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August 2013

Development Possible in Bay of Campeche – Eastern Atlantic Still on Track to Get Active

   Posted by Levi at 8:34pm on August 24, 2013

A couple areas of disturbed weather have developed in the Caribbean and Gulf of Mexico over the last day or so, in response to the unstable pattern in the region. A surface trough developed in the northern Gulf of Mexico a couple days ago, and is bringing rain to the central gulf coast. As I mentioned yesterday on Facebook, although mid-level rotation has been evident, low-level convergence is focused southwest of the main area of thunderstorms, which is keeping the feature decoupled, and development appears unlikely as it moves generally westward along the north gulf coast over the next couple of days. The feature may bring some much-needed rain to coastal Texas.

To the south, a vigorous tropical wave moved into the Yucatan Peninsula last night, and an area of low pressure has developed near the mid-point of the wave axis over land today, designated Invest 95L by the NHC. There appears to be a closed circulation, which may emerge over the extreme southern Bay of Campeche by tomorrow. Given its excellent structure already, development of a tropical depression or storm may ensue immediately after moving over the water if it has enough room away from land. A deep-layer ridge to the north will keep 95L on a generally west or WNW track, and very little time will be spent over water before moving back into Mexico. Thus, the system is expected to be mainly a rainfall threat for Mexico.

Looking to the east, the tropical Atlantic remains quiet for the moment. The ITCZ is much farther north than normal, and low-level wind patterns are very favorable for the development of tropical waves. What is lacking right now is vertical motion to generate thunderstorms. The MJO is expected to move into phase 1 by most of the models during the next week or two, and this should provide a “boost” to the eastern Atlantic beginning by the end of this month and the beginning of September. Once the air finally becomes unstable enough, we should start to see tropical storms forming from tropical waves and ITCZ lows.

A pattern like this can accelerate activity rapidly. If the missing ingredient is added, we could quickly go from no storms at all to multiple storms simultaneously. The global models are starting to see this likely uptick in activity, with the GFS, CMC, and ECMWF now all hinting at development east of the Caribbean in the 6-10 day time frame. Below is the ECMWF forecast for Day 10, showing one or two disturbances trying to develop. This is still in the long-range, but this is the first time this year that the reliable ECMWF has shown tropical development in the central-eastern Atlantic. Take this as another sign that the peak of the season is here, and it won’t be long before our first hurricane forms.

It’s starting to get pretty late for our first hurricane, but in a pattern like we have this year, once the first one forms, it may uncork a burst of storms that doesn’t stop for multiple weeks. Four named storms typically form during the month of September. I think we are likely to see a more active than normal September this year. Be prepared in case any of these storms come your way.




  • stefanie says:

    Thanks Levi.

  • Mike Sphar says:

    Thanks Levi, what moves the MJO? What are the dots on the chart plotting? And why don’t the CPC and Australian BOM plot the movement in sync? CPC seems to lead and BOM seems to follow. And finally why are the models forecasts so different? I don’t see them clustering in your diagram above.

    • Levi says:

      My video from August 20th (the post before this one) gives an explanation of what the MJO is and what the dotted plots mean.

      CPC does update their MJO analysis faster than BOM, but I don’t know for sure why BOM is slower. It may be that BOM waits for reanalysis data to come in, which takes 2-3 days.

      The model forecasts for the MJO, like anything else, often differ, sometimes greatly. They are not in perfect agreement in the plot I showed, but they all agree on some movement towards phases 8, 1, and 2, which is what is relevant to the Atlantic right now.

  • EagleHarbotZig says:

    Great summary, thanks Levi

  • CapeFearCaner says:

    Thanks for the update Levi and I think that you’re right on. I believe that this September and October will be well above average for storm development. Also think that we will see some real intense ones as well!

  • Eric (weather advance) says:

    Hi Levi, I like your update as always, but I have a very good question. I’ve read through some scientific papers & through some of my recent observations that the MJO being its COD in August is rather unfavorable for tropical Atlantic activity, while having the MJO in the COD in September is considerably favorable. Do have any explanation as to how or why this occurring, perhaps this has to do something with the climatology & ITCZ behavior of the eastern Pacific, that peaks earlier than the Atlantic hurricane season? I’m not sure, could you offer any explanation or insight into this? Thanks in advance & keep these posts and videos coming, I always get excited when they come out. 🙂

    • Levi says:

      Hi Eric, I would have to ask first whether this research found that the MJO in the COD is more favorable even than phases 1, 2, and 3 during September? Or is it just more favorable on average?

  • Andrew says:

    I fear the lack of activity now will mean more energy will be available for the Cape Verde storms in September. Also most forecasters are predicting a sudden end to the season without development in the western Caribbean in October similar to 2004.

    I disagree with the sudden end prediction because 2004 had an El Niño pattern in the pacific that shut down the season early. This year, there is no El Niño and the eastern Pacific has a slight cool bias thanks to the cold PDO. That favors late season Caribean development.

    What factors am I missing that would shut off the season early?

  • Felix says:

    yo creo que el mes de septimbre va hace muy activa

  • Nice Article Thanks for share this .

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