TS Erika Discussion 7

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Evans F. Mitchell KD4EFM <GMail>

Aug 26, 2015, 1:14:03 PM8/26/15
to wcfla...@googlegroups.com, South Fla D-Star Google Group



1100 AM AST WED AUG 26 2015


Deep convection associated with Erika has increased during the past

24 hours, but the overall organization of the tropical cyclone has

not changed very much.  Reconnaissance aircraft data indicate that

the center is located near the northwestern edge of the thunderstorm

activity due to moderate northwesterly shear.  The aircraft has

measured believable SFMR winds of around 40 kt this morning, and

the initial intensity is set at that value.


Erika is forecast to pass through an environment of moderate to

strong westerly vertical wind shear during the next two to three

days.  The shear will be caused by an upper-level low that is

expected to remain near eastern Cuba through Friday.  The upper low

is forecast to weaken on Saturday, which should produce a more

conducive upper-level wind pattern over the Bahamas. The NHC

intensity forecast calls for little change in strength through 72

hours, which is in line with the latest statistical guidance.  After

that time, strengthening is indicated due to the expected more

favorable upper-level environment.  The official forecast lies

between the more robust HWRF/GFDL and lower statistical guidance.

An alternative forecast scenario, supported by the GFS model, is

that Erika weakens to a tropical wave due to the shear and

interaction with the Greater Antilles.  The amount of strengthening

on days 4-5 will be dependent in part on how Erika responds to the

the preceding unfavorable shear.


The initial motion estimate is 280/15 kt.  Erika is expected to

move westward to west-northwestward during the next several days

to the south of a subtropical ridge over the western Atlantic.

The track guidance is in good agreement through much of the forecast

period, with the exception of the GFDL model that takes a stronger

storm northwestward much sooner.  The new NHC track is essentially

an update of the previous advisory and is close to a consensus of

the ECMWF, GFS, HWRF, and UKMET.  This is also in good agreement

with the Florida State Superensemble.  One should remember to not

focus on the exact forecast track, especially at the long range

where the average NHC track errors during the past 5 years are about

180 miles at day 4 and 240 miles at day 5.





INIT  26/1500Z 16.1N  57.6W   40 KT  45 MPH

12H  27/0000Z 16.7N  59.9W   45 KT  50 MPH

24H  27/1200Z 17.6N  63.0W   45 KT  50 MPH

36H  28/0000Z 18.7N  65.9W   45 KT  50 MPH

48H  28/1200Z 19.8N  68.7W   45 KT  50 MPH

72H  29/1200Z 22.0N  73.7W   45 KT  50 MPH

96H  30/1200Z 24.4N  77.7W   55 KT  65 MPH

120H  31/1200Z 26.5N  80.5W   65 KT  75 MPH...INLAND



Forecaster Brown




Evans F. Mitchell / KD4EFM

Field Service Tech.

Fisher Communications - Central Florida Division

C: 863-272-1713

O: 904-384-1270



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