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Tropical Storm Franklin Discussion Number   6
NWS National Hurricane Center Miami FL       AL072017
1000 PM CDT Mon Aug 07 2017

Satellite images and radar data from Belize show that Franklin has
an expansive and nearly symmetric circulation.  However, recent
microwave data indicate that the cyclone does not have a
well-defined inner core, which is characterized by an elliptical
ring of convection that is open on the northwest side.  In addition,
cloud tops are not very cold near the center, and the deepest
convection is located in a band well to the east of the center over
the Caribbean Sea.  Earlier Hurricane Hunter aircraft data indicated
that maximum winds were near 50 kt, and since the satellite
presentation has not improved since then, that will remain
Franklin's initial intensity.

Franklin appears to have turned west-northwestward and sped up just
a bit with an initial motion of 300/12 kt.  A mid-tropospheric
ridge extending across the northern and central Gulf of Mexico
should force Franklin west-northwestward and westward across
the Yucatan peninsula and into the Bay of Campeche during the next
day or two, which is handled well by the numerical models.  After
36 hours, there is some latitudinal spread in the track guidance,
likely related to how Franklin's circulation interacts with the
mountainous terrain of Mexico.  Since tropical cyclones in the
western Bay of Campeche historically have tended to turn a little
southward prior to landfall, the updated NHC track forecast is a
little south of the previous forecast, leaning in the direction of
the HFIP Corrected Consensus and the GFS.

Given Franklin's structure and limited time before landfall, the
cyclone is unlikely to strengthen before the center reaches land.
Weakening is anticipated while Franklin takes about 18 hours to
cross the Yucatan peninsula, but the storm should then begin to
restrengthen once it reaches the warm waters of the Bay of Campeche
tomorrow evening.  It does appear that northerly shear may begin to
increase in about 36 hours, but it does not look strong enough to
prevent intensification.  Continuing the pattern of following the
HFIP Corrected Consensus and the ICON intensity consensus, the
official forecast shows Franklin reaching hurricane intensity in
about 48 hours, and then making landfall on the coast of mainland
Mexico as a hurricane between 48 and 72 hours.  Despite what is
explicitly indicated in the forecast, Franklin's low-level center
is likely to dissipate near the mountains of Mexico, with the
mid-level remnants continuing westward across central Mexico.

Based on the updated forecast, the government of Mexico has
discontinued the Hurricane Watch for the east coast of the Yucatan
peninsula but has issued a new Hurricane Watch for parts of the
state of Veracruz in mainland Mexico.


FORECAST POSITIONS AND MAX WINDS

INIT  08/0300Z 19.1N  87.3W   50 KT  60 MPH
 12H  08/1200Z 19.7N  88.9W   40 KT  45 MPH...INLAND
 24H  09/0000Z 20.2N  91.1W   45 KT  50 MPH...OVER WATER
 36H  09/1200Z 20.5N  93.1W   55 KT  65 MPH
 48H  10/0000Z 20.6N  95.2W   65 KT  75 MPH
 72H  11/0000Z 20.0N 100.4W   30 KT  35 MPH...INLAND
 96H  12/0000Z...DISSIPATED

$$
Forecaster Berg

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