The NHC upgraded the tropical wave west of the Cape Verde islands to Tropical Depression Eight this afternoon. I felt this morning the system was a depression and was surprised it wasn’t upgraded. Truthfully, it looked better this morning than it does now and to say the system has now developed enough sufficient convection to be classified is a slap in the face to those who don’t know better and the same damn crap they pulled with Tropical Storm Marty. Have you seen the satellite loops throughout today? Convection’s been decreasing. At least with Marty they issued a special advisory seemingly when a new shift took over. This time, they waited until the next scheduled release. As if to say, yes, we know there’s a depression out there. But, again, we’re responsible for naming and we’re not going to admit we should have upgraded this earlier even when everyone else says we should have. WTF!
Enjoy TD 8 while you can cause I’ll agree with the NHC on this one: it won’t be around long. And don’t expect it to pull a Fred, either.
Tropical Depression Eight - GOES IR - Sep 25, 2009 20:45 UTC
Seriously, is this what we’re looking at? Is this the “developed sufficient convection and circulation to be designated a tropical depression”? What looks better: the above picture or this below:
Tropical Depression Eight - GOES IR - Sep 25, 2009 12:15 UTC
Look at the spiral banding. Look at the central dense overcast. Look at the cold cloud tops earlier as opposed to now. Developed enough sustained convection??? Append that sentence with six hours ago. Unbelievable.
I know: they mean to say “the system has developed enough sustained convection throughout the day that we’re designating it a tropical depression. But, yea, it looks pretty stick now”.
I’m done. I just don’t get it.
Anyway, the forecast is for a turn north to die. Just like Fred did. Maybe better luck for the next one (which I’ll write about tonight or tomorrow morning).
Wind shear is ok for now but will increase tomorrow as much as 30kts (35mph or 56kph).
As the storm moves north it won’t be long before it encounters cooler SST that will inhibit development.
If TD 8 were to become a storm, it would need to maintain convection throughout the afternoon into the evening. That it is not leads me to think even an overnight burst won’t be enough to lead to naming the system. QuikSCAT doesn’t even indicate strong non-contaminated winds – certainly not the 30kts (35mph or 56kph) the NHC states. But, then again, QuikSCAT is also several hundred miles to the southeast with a surface circulation which is odd. I suppose the NHC discredited both the ascending and descending passes. Who knows, anymore?
{ 2 comments… read them below or add one }
The trend in the convection, of course, is not part of the definition of a tropical cyclone, but rather it is the amount of organization that matters. A key factor in determining convective organization is persistence.There are two reasons why the system wasn’t started this morning. First, the 12Z Dvorak classifications (which are assessments of the degree of convective organization) from TAFB and SAB were both T1.5. While we’ve started systems at T1.5 before, we usually like to see T2.0. Secondly, the QuikSCAT pass at 07Z this morning showed little or no evidence of a fully closed surface circulation in the southwest quadrant (you need to look at the scatterometer ambiguities to see this). It was more suggestive of a trough axis.
By this afternoon, the TAFB Dvorak classification had increased to T2.0. I did not personally see the classification worksheet, but I imagine that the persistence of the banding features had a lot to do with the increased T number (the Dvorak technique, for good reason, has constraints as to how fast the T numbers can increase). Systems that maintain convective structures (e.g., bands) for periods of time are considered to be “better organized” than those that do not.
Even though the overall convective vigor of the system may have been on the decline, there were new cells going off this afternoon – enough to make us feel as though the convective structure would likely persist, at least for a day or so. We also judged that the banding structures and core convection had been present long enough after the 07Z QuikSCAT pass to assume that the system had finally fully closed off a circulation. Based on these judgments, we started it this afternoon.
The comment above from Mr. Franklin was from an email exchange with him earlier. I had asked him:
I appreciate the Mr. Franklin’s time greatly.