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Tropical Storm John Forecast Discussion Number 8
2024-09-24 10:52:20| National Hurricane Center (East Pacific)
Issued at 300 AM CST Tue Sep 24 2024 523 WTPZ45 KNHC 240852 TCDEP5 Tropical Storm John Discussion Number 8 NWS National Hurricane Center Miami FL EP102024 300 AM CST Tue Sep 24 2024 John moved inland at around 0315 UTC as a 105 kt Category 3 Hurricane. Since that time, the the storm has apparently turned more leftward and remains just inland, skirting the southern coast of Mexico. While surface observations have been sparse, my best guess is that the storm recently passed just to the north of Acapulco, where the airport earlier reported tropical-storm-force wind gusts and west winds as the pressure dropped to 998 mb. Assuming the small core has continued to quickly weaken, John is being downgraded to a tropical storm, and the initial intensity is 60 kt this advisory. Following fixes from earlier microwave and more recent geostationary satellite imagery, John now appears to be moving northwestward at 310/7 kt. The track forecast, which has been problematic with John from the start, is just as difficult now. John has continued to deviate westward of the previous forecast track and is now moving roughly parallel to the coast of Mexico. To make matters worse, a decent chunk of the of the global models guidance (ECMWF, UKMET) and hurricane regional models (HWRF, HMON) suggest the circulation could continue turning westward and attempt to re-emerge over the Eastern Pacific. Even the GFS and CMC solutions, which appear to dissipate the surface circulation inland over Mexico, show the mid-level circulation persisting and drifting back offshore, leading to the development of a new low-level circulation. Because it is becoming distinctly possible that John does not move far enough inland to dissipate entirely, and the aforementioned continued leftward trends, the latest NHC track forecast is altered quite a bit form the prior forecast, and now shows the possibility that John, albeit as a tropical depression, moving back offshore as it becomes tangled in the larger monsoonal flow. By 72 h, most of the track guidance shows the system moving back inland. The updated track forecast is roughly in between the HCCA and ECMWF trackers, and is of very low confidence given John's track history. It also remains possible the system could dissipate later today if it moves further inland. Intensity-wise, John should continue to rapidly weaken as long as it remains onshore, and the NHC intensity forecast shows the tropical cyclone weakening to a tropical depression later today. However, the new NHC forecast now maintains the system as a depression and does not show dissipation beyond 24 h given the latest track forecast taking the system along the coast of Mexico and not far enough inland to completely dissipate. Some of the models (notably the ECMWF) attempt to also re-intensify John as it gets far enough back offshore, but given the large changes made on this forecast cycle, the NHC intensity will not show that solution quite yet. Even if John remains inland, larger-scale moist monsoonal southeasterly flow will persist along the southern coast of Mexico, likely contributing to catastrophic rainfall both along the coast and inland over the up-slope portion of the mountainous terrain. This is a very dangerous life-threatening flooding scenario. KEY MESSAGES: 1. Tropical Storm John could still producing tropical storm conditions for the next few hours in the tropical storm warning area. 2. Slow-moving John will bring very heavy rainfall to coastal portions of southwest Mexico through the upcoming week. This heavy rainfall will likely cause significant and possibly catastrophic, life-threatening flash flooding and mudslides to the Mexican States of Chiapas, Oaxaca, and southeast Guerrero, particularly in areas near the coast and along the up-slope portion of areas of higher terrain. FORECAST POSITIONS AND MAX WINDS INIT 24/0900Z 17.3N 100.0W 60 KT 70 MPH...INLAND 12H 24/1800Z 17.4N 100.8W 30 KT 35 MPH...INLAND 24H 25/0600Z 17.0N 101.0W 30 KT 35 MPH...OVER WATER 36H 25/1800Z 16.7N 100.9W 30 KT 35 MPH 48H 26/0600Z 16.9N 100.6W 30 KT 35 MPH 60H 26/1800Z 17.4N 100.7W 25 KT 30 MPH...INLAND 72H 27/0600Z 18.1N 101.3W 20 KT 25 MPH...POST-TROP/REMNT LOW 96H 28/0600Z...DISSIPATED $$ Forecaster Papin
Category:Transportation and Logistics
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Tropical Storm John Graphics
2024-09-24 10:51:24| National Hurricane Center (East Pacific)
5-Day Uncertainty Track last updated Tue, 24 Sep 2024 08:51:24 GMT Wind Speed Probabilities last updated Tue, 24 Sep 2024 08:51:24 GMT
Category: Transportation and Logistics
Tropical Storm John Wind Speed Probabilities Number 8
2024-09-24 10:50:51| National Hurricane Center (East Pacific)
Issued at 0900 UTC TUE SEP 24 2024 000 FOPZ15 KNHC 240850 PWSEP5 TROPICAL STORM JOHN WIND SPEED PROBABILITIES NUMBER 8 NWS NATIONAL HURRICANE CENTER MIAMI FL EP102024 0900 UTC TUE SEP 24 2024 AT 0900Z THE CENTER OF TROPICAL STORM JOHN WAS LOCATED NEAR LATITUDE 17.3 NORTH...LONGITUDE 100.0 WEST WITH MAXIMUM SUSTAINED WINDS NEAR 60 KTS...70 MPH...110 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 06Z 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 06Z TUE 18Z TUE 06Z WED 18Z WED 06Z THU 06Z FRI 06Z SAT PERIODS TO TO TO TO TO TO TO 18Z TUE 06Z WED 18Z WED 06Z THU 06Z FRI 06Z SAT 06Z SUN FORECAST HOUR (12) (24) (36) (48) (72) (96) (120) - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - LOCATION KT ZIHUATANEJO 34 1 2( 3) 1( 4) 1( 5) 1( 6) X( 6) X( 6) ACAPULCO 34 99 X(99) X(99) X(99) X(99) X(99) X(99) ACAPULCO 50 66 X(66) X(66) 1(67) X(67) X(67) X(67) $$ FORECASTER PAPIN
Category: Transportation and Logistics