[donsutherland1]

This morning, Tropical Depression 4 formed at 12.0N 31.6W. Historically, August tropical cyclones that have formed in the region bounded by 10.0N-14.0N/26.6W-36.6W have gone on to become hurricanes in 9/11 (82%) cases. 8 of those 9 (89%) tropical cyclones that grew into hurricanes reached Category 2 status or stronger. 4 of those storms became major hurricanes, including David (1979), Andrew (1992), and Frances (2004) which ultimately made U.S. landfall.

Overall, just 3/11 (28%) of the storms that formed in the above vicinity made U.S. landfall. All made initial U.S. landfall on the Florida peninsula. In addition to those landfalling storms, there was a cluster of storms that recurved sharply (e.g., Humberto in 1995) or came westward and then recurved just before landfall (e.g., Irene in 2005). The evolving synoptic pattern appears to rule out a sharp early recurvature. Given the general consensus in the modeling and ensemble guidance, I believe TD 4 will likely take a David-esque track for the next several days. This track is well-supported by the tropical modeling.

http://img.photobucket.com/albums/v327/donsutherland1/td408132007.png

Afterward, it could pose a threat to the Caribbean region. It should be noted that August storms that develop in the vicinity where TD 4 was born have not historically passed south of the Caribbean Islands to Mexico. Hence, while some possibility exists for such a scenario, I believe that it is more likely that TD 4 will eventually pose a Caribbean threat. Then, whether or not it turns toward the USA will remain to be seen.

Finally, initial development could be modest. However, in 2-3 days, the development could accelerate as TD 4 finds itself over 28°-29°C waters, upper ridging and relaxed shear.

All said, I expect TD 4 to grow into a hurricane in the future (probably Category 2 at its peak). It should approach the Caribbean prior to any attempt at recurvature, taking a David-esque path for the next several days.

[gkrangers]

Welcome back.

[~Floydbuster]

Peak Category 2 storms are rare. There have been more Category 3 storms than there have been Category 2 storms....as they tend to either no strengthen beyond Category 1 or strengthen all the way to major status.

[Austin]

Good write up Don.

[inkedmagazine]

donsutherland1, on Aug 13 2007, 01:04 PM, said:

All said, I expect TD 4 to grow into a hurricane in the future (probably Category 2 at its peak). It should approach the Caribbean prior to any attempt at recurvature, taking a David-esque path for the next several days.

I was with you up to here. If there no shear and plenty of warm, un-disturbed water in its path, there's no reason why this storm can't become a Cat 3 or greater.

I expect this storm to pass south of Florida and then into Texas.

[rowjimmy]

inkedmagazine, on Aug 13 2007, 04:40 PM, said:

I was with you up to here. If there no shear and plenty of warm, un-disturbed water in its path, there's no reason why this storm can't become a Cat 3 or greater.

I expect this storm to pass south of Florida and then into Texas.

can you give better reasoning mr inked? perhaps some sound meteorlogical reason other than if/then. plenty of factors other than shear water temp

[40/70 Benchmark]

inkedmagazine, on Aug 13 2007, 04:40 PM, said:

I was with you up to here. If there no shear and plenty of warm, un-disturbed water in its path, there's no reason why this storm can't become a Cat 3 or greater.

I expect this storm to pass south of Florida and then into Texas.

Don always starts conservative and then builds up if necessary, he perfers to err on the side of caution, he does the same with snowfall.

[Cheeznado]

inkedmagazine, on Aug 13 2007, 04:40 PM, said:

I was with you up to here. If there no shear and plenty of warm, un-disturbed water in its path, there's no reason why this storm can't become a Cat 3 or greater.

I expect this storm to pass south of Florida and then into Texas.

As per my post here: vis a vis the climo:

http://www.easternuswx.com/bb/index.php?sh...p;#entry2056932

this is quite unlikely- at least the TX landfall part.

[GaWx]

~Floydbuster, on Aug 13 2007, 01:12 PM, said:

Peak Category 2 storms are rare. There have been more Category 3 storms than there have been Category 2 storms....as they tend to either no strengthen beyond Category 1 or strengthen all the way to major status.

I'm assuming that one thing that contributes to the relative lack of cat. 2's vs. cat. 1's and cat. 3's is simply that the range for a cat. 2 is only 15 mph (96-110 mph range) vs. 22 mph for cat. 1 (74-95 mph) and 20 mph for cat. 3 (111-130 mph). This means that the range for cat. 2's is ~1/3 smaller than that for cat. 1's and 1/4 smaller than that for cat. 3's.
I'm not saying that is the only factor, but I don't think it can be ignored as a fairly significant factor.

[LColonels]

Welcome back, Don! Nice post, as always! I was hoping you'd post something of this nature on the board!

As far as the analysis of his projections, don't dismiss the Cat. 2 possibility. If it is slow to develop, then perhaps it might not be a very strong hurricane as it enters the Caribbean. And storms that enter the Caribbean at this time of the year have to fight many things to remain strong, let along grow stronger. And there are some islands with formidable mountains there, too, such as Puerto Rico and especially Hispaniola. They could severely disrupt the circulation of any storm. So, perhaps it's ramping up just about the time it nears these islands, which would then top off the development curve for a time.

After that, of course, it could easily regenerate with all that bath water in front of it. But, historically speaking, it's not common for a storm to go through those island and come back as strong afterward.

Then again, maybe the storm goes well north or south of P.R. and Hispaniola. Then I'd doubt category 2 would hold it...

[donsutherland1]

Thanks Joe. I agree with your point concerning Dean's strength if it can largely avoid Puerto Rico and Hispaniola. Then, it wouldn't surprise me to see a major hurricane.

[donsutherland1]

Over the last 24 hours TD 4 strengthend into Tropical Storm Dean and maintained a David-esque trajectory (268°). That track is likely to continue for the near-term. As a result, I continue to believe that Dean could pose a threat to the Caribbean within 5 or 6 days. As it approaches the Caribbean, it could take on a more northward trajectory, but a distinct possibility remains for it to perhaps add back to its westerly component for a time afterward if the 8/14 0z run of the ECMWF is correct in depicting high pressure stretching from roughly southern Ontario to southeast New England works out and a weakness in the ridging temporarily closes.

In terms of Dean's intensification, I believe it will gradually intensify through tonight. Later tomorrow its rate of intensification could begin to pick up, especially when Dean moves into 50°W-55°W region. In that vicinity, there is an area of superwarm water with SSTs in the 29°C-30°C vicinity.

As for my estimated track, it is as follows:

11.7N 40.0W
11.8N 45.0W
12.0N 50.0W
13.3N 55.0W
15.0N 60.0W
17.5N 65.0W
20.0N 70.0W

[donsutherland1]

At 11 am, Tropical Storm Dean was centered at 12.4N 46.0W. Dean’s maximum sustained winds had increased to 60 mph.

Since 1851, 14 tropical storms or Category 1 hurricanes passed within 100 nautical miles of Dean’s 5 a.m. position (12.2N 44.2W). 3 (21%) recurved. The present and forecast synoptic pattern all but rules out such a prospect. 6 (43%) of those storms later made U.S. landfall. One (Hurricane #3 in 1899) made North Carolina landfall. The synoptic pattern all but rules out that prospect, as well. 4 of the storms made initial landfall in Florida, though Andrew later made second U.S. landfall in Louisiana. Increasingly, I believe Dean’s initial David-esque track will take it too far to the south to pose a direct Florida landfall threat. That leaves the issue as to whether Dean will turn into the Gulf of Mexico or maintain its general westward trajectory toward the Yucatan and Mexico.

The latest NCEP ensemble mean 500 anomalies forecast for 144 hours and 168 hours suggest a general westward track is plausible.

NCEP Ensemble 500 mb Anomalies (144 hours):
http://img.photobucket.com/albums/v327/donsutherland1/gfsens081520070z144h.gif

NCEP Ensemble 500 mb Anomalies (168 hours):
http://img.photobucket.com/albums/v327/donsutherland1/gfsens081520070z168h.gif

The 8/15 0z run of the ECMWF and 6z run of the GFS are reasonably consistent with that option. As a result, I believe Dean’s endgame is becoming clearer. In my opinion, Dean’s most plausible tracks will likely fall between those of Hurricane #2 (1903) and Hurricane Frederic (1979). There is a distinct possibility it could pass south of Hispaniola and south of Cuba.

In terms of its peak intensity, almost all of the storms that grew into hurricanes and did not recurve prior to landfall peaked at major hurricane status. Seven storms met that criteria. Six (86%) reached major hurricane status. At this time, given the synoptic picture with regard to Dean’s track, likely decrease in shear, modeling, and historic experience, I now believe that Dean will ultimately become a major hurricane. Dean’s rate of intensification should begin to increase by the time it reaches 50°W-55°W and its forward speed slows.

Given last season’s tendency for underdevelopment relative to the modeling, I’m still not inclined to go toward the stronger solutions from the historic data, but will note that a number of the storms peaked at Category 4 or above from the above-noted set of tropical cyclones, including David (1979), Frederic (1980), Andrew (1992), and Frances (2004).

Estimated Track:

13.0N 50.0W
13.5N 55.0W
14.5N 60.0W
15.5N 65.0W
16.5N 70.0W
17.5N 75.0W
19.3N 80.0W
20.3N 85.0W
21.5N 90.0W

Finally, as for TD 5 (likely Erin at landfall), I believe that storm will move ashore in south Texas with maximum sustained winds of about 50 mph.

[HurricaneJosh]

Great analysis, Don! And I respect you putting yourself on the line with such an extended-- and speciific-- forecast track. I still remember how well you did with Wilma 2005. ;)

My chief takewaway from your discussion is that a big Yucatan landfall is a distinct possibility. Interesting.

I'm curious if-- in your scenario-- the cyclone will start to feel more of a poleward pull once it clears the Yucatan and gets into the Gulf, but I won't dare ask. It would be greedy, given how far out your forecast already goes. :D

[donsutherland1]

Thanks Josh.

Right now, I'm thinking Dean will probably make Yucatan landfall and then proceed toward another landfall in northeast Mexico or perhaps south Texas. I have less confidence in the latter landfall.

Best wishes.

[summer1]

Josh, Hey head to Club Med in Cancun and get some PICS!!

[donsutherland1]

At 11 pm, Tropical Storm Dean was centered at 13.1N 50.2W. Throughout the day, it has maintained a general west to somewhat north of west trajectory.

6-Hour Trajectory:
Period ended:
11 am: 275°
5 pm: 287°
11 pm: 270°

This general motion is likely to continue through the near-term. At the same time, Dean is now passing over waters with surface temperatures in the 28°C-29°C range. Its rate of intensification should pick up and it should become a hurricane on Thursday. Already, its maximum sustained winds are 70 mph, so not much intensification is required to reach hurricane status.

Estimated Track:
13.0N 50.0W; Actual: 13.1N 50.1W; Error: 6.9 miles--11.5 hours in advance
13.5N 55.0W
14.5N 60.0W
15.5N 65.0W
16.5N 70.0W
17.5N 75.0W
19.3N 80.0W
20.3N 85.0W
21.5N 90.0W

[HurricaneJosh]

Thanks, Don! I see you're holding pretty steady there with the track prediction. I also see that you're calling for a direct hit on Cancun and Cozumel.

What are your thoughts-- if any, at this point-- Re: the cyclone's intensity as it approaches the Yucatan?

summer1, on Aug 15 2007, 11:26 AM, said:

Josh, Hey head to Club Med in Cancun and get some PICS!!

I will-- and video, too. :)

[blade]

I Think Dean Will Make Landfall At Washington Dc

[jrodd321]

blade, on Aug 16 2007, 12:24 AM, said:

I Think Dean Will Make Landfall At Washington Dc

Me too.