Thursday, October 14, 2010

Sneak Peak

We dodged another bullet with "Paula" weakening and only impacting us slightly with some pockets of rain mainly across the Keys. Central and western Cuba received anywhere between 6-8 inches of rain with isolated spots reporting around 10. But all is not done.

It seems one model is hinting at another system brewing in the Caribbean over the next few days. It will develop in the Central Caribbean in about 120 hours and make a move towards Central Cuba. Let's see if this model pans out.

Check out the link below for the latest model run. Hit forward on the right side of the screen and wait until it runs through 120 hours of data.

Tuesday, October 12, 2010

Paula Power

It appears Paula may be one of the fastest growing storms on record reaching hurricane status in a mere 12 hours. The first advisory was issued on Monday at 5 pm and by Tuesday morning at 5 am it was upgraded to a Category one system. NHC began recording this type of data about 40 years ago and in all that time no system had grown this fast. The closest before was 18 hours with Hurricane Humberto in 2007.

I said it appears Paula managed this feat, that's because by the time the first advisory was issued, NHC had classified it as a tropical storm by-passing depression status all together. Maybe at the end of the hurricane season when NHC looks back at the data, they may include this extra time period and bump it from the top spot. If this happens, it will tie Humberto for fastest intensification.

The big question is where is it headed. Models all agree that a cold front will move into the Gulf over the next few days and push Paula East. Plenty of shear ahead of the front may weaken it as it moves towards Western Cuba.

Five days out models disagree as to what will happen, with some dipping Paula back South into the Western Caribbean, others push it across Cuba, while others take it to the Florida straits. Strength is also an issue. Models hint at a weaker system in 5 days, but it if sits over water for too long, it just may hold on to hurricane status.

Keep watching.

Wednesday, October 6, 2010

Sub Tropical What?

A sub tropical system basically means we have a hybrid storm. It looks like a normal area of low pressure that moves throughout the natiion's midsection, but acts like a warm core tropical low. Its a category for those storms that quite don't fit the typical definition of a Tropical Cyclone.

Here's how NHC defines it:

A sub-tropical cyclone is a low-pressure system existing in the tropical or subtropical latitudes (anywhere from the equator to about 50°N) that has characteristics of both tropical cyclones and mid-latitude (or extratropical) cyclones. Therefore, many of these cyclones exist in a weak to moderate horizontal temperature gradient region (like mid-latitude cyclones), but also receive much of their energy from convective clouds (like tropical cyclones). Often, these storms have a radius of maximum winds which is farther out (on the order of 100-200 km [60-125 miles] from the center) than what is observed for purely "tropical" systems. Additionally, the maximum sustained winds for sub-tropical cyclones have not been observed to be stronger than about 33 m/s (64 kts, 74 mph)).

Many times these subtropical storms transform into true tropical cyclones. A recent example is the Atlantic basin's Hurricane Florence in November 1994 which began as a subtropical cyclone before becoming fully tropical. Note there has been at least one occurrence of tropical cyclones transforming into a subtropical storm (e.g. Atlantic basin storm 8 in 1973).

Subtropical cyclones in the Atlantic basin are classified by the maximum sustained surface winds:

less than 18 m/s (34 kts, 39 mph) - "subtropical depression",
greater than or equal to 18 m/s (34 kts, 39 mph) - "subtropical storm"
Prior to 2002 subtropical storms were not given names, but the Tropical Prediction Center issued forecasts and warnings on them similar to those for tropical cyclones. Since 2003 they are given names from the tropical cyclone list.
For more information see Penn State University's write up on the Subtropical Cyclones.