Upcoming week - August 2-8

[Andrew92]

Evaluating last week

I predicted no tropical cyclone development and no real players to talk about until Saturday. Well, they came late Friday, but being off by a few hours is not a bad thing. Despite my prediction for no new development, an African wave was thought to be watched by the end of the week for potential development, or at least into becoming an invest. That is exactly what happened, the invests as it turned out were declared, but no further development....yet. A nice, easy, quiet week comes to an end and my grade for last week is an A.

Can I keep it up this new week? Let’s see!

Current situation and models

Invest 91L looks well on its way to becoming a tropical depression in the Main Development Region (MDR). Almost all models also support the development of a tropical storm from this disturbance early this week and then moving toward the Lesser Antilles, mostly the Leeward Islands. If this such storm cruises further south into the Caribbean, there is speculation of a chance of a hurricane. If it veers north to the Leeward Islands or north, it may weaken due to a Tropical Upper Tropospheric Trough (TUTT), which produces heavy shear that disrupts and, in some cases, even dissipates decent looking storms.

Another disturbance is about to cross Nicaragua. This was mentioned even in the previous prediction and I mentioned this was highly unlikely to develop, and that remains the case now. No models develop this system either.

Elsewhere, no other development appears imminent this week, per looking at the models.

Recent history

Since 1995, eight new tropical storms have developed during this week:

Felix in 1995
Alberto in 2000
Barry in 2001
Bertha in 2002
Cristobal in 2002
Harvey in 2005
Irene in 2005
Edouard in 2008


Five of these eight came from tropical waves, with three forming off the coast of Africa (Felix, Alberto, and Irene), one in the Gulf of Mexico (Barry), and one south of Bermuda (Harvey). Only one storm of this bunch, Alberto, actually became a hurricane during this week. However, Felix and Irene became hurricanes in later periods, but I’ll discuss that more next week for Felix and the week after for Irene. Of the three frontal low developers, two formed in the Gulf of Mexico (Bertha and Edouard) and one formed off the Southeast coast (Cristobal). None of these three storms became hurricanes, though Edouard came close with 65 mph maximum sustained winds before making landfall in Upper Texas.

Felix, Alberto, and Irene generally followed similar paths to the west-northwest during this upcoming week. Barry meandered erratically in the Gulf of Mexico. Harvey followed a path typically taken by subtropical storms or storms forming from frontal lows. Bertha and Edouard took somewhat similar paths, though Edouard got stronger because it didn’t make landfall in Louisiana and then emerge, which Bertha did – hindering her intensity. And Cristobal meandered erratically for a couple of days before heading harmlessly out to sea.

I would also like to point out that the tropical depression that would eventually become Bonnie developed this week in 2004, but was not yet a tropical storm as the week ended. This came from another tropical wave, forming near the Leeward Islands before opening back into a tropical wave shortly after entering the Caribbean Sea. By week’s end, it was back to being a tropical depression as it entered the Gulf of Mexico.

In addition, there were four storms previously intact coming into this week:

Erin in 1995
Alex in 1998
Alex in 2004
Chris in 2006

Completely forget the 1998 edition of Alex. It dissipated mere hours into this upcoming week and never re-developed. We, therefore, had essentially three previously intact storms. Erin made landfall about two hours into the new week on August 2 near Vero Beach, Florida. It temporarily weakened to a tropical storm before reaching the Gulf of Mexico, where it re-intensified to a borderline C2 hurricane before making landfall near Pensacola. Likewise, 2004 Alex became a hurricane as it neared the Outer Banks, even becoming a C2 as it veered just offshore, though close enough to bring C1 force winds onshore. Then, after at first appearing to weaken, it hit the favorable Gulf Stream waters and became a surprising C3 hurricane north of 35 degrees! As for Chris, what looked like an impending disastrous storm was shut down by strengthening shearing conditions, ultimately causing the storm’s demise on August 3. 2006 was an El Nino year, but Alberto in 2000 (not an El Nino year), after becoming a hurricane during the week, weakened to a tropical storm due to similar shear as the week ended.

So what does this all tell us?

Invest 91L is in a favorable spot to develop. It still doesn’t happen very often, but the years it does also have made for some active hurricane seasons in recent years. A west-northwesterly path would likely be favored, as the Azores-Bermuda high is usually not strong enough to keep storms from moving on that general path or recurving. Even the depression that would become Bonnie in 2004 was, at one point, favored by models to head north after initially developing. The Gulf of Mexico, though, cannot be overlooked, but storms that develop there almost never become hurricanes – in fact, I looked at every hurricane season since 1886 and cannot find a single one that developed into a tropical storm between August 2-8 and became a hurricane there this same period. There were, however, a few close calls, notably Celia in 1970.

Alberto, the only new storm to become a hurricane this upcoming week, only became a C1 during this week. (It did, of course, become a C3 later). But Erin was at least almost a C2 and 2004 Alex became a C3, albeit in an anomalous location. In a more realistic location, however, Alex was still at one point a C2.

Back to looking ahead

It is almost a foregone conclusion that Invest 91L is going to develop into a tropical depression on Monday. Beyond that, this is a challenging prediction. Most models tend to take the storm toward a more northerly track toward the Leeward Islands – also suggested by recent climatology. But the intensity is a little problematic. While there are no current conditions looming immediately ahead of 91L, a strong TUTT taking hold is suggested by models, and Alberto in 2000 weakened from a hurricane to a tropical storm under similar conditions along a similar path forecast by 91L. I actually tend to think that Alberto could be a decent analog for this system, at least during this upcoming week.

Looking elsewhere, I do not see the Nicaraguan system developing. It should move over land with only a rain threat and no development. And while the GOM is a suggested area historically, I do not seen any model forecasting development there.

I predict Tropical Depression #4 will develop Monday morning from Invest 91L and become Tropical Storm Colin later that evening. The storm will then move west-northwest throughout the week toward the Leeward Islands and briefly become a C1 hurricane with maximum sustained winds of about 75-85 mph by about Thursday. A decent TUTT at about the end of the week will then cause Colin to weaken to a tropical storm as it then veers north of the islands around Saturday. By week’s end, the storm will have maximum sustained winds of about 50-60 mph.

Elsewhere, I predict no tropical cyclone development.

Confidence is 70%.

-Andrew92

[Andrew92]

Oh dear, this is looking bad! I wish I'd have gone with Irene as the analog for Colin and not Alberto.

-Andrew92

[NOLA2010]

Oh dear, this is looking bad! I wish I'd have gone with Irene as the analog for Colin and not Alberto.

-Andrew92

yeah so much for a Cat. 1. Also, if 92L develops by the end of the week, you would be wrong there to.


Keep up the good work though

[Andrew92]

Hmmm....on the bright side, I predicted the depression to develop on Monday so that's a point. About the only one, but hey I'll take any remote victory I can get this week right about now.

-Andrew92

[Andrew92]

Let's evaluate, get it over with....

Not a good week, mostly in predicting the life of Colin. What was I thinking, that Colin would become a hurricane? It also moved significantly faster than forecast early on, and was already to Bermuda by week's end! Oof....

But looking a little beyond, there are a couple of silver linings. On the one hand, I was spot-on for development of the tropical depression, and very close to it becoming Colin, at least initially. Yet, the fact that it degenerated so quickly makes me wonder if a post-review on the Tropical Cyclone Report will have no tropical storm intensity for that section. This has happened before, with Tropical Storm Chantal in 2001.

However, I did also predict no other developments during the week, and that was predicted rather accurately.

But given how badly I blew my forecast for Colin, I have no choice but to give myself a big, fat F for the week.

-Andrew92

[JonathanBelles]

I very much appreciate that you admit that you were off for this week, although I would probably give you a B for the week. Colin was a hard storm to forecast especially in the end.