Upcoming week - July 2-8

[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

Last week was, to date this season, my lowest confidence prediction. There was good reason behind that, as Tropical Storm Debby was meandering in the Gulf of Mexico and numerous models gave various solutions for what she might do. The Euro insisted on some sort of a westward turn, as did the HWRF. The Canadian model trended eastward, but not as far as the GFS. These models also practically stalled Debby over the Gulf of Mexico for several days. The GFS never really deviated from its stance, taking her into Florida, before any of the other models, and then off the East Coast out to sea. The GFS did the best job out of all the models… and fortunately for me was the model I generally sided with! In picking that model, I made out a not perfect, but very good, weekly prediction on one of very low-confidence.

Let’s run through. First, I predicted Debby to strengthen no further than where it was already at 60 mph, due to dry air entrainment and shallower water as she approached Apalachee Bay on Monday; all of this happened. The landfall location was also inside my tight window of between St. Marks and Cedar Key. I even predicted weakening before landfall on Tuesday evening. Landfall occurred at the 5 PM advisory on Tuesday evening, with maximum winds of 40 mph (I predicted 40-50 mph). Therefore, this was also nailed to near perfection. Rainfall primarily, but also tornadoes and beach erosion did remain major effects from Debby until she passed through Florida. Now there were a few minor holes in my prediction. First, I predicted Debby to weaken to a tropical depression on Wednesday, but it happened Tuesday night shortly after landfall. I also predicted Debby to re-emerge into the Atlantic over Georgia, instead of near St. Augustine, Florida. Finally, I predicted Debby to become extratropical on Thursday, but she de-generated into a low on Wednesday evening instead. Given that the difference between my predictions and what actually happened with these parts was barely off in all cases, and with minimal effect overall, this was still a very well put-together prediction. This is especially when considering Debby was a very difficult storm for many professionals and models, let alone an amateur like me, to predict.

On top of doing very well on a low-confidence prediction with Debby, I correctly predicted no other tropical developments elsewhere. There was Invest 97L, but it has since faded, and Invests do not count as developments anyway. My prediction wasn’t perfect, but the errors were pretty minor in the grand scheme of things. I have had some low-confidence predictions before, and many did not fare well. However, this one is probably my best one yet. My grade for this past week is an A-.

Now that’s a great way to get back on track after a rough week. Let’s keep it going!

Current situation and models

The Atlantic is quiet as a mouse right now. There are currently no areas of organized thunderstorms threatening to develop in the next few days. Don’t get me wrong, there are tropical waves, but none are doing anything appreciable towards developing further anytime soon. The NOGAPS has tried to develop one of the tropical waves, but is getting no support from any of the other models. There are a couple of low-pressure areas next to each other, one over the Carolinas and one over Georgia. However, thunderstorms from these areas appear to be more related to daytime heating, and would need a few days before developing into anything tropical or subtropical. The GFS seems to indicate this will merge into a front. No model suggests any type of tropical or subtropical development this upcoming week.

Recent history

Since 1960, these storms have developed or occurred in the first week of July:

Becky in 1966
Arlene in 1971
Alice in 1973
Amy in 1975 (already active)
Ana in 1991
Alberto in 1994
Barry in 1995
Bertha in 1996
Ana in 1997
Claudette in 2003
Cindy in 2005
Dennis in 2005
Bertha in 2008

That is now 13 storms in the satellite era, averaging out to one every four years or so. It has been four years since the last storm developed during the first week of July though, Bertha. Of these 13 storms, a surprising seven went on to become hurricanes! Those storms were Becky, Alice, both Bertha’s, Claudette, Cindy, and Dennis. However, one storm, Claudette in 2003, became one at a later date; this storm was actually just starting to develop in the Caribbean on July 8. I would have also mentioned Alex in 2010, but it was onshore and weakening at this point. In addition, Arlene, Amy, Alberto, and Barry all topped out at 65-70 mph, coming close to hurricane intensity. Only the two Ana’s were weaker storms overall, something in that name perhaps?

Also interesting is that seven of these 13 storms developed from frontal systems off the East Coast: Becky, Arlene, Alice, Amy, both Ana’s and Barry. But only two of these storms, Becky and Alice, became minimal category 1 hurricanes; the rest all came short, especially the Ana’s. Also, with the exception of Arlene and Barry, all of these storms formed in what are usually defined as El Nino years.

The other six storms all formed in the deep tropics; interestingly, two storms each formed in the Gulf of Mexico, the Caribbean, and the Main Development Region. Alberto and Cindy formed in the Gulf of Mexico and took northerly paths; Alberto into the Florida Panhandle as a strong tropical storm, Cindy into Louisiana as a category 1 hurricane. Claudette and Dennis both formed in the Caribbean with both becoming hurricanes; Dennis even became a highly unusual category 4 hurricane, while Claudette eventually “only” became a category 1. Finally, both Bertha’s developed fairly close to the African coast and would go on to become category 3 hurricanes for short periods of time. Both followed classic re-curving paths; the 1996 version though would not do so before hitting several land areas such as the Lesser Antilles and North Carolina, while the 2008 version was briefly a threat to Bermuda and that was it in terms of land. To go a little off-topic, the 2008 version of Bertha is also the longest-lasting July storm on record.

Of all six of those storms, only Alberto formed in an El Nino year. It also formed almost coincidentally about where Debby was this past week. The other three storms were all in generally neutral years, though 2008 was a La Nina up to about when Bertha developed.

So what does this all tell us?

Historically, there’s a 50/50 chance roughly of having tropical development off a frontal system or from a tropical wave. However, 2012 is likely to go down as an El Nino year, so development would be more likely to come from a frontal system. This also diminishes the odds of any such storm becoming a hurricane, and even if it happened, would likely only be a category 1 storm. Still, Chris was briefly a hurricane just a couple weeks ago in a similar area, so that idea can definitely not be ruled out. Tropical waves, however, tend to struggle with more hostile conditions during El Nino years like this one, so it’s no surprise that though some are trying to develop, they simply cannot get off the ground. Only Debby has so far, and proved to be an underachiever in terms of wind intensity.

The prediction

Putting it all together, the most likely scenario for any tropical development in my opinion would be from a frontal system off the East Coast. The system emerging off the Carolina coast would be a viable candidate if the thunderstorms that formed today can persist over the next couple of days. The GFS thinks this will merge in with a front, though. No other reliable model foresees this possibility for tropical or subtropical development this upcoming week; but no models predicted storms like Bret, Cindy, or Franklin last year, which formed under similar circumstances. If it did form, it would likely head quickly out to sea, maybe as a brief threat to Bermuda, but be a moderate tropical storm at its peak and lasting no more than two or three days. But I just don’t see it happening this time. I predict no tropical or subtropical activity this upcoming week. Confidence is 85%.

-Andrew92

[thetraveler]

Very nice history lesson and nice synopsis. Have a great evening.

[Andrew92]

Since nothing is imminent in the Atlantic tonight, let's evaluate.

The only remote possibility I could find for any kind of tropical or subtropical activity for this past week was from some type of frontal system off the East Coast. There was a low pressure system emerging over the ocean off the Carolinas which might have look enticing. However, no models foresaw it developing tropically, and the thunderstorms that did develop were primarily from daytime heating. When putting these together, it was just too hard to imagine such a system developing into something with a warmer core. With nothing else looking to develop, I simply called for no activity for the week. That is just what happened, so my grade for this past week is an A.

New week coming up shortly.

-Andrew92