up by the trough and will remain trapped in the Western Caribbean. This is the solution of the latest runs of the ECMWF, UKMET, and HWRF models. However, if Rina remains strong through Friday, it is more likely to get caught up by the trough and drawn into the Florida Keys as a weakening tropical storm on Friday or Saturday. This is the solution of the latest 2 am EDT runs of the GFDL and GFS models. There is high degree of uncertainty which set of model runs will be correct.

Comparing Rina to Hurricane Wilma of 2005
Rina's intensification into a hurricane over the Western Caribbean during the last half of October brings to mind Hurricane Wilma, which also did this in 2005. Wilma went on to become a Category 5 monster, the strongest Atlantic hurricane of all-time. I don't think Rina will be another Wilma, even though the ocean temperatures and total heat content are similar to what Wilma experienced (Figure 3). Wilma had nearly ideal upper-level atmospheric conditions with an anticyclone aloft and light wind shear, under 5 knots. Rina is experiencing 15 - 20 knots of wind shear and is also a smaller storm, and is thus more vulnerable to the effects of wind shear and dry air.