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Tropical Storm Carlotta Discussion Number   2
NWS National Hurricane Center Miami FL       EP032024
200 PM MST Wed Jul 31 2024

The convective structure of the depression has continued to improve 
this afternoon, with plenty of curved bands on satellite imagery 
wrapping cyclonically around a well-defined center. After the prior 
advisory, a late arriving SSMIS pass also showed these cyclonic 
bands well on the 37-GHz channel. Subjective Dvorak intensity 
estimates were T3.0/45-kt from TAFB and T2.5/35-kt from SAB. Given 
the improvement in structure, the initial intensity is set at 40 kt 
this advisory, upgrading Tropical Depression Three-E to Tropical 
Storm Carlotta, the third named storm of the slow-starting 2024 East 
Pacific Hurricane Season. 

Carlotta has been moving a bit more poleward that previously 
expected, with the most recent 12-h motion averaging around 
305/12-kt. This northwestward motion is soon expected to turn back 
more westward as it comes under the influence of a large deep-layer 
ridge centered over the southwestern United States. The global model 
guidance continues to advertise a broad weakness in this ridging 
forming on its western side by days 4-5, and a slowdown with some 
poleward turn is possible in Carlotta's track by the end of the 
forecast period. Overall, the guidance this cycle has shifted more 
northward than before, partially due to the initial position, but 
the NHC track forecast remains in good agreement with the consensus 
aids, in between the GFS and ECMWF solutions.

The improvement in Carlotta's structure also could mean it is more 
poised to intensify faster than previously expected in the 
short-term. This possibility is reflected by the latest intensity 
guidance which is notably higher than before, showing Carlotta 
taking advantage of the favorable low vertical wind shear and warm 
sea-surface temperatures. In fact, the latest SHIPS rapid 
intensification (RI) index now indicates a 30-40 percent chance of 
RI over the next 24 hours. While the NHC intensity forecast will not 
quite show this rate of intensification yet, it is higher than 
before, and now peaks Carlotta as a 85-kt Category 2 hurricane in 
60-72 hours. This intensity forecast is is pretty good agreement 
with the latest HFIP Corrected Consensus Approach (HCCA) forecast, 
but is now a shade under the latest HAFS-A/B forecast. Carlotta is 
still expect to begin moving over cooler waters by days 4-5 which 
should begin to induce a gradual weakening by the end of the 
forecast period.
 
 
FORECAST POSITIONS AND MAX WINDS
 
INIT  31/2100Z 16.2N 108.0W   40 KT  45 MPH
 12H  01/0600Z 16.8N 109.8W   50 KT  60 MPH
 24H  01/1800Z 17.3N 111.8W   60 KT  70 MPH
 36H  02/0600Z 17.7N 113.9W   70 KT  80 MPH
 48H  02/1800Z 17.8N 116.0W   80 KT  90 MPH
 60H  03/0600Z 17.8N 118.2W   85 KT 100 MPH
 72H  03/1800Z 17.8N 120.2W   85 KT 100 MPH
 96H  04/1800Z 18.3N 122.2W   75 KT  85 MPH
120H  05/1800Z 19.3N 124.0W   65 KT  75 MPH
 
$$
Forecaster Papin
 
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