The 2015 Atlantic hurricane season ends Monday. Even with the strongest El Niño since the record 1997-1998 event (2015 may even surpass it this Winter) there are 11 named storms, 4 hurricanes and 2 major hurricanes. In an average Atlantic hurricane season there are 12 named storms, 6 hurricane and 3 major hurricanes. 2015 had a near average number of named storms but a below average number of hurricanes and major hurricanes. This makes sense entirely with long spells of dry air, hostile upper level winds (especially in the Caribbean) and cooler than normal Atlantic water temperatures at times in association with a strong El Niño. The 2015 number of named storms was in line with predictions from NOAA and Dr. Gray and his colleagues at Colorado State University. However, both forecasted fewer major hurricanes. This year’s ACE or Accumulated Cyclone Energy of 60 was relatively low based on the below average number of hurricane and major hurricanes. Many named storms were short-lived in 2015. ACE measures the total energy output of all tropical systems during the entire hurricane season. Two storms made landfall in the U.S. this year. Ana made landfall in South Carolina and Bill made landfall in Texas. For the 10th year in a row Florida was spared from a hurricane landfall. Meanwhile tropical cyclones thrived over the record warm equatorial Pacific waters. In the blockbuster east Pacific season there are 9 major hurricanes. This is the most major hurricanes since reliable record keeping began in 1971. Patricia was the strongest cyclone ever recorded in the Western Hemisphere. Max sustained winds reached an unprecedented 200 mph and pressure bottomed out at 879 mb. The last named storm Sandra is the latest category 4 storm ever observed in the western hemisphere.
While the Atlantic season officially begins on June 1st it was off to an early start. Subtropical storm Ana formed on May 8th over the warm Gulf Stream waters east of the U.S. It was the earliest named storm since Subtropical Storm Ana in 2003. Ana made landfall as a tropical storm near North Myrtle Beach, South Carolina and brought minor street flooding and beach erosion to the coastal Carolinas. It had 45 mph winds at landfall making it the strongest tropical storm ever recorded to hit the U.S. so early in the year.
A few weeks later Tropical Storm Bill quickly developed over warm extreme western Gulf of Mexico waters. The second named storm of the season made landfall in southeast Texas during high tide. It drenched states from Texas to the Ohio Valley. Bill maintained an impressive structure well inland over the U.S. 4 days after landfall. Moderate to high wind shear and dry air prevented tropical depression develop through much of June and July in the Gulf of Mexico, the Caribbean and Atlantic. Ironically the third named storm of the season, Claudette formed in mid July ahead of schedule. The third named storm in the Atlantic typically forms on August 13th. Claudette briefly developed over the warm Gulf Stream in the western Atlantic but dissipated 24 hours later. It was the third short-lived named storm in a row. Remnants of Claudette brought squalls to Newfoundland.
Cape Verde season started a bit early and a series of healthy tropical waves moistened a dry environment west of Africa. In mid August Danny become the first hurricane and first major of the season from one of these Cape Verde type waves. The first major hurricane doesn’t typically form until September 4th. The same features that other tropical disturbances struggled with through the season took a toll of Danny. It dissipated before it reached the Lesser Antilles. Tropical Storm Erika formed shortly after in the eastern Atlantic. It too weakened due to wind shear and dry air and due to these features computer models struggled with the intensity and track which gave Florida a scare. After being disrupted by land interaction with Hispaniola and Cuba Erika dissipated. The remnants brought heavy rain to parts of Florida.
Fred became the second hurricane of 2015 in late August. It rare fashion it reached hurricane strength near the Cape Verde Islands. Fred is the eastern most hurricane to develop in the Atlantic and for the first time ever a hurricane warning was issued for the Cape Verde Islands. The center of Fred officially passed just to the north of the islands but Fred brought heavy squalls, flooding, strong winds and rough surf to the region. Grace was next. The fourth Cape Verde originated storm dissipated over the central Atlantic after being choked by dry African air and sheared by hostile upper level winds. Shortly before the climatological peak of the Atlantic season Henri formed east of Bermuda. It dissipated over the open north Atlantic. In mid September Tropical Depression 9 formed between to the Lesser Antilles and Africa. It fell apart due to strong wind shear over the open Atlantic.
Pesky Tropical Storm Ida was another fish storm over the open Atlantic. It maintained tropical storm strength for nearly a week before more El Niño induced high wind shear and dry air lead to dissipation. In late September Joaquin became the 3rd hurricane of the Atlantic season near the Bahamas. On October 1st it rapidly intensified into the 2nd major hurricane of the season which surpassed the number of major hurricanes forecasted by NOAA and Colorado State University. It pounded the central and southeast Bahamas with major hurricane force winds for 36 hours. Joaquin is the strongest hurricane of the 2015 Atlantic season. It peaked as a strong category 4 hurricane (almost a category 5) with max winds of 155 mph. A strong trough over the eastern U.S. guided it out to sea. The 10th named storm dissipated over the cooler north Atlantic on October 8th.
The 11th named storm of the 2015 Atlantic season, Kate, formed in early November near the Bahamas. Shortly after Kate became the 4th hurricane of the season and the first November hurricane in the Atlantic Basin since Tomas in 2010. It dissipated over cooler waters as it merged with a frontal system on November 12th.
The last week of the 2015 Atlantic hurricane season is here. In rare November fashion Hurricane Kate formed earlier this month over the open north Atlantic. Since then there have been no areas of interest in the Atlantic Basin. Only 16 named storms have formed from November 21st to November 30th since 1851 so the odds are high November 2015 will wrap up next Monday with no more named storms.
On Monday we are tracking two frontal boundaries in the Atlantic but there are no tropical waves. The strongest cold front of the season races out to sea in the western Atlantic. Another stalled boundary and upper level trough sits in the open central Atlantic. There is some scattered convection along this boundary but subtropical/tropical development is not expected at this time.
Officially no tropical depression development is expected over the next 5 days. With that being said models like the Euro and GFS still attempt to spin up weak low pressure northeast of the Bahamas later this week under a weakness in north Atlantic high pressure. This low would race northeast and could bring some squalls to the Canadian Maritimes over the weekend.
With less than 2 weeks left in the 2015 Atlantic hurricane season it’s no surprise that the entire Atlantic basin in generally quiet. Water temperatures are cooling and wind shear values are enhanced as fronts whip through the Gulf and Atlantic. Only 20 named storms have formed from November 11-20 since 1851 in the Gulf, Caribbean and Atlantic. The graphic below is courtesy Google Earth.
There is one area of interest in the Atlantic Tuesday. A weak area of low pressure drifts west in the southwest Caribbean. It combats moderate wind shear and will move over central America mid-week so the odds of tropical depression development are highly unlikely. None of the reliable computer models hint at tropical cyclone development over the next 5 days.
The 2015 El Niño event made history Monday. Weekly sea surface temperatures in the equatorial Pacific surpassed values set in the record 1997-1998 El Niño event. Sea surface temperatures climb to 5.4 degrees Fahrenheit above average in the central Pacific. In late November 1997 sea surface temperatures in this region peaked at 5 degrees Fahrenheit above average. With just one week of data it’s too early to say if the 2015 El Niño has peaked and will gradually start to weaken. The Climate Prediction Center says El Niño will likely peak during the 2015/16 Winter in the Northern Hemisphere. This pattern is set to bring an active and wetter than normal winter to the South with spells of possible severe weather/enhanced tornado threat in Florida. With more storm systems it will likely be cooler than normal with more cloud cover. Meanwhile the northern tier of the country will likely see warmer than normal and drier than normal conditions this winter. The SST anomalies graphic below is courtesy the Climate Prediction Center.
El Niño strengthened during the 2015 Atlantic season and it’s no surprise that the number of named storms and hurricanes is below average. If the season wrapped up today there would be 11 named storms, 4 hurricanes and 2 major hurricanes. In an average Atlantic season there are 12 named storms, 6 hurricanes and 3 major hurricanes. Meanwhile it was a blockbuster season for the east Pacific. In late October category 5 hurricane Patricia became the most powerful tropical cyclone ever measured in the Western Hemisphere with maximum sustained winds of 200 mph and a central pressure of 879 millibars. Both seasons end on November 30th.
Kate becomes the 4th hurricane of the 2015 Atlantic hurricane season Wednesday morning. In rare November fashion Kate is the first November hurricane in the Atlantic basin since Tomas in 2010. On average the 4th hurricane of the Atlantic season forms on September 21st. Despite increased wind shear over the past 24 hours Kate holds its own Wednesday. As of 11 AM max sustained winds top out at 75 mph at it races east-northeast out to sea at a swift 45 mph. Enhanced satellite imagery shows Kate begins to feel the effect of cooler north Atlantic waters as cloud tops are warming (even since early Wednesday morning). As it merges with a frontal system (nor’easter) over the next 24 hours it will become post tropical by Thursday morning.
Here is the National Hurricane Center’s 11 AM advisory. An extratropical Kate may bring squalls to the United Kingdom later this weekend.
Between cooler sea surface temperatures and increased wind shear Kate will lose its tropical characteristics by Thursday morning. While Kate combats 40-50 kt shear Wednesday morning these values climb to an extreme 60-80 kts late Wednesday and Thursday morning.
It may be the last month of the Atlantic hurricane season but we have a healthy and strengthening tropical storm Kate on our hands in the western Atlantic. As of 10 EST Kate is on the verge of becoming a hurricane with 70 mph sustained winds and it races northeast at 21 mph. Kate manages to maintain a well-defined central dense central overcast and Hurricane Reconnaissance Aircraft continues to find strong tropical storm force winds. Kate exited the northwest Bahamas Monday night and quickly accelerates out the sea Tuesday. It taps energy over the warm Gulf Stream under the influence of a front. Moderate and increasing southwest wind shear displaces some convection north and east of its center. These hostile upper level winds and cooler north Atlantic waters will eventually transition Kate into a post tropical system in about 36-48 hours. Kate will also deepen as a larger non tropical area of low pressure in the north Atlantic but poses to threat to land.
Below is the 10 AM EST forecast track. The NHC and computer models maintain category 1 hurricane strength until Kate fully transitions to a post tropical system by Thursday.
November named storms are rare and November hurricanes are even less common. If Kate becomes a hurricane it will be the first November hurricane since Ida in 2009. Since 1980 12 hurricanes have formed in the Atlantic Basin in November.
Tropical Storm Kate becomes the 11th named storm of the 2015 Atlantic hurricane Monday morning near the central Bahamas. Data from Hurricane Reconnaisance Aircraft show Kate continues to strengthen a bit and tropical storm warnings are in effect for the central and northwest Bahamas.. Max sustained winds top out at 45 mph at 10 AM EST. The center of circulation and the core tropical storm force winds will skirt the central Bahamas Monday and clip the northwest Bahamas Monday night. 1-3″ of rainfall is the primary threat. Kate is the first November named storm in the Atlantic basin since Subtropical Storm Melissa in late November 2013. November named storms are pretty rare. Only 5% of named storms form during the last month of the Atlantic hurricane season.
Here is the 10 AM EST track. Kate will safely pass east of the U.S. as it guided by a frontal boundary and will head northeast by Tuesday as it rides the perimeter of the Atlantic subtropical ridge. During this time the tropical storm will strengthen some between the Mid Atlantic region and Bermuda.
By mid-week Kate will merge with a larger stronger non tropical area of low pressure east of New England and south of the Canadian Maritimes. It will become post tropical by Thursday morning, if not sooner. Here is the Euro’s forecast Wednesday afternoon which shows the areas of low pressure combining.
Invest 94L organizes Saturday night and Sunday morning east of the Bahamas and north of Hispaniola. Convection is more concentrated southeast of Turks and Caicos and a tropical depression may be form soon. Water temperatures in this region are in the low to mid 80s, moisture is plentiful and wind shear overhead is low at 10 kts so further organization is possible. As of Sunday morning the odds of tropical depression development sit at 50% by Tuesday and 70% over the next 5 days. Early Sunday morning computer models suggest a west-northwest near or through Turks and Caicos and the Bahamas over the next few days. A northeast track is likely mid-week around a ridge of high pressure (guided by a frontal boundary) and the disturbance will likely combine with a front during this time. Invest 94L is no threat to the U.S. but will likely bring some squalls to Turks and Caicos and the Bahamas through early work week. Interest in Bermuda should keep an eye on Invest 94L.
The likely future track of Invest 94L coincides with November tropical cyclone climatology. A northeast track east of the U.S. and out to sea is expected. November named storms are rare but not non-existent. The last November named storm is subtropical storm Melissa in late November 2013.
As expected Invest 93L merged with a cold front in the Gulf of Mexico and tropical depression development is not expected. This area of low pressure will enhance rainfall/embedded thunderstorms in Florida and for parts of the Southeast as it slow drifts northeast over the next 24-48 hours.
The Atlantic Basin tries to come alive this weekend. There are still about 3 weeks left in the official 2015 Atlantic season. Convection increases near an area of low pressure in the western Gulf of Mexico but this low (now pinned Invest 93L) is broad in nature. There is only a small window for Invest 93 to gain tropical characteristics as it will likely merge with a cold front over the next 24 hours and drift east-northeast. Those odds sit at 20% over the next 2 days per the NHC. If convection increases a Hurricane Reconnaissance Aircraft may investigate Saturday afternoon.
While water temperatures still support tropical depression development in the western Gulf of Mexico upper level winds are less favorable for development. Wind shear over Invest 93L is moderate at 10-30 kts Saturday morning. These values increase Saturday night in the wake of a cold front to 40-50 kts+ making tropical depression development highly unlikely Saturday night and Sunday. Regardless of tropical depression development as low pressure merges with a cold front coverage of showers increases for parts of the northern Gulf coast and Florida late Saturday and Sunday.
For over a week now models have hinted that a tropical low may spin up near Puerto Rico or the Bahamas next week. That feature is still evolving near an area of disturbed weather near the northern Lesser Antilles Saturday. In a few days low pressure may try to close off near the Bahamas as a ridge of high pressure breaks down. Those odds sits at 20% over the next 2 days and 50% over the next 5 days per the NHC Saturday. The next named storm is Kate.
Here’s the 06Z GFS Tuesday evening. It develops a closed low north of the Bahamas that eventually deepens further and races northeast over the open Atlantic Wednesday and Thursday. Water temperatures in this region of the Atlantic have obviously cooled and so the time frame full-blown characteristics drops off mid to late work week. The Euro hints a similar setup but doesn’t really deepen low pressure until late Wednesday or Thursday and at this point it is south of the Canadian Maritimes.
As is often the case in early November most of the Atlantic Basin is nice and quiet Wednesday.The same tropical wave we’ve been tracking for a few days is now making its way westward through the Caribbean bringing pockets of showers and storms to Hispaniola. A strong ridge keeps the Gulf and western Atlantic stable with no areas to watch. No tropical depression development is expected through the weekend but models try to stir something up east of the Bahamas and north of Puerto Rico early next week.
Both the Euro and GFS show a ridge of high pressure breaking down in the Atlantic over the weekend. Both models are on board with low pressure spinning up north of Puerto Rico early next week. The graphic below shows each models solution for next Tuesday afternoon. If a tropical cyclone forms in November it typically forms in the western Atlantic and heads northeast and away from the U.S. That will likely be the case if a named storm (Kate) forms early next week. Interest in Bermuda should keep a watchful eye. The last November named storm was Tropical Storm Melissa in 2013.
The last month of the 2015 Atlantic season is here. Since records go back to 1851 only 35 named storms have formed from November 1st through November 10th in the Atlantic Basin. Most of these formed in the western Caribbean or western Atlantic. Activity steadily declines through the month as water temperatures cool. Not to mention wind shear values rise at times too as fronts whip through regions of tropical development. The graphic below is courtesy Google Earth.
There is only one tropical wave in the entire Atlantic Basin Monday. It is embedded in a belt of high westerly wind shear just east of the Lesser Antilles. It will stay disorganized but a few showers will make it to the eastern Caribbean. The other feature of note is a frontal system along the northern Gulf coast. At the tail end of this boundary there is a burst of scattered convection in the Bay of Campeche. As this boundary washes out over the next few days scattered showers and storms will continue in the central and southern Gulf but they will stay disorganized. Officially no tropical depression development is expected over the next 5 days.
Fast forward 7 days to next Monday and the Atlantic Basin looks to stay quiet, at least according to the European model. A strong ridge stays firmly in place in the Atlantic. The long-range GFS breaks down this ridge early next week. It hints that low pressure may spin up north of Puerto Rico next Tuesday and lift north.