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Rina still a Cat 2, and may have peaked in intensity

By: Dr. Jeff Masters , 1:48 PM GMT on October 26, 2011

There is little change to Category 2 Hurricane Rina, which continues slowly west-northwest at 4 mph towards Mexico's Yucatan Peninsula. The most recent hurricane hunter mission was at 3:58 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 peaked in intensity, and may have weakened slightly since the last hurricane hunter mission. The eye is no longer visible on visible satellite loops, and the storm has a distinctly lopsided appearance, which are both signs that Rina may be weakening. Recent microwave images (Figure 1) suggest that the southern portion of Rina's eyewall may have a gap in it. Wind shear is a moderate 10 - 20 knots due to upper-level winds out of the south. Water temperatures are very warm, 29 - 30°C, but Rina will be leaving a region of high oceanic heat content late tonight, and will not have as much high-energy fuel to sustain itself. Rina has brought sporadic heavy rain squalls to the Yucatan; Cozumel Island airport reported 9.10" of rain yesterday and another 3.25" as of 9 am EDT today. I'm not sure this is correct, since two personal weather stations on the island reported only 1 - 2" of rain over the past two days. The outer rain bands of Rina are visible on Cancun radar and the La Bajada, Cuba radar.

If Rina does make it to Category 3 strength, it would join a very short list of major hurricanes that have occurred this late in the year. Since record keeping began in 1851, there have been only twelve major hurricanes in Atlantic on October 26 or later. Rina is a medium-small hurricane, with hurricane-force winds that extend out 25 miles from the center. The latest estimates of Rina's Integrated Kinetic Energy (IKE) made yesterday afternoon by NOAA's Hurricane Research Division put the damage potential of Rina's storm surge at 2.5 on a scale of one to six. This is a relatively low number for a Category 2 hurricane, and means that storm surge damage will be confined to a relatively small area in the right front quadrant of Rina's eyewall. For comparison, the storm surge damage potential for Hurricane Irene when it was a strong tropical storm approaching Long Island, New York on August 28, 2011 was 4.1 on a scale of 1 to 6, since Irene was a huge storm that put vast areas of the ocean into motion.

Figure 1. Microwave satellite image of Hurricane Rina taken at 7:15 am EDT October 26, 2011. Rina appears to only have the northern half of its eyewall intact. Image credit: Navy Research Lab, Monterey.

Forecast for Rina
The hurricane hunters found that Rina had a large elliptical eye with a diameter of 23 - 34 miles with a gap in the south eyewall during their 3:58 am EDT eye penetration this morning. Rapid intensification usually requires a circular eye with no gap in it, and thus I expect only gradual intensification of Rina can occur today. Wind shear is not expected to increase to the high range until Thursday afternoon, so Rina still has a day and a half to potentially intensify. 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. It is more likely that Rina has peaked in strength, and will begin to weaken. On Thursday, Rina will encounter high wind shear associated with upper-level westerly winds associated with the jet stream and a trough of low pressure moving through the Gulf of Mexico. These conditions should weaken the hurricane, and turn Rina more to the northwest by Thursday and northeast on Friday. Cozumel Island off the coast of Mexico's Yucatan Peninsula appears at the highest risk of receiving a direct hit from Rina; the 5 am EDT Wind Probability Forecast from NHC gave the island a 27% chance of receiving hurricane force winds, the highest chance of any land area in the forecast. If Rina hits Mexico, it would most likely be at Category 1 strength, with Category 2 strength also quite possible. NHC is giving Rina a 21% chance of being a Category 3 or stronger hurricane on Thursday afternoon, and I don't expect the storm will be a major hurricane at landfall. The chief threat from Rina is probably its rains; the hurricane is moving slowly and has the capability of dumping 8 - 16 inches of rain over the coastal Yucatan. Western Cuba is also at risk of receiving heavy rains of 5 - 10 inches.

After Rina makes its closest pass by Cozumel, it is uncertain if the storm will be strong enough to fully "feel" the steering influence of the trough, 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 and HWRF models, with the usually reliable ECMWF model continuing to predict that Rina will dissipate over the Yucatan. However, if Rina grazes the Yucatan and remains strong through Friday, it is more likely to get caught up by the trough and drawn into the Florida Keys or Southwest Florida near Marco Island, as a weakening tropical storm. This is the solution of the latest 2 am EDT run of the GFDL model. The latest 2 am EDT runs of the GFS and NOGAPS models are in-between, predicting that Rina will get very close to the Keys on Saturday, but then weaken and sink southwards towards Cuba. There is high degree of uncertainty which set of model runs will be correct, and the threat to Florida depends strongly upon how much of a blow Mexico receives from the hurricane.

97L in the Central Caribbean not expected to develop
A broad region of low pressure in the Central Caribbean south of Haiti and the Dominican Republic, (Invest 97L), is moving west at 10 - 15 mph. Heavy thunderstorm activity has decreased since yesterday, and is disorganized. The storm is surrounded by a large region of dry air, and this dry air is the main impediment to development. Wind shear is a low 5 - 10 knots, and is expected to remain low through Thursday. None of the reliable models are predicting that 97L will develop, and NHC gave 97L just a 10% chance of developing into a tropical depression by Friday, in their 8 am EDT Tropical Weather Outlook. NHC is no longer interested enough in 97L to generate computer model forecasts of its track. Heavy rains from 97L should reach Jamaica on Thursday, and the Cayman Islands by early Friday morning.

There will be a new post on Rina late this afternoon.

Jeff Masters

The views of the author are his/her own and do not necessarily represent the position of The Weather Company or its parent, IBM.

Reader Comments

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For you demented types who just love winter weather, "enjoy" these lovely photos showing the first real blast of the year. The top one shows downtown Breckenridge, Colorado:


And this is a Wyoming DOT webcam from near Laramie, Wyoming:


No, thanks. SWFL works just fine for me, Rina or not...
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Center can be seen moving WNW/NW on radar.
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@Anyone who wants to answer.

What are the odds that the anticyclone only 700 miles to Rina's SE could move NW and come and sit over Rina and bring the shear down to 5 MPH. The anticyclone is moving around 20 MPH while Rina is moving at 4 MPH. That would be crazy, but there is a slim chance it could happen IMO. I mean there is always a chance even if it's 1%.
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seflhurricane that wat i said and i said it was going to clip it
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Recon now 200 miles out from Rina's center.
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se fl hurricane i agree with u and wat jb said too
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the NW turn has begun and the center is to the right of the next forecast point, i have a feeling that Rina will only have a glansing blow to the yucatan and south florida and the keys will receive a 60-70 MPh Tropical storm with hurricane force gusts
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I live on Cozumel. Dr. Masters we not received the rain fall amounts reported by the airport. Maybe 2 inches max.
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H.Rina's_12pmGMT_ATCF : Starting 25Oct_12pmGMT and ending 26Oct_12pmGMT

The 4(or^"3")eastern line-segments represent HurricaneRina's path,
(^ 1 line-segment between the 2 half-dots is covered by the map's southern border),
the westernmost line-segment is the straightline projection for 26Oct_12pmGMT,
the coastline dumbbell at 18.187n87.849w-SPR is the endpoint of the 26Oct_6amGMT
straightline projection connected to its nearest airport,
and the coastline dumbbell at 20.296n87.364w-TUY is the same for the 26Oct_12amGMT*mapping.

Using straightline projection of the travel-speed&heading derived from the
ATCF coordinates spanning the 6hours between 6amGMT then 12pmGMT :
H.Rina's travel-speed was 4mph(6.4k/h) on a heading of 304.9degrees(NW)
(303.75degrees is midway between WNW and NW)
H.Rina was headed toward passage over Mosquitero,QuintanaRoo,Mexico ~1day19hours from now

Copy&paste 20.296n87.364w-tuy, 18.187n87.849w-spr, 17.3n83.8w-17.3n84.3w, 17.3n84.3w-17.4n84.6w, 17.4n84.6w-17.5n85.0w, 17.5n85.0w-17.7n85.3w, 17.5n85.0w-19.168n87.543w into the GreatCircleMapper for more info

The previous mapping for 26Oct_6amGMT

* The alteration of the endpoint of a TropicalCyclone's previous path also changes its previous travel-speed&heading, and the endpoint of its previous straightline projection...
...but I'm choosing to preserve the historicity of the previous projections.
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Freeze Warning
Statement as of 3:53 AM CDT on October 26, 2011

... Freeze warning in effect from 10 PM this evening to 10 am CDT

The National Weather Service in Amarillo has issued a freeze
warning... which is in effect from 10 PM this evening to 10 am CDT
Thursday for the west half of the Texas and Oklahoma panhandles.

* Event: temperatures will fall into the 26 to 32 degree range
tonight into Thursday morning across mainly along and west of a
Tyrone to Amarillo to Palo Duro Canyon line.

* Timing: temperatures will fall to 32 degrees or lower by 1 am CDT
tonight northwest of a Dalhart to Guymon line... then across the
rest of the west half of Texas and Oklahoma panhandles by 7 am CDT
Thursday. The lowest temperatures will be between 6 and 9 am CDT

* Impacts: the forecast low temperatures tonight into Thursday
morning will likely result in a freeze. Minor snow accumulations
can be expected as well. Those with outdoor sensitive crops...
plants and vegetation should take action to protect them from sub
freezing temperatures.

Precautionary/preparedness actions...

A freeze warning means sub freezing temperatures are imminent or
highly likely. These conditions will kill crops and other
sensitive vegetation.

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I'm in the HWRF camp of dissipation over the Yucatan. The dry air and shear will start doing a number on Rina later tonight into tomorrow, and the storm will simply be too shallow to be grabbed by the trough.
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Amarillo, TX forecast

Rain showers early in the evening...mixing with and turning over to light snow after midnight. Breezy. Snow accumulation less than 1 inch. Lows in the lower 30s. Northeast winds 15 to 25 mph.
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Thanks Dr. M.
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Cat 6 lead authors: WU cofounder Dr. Jeff Masters (right), who flew w/NOAA Hurricane Hunters 1986-1990, & WU meteorologist Bob Henson, @bhensonweather

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