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Tropical Storm Julio Discussion Number   1
NWS National Hurricane Center Miami FL       EP152020
400 PM CDT Sat Sep 05 2020
 
The mid-level remnants of Atlantic Hurricane Nana have moved 
westward and west-northwestward off the southwestern coast of Mexico 
while producing intermittent convection during the last few days. A 
well-defined low formed about a day ago and ASCAT data indicates 
that it has been producing tropical-storm-force winds for the past 
12 h or so. During the past few hours there has also been an 
increase in deep convection near the center of the low, and the most 
recent Dvorak classification from TAFB was T-2.5, indicating that 
the system is sufficiently well-organized to be considered a 
tropical cyclone. Since the low-level center of Nana dissipated 
inland over Central Atlantic, the new tropical storm is named Julio, 
the tenth of the northern East Pacific season. The TAFB Dvorak 
classification and 15Z ASCAT data are the basis for the 35 kt 
initial intensity. Since the ASCAT explicitly showed 35 kt winds and 
that instrument typically under-samples the maximum winds, it is 
possible this intensity is a little conservative.
 
Most of the dynamical models do not acknowledge the existence of 
tiny Julio in their initial conditions. Only the ECMWF and its 
ensemble show a small well-defined low and it therefore is the 
primary basis for the NHC track forecast. In general, Julio should 
continue west-northwestward at a slower forward speed for the next 
couple of days, steered by a mid-level ridge to the northeast. Julio 
is forecast to become a shallow remnant low in a few days and should 
slow down to a crawl before it dissipates early next week. Since the 
forecast is based largely on one modeling system rather than the 
typical NHC consensus approach, confidence in the track forecast is 
fairly low.
 
The tropical storm will be affected by strong easterly wind shear 
for the next day or two and little or no further strengthening is 
likely during that time. Although the shear could decrease by early 
next week, Julio will reach a drier and more stable environment in a 
couple of days. It is therefore forecast to become a remnant low 
within 60 h and dissipate shortly thereafter. The NHC forecast is 
based on a blend of the ECMWF and the statistical DSHP and LGEM 
models since the HWRF and the GFS-dependent HMON models do not 
appear to have a good handle on the initial state of the system.
 
 
FORECAST POSITIONS AND MAX WINDS
 
INIT  05/2100Z 16.1N 102.7W   35 KT  40 MPH
 12H  06/0600Z 16.9N 105.0W   40 KT  45 MPH
 24H  06/1800Z 18.0N 107.5W   40 KT  45 MPH
 36H  07/0600Z 19.0N 109.4W   35 KT  40 MPH
 48H  07/1800Z 19.9N 110.6W   30 KT  35 MPH
 60H  08/0600Z 20.5N 111.0W   25 KT  30 MPH...POST-TROP/REMNT LOW
 72H  08/1800Z...DISSIPATED
 
$$
Forecaster Zelinsky
 
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