Wednesday, August 01, 2012

Tropical Depression 5: August 1, Update A

I am watching a classic oceanographic movie… ‘Jaws’ with a group of friends at the moment (and drinking wine of course). It’s been many years since I saw this film. I’m not sure how many oceanographers were inspired by this movie, but it is a good one!

Our Atlantic blob from yesterday was upgraded to a Tropical Depression at the 5pm (EST) NHC advisory today. It is officially at 12.6N, 50.6W. It’s a messy looking system so I’ll go with this official center for now, although I think it may be a little to the south and east of this location. Central pressure is estimated to be 1008mb, with winds of 35mph. The current forecast track has the system continuing WNW, going over the Windward Islands on Friday afternoon as a Tropical Storm (39-73 mph winds) and reaching Jamaica by Monday afternoon as a Hurricane. I still don’t have very good (high resolution) pressure data which would help in figuring out the track, but this general direction seems reasonable at the moment. I think part of the reason I don’t have good information is because the pressure fields are not very strong at the moment. This suggests that the storm may move a little slower than expected.  

(movie update: man hunting shark now)

Although the Tropical Depression looked stronger during the day it has weakened this evening, in both the convection and the circulation. I agree with the NHC that this is currently a Tropical Depression (which means it has circulation but the winds are less than 39mph). Sea surface water temperatures are a toasty 28-29 deg C, the upper 50m of the ocean is warmer than 26 deg C, and wind shear is pretty weak. These would all help the system to get stronger. However, there is some lovely dry, dusty air to the north and east that is impacting the system. This is called the Saharan Air Layer (SAL) and usually inhibits storm development with dry dusty air blowing off northern Africa (the Sahara Desert in case the name didn’t give that away ;-)). The weakening of the system today means that the storm will not be quick to develop, assuming it survives this part of the journey.      

(movie update: shark winning… boat sinking. umm… I better not say anymore in case you haven’t seen this!).

Meanwhile, interesting things are happening in the far western Pacific! Today both Typhoon Saola (as a strong cat 2 with winds of 105mph) and Typhoon Damrey (as a weak cat 1 with winds of 75mph) went over the southern islands of Japan.  Typhoon Saola, south of Damrey, will pass over northern Taiwan as a cat 1 tonight/tomorrow, and currently has winds of 85mph. They are both heading to China, due to make landfall on Thursday night and Friday morning. Here is a wonderful NASA satellite image of both of these storms:

I’ll be back tomorrow with more! (da-dum, da-dum, da-dum…) ;-)

p.s. movie trivia: ‘Jaws’ was nominated for best picture in 1975, but lost to ‘One Flew Over the Cuckoo’s Nest’. The novel was based on a real shark attack off the coast of New Jersey in 1916. Steven Spielberg told John Williams that the ‘da-dum da-dum’ music wasn’t going to work for the film. John Williams had to convince him that it would be ok. Now it is amongst the most recognized movie music pieces in the world.    

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DISCLAIMER: These remarks are just what I think/see regarding tropical storms - not the opinion of any organization I represent. If you are making an evacuation decision, please heed your local emergency management and the National Hurricane Center's official forecast and the National Weather Service announcements. This is not an official forecast. If I "run away, run away" (Monty Python), I'll let you know.

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