From snowstorms to tropical/subtropical storms?

Since I started working for the GOES-R Proving Ground at HPC/OPC/SAB, I have analyzed a handful of tropical systems transitioning to extratropical systems (i.e. Hurricanes Irene, Lee, Katia, etc.). Early in November, we observed a baroclinic Winter-like system do the reverse. Tropical Storm Sean was born on 11/08 around 09z as a subtropical storm. The potential vorticity (PV) anomaly can be traced back to the Rockies where it produced a fairly significant snowfall from CO through KS and parts of MO. I have created an animation of the PV anomaly’s evolution using the GOES-Sounder RGB Airmass product. You’ll be able to track the anomaly (reddish/orange tinting) as it exits the central Rockies, traverses the Mid-Mississippi Valley into the Ohio Vally, then sinks southeastward to a point off the Southeast coast that is just beyond the Sounder view. After 24 hours, the PV anomaly has all but faded, thus allowing mesoscale processes to take over (some form of barotropic transition) and Sean is born in the Southwest Atlantic. The system moves west-northwest for a time before ejecting to the northeast in strong southwesterly flow ahead of a significant trough moving through the Eastern U.S.

Click on the image below to animate in another window. I have included 3-hourly HPC surface analysis so you can track the surface features in relation to the PV anomalies.

The GOES-Sounder RGB Airmass product with HPC surface analyses overlaid showing the evolution of TS Sean from a mid-latitude system.

For some additional images that really spotlights the features of interest with this evolving system, I have included some MODIS imagery with the HPC surface analysis overlaid. It is easier to see the airmasses and PV anomalies with this imagery as it gives a more representative picture of what we can expect with GOES-R.

The MODIS RGB Airmass product showing the system producing snow in CO.

MODIS RGB Airmass product showing pre-Sean over the central U.S.

MODIS RGB Airmass product with the OPC Atlantic surface analysis overlaid showing the extratropical system sinking southeast while producing very strong winds over the Gulf Stream near NC.

MODIS RGB Airmass product showing the strong PV anomaly sinking southeast as the slow evolution to warm-core begins.

MODIS RGB Airmass product showing the warm-core transition fully underway just prior to Subtropical Storm Sean being born.

MODIS RGB Airmass product showing Sean just before officially becoming a tropical storm.

MODIS RGB Airmass product showing Tropical Storm Sean near peak intensity.

As you can see in the above imagery, MODIS provides some great, detailed imagery to support airmass identification and the baroclinic to barotropic environments. This is a great addition to the GOES-Sounder version of the Airmass product to increase confidence during diagnosis.

Thanks for reading!

2 thoughts on “From snowstorms to tropical/subtropical storms?

  1. Great post Michael. The graphics and animations are wonderful. There are so many things to learn from this post. We need to have you integrate some of thisw into our training modules.

  2. Very nice. great work! Can’t wait to see these products during significant winter events across the west and during our blowing dust season.

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