Tropical Storm Dorian is making a slight comeback this morning, even in the face of a less-than-ideal environment. The dry air situation has not improved, the vertical shear is still moderately strong, but the biggest factor in its recent convective activity must be the warming ocean temperatures below. All other things being equal, a warmer temperature below makes the atmosphere less stable, and better able to support the necessary thunderstorm activity for the development of a tropical cyclone.
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| Views of Dorian at three different wavelengths, sensitive to visible, infrared, and water vapor. The ambient dry air is evident in the water vapor image (brown shades in bottom panel). (NOAA) |
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As of 5am EDT, Dorian's estimated maximum sustained winds are 40mph, and the official NHC forecast gradually dissipates it over the next 24-36 hours... near the eastern Bahamas. This is in agreement with the dynamical models, but in disagreement with the statistical-dynamical models.
The track forecasts from NHC and various dynamical models definitely reflect a weak storm being steered largely by the low-level trade winds. If it should happen to intensify, the trajectory would get nudged northward. But on the westward track, it --or its remnants-- will end up over Hispaniola and Cuba and deliver a lot of rain.
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| Model and official track forecasts for Dorian... note that most don't even keep the storm through the nominal 5-day forecast period (120h). (UAlbany) |
It's not over 'til it's over... so while it does not currently appear to be a landfall threat, I'll be watching it closely. In the near future, Puerto Rico and surrounding islands should expect at least a stormy wet day on Monday. If it weakens much more, it will degenerate into a tropical depression or even an open wave.
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