Weather

"Talking the Tropics With Mike": "Lisa" forms over the far E. Atlantic - Sept. 20th

Sept. 20, 2016 — Tropical storm "Karl" over the Central Atlantic... tropical depression #13 becomes "Lisa" far E. Atlantic....

JUST PAST THE PEAK OF THE HURRICANE SEASON...  You should always be prepared & aware.  First Alert Hurricane Center ** here **.  Reminder that flood insurance policies take 30 days to take effect..... & will not be written when/if a named storm is nearby.

The last NHC advisory on  "Julia"  was issued late Sunday.  Shear finally had its way with the system & that shear will only increase more with the approach of an upper level trough. Convection has increased some as the remnants interact with a frontal boundary & upper level trough while the surface low hugs the east coast just southeast of Chesapeake Bay.  The trough will help accelerate the surface low to the north/northeast then more northeast over the next several days.

Tropical cyclone "Karl" continues to march westward & is fighting the good fight against shear & dry mid & upper level air but has shown some slow additional organization.  The more shallow this system remains, the better chance it ends up farther west in the long run as models have been slowly trending west before a recurve.  In addition -- an important nugget to keep in the back of our mind -- forecast models as a whole this season have often been too far east or too early in other words - with recurvature.  So we have a couple of significant considerations while tracking & forecasting "Karl".  There are indications that conditions over the SW Atlantic later this week could be quite favorable for strengthening.   Forecast models are generally pretty insistent on a full recurve for  "Karl", but the longer the cyclone stays weak, the more west the system is likely to get.   An upper level trough late in the week/weekend will also be pivotal as to whether or not "Karl" takes the sharp turn to the north which is the indication for the moment.  "Karl" could be pretty close to Bermuda by the weekend as a hurricane reaching Jacksonville's latitude but hundreds of miles to the east late Fri. or so.  Given the distance from Jacksonville & expected intensification, easterly swells from "Karl" could reach First Coast beaches by late Thu./Fri.

Water vapor imagery below shows a good deal of dry air over the Central Atlantic which has been helping to limit the intensification of "Karl" so far.

The wind shear (red lines represent strongest shear) analysis shows shear gradually weakening in advance of "Karl".... lots of shear right now over the Southern Caribbean.

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Gulf of Mexico:

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East Atlantic:

Satellite imagery centered on Africa & the far E. Atlantic shows tropical waves continuing to move westward - pretty classic for this time of year.  A wave that moved off Africa over the weekend is now tropical storm "Lisa" - the 12th named storm of the season.  "Lisa" stays over the E. Atlantic & will be of no threat to the U.S.  Yet another wave will move off Africa in a few days.

Lots of warm water to help "feed" tropical cyclones.  Water temps. of 28 degrees Celsius equates to 82 degrees Fahrenheit.  Tropical cyclones generally need at least 80 degree water to thrive.

Sea surface temps. vs. average:

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Over the E. Pacific..... "Paine" is quickly falling apart upon approach to the Northern Baja of California.  Tropical moisture is likely to surge northward into Southern California & Arizona & could result in heavy rain over the next few days.

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