Friday, September 13, 2013

Tropical Storms Humberto and Ingrid: September 13, Update A

It’s Friday the 13th!... and what a crazy long week this was! Definitely time for a second glass of wine. And possibly a bit of fried banana cheesecake with vanilla ice cream. Yum yum! :-) I‘m going to ignore the (now) low pressure formerly known as Gabrielle because I can (she’s bringing some splotches of rain to Canada) and we’ll move straight onto the other two. It seems like the only sensible thing to do.

Tropical Storm Humberto

He took a rapid nose-dive today and is now a weak Tropical Storm with winds of 45mph, estimated central pressure 999mb (TS range: 39-73mph). He is at 24.8N, 33.0W, heading on the forecasted track of W at 9mph. It looks like the wind shear, cooler sea surface temperatures (24 deg C) and dry air all took their toll. You can just about see him in this infrared satellite image of the Atlantic:

There is no convection to speak of (nothing in the oranges or reds)! He still does have circulation in the lower half of the troposphere but nothing in the upper troposphere anymore, which is what we expect for a Tropical Storm. And as you all know about vorticity (circulation) because you all read and memorized my entry yesterday (didn’t you? ;-)), you can see his circulation for yourself! Here is the vorticity ‘map’ (University of Wisconsin) from the upper level of the troposphere:

Comparing this to the plot from yesterday (when he was a hurricane):

you can see the signal that was in the upper levels of the troposphere has vanished. However, as I said, he still does have circulation in the lower half of the troposphere as you can see in the vorticity from the middle of the troposphere:

Given the circulation, but no convection, I think even 45mph may be a little over-estimate. The NHC have him strengthening and becoming a hurricane again next Wednesday. I don’t see this happening – the waters will remain cool, there is still dry air and wind shear. I don’t know if he will survive much beyond tomorrow actually.        

Tropical Storm Ingrid

This one is a little tricky! I see the Tropical Storm designation of Ingrid as more of a conflict between people underestimating nature and scientific accuracy.  Officially she is at 19.2N, 95.2W, and is stationary. Her winds are officially at 60mph (central pressure 993mb), which makes her a mid-intensity storm. She may have been a Tropical Storm for a few hours today, but I am not fully convinced and she’s definitely not one now. Today she has been partly over warm water and that is generating a lot of convection, including some strong thunderstorms (which we see in the summer months in the tropics anyway) with strong winds. She also does have some circulation, but it hasn’t really been as fully isolated as we see in tropical storms – e.g. Humberto. As you can see from the vorticity in the middle of the troposphere (above), she is now well and truly part of a line of vorticity that extends into the Pacific, so she really isn’t a tropical storm in structure at all!

The reason I say this is a tricky one is because there is certainly a lot of strong convection (thundery weather) because of the warm water, so I’m sure there are areas of strong wind. Keeping her at the Tropical Storm designation is probably for the best in terms of alerting people in Mexico to the stormy weather, however speaking with my science hat on, I would have to disagree with this designation.

That’s it for now!
Toodle pip!

Blogs archived at
Twitter @JyovianStorm

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.

No comments: