Watching 97L for Development

Posted By: Marty

Watching 97L for Development - 09/02/13 10:35 AM

A tropical wave identified as Invest 97L by forecasters is now over the islands of the Lesser Antilles. The wave is moving westward at 15 miles per hour. Forecasters believe that a number of factors are prohibiting development of the system at this time; but conditions will become more favorable by midweek when the tropical wave reached the central Caribbean Sea.

97L a Future Threat?

Since my last tropical blog, Erin and Fernand came and pass away and we have been in historic streak of no hurricane for this year. September 11th is the record for the latest storm to form for the year which belong to 2002 season and if 97L doesn't live to the potential, there's a great shot of that being broken. However, a wave left Africa a week ago and it was thought to develops not long after going by Cape Verde and recurve out to the sea harmlessly. However, the wave didn't and is forgotten until 3 days ago when it was tagged as a invest. Didn't take long for the storm to look threatening today when it was able to fire up the thunderstorms.

(Credit: US Navy)

It was looking pretty good until D-MIN came through and now the storm is almost gone. However it would be a mistake to dismiss this storm as the structure is still there.

(Credit: US Navy)

The biggest issue right now is for the structure and the circulation to hang in there as it enter Eastern Caribbean, other wise known as "Graveyard of Atlantic" as it was known to not allow developments of premature storms or kill it completely. Shear and sea temperature is not an issue at all and once it get past East Caribbean, it should take advantage of great conditions in the area. There is no total model support for this storm, but they all have been terrible handling this invest. The intensity models are all predicting for this storm to be at least tropical storm and few of them got 97L making it to a major. However, these models are also taking the storm to Hispanoila which is not going to happen because of East Caribbean limiting the development until Jamaica area and the steering pattern also will disallow this. This should prevent 97L from moving toward northwest for two or three more days. Currently, I got 55% chance of storm ever developing mostly because of the performance of other storms in all basins this season.

(Credit: University of Wisconsin)

Now to get to the fun part, and that's long term forecast. While East Caribbean should limit the development, it should develops eventually around Jamaica. The intensity forecast get tricky at this point as there is a high heat energy potential in NW Caribbean that is famous for giving some past storms so much energy that it became a major hurricane in a flash. However, not all storms take advantage of this so we got to be careful with this. It's extremely difficult to forecast a major a week out and I'm not going to say "oh, we will get a major in Gulf of Mexico in a week" with confidence. Doing so is a great way for a forecast to bust.

However, I wouldn't be surprised if we have a major if the conditions are perfect and the storm track directly over the energy without hitting the land. We could also have a problem in USA if the storm also manage to get between Mexico and Cuba. It's way too early to be worrying about this though but I do have a hurricane strength storm in my forecast heading for western tip of Cuba. I could have gone higher if I want to, but that's jumping the gun if I did so. Here's my forecast:

(Credit: mine for graphic and Weather Underground for map)

As for threat, everybody from Belize to Florida Keys isn't out of game as well as Greater Antilles and Bahamas. Here's a threat map from me:

Threat Level Color Key:

Low Threat (Light Green)- Little or nothing is expected, although the storm need to remain monitored by you in event of sudden and unexpected change.

Moderate Threat (Light Blue)- Tropical storm conditions are expected. Strong sustained winds with powerful gusts is highly likely. Heavy rain, flash flooding, and mudslides are expected. Minor storm surge are possible along the coast. Minor to moderate damages expected.

High Threat (Dark Blue)- Hurricane conditions are expected. Sustained winds will be hurricane force with damaging wind gusts. Heavy rain, flash flooding, and mudslides are expected. Minor to moderate storm surge are expected along the coast. Moderate to heavy damages expected.

Extreme Threat (Purple)- Major hurricane conditions are expected. Sustained winds will be typical of a major hurricane (95 knots/111 mph or greater) along with very damaging wind gusts. Heavy rain, flash flooding, and mudslides are expected. Historic storm surge expected along the coast. Mass devastation is expected in the aftermath of storm.


Posted By: Marty

Re: Watching 97L for Development - 09/03/13 10:25 AM

Invest 97L a Development Threat this Week – Will Bring Heavy Rain To the Greater Antilles

Invest 97L remains elongated today, with the main low centered just north of Barbados, but the overall circulation extending for hundreds of miles WSW and ENE of that location. The system has made no westward progress during the last 24 hours due to low pressure feeding back in a favorable environment near the lesser Antilles. The system should eventually assume a general WNW motion. Due to slower movement than expected, 97L is likely to gain latitude as the subtropical ridge to the north is weakened by a front off of the Carolinas in a few days, and interaction with the greater Antilles appears likely. Heavy rains will be the main concern for the mountainous areas of Puerto Rico, Hispaniola, and Cuba as the system moves somewhat lethargically northwestward. Although the exact track of the system remains uncertain due to its broad nature and vulnerability to center reformations, the system is expected to end up in the general vicinity of Cuba or the Bahamas in 4-6 days. This solution is supported by the 12z runs of the ECMWF and UKMET.

The current environment around 97L remains rather favorable, with anticyclonic wind flow aloft, and a deep moisture field from the surface to 700mb. The main impediment to development remains the system’s elongated structure, being exacerbated now by interaction with another low pressure system to the ESE that is closing distance with 97L. As the system moves westward, development, if any, is expected to be slow, as the system will take time to consolidate, and the central Caribbean trade winds tend to cause low-level divergence and hostile conditions for tropical waves. Potential interaction with Hispaniola and Cuba may also hamper development. However, if 97L can consolidate over open water north or south of the big islands, the environment will become mostly favorable for development of a tropical cyclone late this week and possibly into next week once the system gets farther west and north. With a disturbance this large, we are in a bit of a wait and see game to see if it consolidates, and if so, where and when.

Elsewhere, a tropical wave moving across central America into the western Gulf of Mexico will be monitored for potential development in an unstable atmosphere. For now, no computer models show significant development. A tropical wave is forecasted by most of the global models to develop off of Africa in about a week from now. This will be discussed more once the timetable gets closer.

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