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Tropical Storm Hanna


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Posted
  • Location: Taunton, Somerset
  • Weather Preferences: Snow, thunder, strong winds. HATE:stagnant weather patterns
  • Location: Taunton, Somerset

    Tropical Depression 09L has formed in the Bay of Campeche. The depression is forecast to become a tropical storm before it makes landfall on the west coast of the Yucatan Peninsula in a day or so. If 09L does survive the trek over land, conditions are not favourable for restrengthening in the NW Caribbean.

    Edited by Somerset Squall
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    Posted
  • Location: The Netherlands
  • Location: The Netherlands

    It looks like 09L could become a very interesting system in the near- and far future. For now, though, 09L does not look very healthy. The system consists of a small burst of convection right over the LLCC (low level circulation center), with no banding features evident. This can be seen in the Dvorak image form 09L below:

     

    post-20885-0-67941100-1413990973_thumb.j

    Dvorak satellite image of 09L as of 14:30 UTC.

     

    What can also be seen is that there is a large area of enhanced convection to the east of 09L (indicated by the red circle). This area is associated with the subtropical jet stream, which has been strengthening just north of 09L. This is shown in the analysis below:

     

    post-20885-0-86684000-1413991955_thumb.g

    Wind analysis at 200 hPa height from the COAMPS model as of 06 UTC. The thin grey arrows indicate direction of the wind, while the colours indicate the magnitude of the wind.

     

    The subtropical jet stream is indicated by the black thick arrows (one can also follow the thin grey arrows over the image).

     

    Note that in the image, winds of 15-20 kt are also raging over 09L (denoted by the x) from west-southwest to east-northeast. Those winds are also creating some wind shear over 09L, displacing convection.

     

    Despite the shear and neighborhood of the subtropical jet stream, the NHC is forecasting 09L to become a weak tropical storm before making landfall on the Yucatan Penninsula. 

     

    However, the more interesting part comes after that. It was initially forecasted As 09L would emerge in the western Carribean sea, it would dissipate due to shear and dry air entrainment from the north. However, indications are that 09L may well become a potent storm in the Carribean sea. From the discussion of the NHC:

     

     

     

    If the depression emerges over the northwestern Caribbean Sea in about 3
    days, there is an opportunity for some strengthening. Most of the
    global models, primarily the GFS and the HWRF, forecast a favorable
    upper-level environment for the system to redevelop, if the
    the cyclone survives its path over land. On this basis, the NHC
    forecast now maintains tropical depression status through five days

     

    As a result, the NHC no longer expects 09L to dissipate in the Carribean Sea, but rather stay at depression strength. Below is the latest forecast (as of advisory 3):

     

    post-20885-0-35008100-1413991938_thumb.g

    Track forecast of 09L from the NHC.

     

    However, there are a lot of uncertainties regarding this outcome. For example, 09L could simply dissipate over the Yucatan penninsula, but it could just as easily become a potent tropical storm. Therefore, it will be a very interesting period of model watching associated with this system.

     

    For further reading, below are some links with information about the system:

     

    http://dutch.wunderground.com/blog/JeffMasters/comment.html?entrynum=2839 (blog from Jeff Masters, meteorologist of Wunderground)

     

    http://www.tropicaltidbits.com/ (Video analysis from 09L)

     

    Sources:

    http://www.nrlmry.navy.mil/

    http://www.nhc.noaa.gov/graphics_at4.shtml?5-daynl?large#contents

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    Posted
  • Location: The Netherlands
  • Location: The Netherlands

    How's the system doing?

     

    The tropical depression failed to organize into a tropical storm, and has degenerated into a remnant low over the Yucatan Penninsula. However, the remnants have recently emerged over the western Caribbean Sea (though the system is very poorly organized at the moment). The NHC gives the system a 20 % chance to develop in the next 5 days (10% chance in the next 2 days). From the NHC:

     

     

     

    A broad area of low pressure over the extreme western Caribbean

    Sea is associated with the remnants of Tropical Depression Nine.

    This system is producing disorganized showers and thunderstorms, and

    redevelopment, if any, will be slow to occur while the low drifts

    eastward or meanders for the next few days.

    * Formation chance through 48 hours...low...10 percent.

    * Formation chance through 5 days...low...20 percent.

     

    Track models currently have no clue what will happen with the system, as they are spread between a track toward Florida and landfall on Honduras. This can be seen below:

     

    aal94_2014102418_track_early.png

    Track forecasts from various models of 94L (former 09L)

     

    Most of the intensity models don't intensify 94L, though. However, given the complexity of the situation (as indicated by the large variety of track solutions), little can be said about the future of 94L yet.

     

    If one takes a look at a visible loop of 94L, one can see that there is still some kind of circulation, with broad cyclonic turning evident near 18N, 87W. This can be seen below:

     

    post-20885-0-55069000-1414188175_thumb.g

    Visible satellite animation of 94L (note that the loop does not auto-update itself, it starts after clicking on it)

     

    In spite of the well-defined circulation, there is little, if any, convection directly associated with the system. If this system is going to develop, it will need to develop a lot more sustained deep convection than it has now. 

     

    Concluding, the prospects of 94L developing back into a tropical depression seem marginal at best. However, given the complex situation and the high degree of uncertainty, even in the short-term, it will be very interesting to see how the situation will unfold.

     

    Sources:

    http://www.nhc.noaa.gov/gtwo.php?basin=atlc&fdays=2

    http://www.ral.ucar.edu/guidance/realtime/plots/northatlantic/2014/al942014/

    Edited by Vorticity0123
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    Posted
  • Location: Taunton, Somerset
  • Weather Preferences: Snow, thunder, strong winds. HATE:stagnant weather patterns
  • Location: Taunton, Somerset

    The remnants of Tropical Depression 09L moved into the northwest Caribbean, drifted southward and have organised into Tropical Storm Hanna, just off the coast of Honduras. Winds are at 35kts. Hanna has some very deep convection over the LLCC, and this, unfortunately, are going to provide flooding rains to Honduras. Totals in excess of 10 inches are possible according to NHC. Hanna is just a few hours from landfall, so no further strengthening is expected.

    Hanna's very bizarre track so far:

    post-1820-0-32185600-1414419667_thumb.jp

    Edited by Somerset Squall
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    Posted
  • Location: The Netherlands
  • Location: The Netherlands

    Hanna's very bizarre track so far:

    attachicon.gif10372934_10205211054975497_4156820033130342580_o.jpg

     

    Indeed a very bizarre track, alongside with a very unusual second place of formation, this is definitely an odd cyclone to say the least! Unfortunately it is indeed so close to land that it could bring lots of flooding. 

     

    Even though Hanna developed very close to land, forecast models give the possibility of the system emerging just to the east of the Yucatan Penninsula, after moving west-northwestward. 

     

    aal09_2014102712_track_early.png

    Track model forecasts of Hanna.

     

    Source:

    http://www.ral.ucar.edu/guidance/realtime/plots/northatlantic/2014/al092014/

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    Posted
  • Location: Taunton, Somerset
  • Weather Preferences: Snow, thunder, strong winds. HATE:stagnant weather patterns
  • Location: Taunton, Somerset

    Hanna degenerated into a remnant low over Honduras. The remains have moved west-northwestwards back over water and are now heading towards Belize. Hanna's remains are not expected to redevelop into a tropical cyclone as another landfall will occur soon, however, it cannot be ruled out.

    Edited by Somerset Squall
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