Tropical Storm Ignacio

Tropical Storm Ignacio Forming Track 1700 Hours August 4 2021
Tropical Storm Ignacio Forming Track 1700 Hours August 4 2021

Tropical Storm Ignacio Wind Speed FieldTropical Storm Ignacio – NWS National Hurricane Center Miami FL 500 PM HST Wed Aug 04, 2021 (see NEW Wednesday video below)

The system has not become noticeably better organized since earlier today, with a small area of deep convection near the center and some slightly curved bands of convection well removed to the east and northeast of the center. Microwave imagery also suggests little change in structure. The current intensity is held at 30 kt for now, in agreement with earlier scatterometer observations.

Although the center fixes have some scatter, my best estimate for motion is slowly northwestward, or 325/6 kt. A mid-level ridge to the northeast of the tropical cyclone is forecast to be maintained for the next 48-72 hours. This should keep the system on a generally northwestward heading until late in the forecast period. By that time, the weakening cyclone should turn a little to the left following the low-level environmental winds. The official track forecast is similar to the previous one and just to the right of the multi-model consensus, in slight deference to the GFS solution which is even farther to the right of these tracks.

Since the system should be in a fairly moist, low-shear environment for the next day or so, at least some slight strengthening seems likely. Thereafter, cooler SSTs and increased shear should cause weakening. The official intensity forecast is near or above most of the model guidance.

FORECAST POSITIONS AND MAX WINDS

INIT  05/0300Z 15.3N 136.2W   30 KT  35 MPH - Depression (WSW Hilo, Hawaii)
 12H  05/1200Z 16.0N 136.6W   35 KT  40 MPH - Depression (WSW Hilo, Hawaii)
 24H  06/0000Z 16.9N 137.7W   40 KT  45 MPH - Tropical Storm (WSW Hilo, Hawaii)
 36H  06/1200Z 17.8N 138.9W   35 KT  40 MPH - Tropical Storm (WSW Hilo, Hawaii)
 48H  07/0000Z 18.8N 140.3W   30 KT  35 MPH - Depression (WSW Hilo, Hawaii)
 60H  07/1200Z 19.8N 142.0W   30 KT  35 MPH - Depression (WSW Hilo, Hawaii)
 72H  08/0000Z 20.5N 143.5W   25 KT  30 MPH - Post Tropical (ENE Hilo, Hawaii)
 96H  09/0000Z 22.0N 147.0W   25 KT  30 MPH - Post Tropical (ENE Hilo, Hawaii)
120H  10/0000Z...DISSIPATED

NWS National Hurricane Center Miami FL 1100 AM HST Wed Aug 04, 2021

Satellite images today indicate that the system has been maintaining two hooking bands of convection to the north and south of the center. In addition, scatterometer data shows a well-defined, albeit a touch elongated, center and 30-kt winds. Thus, advisories are being re-started on Tropical Depression Nine-E after a 3-day hiatus, with an initial intensity of 30 kt.

The depression probably only has a few days as a tropical cyclone again because SSTs begin to drop off in a day or so, along with increasing shear and mid-level dry air. Nine-E does have a chance to finally become a tropical storm in the meantime before the aforementioned environmental conditions get less conducive on Friday. The system is likely to degenerate into a remnant low again this weekend (or sooner) as it encounters a very hostile environment. The NHC wind speed forecast is close to the model consensus, but is a smidge higher near peak intensity, owing to the HCCA corrected-consensus guidance.

The depression has been moving slowly toward the north-northwest today. A distant mid-level ridge to the northeast is providing the steering for the cyclone. This ridge should strengthen somewhat during the next few days, causing the depression to gradually turn to the northwest on Thursday and continue that motion through late week. Similar to a lot of forecasts this year, the GFS-based guidance is on the right side of the track envelope while the ECMWF and UKMET solutions lie on the left side. The official track assumes that the GFS shows a bit too deep of a tropical cyclone, and so the NHC prediction leans just west of the consensus throughout the forecast period.

FORECAST POSITIONS AND MAX WINDS

INIT  04/2100Z 14.9N 135.7W   30 KT  35 MPH - Depression (WSW Hilo, Hawaii)
 12H  05/0600Z 15.6N 136.1W   35 KT  40 MPH - Tropical Storm (WSW Hilo, Hawaii)
 24H  05/1800Z 16.5N 136.8W   40 KT  45 MPH - Tropical Storm (WSW Hilo, Hawaii)
 36H  06/0600Z 17.4N 138.0W   35 KT  40 MPH - Tropical Storm (WSW Hilo, Hawaii)
 48H  06/1800Z 18.4N 139.4W   30 KT  35 MPH - Depression (WSW Hilo, Hawaii)
 60H  07/0600Z 19.5N 141.0W   30 KT  35 MPH - Depression (WSW Hilo, Hawaii)
 72H  07/1800Z 20.5N 142.5W   25 KT  30 MPH - Post Tropical (ENE Hilo, Hawaii)
 96H  08/1800Z 21.5N 146.0W   25 KT  30 MPH - Post Tropical (ENE Hilo, Hawaii)
120H  09/1800Z...DISSIPATED

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