Rina passes over Cancun, weakens to a Depression

Since yesterday's update, Rina became even less organized and lost what little deep convection it had.  This was well-timed for Mexico though, since Rina made landfall on Playa del Carmen (the mainland city directly west of Cozumel) at 03Z today (late Thursday night for them) then passed over Cancun.  Its 9-hour traverse over land, combined with the increasingly hostile environment, was responsible for the downgrade to a 30kt Depression at 15Z today.  All that remains is a tiny harmless low-level swirl just off the northeastern tip of the Yucatan peninsula.  For a very Wilma-like origin and track, thankfully the intensity didn't follow suit.

The image below shows a vertical cross-section taken along the shear vector (southerly) from one of the regional hurricane models (HWRF's 06Z analysis).  The fields shown on there are the wind speed (shaded) and relative humidity (lines).  It's easy to see how weak and shallow the vortex is, and the intrusion and overriding of very dry air... the analyzed shear is 27kts too.  This is not an environment that a storm can redevelop in.

Rina is forecast to lose its remaining tropical characteristics and degenerate to a remnant low very shortly, meandering around in the same vicinity due to weak steering flow.

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Rina downgraded to Tropical Storm

In a battle against increasing vertical shear, Rina was downgraded to a 60kt tropical storm at 15Z today.  The center is located just south of Cozumel and heading NNW at 5kts. You can also track it on Cancun's radar: http://smn.cna.gob.mx/radares/cancun/cancun.php

Now that it has weakened and the convective area associated with it has shrunk drastically, it is steered by different layers of the atmosphere.  Deeper systems are steered by a deeper layer, and weaker/shallower systems are steered by a lower and shallower layer.  That said, the forecast track now calls for Rina to stall in place, just meandering around in a loop waiting for some stronger steering flow to pick it up.  The track plot in the map below shows forecasts from 3 dynamical models, and the NHC forecast is basically an average of these.  The thin light lines are prior 00Z forecasts and can be ignored.  The official intensity forecast also follows the model guidance closely: gradual weakening over the next several days.

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Rina nearly a major hurricane

In the past day, Rina has intensified to a 95kt hurricane, with a high likelihood of reaching 100kts... it would become the season's 4th major hurricane.  Visually, it has become a beautiful symmetric storm, with delicate outflow cirrus expanding uniformly away from the center.

It has another couple of days to enjoy a low-shear environment, then as it heads further north toward Cuba, the upper-level winds become quite a bit more hostile.  But in the meantime, the ocean below it is extremely warm not just at the surface, but is warm quite deep too (that minimizes upwelling effects that slow-moving systems are prone to).  The map below shows the depth of the 26C water... Rina's current location has some of the deepest warm water in the entire Atlantic basin.

The forecast is still quite tricky because of the weak steering environment.  In the next few days, it should continue its slow crawl to the N-NW, but after that, its future depends on whether or not it gets "picked up" by a passing mid-latitude trough.  If it does, it will make a turn to the NE and head for Cuba and then Florida... if it doesn't, it should meander slowly to the west or even stay approximately stationary.
Basically... Mexico, Cuba, and Florida should all be watching this very closely.
Some additional strengthening is still possible, and for at least the next day, there's no reason Rina can't strengthen quite a bit.


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