National Hurricane Center (NHC) Pacific Map

000
ABPZ20 KNHC 311730
TWOEP

Tropical Weather Outlook
NWS National Hurricane Center Miami FL
1100 AM PDT Thu Aug 31 2023

For the eastern North Pacific...east of 140 degrees west longitude:

Tropical cyclone formation is not expected during the next 7 days.

$$
Forecaster Reinhart

000
ABPZ20 KNHC 301725
TWOEP

Tropical Weather Outlook
NWS National Hurricane Center Miami FL
1100 AM PDT Wed Aug 30 2023

For the eastern North Pacific...east of 140 degrees west longitude:

Tropical cyclone formation is not expected during the next 7 days.

$$
Forecaster Kelly

5-Day Uncertainty Track last updated Tue, 29 Aug 2023 20:36:36 GMT


Wind Speed Probabilities last updated Tue, 29 Aug 2023 21:43:36 GMT

Issued at 1100 AM HST Tue Aug 29 2023 000 WTPZ45 KNHC 292035 TCDEP5 Post-Tropical Cyclone Irwin Discussion Number 12 NWS National Hurricane Center Miami FL EP102023 1100 AM HST Tue Aug 29 2023 Irwin has failed to produce any convection near its center during the last 15-18 h. Since it no longer satisfies the criteria of a tropical cyclone, Irwin is being designated as a post-tropical cyclone with this advisory. A recent scatterometer pass showed a broad area of winds at or slightly above 30 kt in the northwestern quadrant, and so the initial intensity remains 35 kt. The post-tropical cyclone is moving slightly south of due west (260/15 kt). A general westward motion at a gradually slower forward speed is expected over the next several days while Irwin is steered by a low-level ridge over the eastern Pacific. Gradual weakening is forecast as the shallow cyclone spins down over cooler waters and in a drier, more stable environment. While some intermittent bursts of convection could occur during the next couple of days, the overall environment does not appear conducive for Irwin to regenerate to a tropical cyclone. This is the last NHC advisory on Irwin. For additional information on the post-tropical cyclone, please see High Seas Forecasts issued by the National Weather Service, under AWIPS header NFDHSFEPI, WMO header FZPN02 KWBC, and on the web at ocean.weather.gov/shtml/NFDHSFEPI.php FORECAST POSITIONS AND MAX WINDS INIT 29/2100Z 19.1N 130.3W 35 KT 40 MPH...POST-TROPICAL 12H 30/0600Z 18.9N 132.4W 30 KT 35 MPH...POST-TROP/REMNT LOW 24H 30/1800Z 18.8N 134.7W 30 KT 35 MPH...POST-TROP/REMNT LOW 36H 31/0600Z 18.8N 136.5W 30 KT 35 MPH...POST-TROP/REMNT LOW 48H 31/1800Z 18.9N 138.0W 30 KT 35 MPH...POST-TROP/REMNT LOW 60H 01/0600Z 19.0N 139.3W 25 KT 30 MPH...POST-TROP/REMNT LOW 72H 01/1800Z 19.0N 140.3W 25 KT 30 MPH...POST-TROP/REMNT LOW 96H 02/1800Z 19.0N 141.5W 25 KT 30 MPH...POST-TROP/REMNT LOW 120H 03/1800Z 19.5N 143.5W 20 KT 25 MPH...POST-TROP/REMNT LOW $$ Forecaster Reinhart

Issued at 2100 UTC TUE AUG 29 2023 000 FOPZ15 KNHC 292034 PWSEP5 POST-TROPICAL CYCLONE IRWIN WIND SPEED PROBABILITIES NUMBER 12 NWS NATIONAL HURRICANE CENTER MIAMI FL EP102023 2100 UTC TUE AUG 29 2023 AT 2100Z THE CENTER OF POST-TROPICAL CYCLONE IRWIN WAS LOCATED NEAR LATITUDE 19.1 NORTH...LONGITUDE 130.3 WEST WITH MAXIMUM SUSTAINED WINDS NEAR 35 KTS...40 MPH...65 KM/H. Z INDICATES COORDINATED UNIVERSAL TIME (GREENWICH) PACIFIC DAYLIGHT TIME (PDT)...SUBTRACT 7 HOURS FROM Z TIME HAWAIIAN STANDARD TIME (HST)...SUBTRACT 10 HOURS FROM Z TIME WIND SPEED PROBABILITY TABLE FOR SPECIFIC LOCATIONS CHANCES OF SUSTAINED (1-MINUTE AVERAGE) WIND SPEEDS OF AT LEAST ...34 KT (39 MPH... 63 KM/H)... ...50 KT (58 MPH... 93 KM/H)... ...64 KT (74 MPH...119 KM/H)... FOR LOCATIONS AND TIME PERIODS DURING THE NEXT 5 DAYS PROBABILITIES FOR LOCATIONS ARE GIVEN AS OP(CP) WHERE OP IS THE PROBABILITY OF THE EVENT BEGINNING DURING AN INDIVIDUAL TIME PERIOD (ONSET PROBABILITY) (CP) IS THE PROBABILITY OF THE EVENT OCCURRING BETWEEN 18Z TUE AND THE FORECAST HOUR (CUMULATIVE PROBABILITY) PROBABILITIES ARE GIVEN IN PERCENT X INDICATES PROBABILITIES LESS THAN 1 PERCENT PROBABILITIES FOR 34 KT AND 50 KT ARE SHOWN AT A GIVEN LOCATION WHEN THE 5-DAY CUMULATIVE PROBABILITY IS AT LEAST 3 PERCENT. PROBABILITIES FOR 34...50...64 KT SHOWN WHEN THE 5-DAY 64-KT CUMULATIVE PROBABILITY IS AT LEAST 1 PERCENT. - - - - WIND SPEED PROBABILITIES FOR SELECTED LOCATIONS - - - - FROM FROM FROM FROM FROM FROM FROM TIME 18Z TUE 06Z WED 18Z WED 06Z THU 18Z THU 18Z FRI 18Z SAT PERIODS TO TO TO TO TO TO TO 06Z WED 18Z WED 06Z THU 18Z THU 18Z FRI 18Z SAT 18Z SUN FORECAST HOUR (12) (24) (36) (48) (72) (96) (120) - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - LOCATION KT 20N 135W 34 X 3( 3) 1( 4) X( 4) X( 4) X( 4) X( 4) 20N 140W 34 X X( X) X( X) 2( 2) 4( 6) 1( 7) X( 7) $$ FORECASTER REINHART

Issued at 1100 AM HST Tue Aug 29 2023 000 WTPZ35 KNHC 292034 TCPEP5 BULLETIN Post-Tropical Cyclone Irwin Advisory Number 12 NWS National Hurricane Center Miami FL EP102023 1100 AM HST Tue Aug 29 2023 ...IRWIN BECOMES A POST-TROPICAL CYCLONE... ...THIS IS THE LAST NHC ADVISORY... SUMMARY OF 1100 AM HST...2100 UTC...INFORMATION ----------------------------------------------- LOCATION...19.1N 130.3W ABOUT 1340 MI...2155 KM W OF THE SOUTHERN TIP OF BAJA CALIFORNIA MAXIMUM SUSTAINED WINDS...40 MPH...65 KM/H PRESENT MOVEMENT...W OR 260 DEGREES AT 17 MPH...28 KM/H MINIMUM CENTRAL PRESSURE...1003 MB...29.62 INCHES WATCHES AND WARNINGS -------------------- There are no coastal watches or warnings in effect. DISCUSSION AND OUTLOOK ---------------------- At 1100 AM HST (2100 UTC), the center of Post-Tropical Cyclone Irwin was located near latitude 19.1 North, longitude 130.3 West. The post-tropical cyclone is moving toward the west near 17 mph (28 km/h). This general motion with a gradual decrease in forward speed is expected over the next few days. Satellite wind data indicate that maximum sustained winds are near 40 mph (65 km/h) with higher gusts. Gradual weakening is forecast during the next few days. Tropical-storm-force winds extend outward up to 70 miles (110 km) to the northwest of the center. The estimated minimum central pressure is 1003 mb (29.62 inches). HAZARDS AFFECTING LAND ---------------------- None NEXT ADVISORY ------------- This is the last public advisory issued by the National Hurricane Center on Irwin. For additional information on the post-tropical cyclone, please see High Seas Forecasts issued by the National Weather Service, under AWIPS header NFDHSFEPI, WMO header FZPN02 KWBC, and on the web at ocean.weather.gov/shtml/NFDHSFEPI.php $$ Forecaster Reinhart

...IRWIN BECOMES A POST-TROPICAL CYCLONE... ...THIS IS THE LAST NHC ADVISORY... As of 11:00 AM HST Tue Aug 29 the center of Irwin was located near 19.1, -130.3 with movement W at 17 mph. The minimum central pressure was 1003 mb with maximum sustained winds of about 40 mph.

Issued at 2100 UTC TUE AUG 29 2023 000 WTPZ25 KNHC 292034 TCMEP5 POST-TROPICAL CYCLONE IRWIN FORECAST/ADVISORY NUMBER 12 NWS NATIONAL HURRICANE CENTER MIAMI FL EP102023 2100 UTC TUE AUG 29 2023 NOTICE... LAND-BASED TROPICAL CYCLONE WATCHES AND WARNINGS ARE NO LONGER INCLUDED IN THE TROPICAL CYCLONE FORECAST/ADVISORY...(TCM). CURRENT LAND-BASED COASTAL WATCHES AND WARNINGS CAN BE FOUND IN THE MOST RECENTLY ISSUED TROPICAL CYCLONE PUBLIC ADVISORY...(TCP). POST-TROPICAL CYCLONE CENTER LOCATED NEAR 19.1N 130.3W AT 29/2100Z POSITION ACCURATE WITHIN 30 NM PRESENT MOVEMENT TOWARD THE WEST OR 260 DEGREES AT 15 KT ESTIMATED MINIMUM CENTRAL PRESSURE 1003 MB MAX SUSTAINED WINDS 35 KT WITH GUSTS TO 45 KT. 34 KT....... 0NE 0SE 0SW 60NW. 12 FT SEAS..120NE 45SE 45SW 90NW. WINDS AND SEAS VARY GREATLY IN EACH QUADRANT. RADII IN NAUTICAL MILES ARE THE LARGEST RADII EXPECTED ANYWHERE IN THAT QUADRANT. REPEAT...CENTER LOCATED NEAR 19.1N 130.3W AT 29/2100Z AT 29/1800Z CENTER WAS LOCATED NEAR 19.3N 129.6W FORECAST VALID 30/0600Z 18.9N 132.4W...POST-TROP/REMNT LOW MAX WIND 30 KT...GUSTS 40 KT. FORECAST VALID 30/1800Z 18.8N 134.7W...POST-TROP/REMNT LOW MAX WIND 30 KT...GUSTS 40 KT. FORECAST VALID 31/0600Z 18.8N 136.5W...POST-TROP/REMNT LOW MAX WIND 30 KT...GUSTS 40 KT. FORECAST VALID 31/1800Z 18.9N 138.0W...POST-TROP/REMNT LOW MAX WIND 30 KT...GUSTS 40 KT. FORECAST VALID 01/0600Z 19.0N 139.3W...POST-TROP/REMNT LOW MAX WIND 25 KT...GUSTS 35 KT. FORECAST VALID 01/1800Z 19.0N 140.3W...POST-TROP/REMNT LOW MAX WIND 25 KT...GUSTS 35 KT. EXTENDED OUTLOOK. NOTE...ERRORS FOR TRACK HAVE AVERAGED NEAR 100 NM ON DAY 4 AND 125 NM ON DAY 5...AND FOR INTENSITY NEAR 15 KT EACH DAY OUTLOOK VALID 02/1800Z 19.0N 141.5W...POST-TROP/REMNT LOW MAX WIND 25 KT...GUSTS 35 KT. OUTLOOK VALID 03/1800Z 19.5N 143.5W...POST-TROP/REMNT LOW MAX WIND 20 KT...GUSTS 30 KT. REQUEST FOR 3 HOURLY SHIP REPORTS WITHIN 300 MILES OF 19.1N 130.3W THIS IS THE LAST FORECAST/ADVISORY ISSUED BY THE NATIONAL HURRICANE CENTER ON IRWIN. FOR ADDITIONAL INFORMATION ON THE POST-TROPICAL CYCLONE PLEASE SEE HIGH SEAS FORECASTS ISSUED BY THE NATIONAL WEATHER SERVICE...UNDER AWIPS HEADER NFDHSFEPI AND WMO HEADER FZPN02 KWBC. $$ FORECASTER REINHART

000
ABPZ20 KNHC 291723
TWOEP

Tropical Weather Outlook
NWS National Hurricane Center Miami FL
1100 AM PDT Tue Aug 29 2023

For the eastern North Pacific...east of 140 degrees west longitude:

Active Systems:
The National Hurricane Center is issuing advisories on Tropical
Storm Irwin, located more than 1200 miles west of the southern tip
of the Baja California peninsula.

Tropical cyclone formation is not expected during the next 7 days.

$$
Forecaster Reinhart

5-Day Uncertainty Track last updated Mon, 28 Aug 2023 20:32:14 GMT


Wind Speed Probabilities last updated Mon, 28 Aug 2023 21:35:41 GMT

Issued at 1100 AM HST Mon Aug 28 2023 000 WTPZ45 KNHC 282031 TCDEP5 Tropical Storm Irwin Discussion Number 8 NWS National Hurricane Center Miami FL EP102023 1100 AM HST Mon Aug 28 2023 Deep convection has been fading away, and Irwin is getting closer to becoming a post-tropical cyclone. Satellite imagery suggests mid-level dry air is wrapping around much of circulation and an area of decaying convection remains over the northern portion of storm. The initial intensity remains at 35 kt based on recent ASCAT passes. Irwin has yet to make its much anticipated westward turn and is still moving west-northwestward at 9 kt. Still, model guidance insists the cyclone will go to the west shortly and remains tightly clustered. The general westward motion, with a increase in forward speed, is expected to continue through the forecast period. The latest track forecast has shifted to the north and lies between the previous forecast and the simple consensus aids. The storm appears to be in the process of weakening. The extent of tropical-storm-force winds in the northeast quadrant has decreased significantly based on the satellite-derived surface wind data. Sea surface temperatures and mid-level relative humidities are expected to decrease along the forecast track and Irwin is expect weaken further in the next day or so. The storm is still forecast to become a remnant low within 48 hours, though this could happen sooner. FORECAST POSITIONS AND MAX WINDS INIT 28/2100Z 18.6N 124.2W 35 KT 40 MPH 12H 29/0600Z 19.0N 126.3W 30 KT 35 MPH 24H 29/1800Z 19.0N 129.0W 30 KT 35 MPH 36H 30/0600Z 18.9N 131.7W 30 KT 35 MPH 48H 30/1800Z 19.0N 134.0W 30 KT 35 MPH...POST-TROP/REMNT LOW 60H 31/0600Z 19.0N 136.0W 30 KT 35 MPH...POST-TROP/REMNT LOW 72H 31/1800Z 19.2N 137.7W 30 KT 35 MPH...POST-TROP/REMNT LOW 96H 01/1800Z 19.3N 140.2W 30 KT 35 MPH...POST-TROP/REMNT LOW 120H 02/1800Z 19.2N 142.4W 25 KT 30 MPH...POST-TROP/REMNT LOW $$ Forecaster Bucci

Issued at 2100 UTC MON AUG 28 2023 000 FOPZ15 KNHC 282030 PWSEP5 TROPICAL STORM IRWIN WIND SPEED PROBABILITIES NUMBER 8 NWS NATIONAL HURRICANE CENTER MIAMI FL EP102023 2100 UTC MON AUG 28 2023 AT 2100Z THE CENTER OF TROPICAL STORM IRWIN WAS LOCATED NEAR LATITUDE 18.6 NORTH...LONGITUDE 124.2 WEST WITH MAXIMUM SUSTAINED WINDS NEAR 35 KTS...40 MPH...65 KM/H. Z INDICATES COORDINATED UNIVERSAL TIME (GREENWICH) PACIFIC DAYLIGHT TIME (PDT)...SUBTRACT 7 HOURS FROM Z TIME HAWAIIAN STANDARD TIME (HST)...SUBTRACT 10 HOURS FROM Z TIME WIND SPEED PROBABILITY TABLE FOR SPECIFIC LOCATIONS CHANCES OF SUSTAINED (1-MINUTE AVERAGE) WIND SPEEDS OF AT LEAST ...34 KT (39 MPH... 63 KM/H)... ...50 KT (58 MPH... 93 KM/H)... ...64 KT (74 MPH...119 KM/H)... FOR LOCATIONS AND TIME PERIODS DURING THE NEXT 5 DAYS PROBABILITIES FOR LOCATIONS ARE GIVEN AS OP(CP) WHERE OP IS THE PROBABILITY OF THE EVENT BEGINNING DURING AN INDIVIDUAL TIME PERIOD (ONSET PROBABILITY) (CP) IS THE PROBABILITY OF THE EVENT OCCURRING BETWEEN 18Z MON AND THE FORECAST HOUR (CUMULATIVE PROBABILITY) PROBABILITIES ARE GIVEN IN PERCENT X INDICATES PROBABILITIES LESS THAN 1 PERCENT PROBABILITIES FOR 34 KT AND 50 KT ARE SHOWN AT A GIVEN LOCATION WHEN THE 5-DAY CUMULATIVE PROBABILITY IS AT LEAST 3 PERCENT. PROBABILITIES FOR 34...50...64 KT SHOWN WHEN THE 5-DAY 64-KT CUMULATIVE PROBABILITY IS AT LEAST 1 PERCENT. - - - - WIND SPEED PROBABILITIES FOR SELECTED LOCATIONS - - - - FROM FROM FROM FROM FROM FROM FROM TIME 18Z MON 06Z TUE 18Z TUE 06Z WED 18Z WED 18Z THU 18Z FRI PERIODS TO TO TO TO TO TO TO 06Z TUE 18Z TUE 06Z WED 18Z WED 18Z THU 18Z FRI 18Z SAT FORECAST HOUR (12) (24) (36) (48) (72) (96) (120) - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - LOCATION KT 20N 125W 34 29 X(29) X(29) X(29) X(29) X(29) X(29) 20N 130W 34 X 2( 2) 15(17) X(17) X(17) X(17) X(17) 20N 135W 34 X X( X) X( X) 6( 6) 6(12) 1(13) X(13) 20N 140W 34 X X( X) X( X) X( X) 1( 1) 5( 6) 1( 7) $$ FORECASTER BUCCI

Issued at 1100 AM HST Mon Aug 28 2023 000 WTPZ35 KNHC 282030 TCPEP5 BULLETIN Tropical Storm Irwin Advisory Number 8 NWS National Hurricane Center Miami FL EP102023 1100 AM HST Mon Aug 28 2023 ...IRWIN MOVING WEST-NORTHWESTWARD OVER COOLER WATERS... SUMMARY OF 1100 AM HST...2100 UTC...INFORMATION ----------------------------------------------- LOCATION...18.6N 124.2W ABOUT 970 MI...1560 KM WSW OF THE SOUTHERN TIP OF BAJA CALIFORNIA MAXIMUM SUSTAINED WINDS...40 MPH...65 KM/H PRESENT MOVEMENT...WNW OR 300 DEGREES AT 10 MPH...17 KM/H MINIMUM CENTRAL PRESSURE...997 MB...29.44 INCHES WATCHES AND WARNINGS -------------------- There are no coastal watches or warnings in effect. DISCUSSION AND OUTLOOK ---------------------- At 1100 AM HST (2100 UTC), the center of Tropical Storm Irwin was located near latitude 18.6 North, longitude 124.2 West. Irwin is moving toward the west-northwest near 10 mph (17 km/h). A turn toward the west is expected shortly and this motion is expected to continue for the next few days. Maximum sustained winds are near 40 mph (65 km/h) with higher gusts. Gradual weakening is expected over the next day or so and Irwin is forecast to become a remnant low by Wednesday, if not sooner. Tropical-storm-force winds extend outward up to 140 miles (220 km) from the center. The estimated minimum central pressure is 997 mb (29.44 inches). HAZARDS AFFECTING LAND ---------------------- None NEXT ADVISORY ------------- Next complete advisory at 500 PM HST. $$ Forecaster Bucci

...IRWIN MOVING WEST-NORTHWESTWARD OVER COOLER WATERS... As of 11:00 AM HST Mon Aug 28 the center of Irwin was located near 18.6, -124.2 with movement WNW at 10 mph. The minimum central pressure was 997 mb with maximum sustained winds of about 40 mph.

Issued at 2100 UTC MON AUG 28 2023 000 WTPZ25 KNHC 282030 TCMEP5 TROPICAL STORM IRWIN FORECAST/ADVISORY NUMBER 8 NWS NATIONAL HURRICANE CENTER MIAMI FL EP102023 2100 UTC MON AUG 28 2023 NOTICE... LAND-BASED TROPICAL CYCLONE WATCHES AND WARNINGS ARE NO LONGER INCLUDED IN THE TROPICAL CYCLONE FORECAST/ADVISORY...(TCM). CURRENT LAND-BASED COASTAL WATCHES AND WARNINGS CAN BE FOUND IN THE MOST RECENTLY ISSUED TROPICAL CYCLONE PUBLIC ADVISORY...(TCP). TROPICAL STORM CENTER LOCATED NEAR 18.6N 124.2W AT 28/2100Z POSITION ACCURATE WITHIN 40 NM PRESENT MOVEMENT TOWARD THE WEST-NORTHWEST OR 300 DEGREES AT 9 KT ESTIMATED MINIMUM CENTRAL PRESSURE 997 MB MAX SUSTAINED WINDS 35 KT WITH GUSTS TO 45 KT. 34 KT.......120NE 0SE 0SW 0NW. 12 FT SEAS.. 90NE 0SE 0SW 90NW. WINDS AND SEAS VARY GREATLY IN EACH QUADRANT. RADII IN NAUTICAL MILES ARE THE LARGEST RADII EXPECTED ANYWHERE IN THAT QUADRANT. REPEAT...CENTER LOCATED NEAR 18.6N 124.2W AT 28/2100Z AT 28/1800Z CENTER WAS LOCATED NEAR 18.4N 123.8W FORECAST VALID 29/0600Z 19.0N 126.3W MAX WIND 30 KT...GUSTS 40 KT. FORECAST VALID 29/1800Z 19.0N 129.0W MAX WIND 30 KT...GUSTS 40 KT. FORECAST VALID 30/0600Z 18.9N 131.7W MAX WIND 30 KT...GUSTS 40 KT. FORECAST VALID 30/1800Z 19.0N 134.0W...POST-TROP/REMNT LOW MAX WIND 30 KT...GUSTS 40 KT. FORECAST VALID 31/0600Z 19.0N 136.0W...POST-TROP/REMNT LOW MAX WIND 30 KT...GUSTS 40 KT. FORECAST VALID 31/1800Z 19.2N 137.7W...POST-TROP/REMNT LOW MAX WIND 30 KT...GUSTS 40 KT. EXTENDED OUTLOOK. NOTE...ERRORS FOR TRACK HAVE AVERAGED NEAR 100 NM ON DAY 4 AND 125 NM ON DAY 5...AND FOR INTENSITY NEAR 15 KT EACH DAY OUTLOOK VALID 01/1800Z 19.3N 140.2W...POST-TROP/REMNT LOW MAX WIND 30 KT...GUSTS 40 KT. OUTLOOK VALID 02/1800Z 19.2N 142.4W...POST-TROP/REMNT LOW MAX WIND 25 KT...GUSTS 35 KT. REQUEST FOR 3 HOURLY SHIP REPORTS WITHIN 300 MILES OF 18.6N 124.2W NEXT ADVISORY AT 29/0300Z $$ FORECASTER BUCCI

000
ABPZ20 KNHC 281740
TWOEP

Tropical Weather Outlook
NWS National Hurricane Center Miami FL
1100 AM PDT Mon Aug 28 2023

For the eastern North Pacific...east of 140 degrees west longitude:

Active Systems:
The National Hurricane Center is issuing advisories on Tropical
Storm Irwin, located nearly 1000 miles west-southwest of the
southern tip of the Baja California peninsula.

Tropical cyclone formation is not expected during the next 7 days.

$$
Forecaster Bucci

5-Day Uncertainty Track last updated Sun, 27 Aug 2023 20:43:32 GMT


Wind Speed Probabilities last updated Sun, 27 Aug 2023 21:35:39 GMT

Issued at 1100 AM HST Sun Aug 27 2023 791 WTPZ45 KNHC 272042 TCDEP5 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

Issued at 1100 AM HST Sun Aug 27 2023 000 WTPZ35 KNHC 272041 TCPEP5 BULLETIN Tropical Storm Irwin Advisory Number 4 NWS National Hurricane Center Miami FL EP102023 1100 AM HST Sun Aug 27 2023 ...IRWIN MOVING WEST-NORTHWESTWARD OVER THE TROPICAL EASTERN PACIFIC WITH NO CHANGE IN STRENGTH... SUMMARY OF 1100 AM HST...2100 UTC...INFORMATION ----------------------------------------------- LOCATION...17.2N 121.3W ABOUT 835 MI...1345 KM WSW OF THE SOUTHERN TIP OF BAJA CALIFORNIA MAXIMUM SUSTAINED WINDS...40 MPH...65 KM/H PRESENT MOVEMENT...WNW OR 295 DEGREES AT 10 MPH...17 KM/H MINIMUM CENTRAL PRESSURE...998 MB...29.47 INCHES WATCHES AND WARNINGS -------------------- There are no coastal watches or warnings in effect. DISCUSSION AND OUTLOOK ---------------------- At 1100 AM HST (2100 UTC), the center of Tropical Storm Irwin was located near latitude 17.2 North, longitude 121.3 West. Irwin is moving toward the west-northwest near 10 mph (17 km/h). A turn toward the west is anticipated on Monday. Maximum sustained winds are near 40 mph (65 km/h) with higher gusts. Some strengthening is expected in the short term. Weakening is forecast to begin Monday night. Tropical-storm-force winds extend outward up to 60 miles (95 km) from the center. The estimated minimum central pressure is 998 mb (29.47 inches). HAZARDS AFFECTING LAND ---------------------- None NEXT ADVISORY ------------- Next complete advisory at 500 PM HST. $$ Forecaster Roberts

...IRWIN MOVING WEST-NORTHWESTWARD OVER THE TROPICAL EASTERN PACIFIC WITH NO CHANGE IN STRENGTH... As of 11:00 AM HST Sun Aug 27 the center of Irwin was located near 17.2, -121.3 with movement WNW at 10 mph. The minimum central pressure was 998 mb with maximum sustained winds of about 40 mph.