At 5 pm, the National Hurricane Center reported the formation of Tropical Depression 9. Per earlier discussions, I expect TD 9 will develop into a hurricane and possibly a major one.

Historical climatology (1950-2004) applying the position at which TD 9 formed and storms that formed within +/- 2.0° latitude and +/- 3.0° longitude in August is very consistent with that which used the Invest.95L point of origin:

Total storms: 11
Hurricanes: 9 (82%)
Major hurricanes: 5 (45%)
U.S. landfalls: 3 (27%)

Among the pool of above storms are Hurricane David (1970), Hurricane Andrew (1992), and Hurricane Frances (2004).

Trivia: There was a previous storm named "Irene" that formed in the general vicinity in which TD 9 developed: Hurricane Irene (1981). That hurricane formed in September and reached Category 3 status, but did not make U.S. landfall.

Conclusion: TD 9 should grow into a hurricane and possibly a major one. Although odds currently lean against Caribbean/U.S. landfall, there remains a real possibility of such landfall. The modeling could well trend to the south and west over time.

so you think this could be a threat? i am thinking if harvey slows and intensifies, it will make irene more likely to recurve

Rainstorm,

It's a little early to pin down with a good degree of certainty whether TD 9 (future Irene) will actually threaten, much less make U.S. landfall. Historically, 25%-30% of tropical depressions/tropical storms passing through the general vicinity made such landfall. So, the landfall threat is probably low to moderate at this point in time.

If the system slows, there could be increased opportunity for such landfall as Harvey's weakness erodes. Right now, I believe this system will probably track along the southern envelope of the model guidance for the next day or so--the models might well trend south and west over the next few days.

Finally, TD 9 should become a tropical storm, probably at some point on Friday, and then eventually a hurricane.

This system is not impressing me tonight.

TD 9 Resuming West-Northwest Track

Over the past 6 hours, TD 9 has taken a 285° trajectory (west-northwest). That is in contrast to the overall northwest movement over the past 12 and 24 hours:

TD 9's Trajectory:
Period ended August 5, 2005, 5 pm:
24-hours: 312° (northwest)
12-hours: 309° (northwest)
6-hours: 285° (west-northwest)

Overall, I believe TD 9 will take a generally west-northwest to sometimes northwest course over the next several days. Some of the model guidance begins to diverge dramatically over the medium-term. The 8/5/2005 12z run of the ECMWF tends to take TD 9 on a mainly westerly/west-northwesterly track near and after 5 days. My initial estimate for TD 9's track through 55.0W leans on the ECMWF for the medium-term. Hence, I chose to maintain a generally west-northwest track through that point rather than starting significant recurvature. In coming days, a better idea should be in order.

Estimated Track (increments of 5.0° longitude):
17.5N 40.0W
19.9N 45.0W
21.9N 50.0W
24.2N 55.0W

Finally, as TD 9 had tracked and/or had its center located almost 4° farther to the north than yesterday evening, its development will likely be slower than anticipated due to somewhat cooler SSTs. Nonetheless, I do not believe its development will be denied. I still believe it should become a tropical storm and then later a hurricane.

Thanks for the good work Don. I think that this system will slowly become better oreganized. With the new convection starting to fire to the south.

probably will be a cane

TD 9 Slowly Strengthening

TD 9 has maintained a general west to west-northwest track over the past 24 hours and is now situated at 17.9N 42.3W. Such a trajectory is increasingly likely to continue through 55.0W to 60.0W longitude.

Trajectory of TD 9:
6 hour increments for the period ended at:

August 5, 2005 5 pm: 285° (west-northwest)
August 5, 2005 11 pm: 288° (west-northwest)
August 6, 2005: 5 am: 274° (west)
August 6, 2005: 11 am: 285° (west-northwest)

Given its motion and the latest model guidance, I have made some revisions to my initial track and continued a general west-northwest movement to 60.0W longitude. Some models have hinted at more substantial recurvature commencing prior to 60.0W, so that's a situation that will bear watching.

Estimated Track (increments of 5.0° longitude):
18.8N 45.0W
20.5N 50.0W
22.5N 55.0W
25.5N 60.0W

TD 9 will likely become a tropical storm in less than 24 hours. Later, things remain on track for development into a hurricane.

great work, don. it looks like td9 has shifted north once again

Morning thoughts...

As Rainstorm noted, at 5 am, TD 9's center was again relocated to the north to 19.6N 44.7W.

In spite of substantial shear to TD 9's north and east, the system has persisted and appears to be developing increased convection. As TD 9 continues to move slowly away from the upper level low that has bedeviled it, it should be moving into an environment with gradually relaxing shear. At the same time, the hurricane heat content of the waters over which it should be passing should be increasing.

As a result, I believe TD 9 will likely become a tropical storm later today and then a hurricane down the road. The track remains the same as that from last evening.

Estimated Track (increments of 5.0° longitude):
19.6N 45.0W
21.3N 50.0W
24.0N 55.0W
27.5N 60.0W

thanks don. any chance it becomes absorbed by the ull?

Rainstorm,

I don't believe Irene will be absorbed by the ULL. I do believe it will eventually recurve and avoid U.S. landfall. Today's run of the ECMWF (12z) offers added confidence in such an idea.