Upcoming week - October 22-28

[Andrew92]

The following post is NOT an official forecast and should not be used as such. It is just the opinion of the poster and may or may not be backed by sound meteorological data. It is NOT endorsed by any professional institution or storm2k.org. For official information, please refer to the NHC and NWS products.

Evaluating last week

This last week there was one active storm, Rafael. It was not yet a hurricane coming into the week, but I expected it to do so on Monday, and it did. Intensity forecasts peaked this storm at 80-85 mph but appeared to be trending upward as Rafael got better organized a bit faster than previously forecast. Based on that, I went a little higher with my intensity prediction and said Rafael would top out at 85-90 mph on Tuesday, which also happened – the peak intensity was indeed 90 mph. Rafael also began accelerating that day, which I correctly anticipated. I also was accurate in a weakening trend beginning on Wednesday, but the storm remained a minimal hurricane through the day and did not weaken to a tropical storm as I anticipated. In fact, Rafael never weakened like I thought it would, remaining a hurricane until becoming extratropical on Thursday. However, the storm did track north-northeast quickly and passed east of Bermuda, and well southeast of Newfoundland. Really, when looking at this storm, I did a pretty good job predicting what would happen, only incorrect on him not weakening nearly as fast as I thought on the way to becoming extratropical. Even the timing of all of these events with Rafael was nearly perfect.

On top of doing a good job on Rafael, I also correctly predicted no other tropical developments for the past week. One system is getting close in the Caribbean, with another threatening to develop over the open Atlantic, but neither have pulled the trigger just yet. Overall, I had a very decent week, though not quite perfect. Rafael’s lack of weakening trend does hurt but not much. I give myself a low-end A- for this past week.

Could these two new disturbances develop this week? Let’s take a look…

Current situation and models

As mentioned, there are two areas to watch this upcoming week: one in the Caribbean (Invest 99L) and one over the open Atlantic (Invest 90L).

Let’s start with Invest 99L in the Caribbean. This system is beginning to show a nice circulation south of Jamaica, though there is not much deep convection near the center. Still, waters are plenty warm in this area, shear is not very strong, and the air is moist. Therefore, ingredients are there for this system to gradually develop further during the coming days. From there, the GFS and Euro models both show a fairly slow-moving storm heading north, reaching Jamaica late Wednesday and eastern Cuba on Thursday. Both of these models show a fairly steadily intensifying system, not very quickly, but not too slowly either. Once this system passed Cuba and reaches the Bahamas by Friday, the models diverge in track. The Euro takes this system on a west-of-north path through the Bahamas at first as a weaker storm, and then very close to the East Coast during the weekend as a very impressive storm, possible a moderate hurricane. In fact, by Sunday night, this model has the storm right off the Outer Banks with a pressure in the low 980’s, but as a pretty large storm too. On the other hand, the GFS also weakens the storm and then begins to re-intensify it during the weekend, but takes it on a northeasterly track towards Bermuda by Sunday. The GFS has done a remarkably good job this year, but the Euro was closer to being right on the track with Rafael when they diverged early in his life.

Invest 90L does not pose anywhere near the kind of threat that 99L does. It is over open waters, far from land, and is expected by both the GFS and Euro to quickly re-curve northeast. The GFS actually makes this a smallish but potent little storm on its way out to sea, keeping it active through the weekend as it passes south and east of the Azores. The Euro, meanwhile, doesn’t ever make this system much of anything, maybe a weak tropical storm and nothing more.

Nothing else appears to be coming down the horizon for this upcoming week.

Recent history

Since 1960, these storms have formed or were already active in the Caribbean during this upcoming week:

Hattie in 1961
Gilda in 1973 (already active – actually also no longer in the Caribbean, but very close)
Joan in 1988 (already active)
Mitch in 1998
Wilma in 2005 (already active)
Alpha in 2005
Beta in 2005
Noel in 2007
Richard in 2010 (already active)
Rina in 2011

Ten storms have occurred here in this upcoming week during the satellite era. Six of these were newly formed storms, while four developed prior to this week. Of these ten, eight would go on to become hurricanes, and six of them were major hurricanes at some point, even if just briefly. However, most of these storms took westerly paths in either Central America or the Yucatan Peninsula, even if they eventually did re-curve, such as Mitch and Wilma. Storms not reaching these areas, or at least close to these areas, included Gilda, Alpha, and Noel. Gilda was a strong tropical storm as it headed northeast and skirted the East Coast. Alpha never got off the ground as it re-curved near Haiti, but did also have to deal with Wilma to its north, which absorbed it. Finally, Noel did become a hurricane, but not until it had just passed the Bahamas and was about to become extratropical while skirting the East Coast. It also peaked as a very minimal hurricane with winds of 80 mph. However, it did also become a quite intense extratropical storm for the Maritime Provinces later.

Also since 1960, these storms formed or were already active over the open tropical or subtropical Atlantic during this upcoming week:

Helena in 1963
Heidi in 1967 (already active)
An unnamed hurricane in 1970 (already active)
Holly in 1976 (already active)
Kendra in 1978
A subtropical storm in 1979
Grace in 1991
Frances in 1992
Sebastien in 1995 (already active)
Tanya in 1995
Lili in 1996 (already active)
Jose in 1999 (already active)
A subtropical storm in 2000
Lorenzo in 2001
Nicholas in 2003 (already active)

That is a total of 15 storms that have occurred during this upcoming week in these areas. I should note that Kendra and the 2000 subtropical storm also come close to fitting the bill for the type of track that Invest 99L could follow. Kendra briefly became a minimal hurricane, while the subtropical storm peaked as 65 mph. Both of these storms skirted the East Coast.

Of the other 13, seven were newly formed, and seven were previously active. Of these 13, nine either became hurricanes or in the case of the 1979 subtropical storm, gathered winds of that intensity. However, none of these storms hit category 3 intensity during this upcoming week. Lili previously was one near the Bahamas, but was a weaker storm by this point past Bermuda. Failing to become hurricanes were Helena, Sebastien, Lorenzo, and Nicholas. Sebastien and Nicholas did briefly come close with 65-70 mph winds at their peaks, while the other two just never got off the ground. All of these storms generally took re-curving paths to the northeast, only threatening Bermuda and the Azores.

So what does this all tell us?

The Caribbean system is likely to develop further either on Monday or early Tuesday. The type of track that it is likely to follow will not allow it to develop into much it appears, especially if it reaches Jamaica by Wednesday night and Cuba on Thursday. This system will still be a potentially dangerous rainmaker, especially in mountainous areas. A better opportunity to strengthen would be during the weekend over the more open Atlantic, regardless of a northerly track near the East Coast like the Euro, or a northeasterly track out to sea like the GFS. Tracks for storms in this area during this upcoming week are more supportive of the GFS’s solution. However, one must be careful, because the Euro was more accurate on the very recent Rafael’s track more west into the Caribbean. This means the East Coast, from the Outer Banks northward especially, absolutely should be prepared in case this potentially dangerous system heads your way.

Meanwhile, storms in the open Atlantic have a surprising tendency to overachieve when developing under circumstances like Invest 90L’s. The GFS may indeed be onto something by having a small but feisty little system that nonetheless threatens probably only the Azores, and may even pass south and east of there. This system will still probably be no more than a minimal hurricane though as it makes this northeastward track.

The Prediction

Two reliable models are showing quite diverging solutions for both Invest 99L and Invest 90L for this upcoming week. Let’s start with my prediction for 99L. I predict this disturbance will become a tropical depression late on Monday and Tropical Storm Sandy on Tuesday as it heads north slowly towards Jamaica. Sandy will slowly intensify before approaching Jamaica on Wednesday night with winds of about 50-65 mph. By Thursday, she will reach eastern Cuba with a similar intensity. Sandy will weaken over the mountains of eastern Cuba to a 45-50 mph storm over the Bahamas on Friday. Then, Sandy will track north-northeast, skirt the East Coast, and become a hurricane on Saturday through Sunday afternoon, topping out with maximum winds of 80-90 mph. Sandy will be very near Bermuda by the end of Sunday as a strong tropical storm or minimal hurricane, with maximum winds of 65-75 mph. Confidence is 50%, and please, residents of Jamaica, Cuba, the Bahamas, the East Coast, and Bermuda, do NOT treat this as if it is an official forecast! Please turn to the National Hurricane Center for official forecasts, and your local authorities for what to do if this system threatens and/or hits your area. Thank you.

And what about Invest 90L? I predict this system will slowly develop into a tropical depression by Wednesday, and Tropical Storm Tony that evening as well while heading north-northeast or northeast. This storm will continue along that track and briefly become a minimal hurricane on Friday, but weaken back to a tropical storm by Saturday night south of the Azores. Tony will then become extratropical on Sunday. Confidence is also 50%.

Lastly, I predict no other tropical cyclones in the Atlantic during this upcoming week. Confidence is 90%.

-Andrew92

[Andrew92]

Time to evaluate. Wow what a storm we've got!

This past week two tropical cyclones developed, Sandy and Tony, and I predicted them both to occur. Sandy took place originally in the Caribbean while Tony was over open waters, never a threat to land. On that regard, I did a great job on Tony, identifying it is an out-to-sea storm. However, I greatly overestimated its intensity. I thought Tony might sneak in and become a hurricane! It instead only peaked at 50 mph. I was also a good two days off on the timing of this storm, predicting it to develop on Wednesday and dissipate by Sunday; instead, it developed Monday and dissipated on late Thursday to early Friday. So overall, I didn’t do so well with Tony, but I did at least see a disorganized system developing, something I have struggled with a lot in the past.

But the main event for this past week was Sandy. I did a little better overall on this storm, though I was way off again on the intensity portion. The track was overall very-well predicted along with the timing of events. I predicted the Jamaica landfall for Wednesday and the Cuba landfall for early Thursday, which both happened. Sandy did reach the Bahamas a little earlier than I thought, but still took a track that generally skirted the East Coast through the weekend. Yes, I know it is forecast to head inland by tomorrow night or Tuesday, but that’s a different story – the point was I predicted it to be offshore of the United States, though a lot closer to Bermuda than where it is now. So overall, I executed the track well. But I greatly underestimated the intensity. Sandy first became a tropical storm a day before I thought it would, and intensified a lot faster in the Caribbean than I expected. I thought Sandy would be struggling to organize as a moderate tropical storm, but she nearly became a category 3 hurricane, with a pressure definitely supporting that intensity of 954 mb as she hit Cuba. I guess on one front, I nailed her being a minimal hurricane during the weekend, at least by wind speed. But the evolution of Sandy to become as strong as she got prior to then, and [i]weakening[/b] to get there instead of strengthening as I thought would happen knocks this part of the prediction down a couple pegs. That said, my warning was well-advised for Jamaica, Cuba, the Bahamas, the East Coast, and Bermuda, given the immense size of this storm; though I didn’t think about Sandy hitting Haiti either.

Overall, my grade for Sandy is a C+ and my grade for Tony a D+. Sandy was the bigger deal to try to pin down, as Tony was never a threat overall. Therefore, I will indeed give myself a C+ for this past week.

New week coming up shortly. It's a doozy of one.

-Andrew92