Tropical Cyclone Discussion
Issued by NWS
Issued by NWS
617 WTNT42 KNHC 011453 TCDAT2 Tropical Storm Kirk Discussion Number 8 NWS National Hurricane Center Miami FL AL122024 1100 AM AST Tue Oct 01 2024 Kirk`s structure on satellite is gradually becoming better organized, with deep convective bands attempting to wrap around the center, though there still remains evidence that dry air could be getting into the core on the western side. Some of this less humid air could be getting imported due to subtle northerly mid-level shear above 20-kt as diagnosed by the ECMWF analysis this morning. With that said, we have received some fortuitous surface data from a moored PIRATA buoy (13008) that Kirk passed close by this morning at around 09 UTC. The buoy reported sustained tropical-storm-force winds at 4 meters, and a concurrent minimum pressure down to 990 mb. Thus the initial intensity has been raised to 60 kt with an estimated minimum pressure a little lower at 988 mb. This intensity is a little above the subjective Dvorak estimates but closest to the latest DPRINT estimate from UW-CIMSS. Kirk is still moving west-northwestward, estimated at 300/11 kt. This motion with perhaps a slight slowdown should continue over the next couple of days as Kirk is primarily steered along the southwestern edge of a subtropical ridge positioned to its north. The western extent of this ridge will become eroded by a long-wave trough offshore of eastern North America towards the latter part of this week, allowing Kirk to turn first northwestward and then northward by the end of the forecast period. The track guidance continues to be in good agreement, and the latest NHC track forecast lies near the middle of the guidance envelope, very similar to the prior advisory and between the consensus aids HCCA and TVCN. While Kirk is stronger this morning, it is feeling some of the effects of the aforementioned mid-level shear, preventing convection from fully wrapping around the center. However, other environmental factors, namely warm 28-30 C sea-surface temperatures and plenty of deep-layer moisture, are quite conducive for strengthening. For now, the shear is anticipated to prevent a faster rate of intensification, but Kirk should become a hurricane later today. After 24 h, even the mid-level shear is expected to decrease, and a faster period of intensification is likely in the 24-60 h period. The NHC intensity forecast shows Kirk becoming a major hurricane at the end of this period. In addition, Kirk`s wind field is also forecast to grow in size by the end of the week. Thereafter, hard to predict inner-core structural changes will likely lead to fluctuations in intensity, though by day 5 shear begins to increase again with weakening beginning by that time. However, Kirk will likely remain a large and formidable hurricane. The NHC intensity forecast is close the middle of the guidance envelope early on but is near the higher end of the aids in 72 h. FORECAST POSITIONS AND MAX WINDS INIT 01/1500Z 15.3N 39.2W 60 KT 70 MPH 12H 02/0000Z 16.0N 40.7W 65 KT 75 MPH 24H 02/1200Z 17.0N 42.4W 75 KT 85 MPH 36H 03/0000Z 18.2N 43.9W 85 KT 100 MPH 48H 03/1200Z 19.3N 45.3W 95 KT 110 MPH 60H 04/0000Z 20.5N 46.8W 105 KT 120 MPH 72H 04/1200Z 21.6N 48.3W 110 KT 125 MPH 96H 05/1200Z 25.0N 51.0W 110 KT 125 MPH 120H 06/1200Z 30.0N 51.0W 95 KT 110 MPH $$ Forecaster Papin