Update - Friday, October 28, 2011 - 8:30 PM EDT
Rina has decoupled near the northern tip of the Yucatan over the past day or so. Deep convection - with widespread rain and strong thunderstorms, the remnants of Rina - continues streaming into south Florida tonight, where numerous Flood Advisories and Special Marine Warnings have been issued. A few thunderstorms may approach severe limits, and could risk an isolated, brief waterspout and/or tornado.

Rina's post-tropical low level circulation is being shunted to the southeast, where it is merging with the remnants of Invest 97L over the northwestern Caribbean. The chance of this merger generating into a new tropical cyclone anytime soon is very low.

Ciel

Update - Thursday, October 27, 2011 - 7:30AM EDT
Rina has weakened more overnight and is barely a hurricane, and probably will be downgraded later today. The shear continues to win, and this sets the impact that the front north of it to basically push it back south, and weakening. Chances of it coming more northward are slim to none anytime soon. It is basically going to drift around in the same area of the Caribbean, under shear, for the foreseeable future.
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The NHC forecast loops it back southward and degrades it to a depression or remnant low on the 31st.

Update - Wednesday, October 26, 2011 - 8PM EDT

Rina has weakened to a Category 1 hurricane as it has now entered the shearing zone, this along with the fact it never made it to major hurricane status is increasing the odds it will be weak if it nears Florida, still quite a bit of low confidence in the forecast but odds now slightly favor it staying mostly south of Florida, although parts of South Florida will likely still receive rain.

We are now Recording Cancun Radar

Update - Tuesday, October 25, 2011 - 6AM EDT
Hurricane Rina has strengthened overnight to a category 2 hurricane. Recon has found a slightly open eye, but very strong surface conditions in Rina. It is likely to strengthen some more today, possibly into a major hurricane. A visible eye may appear later today.

Hurricane Watches are now up for parts of the Yucatan up to and including Cancun and Cozumel. If the forecast verifies, conditions will begin to worsen in Cancun on Thursday with closest approach or landfall Late Thursday night/early Friday morning.

After 48 hours, conditions around Rina are expected to become hostile and weaken the storm, but until then it may have a shot at rapid intensification today, the official forecast caps at 115MPH, but that may be conservative with this setup.

The big question is for what occurs beyond this, the current official forecast (which is notably highly uncertain) weakens the storm and moves it more easterly, moving it slowly, and possibly looping. Some of the models bring it more northerly, with the GFDL model actually having it get caught up in the flow and rapidly dragged across south Florida. That seems not as likely fortunately. However, everyone in the cone of uncertainty needs to watch this system closely, and the windspeed probability graphics are one of the better ways to gauge storm probability.

In short Cancun and the northeastern Yucatan needs to start preparing for a major hurricane, Cuba and south Florida need to monitor the situation, especially toward the weekend. The largest concern is that the storm gets caught up in the easterly steering flow and rapidly dragged across Florida, the main reason that the National hurricane center is not predicting that is that the storm weakens enough not to be affected before it reaches that latitude. It will be a delicate balancing act, if Rina strengthens more than expected chances for it to get dragged further north go up. Therefore the next 48 hours will tell a lot. Watch closely today to see how much Rina strengthens.

We are now Recording Cancun Radar

Update - Monday, October 24, 2011 - 7PM EDT
Hurricane Rina continues organizing this evening, and indeed appears poised for the potential of an intensification phase, yet again, overnight. Very deep, "hot" convection is underway right over the center, and upper-level outflow is fairly well established all around, and especially so to the north of the cyclone.

On the other hand, dry air and high shear close to Rina could become a forecast buster. Rina remains a relatively small tropical cyclone, and as such, will continue to be susceptible to rapid fluctuations in intensity. Also, there is some question given Rina's very slow motion if an area of disturbed weather to its east, Invest 97L, may catch up to it enough that it begins interacting with it by mid week. Given Rina's size, such involvement could put another fly in the ointment of any well intentioned forecast.

On the whole, all interests in the western Caribbean and northeast up into Florida should be following this tropical cyclone closely, and be prepared for possible changes in track and/or intensity. Rina will likely continue to be a challenge to predict.

Of historic note, Hurricane Rina has joined an elite group of rapidly intensifying tropical cyclones. Interestingly, a disproportionate number of these (half of this admittedly very tiny sample) made Texas landfalls.

Most recently, Humberto (2007) went from 25 Kts to 80 Kts within 24 hours.

At least three tropical cyclones on record have tied, or even surpassed that milestone:

Celia (1970) underwent an incredible initial Rapid Intensification, blasting from 30 Kts on 08/01 at 0600Z all the way up to a 100 Knot Major Hurricane within just eighteen hours. Celia was the first Major of the 1970 Atlantic hurricane season, and is believed to have reached peak intensity as it made landfall around Corpus Christi, Texas.

Arlene (1963) was estimated to have gone from 30 Kts on 08/01 1800Z to a 90 Kt Cat 2 within 24 hours. Hurricane Arlene was remembered for producing some of the most rainfall over Bermuda from any tropical cyclone in recorded history.

Flora (also in 1963) was estimated to have shot from 30 Kts on 09/29 0600Z up to 85 Kts within 24 hours. Owing to slow movement and a loop while traveling near and over land, Flora is remembered for being the wettest Tropical Cyclone on record in Cuba, Haiti, and the Dominican Republic, and consequently was one of the deadliest Atlantic hurricanes in history, taking over 7,000 lives.

Ciel

Update - Monday, October 24, 2011 - 2PM EDST
Just a quick update to note that Rina has intensified to hurricane status as confirmed by Recon and latest visible satellite imagery. Update bulletins will be issued shortly by NHC. In the last few hours Rina has become stationary.

ED

The forecast now takes Hurricane Rina to major hurricane status, and this seems likely given the current satellite presentation.

Original Post
Tropical Storm Rina has held overnight as a minimal tropical storm, it has good outflow to the north and moderate conditions for development, it is currently forecast to become a category 1 hurricane as it approaches the Yucatan, possibly Saturday.

Beyond that, things get tricky, both in track and intensity, but it is enough to say those in south Florida and the Keys will want to pay attention to this, as it is a slow mover it will take quite a while to reach Florida, quite possibly until 7 or 8 days from now. It is likely to be weaker if it makes it that far north.

Generally, if the storm remains weak it will more likely head inland over the Yucatan, whereas if it hits a good spin up and strengthens a good deal, it will likely head more northerly into the Gulf of Mexico before getting kicked eastward, likely being weakened in the process.

There is a good deal of dry air to the north and west of Rina, which will probably be the largest factor in keeping it weaker, the water temperature and other atmospheric conditions are mostly favorable. This morning satellite presentation is very good, and it is likely that Rina will strengthen some today. Recon is scheduled to leave around 11 AM this morning to take measurements in and around Tropical Storm RIna

Want to speculate on where Rina ultimately goes, let us know in the Forecast Lounge.

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