Archive for August, 2016|Monthly archive page

Tropical Storm Hermine – Tallahassee Alert –

 

THIS IS A VERY “TIME-SENSITIVE” REPORT

After viewing the graphic below my concerns for the residents of Tallahassee have increased; of course it goes without saying that my concerns are for everyone who might have to deal with this storm – no matter where they might be located.  Mainly, there are three factors involved in my concern for the 7th most highly populated city in Florida and its capital city.  One is that there is a strong chance that Hermine will become a hurricane before reaching the Florida coast.

Another:  The minimum distance from Gulf of Mexico waters to Tallahassee is about 25 miles.  One might consider 25 miles to be an adequate “buffer” to provide friction and thus slow down the winds approaching the city.  I think that assumption would be a mistake.  Furthermore, when surface or near-surface winds leave the water for land the slight slowing that might occur would tend to cause more air to rise.  A similar rising is what causes lake effect snows in certain Great Lakes coastal or near-coastal downwind locations.  In the case of humid winds from Hermine possibly decelerating due to friction over the land when approaching Tallahassee, the net effect could very well be more vertical cloud development (due to a greater amount of rising air) than would have occurred otherwise.  This phenomenon can intensify thunderstorms, the gusts that spill out from them, and the chaos that can generate tornadoes.  The increase in rainfall amounts can be dramatic.  So – be careful what you wish for.  Flooding is typically a bigger issue than the wind velocities in these cases.

Here is the third cause for my concern:  The graphic below from the National Weather Service showing the “cone of uncertainty” (8 PM EST, 8-31-2016) causes me to consider that Tallahassee might very well be under the right-hand leading quadrant of the storm when it makes landfall.  The right-hand leading quadrants of tropical cyclonic systems are usually the quadrants with the highest wind velocities, greatest probability for tornadoes, heaviest rains, and in coastal areas the greatest storm surge height.  The fact that currently the whole storm is beginning to move faster can increase the danger of the right-hand leading quadrant.

I urge residents of the Tallahassee area to be alert during the approach, passage, and departure of what is now Tropical Storm Hermine.  Do not take it lightly just because it is on the low side of the tropical storm wind velocity range at this time (evening of 8-31-2016).  

CLICK ON THE IMAGE BELOW TO ENLARGE. 

2016-8-31 8pm EST

CLICK ON THE IMAGE ABOVE TO ENLARGE. 

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Update On Tropical Depression Nine (AL09) 8-29-2016, 10:30 pm EST

Compare this to the previous posting which was 24 hours earlier and you will see some change in the tracking model forecasts – which is to be expected.

I have greatest confidence in the TVCA run which is a consensus of 5 other models which have been good performers over the last few years.  Generally, the TVCA model is very close to the National Hurricane Center’s “official” track that is the basis for the “uncertainty” cones released to the public.  If you are one to pay attention to which models get mentioned or shown in weather reports you have surely heard of the “European model” which is labeled ECMWF.  You won’t find it on these spaghetti illustrations; Data from this model is restricted from being redistributed according to international agreement.   However, the National Weather Service official track runs very close to being the same as the ECMWF.  The BAMM and related models are still useful for long term runs but in this case I think you can pretty much ignore them (the ones that run off toward the west). 

Suppose you lived along the Nature Coast of Florida, (e.g. Citrus County) then you might feel that you have nothing to be concerned about because the tracks seem to be shifting northward.  But please remember, these tracks are merely forecasting the storm’s center.  In most cases the strongest winds are at the right hand, leading quadrant of such storms, which, in this case might cause Citrus County some concerns. 

Please be sure to click on the graphic for enlargement.

 

2016-8-30 L 0000z

Invest 99L Has Become Tropical Depression AL09

REMINDER:  THIS IS A TIME-SENSITIVE REPORT

As of late this afternoon, 8-29-2016, Invest 99L has strengthened to a tropical depression.  For up-to-date information on the system, I recommend Dr. Jeff Masters’ weblog (blog).  See link below:

https://www.wunderground.com/

Go to the top of the page and click on News & Blogs.

As of the time of this writing, Dr. Masters expresses reasonable confidence that the system will track in such a way that a landfall will occur somewhere in the Florida coast north of Tampa.  I urge all interested persons to pay close attention to Dr. Masters’ postings, the Weather Channel tropical reports, and your local news.

Here is the most recent version from my favorite spaghetti chart source, the National Center for Atmospheric Research in Boulder, Colorado (CLICK ON IMAGE TO ENLARGE):

2016-8-29 Model tracks