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| #1097700 (Received by flhurricane at: 5:09 AM 02.Jul.2022) TCDAT2 Tropical Storm Bonnie Discussion Number 19 NWS National Hurricane Center Miami FL AL022022 400 AM CDT Sat Jul 02 2022 Overall, Bonnie`s structure is holding together quite well as the storm moves across Central America. While the coldest cloud tops near the center have warmed somewhat, radar from the Nicaraguan Weather Service in Las Nubes shows a healthy reflectivity structure. In fact, after the last center fix the Air Force Reserve Hurricane Hunter aircraft made indicated a formative eyewall was developing with Bonnie, a similar signature is now also currently observed with Bonnie over Lake Nicaragua. Assuming there has been some weakening of the wind field since Bonnie began moving over land, the intensity is being reduced to an uncertain 35 kt for this advisory. Bonnie was moving just north of due west from the recon fixes last night, and the initial motion has been maintained at 275/14 kt. A strong deep-layer ridge poleward of Bonnie should continue to steer the cyclone west to west-northwestward for the majority of the forecast period after it moves offshore. This track continues to take Bonnie roughly parallel to the southern coast of Central America and Mexico. The track guidance remains in good agreement this cycle, and only slight changes to the forecast track were made, mostly a somewhat faster motion at the end of the forecast period. While the relatively small size of the tropical cyclone is currently forecast to keep the highest winds offshore, interests in coastal El Salvador, Guatemala, and southwestern Mexico should continue to monitor Bonnie`s track for the next few days, as any northward track adjustments could require tropical storm watches for portions of this coastline. So far Bonnie`s structure does not appear to be that adversely affected by its ongoing land interaction crossing Central America, perhaps because it is traversing a relatively flat gap across Lake Nicaragua, in between higher terrain to its north or south. However, one thorn in the system`s short-term intensity forecast is that sea surface temperatures (SSTs) just offshore Nicaragua are not all that warm, only between 26-27 C with a very shallow depth of these marginally warm waters for the first 24 h or so. For this reason, only slow intensification is forecasted early on, which is under the majority of the guidance in this time frame. Afterwards, SSTs markedly warm to above 28 C, and vertical wind shear is expected to remain only light to moderate. Thus, a faster rate of intensification is anticipated after 36 h, and Bonnie is still forecast to become a hurricane in about three days. The latest intensity forecast has been adjusted downward in the short-term, but still peaks the storm as a 75-kt hurricane at the end of the forecast period. It is worth mentioning that Bonnie`s low-level circulation is expected to survive its passage across Central America, similar to that of Hurricane Otto back in 2016. Thus, the system is expected to retain its name even after it moves into the far eastern Pacific later today. The intermediate advisory at 1200 UTC will be issued under the same Atlantic header as before. Product headers will change to eastern Pacific headers beginning with the next complete advisory at 1500 UTC, with the ATCF identifier changing from AL022022 to EP042022. KEY MESSAGES: 1. Heavy rainfall is expected across portions of Nicaragua and Costa Rica today. Life-threatening flash flooding and mudslides are expected. 2. Tropical storm conditions are expected along the Caribbean coasts of Costa Rica and Nicaragua within the Tropical Storm Warning areas for the next several hours, and along the Pacific coasts of Costa Rica and Nicaragua today. FORECAST POSITIONS AND MAX WINDS INIT 02/0900Z 11.3N 85.1W 35 KT 40 MPH...OVER LAKE NICARAGUA 12H 02/1800Z 11.3N 87.1W 35 KT 40 MPH...OVER PACIFIC OCEAN 24H 03/0600Z 11.5N 89.4W 40 KT 45 MPH 36H 03/1800Z 12.0N 91.9W 45 KT 50 MPH 48H 04/0600Z 13.0N 95.0W 55 KT 65 MPH 60H 04/1800Z 13.9N 98.0W 60 KT 70 MPH 72H 05/0600Z 14.7N 101.0W 65 KT 75 MPH 96H 06/0600Z 16.0N 106.4W 75 KT 85 MPH 120H 07/0600Z 16.4N 110.5W 75 KT 85 MPH $$ Forecaster Papin |