000
WTPZ44 KNHC 302037
TCDEP4
 
Tropical Depression Nine-E Discussion Number   1
NWS National Hurricane Center Miami FL       EP092021
200 PM PDT Fri Jul 30 2021

An area of low pressure that NHC has been monitoring during the 
past several days over the eastern Pacific, has developed a 
well-defined surface center, as indicated in a recent 
scatterometer overpass, and has acquired sufficient organized 
convection to be classified as a 25-kt tropical depression.  The 
northwesterly shear which has been curtailing genesis over the past 
couple of days has diminished just enough to allow the system to 
become better organized, particularly, in the east and south 
portions of the cyclone.

The depression is embedded in weak easterly steering currents 
created by a deep-layer cut-off low and associated trough situated 
along 125W.  As a result, the depression is temporarily drifting 
west-southwestward, or 255/4 kt.  Large-scale models indicate that 
the cut-off feature will lift northward during the next 24-36 hours 
allowing a mid-tropospheric ridge to build in over the eastern 
Pacific.  Accordingly, the cyclone should track generally westward 
at an increased forward speed beyond mid period.  The official 
forecast follows suit and is based on a blend of the top forecast 
track performers, HFIP Corrected Consensus Approach (HCCA) and the 
multi-model consensus TVCN.

Now that the shear is weakening and the upper tropospheric winds are 
predicted to become more favorable, (easterly, and little more 
diffluent) steady strengthening is expected while the cyclone 
traverses deep, warm oceanic temperatures.  The NHC intensity 
forecast is near the HFIP Corrected Consensus Approach (HCCA) and 
the IVCN intensity aid and is below the Decay-SHIPS 
statistical-dynamical guidance beyond the 72-hour period.

 
FORECAST POSITIONS AND MAX WINDS
 
INIT  30/2100Z 12.3N 125.8W   25 KT  30 MPH
 12H  31/0600Z 12.0N 126.4W   30 KT  35 MPH
 24H  31/1800Z 11.7N 126.9W   30 KT  35 MPH
 36H  01/0600Z 11.7N 127.9W   35 KT  40 MPH
 48H  01/1800Z 11.8N 129.5W   35 KT  40 MPH
 60H  02/0600Z 12.1N 131.1W   40 KT  45 MPH
 72H  02/1800Z 12.5N 132.6W   40 KT  45 MPH
 96H  03/1800Z 13.2N 135.8W   45 KT  50 MPH
120H  04/1800Z 13.9N 138.9W   50 KT  60 MPH
 
$$
Forecaster Roberts