Even though the tropical Atlantic is quiet today, on the other side of the world Typhoon Danas is roaring through the Pacific. Typhoon Danas had maximum winds of 130-140 mph when it struck Okinawa overnight, and it looks like a classic mature typhoon/hurricane on satellite imagery. Very strong convection is surrounding an almost symmetric eye, with well formed spiral bands feeding into the strongest convection. Outflow continues to be vigorous, and sea surface temperatures are hot, so I expect Danas to remain a super Typhoon for at least today. There is some dry air entrainment and wind shear which will inhibit strengthening a bit, especially on the western side of the typhoon.
Josh from Icyclone.com is riding out Danas on Okinawa, and observed minimum pressures near 950 mb. Below is a radar shot courtesy of Josh’s quick thinking to save it, the structure is reminiscent of hurricane Andrew in Miami in 1992.
Satellite imagery this morning indicates that the surface circulation of tropical storm Karen has become well displaced from it’s associated deep convection, indicating strong vertical wind shear. This has caused Karen to weaken, and it’s maximum estimated winds are down to 40 mph.
Karen is slowly moving north, and its center should cross the Louisiana coastline sometime on Sunday. Even though the water is hot, vertical wind shear will likely prevent intensification, so Karen will only be a weak tropical storm at landfall. Brief tropical downpours and some gusty winds can be expected across the northern Gulf coast over the next several days.
Tropical storm Karen is currently centered near 25 N, 90 W and is slowly heading towards the north. Satellite imagery this morning indicates Karen is being battered by vertical wind shear, resulting in most of the storm’s convection being displaced to the east of the surface circulation. This is an unfavorable configuration for intensification, and Karen has in fact weakened based on aircraft reconnaissance data. The minimum central pressure has risen to 1003 mb and maximum flight level winds are down to 50-60 mph.
The steering currents around Karen are becoming quite weak as the Bermuda high recedes to the east and a continental high pressure system approaches from the west, which is why Karen is moving so slowly this morning. The lack of vigorous steering currents makes the forecasted trajectory of Karen more uncertain. At this point Karen could make landfall anywhere from Louisiana to the panhandle of Florida, which can be seen in the current National Hurricane center forecast path. I wouldn’t be surprised to see the center of the track shift east, since vertical wind shear is ‘dragging’ the convection in that direction, which results in a shift in the surface center towards the convection.
If wind shear continues at current levels Karen would make landfall as a weak to moderate tropical storm, but if shear relaxes Karen may have the chance to intensify as it moves over the hot waters of the Gulf of Mexico. The GFS computer model is suggesting Karen will intensify as it turns towards the coast, but this may be more of an extra-tropical transition than purely tropical intensification. If the outflow channel of Karen is enhanced enough, and shear is low enough so that it doesn’t strip the convection from the surface center, then perhaps Karen could become a minimal hurricane. In the past such scenarios have unfolded quickly in sheared systems like Karen.
The outer rainbands of tropical storm Karen are already overspreading the Bayous of Louisiana, and the weather should continue to deteriorate today along the northern Gulf coast. Hurricane watches are in effect from eastern Louisiana to near Pensacola, Florida, and residents along that stretch of coastline should watch Karen closely and prepare. Karen will likely be mostly a flooding event due to heavy rains and some storm surge, but that can still be quite dangerous along the low lying areas of the northern Gulf coast.
Aircraft reconnaissance this morning has found that the tropical disturbance near the Yucatan peninsula has developed a closed surface circulation, so now it’s officially a tropical cyclone. Wind speeds up to 70 mph at flight level were measured to the northwest of the center, suggesting that this is already a strong tropical storm with surface wind speeds of ~60 mph. The center is located near 22 N, 87.5 W, which is just north of the Yucatan peninsula.
The tropical storm has an impressive amount of deep convection, though the convection is displaced well to the east of the center, possibly due to vertical wind shear. It’s not uncommon for a tropical storm to be asymmetric like this one early in it’s life cycle. Outflow is well established around the convection, aside from the western semicircle of the storm where outflow is being inhibited by an upper-level jet stream. There is also likely quite a bit of dry air being ingested into the tropical storm from the semi-arid Yucatan peninsula. On the other hand sea surface temperatures are very hot this time of year in the Gulf of Mexico, which favors development. Overall the environment is favorable for continued strengthening, but strengthening will be slow until the convection becomes more lined up with the surface circulation.
Karen is expected to head slowly northwestward across the Gulf of Mexico over the next few days, and probably will reach the northern Gulf coast in 3-4 days. This will give it plenty of time to intensify, so interests from the panhandle of Florida to Texas should keep an eye on Karen. It’s too early to pin down specifically where Karen will make landfall, or how strong it will be.
A tropical wave that has been slowly moving through the Caribbean this week has become much more organized overnight based on satellite imagery. There is abundant deep convection across the disturbance, which will help generate low pressure by evacuating mass out of the lower levels of the atmosphere. Satellite loops suggest there’s a sharp wind shift across the middle of the disturbance, which may be the beginnings of a low-level closed circulation. Waters are very hot in the northwestern Caribbean this time of year, and vertical wind shear appears to be weak since outflow is fanning out relatively uninhibited around most of the disturbance. Thus, environmental conditions are favorable for this disturbance to become a tropical cyclone.
Global forecasting models also suggest this disturbance will become a tropical cyclone as it slowly heads northwest. It’s likely going to cross the Yucatan peninsula, which may weaken it for a bit, but after that it will move into the Gulf of Mexico. The Gulf of Mexico is a very favorable region for tropical cyclone intensification this time of year, so interests across the Gulf of Mexico, and more specifically the northern Gulf coastline, should keep an eye on this disturbance. Heavy tropical downpours associated with this disturbance are already overspreading Cuba and southern Florida.
Satellite imagery this afternoon indicates that tropical storm Manuel is intensifying, with vigorous convection evident around the center and well-defined spiral bands. It’s rare to see a tropical cyclone in the Gulf of California, let alone an intensifying one, since the Gulf of California is such a narrow body of water. A tropical cyclone has to follow the perfect track to thread the gap between Baja California and the Sierra Madre Occidental mountains on the mainland. The mountains to either side of Manuel act to weaken the circulation, as well as the dry air coming off the hot Mexican deserts, but despite all that Manuel is intensifying and expected to become a hurricane. The sea surface temperatures in the Gulf of California are notoriously hot for that latitude, which is probably one of the main driving forces behind Manuel’s current intensification phase. Also wind shear is weak, allowing Manuel to become more and more organized rather than getting ripped apart.
Hurricane watches have been issued for a large swath of the mainland Mexico coastline, with tropical storm watches along the Baja California coastline. Manuel is projected to move very slowly as it approaches the coast, and perhaps even stall on the coastline, due to a lack of steering currents and also because hurricanes tend to get literally caught up on mountains due to friction. Manuel will likely fall apart as it interacts with the mountains, and then it’s remnants will head back towards Baja California as shown in the below National Hurricane Center forecast.
The biggest threat with Manuel will be flash floods in the mountains, since Manuel is moving very slowly and at the same time funneling lots of rich tropical moisture up the slopes of the mountains. This moisture rich air condenses as it rises and cools, resulting in heavy downpours. Additionally, the area Manuel is impacting is a desert, so they’re not used to much rainfall.
Tropical storm Dorian is located near 17 N 37 W this afternoon with estimated maximum sustained winds of 60 mph and a minimum pressure of 999 mb. Satellite imagery of Dorian is impressive this afternoon, there is a well-defined circulation apparent in the low level clouds, and convective plumes are firing right over the center. Environmental conditions are far from perfect for strengthening however, Dorian is on the southern edge of a Saharan Air Layer (SAL) outbreak, resulting in significant dry air entrainment and wind shear. This is why Dorian hasn’t been strengthening quickly, and at times (like this morning) convection was almost absent and Dorian was likely weakening. Dorian is a relatively small tropical cyclone, which makes it more prone to dry air and wind shear.
I expect Dorian will hold its own against the dry air and shear, but probably won’t become a hurricane until conditions improve down the road. There is alot of dry air ahead of Dorian, and it appears the environment won’t moisten up until Dorian is north of the Lesser Antilles. On the other hand sea surface temperatures are increasingly warm towards the west, so that’ll help Dorian gain some steam or at least maintain.
Dorian is moving WNW at a relatively quick 17 mph, and is expected to pass to the north of the Lesser Antilles and Puerto Rico Sunday and Monday. The GFS model is suggesting Dorian might go further south than currently projected by the National Hurricane Center, possibly impacting Puerto Rico and the Virgin Islands Monday. Interests around Puerto Rico should keep a close eye on Dorian, especially since environmental conditions will improve as Dorian approaches Puerto Rico, and it could possibly become a hurricane.
Dorian may be a threat to the Bahamas and southeastern United States later next week, especially if it takes a more northerly route and avoids interaction with the high terrain of Hispaniola and Cuba. At this point it’s too early to speculate about any specific impacts, since it’s still possible Dorian could hit Hispaniola and dissipate, which is what the GFS model suggests. Interests in the southeast USA and the Bahamas should monitor Dorian just in case.
Tropical storm Chantal has developed in the Atlantic ocean and is currently located near 12 N 53 W, which is to the east of the Lesser Antilles and to the north of the mouth of the Amazon River. Maximum wind speeds are estimated to be 45 mph with a minimum pressure of 1005 mb. Chantal is heading towards the west northwest (WNW) at a brisk 25 mph, which will bring it over the Lesser Antilles tomorrow. Since Chantal developed from a tropical wave which left the African continent near the Cape Verde islands, it’s considered a Cape Verde storm. Cape Verde storms are oftentimes the most vigorous tropical cyclones in the Atlantic ocean, since they have many days to develop as they cross the warm expanses of the Atlantic.
Chantal is a relatively small tropical storm at about 500 km across, but that’s still enormous compared to your average popup thunderstorm in the southeast United States. The structure of Chantal is well organized for a weak tropical storm, with spiral cloud bands and a closed low level circulation. Sea surface temperatures are at 28-30 C in the path of Chantal which is favorable for strengthening. On the other hand there is quite a bit of dry air being entrained into Chantal due to a Saharan Air Layer (SAL) outbreak, which tends to inhibit strengthening. There is some vertical wind shear as indicated by higher clouds outracing lower clouds, but overall it is light enough to allow strengthening. When considering all the environmental factors I think Chantal will continue slowly strengthening, but dry air and light shear will probably prevent Chantal from becoming stronger than a tropical storm for at least the next couple of days.
Interests in the Lesser Antilles should be prepared for tropical storm impacts starting tomorrow morning, and tropical storm warnings are in effect for most of the island chain. Chantal will move into the eastern Caribbean later on Tuesday, and is forecast to hit Hispaniola on Wednesday. It is possible Chantal could intensify into a minimal hurricane before reaching Hispaniola. Puerto Rico may receive impacts from Chantal as well and should watch this storm closely, tropical storm watches are already in effect for Puerto Rico. If Chantal hits Hispaniola it will likely be torn to shreds by the mountains, but it is too soon to tell if that will happen since it could end up traveling south of Hispaniola. Jamaica, Cuba, and the southeastern United States should keep an eye on Chantal just in case. I will continue to update.
Infrared imagery indicates that a Polar Low has developed in the Labrador Sea (below). A Polar Low is a warm core convective vortex similar to a tropical cyclone, they often have an eye feature and spiral bands. This Polar Low is being fueled by the huge temperature contrast between frigid Arctic air and the unfrozen Labrador Sea. Ocean waters are hovering right around freezing (32 F) while the overlying air is 0 to 10 F, resulting in vigorous heat fluxes. This process is slightly different than a tropical cyclone which obtains most of its energy from latent heat fluxes rather than the air-sea temperature contrast. Another difference between Polar Lows and tropical cyclones is that Polar Lows are usually much shallower since the tropopause is much shallower near the Poles than in the Tropics. Structurally they are almost the same though, both being warm core vortices with their most vigorous winds near the surface.
The Polar Low is heading due south towards the coast of Newfoundland. It’s difficult to forecast Polar Lows due to their small size, global forecast models like the GFS barely resolve them. The GFS shows the Polar Low getting near the Newfoundland coast and then curving southeast back out to sea, but it doesn’t initialize the Polar Low in a realistic way. If the Polar Low were to hit land, which is possible, it could bring tropical storm force wind gusts and heavy snow squalls, so if you happen to be living on the frozen Labrador Sea coast it’s probably a good ideal to keep an eye on this storm.
Visible satellite imagery reveals 2 powerful cyclones in the northernmost reaches of the Pacific this evening. The stronger of the two is centered over the Aleutian Islands and Alaskan Peninsula and is heading slowly northeast. It is causing wind gusts up to hurricane force on the Alaskan coastline and stirring up 20-30 foot waves, and bringing heavy snows to interior locations. The other cyclone is well to the southwest of the westernmost Aleutian Islands, but should start impacting the islands over the next day. Both systems are feeding on the temperature gradient between the frigid Arctic (note the sea ice between Russia and Alaska in the image) and the relatively warm Pacific, which is a common occurrence throughout the Winter.