Katia too close for comfort?

Sorry for the lack of posts the last couple of days as I took time off to visit family in NJ. Upon returning to the working world (yes, I had to work today), I see that Katia looks much better, Lee is inland (didn’t see that happening so fast last week), and we have a new storm in the embryonic stage in the Eastern Atlantic. Meanwhile, the rest of the ocean basins are quiet. Looking at the Madden-Julien Oscillation (MJO), the current phase is usually not supportive of tropical activity in the Atlantic, but no one told mother nature. Even with broadscale subsidence (sinking air, promoting dry, stable conditions), we have a hurricane that has strengthened to 115 mph or a Category 3 storm.

Rainbow infrared satellite image of Hurricane Katia on 09/05/11

The satellite image above shows a well-defined eye surrounded by very deep convection in the eyewall. Outflow (which provides evacuation of latent heat at high levels) is well established, although the storm does look a bit elliptical. This stretching in a SW-NE axis is due to an upper-low to the northeast of the hurricane, which is providing a bit of shear from the N-NE.

18z track guidance for Hurricane Katia via NCAR

I wish I could say that the track forecast philosophy on Katia was straight-forward, but I would be lying. Sure, the above image shows a recurvature into the westerlies, keeping this dangerous storm well away from the U.S. and Canada. The problem I see is that the models are having a tough time handling the evolution of Lee’s remains. As of right now, I think Katia has a 75% chance of staying out at sea, but I think we need to see how Lee’s remains cutoff (due to blocking over Greenland – positive NAO) behave in the next 24-48 hours before the East Coast can breathe a full sigh of relief. The CMC model has had a scary forecast for the past 24 hours.

102 hour forecast of the 12z Canadian model (CMC) on 09/05/11

Above is the 102 hour forecast from the 12z CMC model which shows a dangerously close approach of Katia (black circle) to the Outer Banks and Mid-Atlantic. This would provide tropical storm force winds and more beach erosion. This model is an outlier for now, but never dismiss a model solution until you know full well the storm is already recurving. The red circle is an area of lower pressure that develops near the Yucatan which should be watched and the blue circle will be talked about below.

18z track guidance for AL95 (invest area) on 09/05/11 via NCAR
144 hour forecast from the 12z ECMWF (European model) on 09/05/11

Above is the 18z track guidance for invest AL95 in the Eastern Atlantic which has the possibility of becoming the 14th tropical cyclone of the season tomorrow. The system looks fairly organized with a vigorous circulation noted today on visible satellite imagery. The track philosophy is to take AL95 west towards the Leeward Islands by the end of the week. The 12z ECMWF model run showed the possibilities on the table for later this week with a low in the Gulf of Mexico (red circle) and AL95 becoming a tropical storm or hurricane in the Northeast Caribbean (blue circle) or just north of the Virgin Islands (blue circle on the 12z CMC plot above). Either way, we continue to be in an active pattern for tropical development, even with otherwise hostile conditions in the Atlantic. The MJO phase will only becoming more favorable around the 20th into the early part of October. At this rate, we should have around 25 storms for the year. Amazing!

Quickly, expect very heavy rainfall this week for the Appalachians with lesser amounts into the coastal Mid-Atlantic, but still quite a bit on saturated soil. I have included the 5 day rainfall accumulation forecast from HPC below.

5 day rainfall accumulation forecast from the Hydrometeorological Prediction Center (HPC) valid at 23z 09/05/11

Thanks for reading!

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