Bonnie will soon move offshore of Nicaragua and emerge over the pacific.
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.
CHANGES WITH THIS ADVISORY:
SUMMARY OF WATCHES AND WARNINGS IN EFFECT:
A Tropical Storm Warning is in effect for...
- Limon Costa Rica northward to Sandy Bay Sirpi Nicaragua
- Cabo Blanco Costa Rica northward to the border of Nicaragua and Honduras
A Tropical Storm Warning means that tropical storm conditions are expected somewhere within the warning area, in this case within 6 to 12 hours.
Interests along the Pacific coasts of El Salvador, Guatemala, and southern Mexico should monitor the progress of Bonnie.
For storm information specific to your area, please monitor products issued by your national meteorological service.
Key messages for Tropical Storm Bonnie can be found in the Tropical Cyclone Discussion under AWIPS header MIATCDAT2 and WMO header WTNT42 KNHC.
RAINFALL: Bonnie will continue to produce heavy rain across portions of Nicaragua and Costa Rica through today. The following storm total rainfall amounts are expected:
Nicaragua and Costa Rica: 4 to 8 inches, localized 12 inches. This rainfall is expected to result in lifethreatening flash flooding and mudslides.
WIND: Tropical storm conditions are occurring in the Tropical Storm Warning area along the Caribbean coasts of Nicaragua and Costa Rica, and these will likely continue for several more hours.
STORM SURGE: Water levels are expected to subside along the Caribbean coast of Nicaragua later this morning.
At 700 AM CDT (1200 UTC), the center of Tropical Storm Bonnie was located near latitude 11.2 North, longitude 85.8 West. Bonnie is moving toward the west near 14 mph (22 km/h), and a continued westward motion with a gradual decrease in forward speed is expected later today. A westnorthwestward motion is expected to begin tonight or on Sunday and continue into Tuesday. On the forecast track, Bonnie will emerge over the eastern Pacific Ocean in the next couple of hours. Bonnie will then move offshore of but parallel to the coasts of El Salvador, Guatemala, and southern Mexico today through Tuesday.
Maximum sustained winds remain near 40 mph (65 km/h) with higher gusts. Gradual strengthening is forecast after Bonnie emerges over the eastern Pacific later this morning and should continue through Tuesday.
Tropicalstormforce winds extend outward up to 70 miles (110 km) from the center.
The estimated minimum central pressure is 1002 mb (29.59 inches).
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.
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