After a week of watching and waiting Tropical Depression 16 forms in the southwest Caribbean early Monday. It quickly became upgraded to Otto, the 15th named storm of the 2016 Atlantic season Monday afternoon. Tiny Tropical Storm Otto is stationary at 1PM EST with max sustained winds of 50 mph. It is embedded in a pocket of moderate southwesterly shear but sits over very warm Caribbean waters. Gradual organization is likely early this week. Hurricane hunters will investigate the disturbance Tuesday. Otto headed for Nicaragua and Costa Rica Thursday as a possible category 1 hurricane. Remnants of Otto will emerge in the east Pacific Friday and Saturday. November named storms rare. Late November named storms are even rarer. According Dr. Klotzbach of Colorado State University the formation of Otto in the western Caribbean is the 4th latest on record since 1851. Just last year there was a November named storm, Hurricane Kate. Kate formed in early November.
The 12Z GFS is in line with the official NHC intensity forecast and develops Hurricane Otto by Thursday morning. By Friday, this model suggests a strengthening hurricane will make landfall in southeast Nicaragua. This is a little further north than the NHC forecast. Meanwhile the 0Z ECMWF model keeps Otto much weaker with a landfall further south near the Nicaragua/Costa Rica border Thursday afternoon. There are still a couple days to tweak this forecast.
The main threat for portions of Central America will be heavy rainfall. Parts of Nicaragua, Costa Rica and Panama will see several inches of rain mid to late work week. Some areas could pick up 10 to 15 inches off rainfall near higher terrain. Flash flooding and dangerous mudslides are possible.
While convection increases near Invest 90L in the extreme southwest Caribbean Saturday the disturbance is still disorganized. The broad area of low pressure has not moved much over the past few days and it will continue to meander uncomfortably close to Central America in the days ahead. Wind shear is moderate overhead which limits organization in the short-term. Tropical depression development is unlikely the next 2 days but there is medium 50% chance by Thursday.
The 0Z Euro is still the most aggressive model in development over the next 7 days. By Thursday morning a weak tropical depression sits east of Nicaragua and Panama. By next weekend this model brings heavy rain and a weak hurricane to this area. Meanwhile the 06Z GFS brings a weak Tropical Storm Otto into Nicaragua Thursday morning with deep tropical moisture exiting by late week/next weekend.
Regardless of development heavy rain is possible for portions of Central America by mid to late work week. Of course specific amounts depend of the exact track. The GFS brings several inches of rain to Panama and Nicaragua between now and Friday afternoon.
As of Wednesday afternoon, Invest 90L in the Southwest Caribbean remained very disorganized and lacked much convection. However, a modest swirl was still evident on enhanced satellite imagery, and the odds of development are still rather high over the next 5 days. The National Hurricane Center has 2 day odds at 30%, but 5 day odds at 80%.
Regardless of development, 90L will be a slow and erratic mover. There is little steering current in the Southwest Caribbean over the next week, and so the models are split in every which direction of where 90L will meander. Below are several model forecasts through next Tuesday.
As for actual development, the European model has been the most aggressive. By the middle of next week, the operational run shows Tropical Storm Otto in the Southwest Caribbean, and several of its more prominent ensemble members show the same solution. They also show little in the way of movement in that timeframe. Here is the forecast from the ECMWF for one week from today.
Meanwhile, the GFS hasn’t showed as much development, and keeps 90L as a tropical depression, or even just a broad area of low pressure. Here is the GFS solution for the middle of next week.
Even though its late in the season, there are a couple factors working in favor of tropical development for Invest 90L. The wind shear over the Southwest Caribbean will remain quite light over the next week, and sea surface temperatures are above average (~1° above normal).
Regardless of development, the biggest threat for 90L looks to be heavy rain. While most of the models keep the heaviest rain offshore, a wobble or shift west in the track could mean very heavy rain for portions of Central America.
An area of disturbed weather, now pinned Invest 90L, shows some signs of gradual organization Tuesday in the southwest Caribbean. Outflow has improved, pressure has dropped some and convection is scattered. A tropical depression/Tropical Storm Otto is likely to form later this week or this weekend. Invest 90L will move little in the days ahead and meander near Central America.
Wind shear favors gradual strengthening in the Caribbean. Wind shear is low overhead at 5-10 kts. Hostile upper level winds will remain well north of Invest 90L. The graphic below shows the green favorable shear over the area of disturbed weather and the red unfavorable shear over the Gulf of Mexico and northwest Caribbean. The graphic below is courtesy the University of Wisconsin.
There won’t be much steering to guide Invest 90L and it could meander in the Caribbean near Central America for 7+ days. This could spell a heavy rain threat for some . Strong high pressure over the eastern U.S. will keep this disturbance well south of Florida and the U.S.. Here is the 18Z computer model forecast through next Monday. A wobble west towards Central America or north and east towards Jamaica and Hispaniola will make a huge difference in any tropical impacts in these locations.
While the future track of possible Otto remains unknown, so is the future intensity. Some models are more aggressive than others. The 12Z Euro shows a stronger possible Hurricane Otto over the warm Caribbean waters by next Tuesday. The 12Z GFS shows a weaker Tropical Storm Otto closer to Central America. This would mean a heavy rain threat and tropical storm conditions for portions of Central America. Stay tuned as this is a ways off.
The southwest Caribbean is a place to watch for tropical depression development this week. Only 5% of named storms form in November so it is rare, but not impossible. Most recently Kate became a hurricane in November 2015. On Monday it’s a wait and see situation. Wind shear is low in the extreme southwest Caribbean and broad low pressure may form over the next 5 days. Officially, there is a medium chance of tropical depression development by Saturday. The next named storm is Otto. The movement would be slow north or northeast.
This is a favorable spot for a tropical low to develop. Sea surface temperatures in the low to mid 80s are plenty warm for organization.
Computer models and some ensembles are on board with tropical depression development late work week/this weekend. The 12Z European model shows a tropical depression/possible weak Tropical Storm Otto Friday near Central America. The 12Z GFS is slower to develop this feature but does show pressure lowering in the vicinity Friday.
One change in the computer models over the past few days is the slow movement of the possible future tropical depression/named storm. With a series of highs building in over the Southeast U.S. the low may be suppressed south and meander in the Caribbean for several days. This could pose a heavy rain threat for Central America/some of the islands. Below is the 12Z European model versus the 12Z GFS model Monday afternoon. The Euro shows a weak Tropical Storm Otto drifting near Hispaniola. The GFS suggests an even slower moving and also weak tropical cyclone over the warm waters of the southwest Caribbean.
There are about 2 weeks left in the 2016 Atlantic Hurricane Season. Wind shear and cooler water temperatures have limited activity this month. So far there are no named November storms. Our attention closes in on the southwest Caribbean this upcoming work week. The long-range European model has been incredibly insistent on developing low pressure in the western Caribbean. Officially, there is a low chance broad low pressure forms in the southwest Caribbean by mid-work week.
The 0Z Euro develops a tropical low Wednesday and Thursday in the southwest Caribbean at the tail end of an old frontal boundary. Steering currents bring this possible tropical depression/Tropical Storm Otto northeast towards Puerto Rico, Cuba and the Bahamas by next weekend/early next week.
Meanwhile the GFS does not develop a tropical feature as wind shear may be too high. Below is the wind shear forecast for Thursday morning. Regardless, we will monitor the Caribbean this week for any developments.
It’s the final stretch of the 2016 Atlantic Hurricane season. Wind shear has kept the Atlantic Basin in check. On Monday upper level winds are unfavorable for tropical depression development in the Gulf of Mexico, northwest Caribbean and Atlantic. There are no signs of any tropical depression development over the next 5 days.
It’s a ways off, but long-range models hint that the western Caribbean is a place to watch in about 7-10 days. While wind shear has been high in the northwest Caribbean it has been significantly lower in the southwest Caribbean. Below is the forecast as pressure begins to lower next Monday evening. Climatology favors a northeast track mid-week next week. We’ll keep you posted if model trends continue.
The final month of the 2016 Atlantic hurricane season begins Tuesday. It’s typically the quietest month of the season. Only 5% of named storms form in November. While named storms in November are less common compared to other months, they do occur. Most recently, Kate became a hurricane in the Atlantic in 2015. According to the National Hurricane Center more than 100 tropical cyclones have been tracked during November.
Tropical systems that form in November often originate in the western Caribbean or near the Bahamas. This can be along decaying frontal boundaries. Any storms that do form and gain tropical characteristics tend to track northeast over the open Atlantic. High wind shear and cooler water temperatures limit tropical cyclones in November.
Wind shear is incredibly high in the Gulf of Mexico, the northwest Caribbean and the western and central Atlantic Tuesday. This is indicated by the unfavorable red color on the graphic below (courtesy University of Wisconsin). There are a few pockets of slightly more favorable upper level winds in the south and eastern Caribbean. We’ve been eyeing a weakening area of low near Puerto Rico. Clearly high westerly shear took a toll on the low as it moves northeast. Officially, per the NHC, no tropical depression development is expected over the next 5 days.
As mentioned over the weekend the GFS and European model hint that low pressure will spin up over the open central Atlantic later this work week. That is still the case Tuesday. At this point this appears to be a non tropical area of low pressure and won’t impact any land masses.
The final days of October are here and the Atlantic Basin is quiet overall. Broad low pressure near Central America will continue to weaken Sunday. Wind shear remains high and it moves over land early work week. Elsewhere an old frontal boundary stirs up convection in the Atlantic south and east of Bermuda. Upper level winds are hostile in this region. A trough near the Southeast Bahamas and north of Hispaniola enhances scattered convection. This feature also sits in a region of hostile upper level winds. There is only one tropical wave. It moves over the Lesser Antilles late Sunday and Monday with limited shower activity. Officially, no tropical depression development is expected over the next 5 days.
Both the European model and GFS model hint that low pressure may spin up along a frontal boundary mid to late work week. This is northeast of the Lesser Antilles over the open central Atlantic. Wind shear is too high for significant tropical development, but it worth watching. If low pressure develops and gains any tropical characteristics it heads northeast away from land and the U.S.. Below is the European wind shear forecast for Thursday morning.
Only 5% of named storms form in November as wind shear is often high and water temperatures have cooled. Any named storms that do form in the last month of the Atlantic season typically form in the western Caribbean or near the Bahamas and head northeast. If low pressure develops mid-work week the northeast steering is in line with climatology.
October 2016 winds down and it is likely to wrap up with no more named storms. It has been an active month. While Matthew formed in late September it made landfall in Haiti, Cuba, and the Bahamas as a major hurricane in early October. Matthew also made landfall as a hurricane in South Carolina. Major hurricane Nicole lashed Bermuda in mid October. We continue to watch the western Caribbean, the Gulf of Mexico and the western Atlantic in the days ahead. These areas favor tropical depression development in late October. Fortunately, the atmosphere does not favor tropical organization over the next 5+ days in these locations.
On Tuesday two frontal systems keep upper level winds hostile in the western Caribbean, Gulf of Mexico, and western Atlantic. A tropical wave between the Lesser Antilles and Africa is still disorganized. Wind shear is moderate overhead and will increase as this disturbance moves westward at 10-15 mph. The GFS hinted at possible tropical depression development with this feature, but it has now backed off on that possibility. This isn’t a typical region we watch for tropical cyclone development in late October, so this makes perfect sense. Wind shear is too high.
The European wind shear forecast shows the extent of unfavorable upper level winds in the Atlantic Basin. With an active upper level pattern and fronts moving off the Southeast coast every few days wind shear will remain moderate to high over the next 5-10 days.
Meanwhile in the eastern Pacific major hurricane Seymour continues the strengthen. The tiny and powerful storm will strengthen further on Wednesday over warm waters and under light wind shear. Beyond mid-week wind shear increases. Seymour will dissipate before its remnant moisture approaches the west coast of the U.S. late this weekend.