ZCZC MIATCDEP5 ALL TTAA00 KNHC DDHHMM Tropical Storm Irwin Discussion Number 4 NWS National Hurricane Center Miami FL EP102023 1100 AM HST Sun Aug 27 2023 The cloud pattern has changed little in appearance this morning. The center of circulation remains displaced to the north of a shapeless deep convective mass, likely due to a combination of modest northeasterly shear and dry mid-tropospheric air intruding from the northwest. A scatterometer pass over the eastern half of the cyclone indicated southerly winds of 35-37 kt well removed from the center, and the initial intensity is held at 35 kt for this advisory. Irwin should be able to produce sufficient deep convection, particularly in the eastern semicircle, along with intermittent bursts near the center, thereby maintaining its tropical storm status in the short term. Subsequently, the relatively large circulation should take some time to spin down similar to what the global and regional guidance suggests. Decreasing SSTs and a dry, stable marine layer air mass is expected to cause the cyclone to weaken to a depression in a few days and degenerate into a remnant low toward the end of the forecast period. Using surface center fixes from visible and recent microwave imagery, along with the previously mentioned partial METOP-B/C scatterometer wind overpasses, gives an estimated initial motion of west-northwestward, or 295/9 kt. A subtropical high pressure anchored to the north of the cyclone should maintain a generally west-northwestward to westward heading through day 5. Along-track inconsistency in the models continues to complicate the forecast track solution. The best approach in this case, however, is to side with a compromise of the best-performing HCCA and TVCE consensus guidance, and is the basis of the official forecast. FORECAST POSITIONS AND MAX WINDS INIT 27/2100Z 17.2N 121.3W 35 KT 40 MPH 12H 28/0600Z 17.7N 122.5W 40 KT 45 MPH 24H 28/1800Z 18.4N 124.6W 40 KT 45 MPH 36H 29/0600Z 18.6N 127.2W 35 KT 40 MPH 48H 29/1800Z 18.6N 130.0W 35 KT 40 MPH 60H 30/0600Z 18.4N 132.7W 35 KT 40 MPH 72H 30/1800Z 18.4N 135.2W 30 KT 35 MPH 96H 31/1800Z 18.8N 138.9W 30 KT 35 MPH...POST-TROP/REMNT LOW 120H 01/1800Z 19.1N 141.4W 25 KT 30 MPH...POST-TROP/REMNT LOW $$ Forecaster Roberts NNNN
Alternate Formats
About Alternates -
E-Mail Advisories -
RSS Feeds
Cyclone Forecasts
Latest Advisory -
Past Advisories -
About Advisories
Marine Forecasts
Latest Products -
About Marine Products
Tools & Data
Satellite Imagery -
US Weather Radar -
Aircraft Recon -
Local Data Archive -
Forecast Verification -
Deadliest/Costliest/Most Intense
Learn About Hurricanes
Storm Names
Wind Scale -
Prepare -
Climatology -
NHC Glossary -
NHC Acronyms -
Frequently Asked Questions -
AOML Hurricane-Research Division
About Us
About NHC -
Mission/Vision -
Other NCEP Centers -
NHC Staff -
Visitor Information -
NHC Library
NOAA/
National Weather Service
National Centers for Environmental Prediction
National Hurricane Center
11691 SW 17th Street
Miami, Florida, 33165-2149 USA
nhcwebmaster@noaa.gov
Disclaimer
Privacy Policy
Credits
About Us
Glossary
Career Opportunities
Page last modified: Monday, 18-Dec-2023 12:10:13 UTC