Monthly Archives: November 2016

Tropical Cyclone Nada Develops Near Sri Lanka

Tropical Cyclone Nada developed over the Bay of Bengal near Sri Lanka.  At 10:00 a.m. EDT on Wednesday the center of Tropical Cyclone Nada was located at latitude 10.1°N and longitude 83.5°E which put it about 295 miles (475 km) east-southeast of Chennai, India.  Nada was moving toward the west-northwest at 14 m.p.h. (23 km/h).  The maximum sustained wind speed was 50 m.p.h. (80 km/h) and there were wind gusts to 65 m.p.h. (105 km/h).  The minimum surface pressure was 997 mb.

Microwave satellite imagery indicates that Tropical Cyclone Nada has a well organized, circular low level circulation.  However, most of the thunderstorms are occurring in bands southwest of the center and north of the center.  There are mostly low clouds and showers in the circular bands south and east of the center of circulation.  An upper level ridge over the northern Bay of Bengal is producing easterly winds which are causing moderate vertical wind shear.  The upper level easterly flow is inhibiting the development of thunderstorms east of the center of Tropical Cyclone Nada and those winds may be tilting the circulation toward the west.

The environment surround Tropical Cyclone Nada consists of factors that are favorable for intensification and factors that are unfavorable.  Tropical Cyclone Nada is moving over water where the Sea Surface Temperature is near 29°C.  So, there is sufficient energy in the upper ocean to support intensification.  However the easterly winds in the upper levels are restricting upper level divergence to the east of the tropical cyclone.  Moderate vertical wind shear will limit intensification unless the upper level winds weaken.  If the upper level winds do weaken, then Nada could strengthen given its well developed low level circulation.  Tropical Cyclone Nada only has about 24 to 30 hours before it reaches the coast of India and it will start to weaken once it moves over land.

A subtropical ridge north of Nada is steering the tropical cyclone toward the west-northwest and that general motion is expected to continue.  On its anticipated track the center of Tropical Cyclone Nada will pass north of Sri Lanka and it will approach the southeast coast of India in 24 to 30 hours.  Nada is likely to make a landfall south of Cheannai, India near Pondicherry.  Tropical Cyclone Nada is expected to continue to move to the west and it could emerge over the Arabian Sea in two or three days.

Tropical Cyclone Nada will bring gusty winds and locally heavy rain to northern Sri Lanka and southern India.  Locally heavy rain could cause flooding and mudslides in parts of northern Sri Lanka and Tamil Nadu, Kerala and Karnataka states in India.

Tropical Storm Otto Crosses Into the Eastern North Pacific Ocean

Tropical Storm Otto moved steadily along the border between Nicaragua and Costa Rica and crossed into the eastern North Pacific Ocean on Thursday night.  At 10:00 p.m. EST on Thursday the center of Tropical Storm Otto was located at latitude 10.9°N and longitude 85.6°W which put it about 20 miles (30 km) north of Liberia, Costa Rica.  Otto was moving toward the west at 13 m.p.h. (20 km/h).  The maximum sustained wind speed was 70 m.p.h. (110 km/h) and there were wind gusts to 85 m.p.h. (140 km/h).  The minimum surface pressure was 990 mb.

The structure of Tropical Storm Otto remained intact as it crossed from the southwestern Caribbean Sea to the eastern North Pacific Ocean.  Radar images from Nicaragua and infrared satellite images both showed that the eye continued to exist.  A ring of strong thunderstorms still surrounds the eye and those storms are generating upper level divergence.

Tropical Storm Otto will be moving through an environment favorable for intensification.  It will move over water where the Sea Surface Temperature is near 28°C on Friday, and it will move over warmer water during the weekend.  The upper level winds are weak and there is little vertical wind shear.  Tropical Storm Otto is likely to strengthen back into a hurricane once the entire circulation moves over the eastern North Pacific Ocean and a period of rapid intensification is possible.

A ridge north of Otto is steering the tropical storm toward the west and that general motion is expected to continue for several more days.  On its anticipated track Tropical Storm Otto is expected to move steadily away from the west coast of Nicaragua and Costa Rica.

Tropical Storm Tokage Develops Over the Central Philippines

A distinct center of circulation developed within a cluster of thunderstorms over the central Philippines on Thursday and the Japan Meteorological Agency designated the system as Tropical Storm Tokage.  At 10:00 p.m. EST on Thursday the center of Tropical Storm Tokage was located at latitude 11.7°N and longitude 122.0°E which put it near the northwestern tip of Panay Island and about 235 miles (380 km) south-southeast of Manila, Philippines.  Tokage was moving toward the west-northwest at 13 m.p.h. (20 km/h).  The maximum sustained wind speed was 40 m.p.h. (65 km/h) and there were wind gusts to 50 m.p.h. (80 km/h).  The minimum surface pressure was 1000 mb.

The core of the circulation of Tropical Storm Tokage is still organizing.  An inner band of thunderstorms wraps around the western and southern sides of the center of circulation.  An outer rainband wraps around the northern side of the circulation from the northeastern to the southwestern quadrants.  Thunderstorms near the core of Tokage are generating upper level divergence which is pumping mass away to the west and north of the tropical storm.

Tropical Storm Tokage will be moving through an environment that is favorable for intensification.  Tokage will be moving over water where the Sea Surface Temperature is near 29°C.  An upper level ridge east of Tokage is producing southeasterly winds which are blowing against the tropical storm.  Although those winds are restricting upper level divergence on the southeast side of Tokage, the overall effect of the vertical wind shear is minor.  Tropical Storm Tokage is likely to intensify during the next day or two and it could reach typhoon intensity.

Tokage is moving around the southwestern portion of a subtropical ridge which is steering the tropical storm to the west-northwest.  That general motion is expected to continue for another 12 to 24 hours.   After that time Tropical Storm Tokage will reach the western end of the subtropical ridge and it will begin to move toward the north.  On its anticipated track Tropical Storm Tokage will pass near Mindoro Island and the Calamian Group during the next 12 hours.  It will bring gusty winds and heavy rain to those islands.  Tokage is likely to pass west of Luzon.

Hurricane Otto Strengthens As It Nears Nicaragua and Costa Rica

Hurricane Otto strengthened quickly on Thursday morning as it neared the coast of Nicaragua and Costa Rica.  At 7:00 a.m. EDT on Thursday the center of Hurricane Otto was located at latitude 11.0°N and longitude 82.9°W which put it about 90 miles (150 km) southeast of Bluefields, Nicaragua.  Otto was moving toward the west at 8 m.p.h. (13 km/h).  The maximum sustained wind speed was 105 m.p.h. (170 km/h) and there were wind gusts to 125 m.p.h. (200 km/h).  The minimum surface pressure was 976 mb.

A Hurricane Warning is in effect for the portion of the coast from Limon, Costa Rica to Bluefields, Nicaragua.  A Hurricane Watch has been issued for the portions of the coast from Bluefields to Sandy Bay Sirpi, Nicaragua and from the Panama/Costa Rica border to Limon, Costa Rica.  Tropical Storm Warnings are in effect for the portions of the coast from Bluefields to Sandy Bay Sirpi, Nicaragua and from Puntarenas, Costa Rica to Puerto Sandino, Nicaragua.

An Air Force Reserve Hurricane Hunter aircraft found that Hurricane Otto strengthened quickly during the overnight hours.  The reconnaissance plane found a circular eye with a diameter of 23 miles (37 km).  The eye is surrounded by a ring of strong thunderstorms.  Additional bands of thunderstorms are occurring north and west of the center of circulation.  Thunderstorms in the core of Hurricane Otto are generating upper level divergence which is pumping mass away from the center.

Hurricane Otto is a small hurricane.  Winds to hurricane force extend out about 20 miles (32 km) from the center of circulation.  Winds to tropical storm force extend out about 70 miles (110 km) from the center.  The Hurricane Intensity Index (HII) is 17.8.  The Hurricane Size Index (HSI) is 8.4 and the Hurricane Wind Intensity Size Index (HWISI) is 26.2.  These indices indicate that Hurricane Otto is capable of causing localized serious wind damage.

Hurricane Otto is moving through a favorable environment and it could strengthen further before it reaches the coast of Nicaragua and Costa Rica.  Otto is moving over water where the Sea Surface Temperature is near 29°C.  The upper level winds are weak and there is little vertical wind shear.

A ridge of high pressure north of Otto is steering the hurricane toward the west and that general motion is expected to continue today.  On its anticipated track the center of Hurricane Otto will make landfall over southern Nicaragua or northern Costa Rica later today.

In addition to localized serious wind damage Hurricane Otto will produce a storm surge along the coast of Nicaragua and Costa Rica.  The surge will be highest north of where the center makes landfall because that is where the wind will push the water toward the coast.  Hurricane Otto will produce very heavy rain over parts of Nicaragua and Costa Rica.  The heavy could cause serious flooding and mudslides in some locations.  Outer rainbands could also produce heavy rain over portions of Honduras and El Salvador.

Hurricane Otto Approaching Nicaragua and Costa Rica

After weakening to a tropical storm earlier on Wednesday Hurricane Otto intensified as it approached the border between Nicaragua and Costa Rica.  At 10:00 p.m. EST on Wednesday the center of Hurricane Otto was located at latitude 11.2°N and longitude 82.2°W which put it about 120 miles east-southeast of Bluefields, Nicaragua.  Otto was moving toward the west at 9 m.p.h. (15 km/h).  The maximum sustained wind speed was 85 m.p.h. (140 km/h) and there were wind gusts to 100 m.p.h. (160 km/h).  The minimum surface pressure was 981 mb.

A Hurricane Warning is in effect for the portion of the coast from Limon, Costa Rica to Bluefields, Nicaragua.  Hurricane Watches have been issued for the portions of the coast from Bluefields to Sandy Bay Sirpi, Nicaragua and from the Panama/Costa Rica border to Limon, Costa Rica.  Tropical Storm Warnings are in effect for the  portions of the coast from Bluefields to Sandy Bay Sirpi, Nicaragua, from Puntarenas, Costa Rica to Puerto Sandino, Nicaragua and for San Andres Island.

Hurricane Otto had meandered over the same water long enough to mix cooler water to the surface.  The cooler water reduced the energy transfer to the atmosphere and the inner core of Otto weakened.  The eye disappeared and Otto weakened below hurricane intensity.  When Otto began to move west, the core of the circulation moved away from the cooler water.  Thunderstorms developed rapidly near the center of circulation and the inner core began to redevelop.  A reconnaissance plane found that the wind speed had increased above hurricane intensity again.

Hurricane Otto has a very small circulation.  Winds to hurricane force only extend out about 12 miles (19 km) from the center of circulation.  Winds to tropical storm force extend out about 70 miles (110 km) from the center.  The Hurricane Intensity Index (HII) is 12.7.  The Hurricane Size Index (HSI) is 4.7 and the Hurricane Wind Intensity Size Index (HWISI) is 17.4.  These indices indicated that Hurricane Otto is capable of causing localized minor wind damage.

The small circulation of Hurricane Otto is more symmetrical.   There are indications that a circular eye and eyewall could be reforming at the center of the hurricane.  Several bands of thunderstorms are rotating around the core of Otto.  Thunderstorms at the core were generating upper level divergence which pumped out mass and allowed the surface pressure to decrease on Wednesday evening.

Hurricane Otto will be moving through an environment that is favorable for intensification until it makes landfall.  Otto will be moving over water where the Sea Surface Temperature is near 29°C.  An upper level ridge east of the hurricane is producing southeasterly winds which are flowing near the top of the circulation.  However, those winds are weaker than they were yesterday and the vertical wind shear is less.  Hurricane Otto could strengthen further during the next few hours.

A ridge to the north of Otto is steering the hurricane toward the west and that general motion is expected to continue for another day or two.  On its anticipated track Hurricane Otto will make a landfall on the coast between the Nicaragua/Costa Rica border and Monkey Point, Nicaragua.  Winds blowing toward the coast will produce a storm surge along the southern coast of Nicaragua.  Otto could drop heavy rain over Nicaragua and Costa Rica.  Outer bands may also produce locally heavy rain over parts of Honduras and El Salvador.  The rain may be heavy enough to cause flooding and mudslides.

Otto Becomes a Hurricane, Watches and Warnings Issued

Tropical Storm Otto intensified into a hurricane on Tuesday as it meandered over the southwestern Caribbean Sea.  At 4:00 p.m. EST on Tuesday the center of Hurricane Otto was located at latitude 10.5°N and longitude 79.6°W which put it about 235 miles (375 km) east of Limon, Costa Rica.  Otto was moving toward the west at 2 m.p.h. (3 km/h).  The maximum sustained wind speed was 75 m.p.h. (120 km/h) and there were wind gusts to 90 m.p.h. (145 km/h).  The minimum surface pressure was 984 mb.

Hurricane Watches have been issued for the portion of the coast from the Costa Rica/Panama border to Bluefields, Nicaragua.  Tropical Storm Warnings have been issued for the portion of the coast from Nargana to Colon, Panama and for San Andres Island, Colombia.  Tropical Storm Watches have been issued for the portions of the coast from Colon, Panama to the Panama/Costa Rica border and from Bluefields to Sandy Bay Sirpi, Nicaragua.

The inner core of Hurricane Otto became more circular and symmetrical on Tuesday.  An eyelike feature appeared on microwave satellite imagery and hints of an eye were seen intermittently on visible imagery during the day.  There appeared to be breaks in the eyewall on the southeast side of the eye.  Most of the stronger thunderstorms are forming northwest of the eye.  Convective activity outside the core of Hurricane Otto is more asymmetrical.  There are some thinner rainbands north and west of the center where winds from a high pressure system are converging into the circulation of Otto.  There are fewer showers and thunderstorms in the southeastern quadrant of the circulation.  Thunderstorms around the center of the hurricane are generating upper level divergence at the very top of the circulation.

Hurricane Otto has a very small circulation.  Winds to hurricane force only extend out about 10 miles (15 km) from the center of circulation.  Winds to tropical storm force only extend out about 70 miles (110 km) from the center.  The Hurricane Intensity Index (HII) for Otto is 10.4.  The Hurricane Size Index (HSI) is 3.2 and the Hurricane Wind Intensity Size Index (HWISI) is 13.6.

Hurricane Otto will be moving through an environment that will be favorable for intensification.  It will move over water where the Sea Surface Temperature is 29°C.  An upper level ridge located east of Otto is generating southeasterly winds which are blowing against the upper portion of the circulation of the hurricane.  Those winds appear to be hitting Otto just under the level of upper level divergence at the top of the circulation.  So, the upper level winds and vertical wind shear appear to be restricting upper level divergence to the south of the circulation, but they do not appear to be completely blocking divergence.  The speed of the upper level winds is forecast to decrease.  If the vertical shear decreases, then Hurricane Otto could strengthen.

A ridge of high pressure is forecast to build north of Hurricane Otto.  That ridge will steer Otto toward the west and the hurricane could start to move faster on Wednesday.  On its anticipated track Hurricane Otto could approach the coast of Costa Rica and Nicaragua on Thursday.

Hurricane Otto is a small hurricane, but it could cause localized minor wind damage.  Heavy rain, flash floods and mudslides are a much greater threat.  Hurricane Otto could bring flooding rains to portions of Nicaragua, Honduras, Panama, Costa Rica, Guatemala and El Salvador.

On a historical note Hurricane Martha formed during this time of year in 1969 in almost exactly the same area where Hurricane Otto formed.  Hurricane Martha moved southward and weakened.  Martha officially made landfall in Panama as a tropical storm, but it did cause flooding rains and fatalities in parts of Costa Rica.

TD 16 Becomes Tropical Storm Otto

The National Hurricane Center named former Tropical Depression 16 as Tropical Storm Otto on Monday afternoon based on data from satellites.  At 4:00 p.m. EST the center of Tropical Storm Otto was located at latitude 11.3°N and longitude 79.2°W which put it about 315 miles (505 km) east of Bluefields, Nicaragua.  Otto was stationary.  The maximum sustained wind speed was 50 m.p.h. (80 km/h) and there were wind gusts to 65 m.p.h. (105 km/h).  The minimum surface pressure was 1000 mb.

The structure of Tropical Storm Otto has not changed appreciably during today.  Most of the thunderstorms are occurring in bands north and west of the center of circulation.  There are fewer thunderstorms in the southeastern quadrant of the circulation.  Otto is a small tropical storm.  Winds to tropical storm force only extend out about 35 miles (55 km) from the center.  Thunderstorms are generating upper level divergence which is pumping mass out north and west of the tropical storm.

Tropical Storm Otto will move through an environment that will be favorable for intensification.  It will move over water where the Sea Surface Temperature will be near 29°C unless Otto moves so slowly that its own circulation mixes cooler water to the surface.  Southerly winds in the upper levels are generating moderate vertical wind shear, but those winds are expected to weaken.  When the vertical shear diminishes, Tropical Storm Otto will be likely to intensify and it could become a hurricane.

Tropical Storm Otto is currently in a region where the steering currents are weak.  However, a ridge of high pressure is forecast to build north of Otto, and the ridge is likely to steer the tropical storm toward the west.  On its anticipated track Tropical Storm Otto could approach the coast of Nicaragua and Costa Rica in 48 to 72 hours.

Tropical Storm Otto could be a hurricane by the time it reaches the coast of Nicaragua and Costa Rica.  Otto will be capable of bringing gusty winds and heavy rain to portions of Nicaragua, Costa Rica, northern Panama, Honduras, El Salvador and southern Guatemala.  The locally heavy rain could produce flash floods and mudslides in areas of steep terrain.

Tropical Depression 16 Develops Over Southwest Caribbean Sea

The National Hurricane Center upgraded Invest 96L to Tropical Depression 16 on Monday morning.  At 10:00 a.m. EST on Monday the center of Tropical Depression 16 was located at latitude 11.5°N and longitude 79.3°W which put it about 305 miles (495 km) east of Bluefields, Nicaragua.  Tropical Depression 16 was stationary.  The maximum sustained wind speed was 35 m.p.h. (55 km/h) and there were wind gusts to 45 m.p.h. (75 km).  The minimum surface pressure was 1002 mb.

An Air Force Reserve Hurricane Hunter aircraft investigated the area of low pressure over the southwestern Caribbean Sea on Sunday afternoon and it found a distinct surface center with a lower pressure.  When more thunderstorms formed near the center of circulation early on Monday, the National Hurricane Center designated the system as Tropical Depression 16.

The circulation of Tropical Depression 16 is fairly well organized.  It has a tight core and several bands of thunderstorms.  Most of the bands are occurring north and west of the center of circulation.  There are fewer thunderstorms in the southeastern quadrant of the circulation.  The thunderstorms north of the center are generating upper level upper level divergence.  Southerly winds appear to be inhibiting upper level divergence to the south of the tropical depression.

Tropical Depression 16 is in an environment that is slightly favorable for intensification.  It is moving over water where the Sea Surface Temperature is near 29°C.  However, the depression and its precursor have been over the same area for almost a week.  So, the winds in Tropical Depression 16 are gradually mixing cooler water to the surface.  An upper level ridge to the east and an upper level trough to the west are generating southerly winds which are blowing across the top of the depression.  The southerly winds are generating moderate vertical wind shear and they are inhibiting upper level divergence to the south.  The mixed environmental factors will limit intensification in the short term.  The upper level winds are forecast to weaken in a day or two and more intensification could occur when that happens.  Tropical Depression 16 is likely to intensify into a tropical storm and it could become a hurricane later this week.

The steering currents are weak around Tropical Depression 16 and it may move little during the next 24 to 36 hours.  A ridge of high pressure is forecast to build north of the depression and the ridge is forecast to steer it slowly toward the west later this week.  Tropical Depression 16 could approach the coast of Nicaragua in about three days.  It could be a hurricane at the time.

Invest 90L Organizing North of Panama

The structure of the low pressure system designated as Invest 90L became better organized on Saturday over the southwestern Caribbean Sea north of Panama.  At 7:00 p.m. EDT on Saturday the center of Invest 90L was located at latitude 10.8°N and longitude 80.9°W which put it about 220 miles (355 km) east-southeast of Bluefields, Nicaragua.  Invest 90L was moving toward the east at 3 m.p.h. (5 km/h).  The maximum sustained wind speed was 35 m.p.h. (55 km/h) and there were wind gusts to 45 m.p.h. (70 km/h).  The minimum surface pressure was 1006 mb.

More thunderstorms developed closer to the center of circulation on Saturday.  A band of stronger thunderstorms formed south of the center and a second band of storms developed northeast of the center.  Other rainbands appeared to be forming in other areas of the circulation.  Storms in the band northeast of the center began to produce upper level divergence that was pumping mass away.  An improved convective structure could be a indication that Invest 90L is developing into tropical depression.

The atmospheric environment became more favorable for tropical development on Saturday.  Upper level southwesterly winds which were blowing across the top of the low pressure system weakened on Saturday  and the vertical wind shear lessened.  Less shear allowed more thunderstorms to develop and persist.  Since Invest 90L has meandered over the same part of the southwestern Caribbean Sea for several days, it has mixed slightly cooler water to the surface.  However, the water in that part of the Caribbean Sea is very warm and Invest 90L is moving over water where the Sea Surface Temperature is still near 29°C.  The environment is favorable for development of a tropical cyclone and Invest 90L could become a tropical depression or a tropical storm at any time.

Invest 90L is located underneath an upper level ridge and the steering currents are weak.  The low pressure system drifted toward the east on Saturday and some models are suggesting that Invest 90L could make a slow counterclockwise loop over the southwestern Caribbean Sea during the next few days.

Invest 90L Meandering Over Southwest Caribbean Sea

An area of low pressure designated as Invest 90L has meandered over the southwestern Caribbean Sea during the past several days.  At 7:00 p.m. EST on Thursday the center of Invest 90L was located at latitude 12.3°N and longitude 81.3°W which put it about 170 miles (275 km) east of Bluefields, Nicaragua.  Invest 90L was moving toward the west at 3 m.p.h. (5 km/h).  The maximum sustained wind speed was 25 m.p.h. (40 km/h) and there were wind gusts to 35 m.p.h. (55 km/h).  The minimum surface pressure was 1006 mb.

Invest 90L consists of a broad area of low pressure over the southwestern Caribbean Sea.  There is a definite area of counterclockwise rotation, but the is no well defined core at the center of the low.  There is a swirl of low clouds and showers at the center of Invest 90L, but there are no thunderstorms near the center.  Thunderstorms form and dissipate in bands around the periphery of the circulation.

The environment around the southwestern Caribbean Sea is not as favorable for the development of a tropical cyclone as it was earlier this week.  Invest 90L is moving over water where the Sea Surface Temperature is near 29°C.  However, northerly winds blowing across the Gulf of Mexico have transported drier air over the northwestern Caribbean Sea.  The drier air has not reached Invest 90L, but the drier air is just to the northwest of the low pressure system.  An upper level trough over the Gulf of Mexico is producing southwesterly winds which are blowing over the top of Invest 90L.  Those winds are generating moderate vertical wind shear which is inhibiting the organization of the low pressure system.  Even with the inhibiting factors the National Hurricane Center is indicating that the probability of the formation of a tropical cyclone during the next five days is 70%.

The fact that there is only a low level circulation means that Invest 90L is being steering by winds closer to the surface.  The winds in the lower levels have been pushing the low pressure system very slowly toward the west.  Guidance from numerical models suggests that Invest 90L could meander over the southwestern Caribbean Sea for several more days.