Hurricane Season 2011 # 4

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TS RINA FACES SERIOUS OBSTACLES- IF IT OVERCOMES THEM, IT COULD BE A REAL PROBLEM

It was exactly six years ago today that we were in the midst of dealing with a powerful hurricane Wilma as it tore through south Florida. At one point, Wilma was the most intense Atlantic hurricane ever recorded. It went on to deal a significant punch to portions of the Yucatan peninsula before moving northeast and in to south Florida where it knocked out power for at least 6 million people, some until near Thanksgiving of that year. My point is- this time of year is climatologically favorable for strong Caribbean hurricanes that can reach land, including Florida. Now, six years later, we have tropical storm Rina in a similar position as Wilma was, tucked in to the northwest Caribbean Sea. Will the final outcome be just as similar or vastly different? Let's take a look at what we know.

First off, the NHC is forecasting Rina to become a hurricane as it approaches the northeast Yucatan later this week. Water temperatures in the region are very warm as is the heat content value. In other words, the water is not only warm at the surface, but also quite deep below the surface so that as the ocean is churned up, more warm water comes to the surface, not cooler water. This provides an incredible amount of heat energy for torpical cyclones and Rina could take advantage of this. On the other hand, there is an obvious lack of vertical instability across the region due to dry air in the atmoshphere. Tropical cyclones need very unstable and moist air to generate the powerful upward motion that leads to convection or thunderstorm activity. I would say that dry air is perhaps a more prolific killer of hurricanes than any other factor. Cold water is a slow process as it has to slowly eat away at away at the energy source. Dry air, especially that is entrained within the circulation itself, can literally deflate a tropical cyclone in a matter of hours, sometimes less. Think back to Irene. It was forecast by some to become an intense hurricane off the North Carolina coast. Instead, dry mid-level air became pulled in to the circulation and down the convection went. Irene never recovered. The NHC mentions this dry air in their latest discussion and if Rina gets involved with that, it will almost certainly mean it cannot strengthen much at all.

On the other hand, if Rina is able to fight off the dry air and create its own moist environment, taking advantage of the very warm water across the region, it could intensify fairly substantially. For what ever reason, this is what the GFDL and HWRF models indicate as both predict a very strong hurricane to materialize. Conversely, the SHIPS intensity model, which is not as robust or dynamic as the GFDL and HWRF models, only shows modest strengthening but not even to hurricane status. Regardless, the NHC's official forecast shows 75 mph in about four days. It is possible that Rina never makes it to that intensity but I caution you too that it is also possible for Rina to be considerably stronger. Remember that intensity forecasts are notoriously prone to errors. This is why it is important to always be ready when a tropical cyclone is heading your way. There was not one model that predicted Ophelia would become a category four hurricane way out in the open Atlantic at 33.8 degrees north latitude. Intensity forecasts were off by as much as 60 knots for Ophelia and it was over only barely warm enough water to even sustain itself. Odds are that Rina will succomb to the hostile October (and seasonal) environment that lies before it. This is not 2005 when everything was perfect from June through January of 2006. So far, the season has produced an overwhelming amount of stable air across much of the tropics. While this could change with Rina, there is little reason to doubt that it will right now.

As far as the track is concerned, a lot depends on intensity. Again, the GFDL and HWRF models show a strong, well developed hurricane coming out of the Caribbean and tracking in to south Florida. The NHC is not buying this scenario right now due to the limiting factors I mentioned above. The global models, specifically the GFS and ECMWF show no impact to Florida. However, interests along the eastern coast of the Yucatan need to follow Rina's progress closely. It is too soon to know with much certainty whether or not the storm will have a direct impact on the region but the current forecast indicates a possible landfall along the northeast coast in about five days. Obviously this can change, and probably will but for now, Rina is a possible threat to land. We'll know more as each day passes and we see how the steering and intensity situation plays out. I wll be very interested to see if the hurricane specific models, the GFDL and HWRF, are correct or if they have lost touch with reality and come no where near being accurate with this situation. It will be an interesting week ahead to be sure.

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Op dinsdag 25 oktober 2011 12:27 schreef aloa het volgende:
Rina is nu een cat2

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Cyclone Keila soaking Arabia
Tropical Cyclone Keila, an unusual visitor to Arabia, will unleash drenching rain as it hovers near the south coast of Arabia for the next day or so.

Flash flooding will be the greatest storm threat to life and property, as Keila's moderate intensity will preclude widespread high winds over land.

In southwestern Oman, Keila has already triggered rainfall of 50 to 100 mm (2 to 4 inches) in the area of Salalah and the port of Raysut. This amount is comparable to a normal year's rainfall. What is more, as much more rain could pelt the area before the storm dissipates along the coast near the Oman-Yemen border.

Tropical cyclones are rare events along the coast of Oman and Yemen. When they have made landfall, they have historically triggered flash flashing, as happened with severe, destructive Tropical Cyclone Gonu in June 2007.

Another cyclonic storm struck Yemen from the Gulf of Aden in October 2008, resulting in severe flooding.