055 WTPZ43 KNHC 072120 TCDEP3 Tropical Storm Henriette Discussion Number 15 NWS National Hurricane Center Miami FL EP082025 1100 AM HST Thu Aug 07 2025 Henriette has been producing a smaller area of deep convection than earlier, as it seems to be struggling a bit with dry air and sea-surface temperatures near 24 C. The latest subjective Dvorak current intensity estimates are 2.5/35 kt from TAFB and 1.5/25 kt from SAB. The latest objective estimates from UW-CIMMS range from about 30 to 40 kt. A recent 1914 UTC ASCAT-C pass suggests that Henriette has likely weakened a bit from earlier. Based on the above data, the initial intensity is lowered to 40 kt for this advisory. The motion of 280/14 kt is unchanged from the previous advisory. This motion will continue through today as Henriette is steered by mid-level ridging well to its north. The cyclone will then round the southwestern periphery of the mid-level ridge as a large deep-layer trough approaches from the west. These features will cause Henriette to gradually turn toward the northwest in a couple of days. Very little change has been made to the NHC track forecast, which lies near the tightly clustered consensus aids. Confidence in the track forecast is high through the weekend, and Henriette will not directly impact the Hawaiian Islands. Henriette is expected to continue moving over cool ocean waters near 24C for another 36 h before it begins to gradually move over increasing water temperatures. The tropical storm will also continue moving through a very dry environment. Most of the guidance shows the storm maintaining a 35-40 kt intensity during this time. Henriette is also expected to encounter colder than normal mid- and upper-level temperatures in a couple of days. If Henriette survives the next 48 h or so, then strengthening would appear likely later in the forecast period due to increasing sea-surface temperatures, very low vertical wind shear, and decreasing mid- to upper-level temperatures as the aforementioned deep-layer trough approaches. The official forecast shows some slight weakening in the short term, followed by strengthening to a hurricane by day 4 well to the north of Hawaii. The latest NHC forecast is near the intensity consensus and close to the higher end of the guidance at day 4 and 5. It should be noted that the HAFS models are showing a slightly higher intensity than the NHC forecast. FORECAST POSITIONS AND MAX WINDS INIT 07/2100Z 18.9N 136.8W 40 KT 45 MPH 12H 08/0600Z 19.3N 139.2W 40 KT 45 MPH 24H 08/1800Z 19.9N 142.2W 40 KT 45 MPH 36H 09/0600Z 20.9N 145.0W 40 KT 45 MPH 48H 09/1800Z 22.1N 147.5W 40 KT 45 MPH 60H 10/0600Z 23.5N 150.0W 45 KT 50 MPH 72H 10/1800Z 25.2N 152.3W 55 KT 65 MPH 96H 11/1800Z 28.9N 156.7W 70 KT 80 MPH 120H 12/1800Z 32.6N 160.6W 65 KT 75 MPH $$ Forecaster Hagen
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