Monthly Archives: October 2019

Tropical Storm Nestor Speeds Toward Northwest Florida

Tropical Storm Nestor sped toward northwest Florida on Friday afternoon.  The National Hurricane Center designated a strong low pressure system over the Gulf of Mexico as Tropical Storm Nestor on Friday afternoon.  At 2:00 p.m. EDT on Friday the center of Tropical Storm Nestor was located at latitude 26.3°N and longitude 89.5°W which put it about 355 miles (570 km) southwest of Panama City, Florida.  Nestor was moving toward the northeast at 22 m.p.h. (35 km/h).  The maximum sustained wind speed was 60 m.p.h. (95 km/h) and there were wind gusts to 75 m.p.h. (120 km/h).  The minimum surface pressure was 1001 mb.

Tropical Storm Warnings were in effect for the portions of the coast from Grand Isle, Louisiana to the mouth of the Pearl River, Mississippi and from the Mississippi/Alabama border to Yankeetown, Florida.  A Storm Surge Warning was in effect for the portion of the coast from Indian Pass to Clearwater Beach, Florida.

Tropical Storm Nestor exhibited an asymmetrical structure that is commonly seen in late season tropical storms over the Gulf of Mexico.  The strongest thunderstorms were occurring in bands in the eastern side of Nestor.  Bands in the western half of the circulation consisted primarily of showers and lower clouds.  The tropical storm force winds were occurring in the eastern half of Tropical Storm Nestor.  Winds to tropical storm force extended out 175 miles (280 km) in the eastern side of the circulation.  The winds in the western half of Nestor were mostly less than tropical storm force.

Drier air was being pulled around the western side of Tropical Storm Nestor.  In addition, an upper level trough over the western Gulf of Mexico was producing southwesterly winds which were blowing toward the top of the circulation.  Those winds were causing moderate vertical wind shear.  The combination of the drier air and the vertical wind shear was responsible for the asymmetrical distribution of thunderstorms and strong winds in the eastern half of the circulation.

Tropical Storm Nestor will move through an environment only marginally favorable for further intensification during the next 12 hours.  Nestor will move over water where the Sea Surface Temperature is near 29°C.  So, there is plenty of energy in the upper part of the Gulf of Mexico to support intensification.  However, the drier air and wind shear will inhibit intensification.  Tropical Storm Nestor will start a transition to an extratropical cyclone on Saturday.  Nestor could strengthen somewhat during the extratropical transition, but it could be over land before that occurs.

The upper level trough over the Western Gulf of Mexico will steer Nestor quickly toward the northeast during the next 48 hours.  On its anticipated track Tropical Storm Nestor could make landfall on the coast of northwest Florida between Panama City and Apalachicola.  Nestor will bring gusty winds to northern Florida on Saturday.  Strong southerly winds on the eastern side of Tropical Storm Nestor will push water toward the coast and a storm surge of 3 to 6 feet (1 to 2 meters) will occur around the northeastern Gulf of Mexico.  Nestor could drop locally heavy rain over parts of northern Florida, southeast Alabama, southern Georgia and South Carolina.  Tropical Storm Nestor will make landfall near where Hurricane Michael did so much damage in 2018.  Recovery efforts have been slow in that area and Nestor could set back the ongoing recovery from Hurricane Michael.

Tropical Storm Octave Forms over Eastern North Pacific

Tropical Storm Octave formed over the Eastern North Pacific Ocean on Thursday evening.  At 11:00 p.m. EDT on Thursday the center of Tropical Storm Octave was located at latitude 9.8°N and longitude 127.2°W which put it about 1455 miles (2345 km) southwest of the southern tip of Baja California.  Octave was moving toward the west at 3 m.p.h. (5 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 1006 mb.

More thunderstorms formed near the center of a small low pressure system between Mexico and Hawaii and the National Hurricane Center designated the system as Tropical Storm Octave.  The circulation around Octave exhibited more organization and tropical characteristics on Thursday evening.  There was a distinct low level center of circulation with thunderstorms.  Several bands of showers and thunderstorms were revolving around the center.  Storms near the center generated upper level divergence which pumped mass away from the tropical storm.  The circulation around Tropical Storm Octave was small.  Winds to tropical storm force only extended out 35 miles (55 km) from the center of circulation.

Tropical Storm Octave will move through an environment mostly favorable for intensification.  Octave will move over water where the Sea Surface Temperature is 28°C.  It will be in a region where the upper level winds are weak and there will be little vertical wind shear.  However, there appears to be drier air north of Tropical Storm Octave.  If the circulation pulls drier air into the core of Octave, then thunderstorms around the center would weaken which would make intensification unlikely.  Tropical Storm Octave could strengthen a little during the next 24 hours.

Tropical Storm Octave will be in a region where the winds at the steering level are weak.  Octave is forecast to move little during the next few days.  Because Tropical Storm Octave will not move much, it will remain well away from any land area.

Tropical Storm Neoguri Forms East of Northern Luzon

Tropical Storm Neoguri formed east of northern Luzon on Thursday.  At 5:00 p.m. EDT on Thursday the center of Tropical Storm Neoguri was located at latitude 20.1°N and longitude 129.4°E which put it about 470 miles (755 km) south-southeast of Okinawa and about 500 miles (800 km) east-northeast of the northern end of Luzon.  Neoguri was moving toward the north-northwest at 7 m.p.h. (11 km/h).  The maximum sustained wind speed was 45 m.p.h. (75 km/h) and there were wind gusts to 60 m.p.h. (95 km/h).  The minimum surface pressure was 997 mb.

A distinct low level center of circulation developed on the western side of a cluster of thunderstorms east of northern Luzon on Thursday and the Japan Meteorological Agency designated the system as Tropical Storm Neoguri.  The circulation around Neoguri exhibited much more organization.  The inner part of a rainband wrapped around the center of circulation.  A broken ring of thunderstorms formed around the southwestern half of the center and an elliptical eyelike feature appeared on microwave satellite images.  The long axis of the elliptical eye was oriented northeast to southwest.  Bands of showers and thunderstorms developed in the eastern half of Tropical Storm Neoguri.  Bands in the western half of the circulation consisted primarily of showers and lower clouds.  Thunderstorms near the center generated upper level divergence which pumped mass away to the northeast of the tropical storm.

Tropical Storm Neoguri will move through an environment mostly favorable for intensification during the next 24 to 36 hours.  Neoguri will move over water where the Sea Surface Temperature is near 28°C.  It will move under the western part of an upper level ridge where the winds are weaker.  There will not be a lot of vertical wind shear during the next 24 hours.  There appears to be drier air to the northwest of Tropical Storm Neoguri, which may be the reason why the rainbands in the western half of the circulation are weaker.  If Neoguri pulls drier air into the core of the circulation, then that would inhibit intensification.  On the other hand, if an eye does form completely, then Tropical Storm Neoguri could strengthen into a typhoon.

The future track of Tropical Storm Neoguri will depend on how strong it becomes.  If Neoguri strengthens, then a trough over China will likely steer the tropical storm toward the northeast.  However, if drier air gets pulled into the core of the circulation, then a weaker Tropical Storm Neoguri would be steered by winds closer to the surface.  A high pressure system over the Western North Pacific would steer Tropical Storm Neoguri toward the west.  Guidance from numerical models is split between these two scenarios.  Some models forecast a track toward the northeast and other models predict a track toward the west.  Tropical Storm Neoguri did not move much on Thursday and either scenario is possible.

Low Pressure System Forms Over Southwest Gulf of Mexico

A surface low pressure system formed over the southwestern Gulf of Mexico on Wednesday.  At 8:00 p.m. EDT on Wednesday the center of the low pressure system was located at latitude 20.8°N and longitude 95.4°W which put it about 70 miles (110 km) east-southeast of Nautla, Mexico.  The low was moving toward the north at 9 m.p.h. (15 km/h).  The maximum sustained wind speed was 30 m.p.h. (50 km/h) and there were wind gusts to 40 m.p.h. (65 km/h).  The minimum surface pressure was 1009 mb.

The northern end of a trough of low pressure moved over the Bay of Campeche on Wednesday and a surface low formed when the trough moved over the southwestern Gulf of Mexico.  More thunderstorms developed near the center of the low pressure system.  Divergence from a surface high pressure system over the U.S. was converging with the northern periphery of the circulation around the surface low and a band of showers and thunderstorms was occurring over the west central Gulf of Mexico.  Storms near the center of the low were starting to generate some upper level divergence.

The low pressure system will move through an environment that will be favorable for intensification during the next 24 to 36 hours.  The low will move over water where the Sea Surface Temperature is near 29°C.  It will move under an upper level ridge where the winds are weak and divergent.  The low could intensify slowly if it gets better organized on Thursday.  The National Hurricane Center is indicating that there is a 60% probability of formation of either a tropical or subtropical storm.  A reconnaissance plane has been tentatively tasked to investigate the low pressure system on Thursday afternoon.

The upper level ridge over the surface low pressure system will steer the low toward the northeast during the next several days.  On its anticipated track the low could approach the northeastern coast of the Gulf of Mexico on Friday.  The low will bring gusty winds and locally heavy rain.  The winds will generate higher waves and there could be a storm surge of 3 to 6 feet (1 to 2 meters).

Tropical Low Pressure System Will Drop Heavy Rain on Southern Mexico

A tropical low pressure system designated Potential Tropical Cyclone Seventeen-E by the National Hurricane Center will drop heavy rain on parts of southern Mexico.  At 11:00 p.m. EDT on Tuesday the center of Potential Tropical Cyclone Seventeen-E was located at latitude 13.7°N and longitude 93.4°W which put it about 210 miles (340 km) southeast of Salina Cruz, Mexico.  It was moving toward the west-northwest at 10 m.p.h. (16 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. (75 km/h).  The minimum surface pressure was1005 mb.

The government of Mexico issued a Tropical Storm Watch for the portion of the coast from Barra de Tonala to Puerto Escondido.

A large low pressure system moved slowly from the western Caribbean Sea into the extreme Eastern North Pacific Ocean west of Guatemala during the past few days.  The low pressure system dropped heavy rain over parts of Nicaragua, Honduras, El Salvador, Guatemala and Belize.  Several smaller centers of circulation developed within the larger low pressure system on Tuesday.  More thunderstorms developed around one of the smaller centers west of Guatemala on Tuesday evening and the sustained wind speed increased to 35 m.p.h. (55 km/h).  Some bands of showers and thunderstorms were beginning to develop around the low pressure system.  A potential primary rainband appeared to be wrapping around the western and southern portions of the center of circulation.

The low pressure system will move through an environment favorable for some intensification on Wednesday.  The low will move over water where the Sea Surface Temperature is near 29.5°C.  An upper level high over the eastern Gulf of Mexico will produce northeasterly winds which will blow toward the top of the low pressure system.  Those winds will cause some vertical wind shear which will inhibit intensification.  The low pressure system will be close to the coast of Mexico, which will also limit intensification.  The low pressure system could intensify while the center is over the warm water.  It is forecast to become a tropical storm on Wednesday, which is why the Tropical Storm Watch was issued.

A high pressure system over the eastern Gulf of Mexico and northwestern Caribbean Sea will steer Potential Tropical Cyclone Seventeen-E toward the northwest during the next several days.  On its anticipated track the low pressure system could make landfall on the coast of Mexico between Barra de Tonala and Puerto Escondido within 24 hours.  It will bring gusty winds to that portion of the coast.  The low pressure system will drop heavy rain on parts of Chiapas and Oaxaca.  It could cause flash floods in some locations.

Tropical Depression Fifteen Forms Southeast of Cabo Verde Islands

Tropical Depression Fifteen formed southeast of the Cabo Verde Islands on Monday.  At 5:00 p.m. EDT on Monday the center of Tropical Depression Fifteen was located at latitude 13.2°N and longitude 20.2°W which put it about 320 miles (515 km) southeast of the Cabo Verde Islands.  The depression was moving toward the northwest at 8 m.p.h. (13 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. (75 km/h).  The minimum surface pressure was 1006 mb.

A large, well developed low pressure system embedded in the northern end of a tropical wave moved over the Atlantic Ocean west of North Africa on Monday.  Bands of showers and thunderstorms began to strengthen when the low moved over water and the National Hurricane Center designated the system as Tropical Depression Fifteen.  Bands of showers and thunderstorms were revolving around the center of the depression.  Storms closer to the center were generating upper level divergence which was pumping mass away from Tropical Depression Fifteen.  The circulation around the depression was quite large.  The diameter of the low level circulation was about 500 miles (800 km).

Tropical Depression Fifteen will move through an environment favorable for intensification during the next 24 to 48 hours.  The depression will move over water where the Sea Surface Temperature is near 28°C.  It will move under the western end of an upper level ridge centered over North Africa.  The upper level winds will be weak and there will be little vertical wind shear during the next day or two.  Tropical Depression Fifteen is likely to strengthen into Tropical Storm Nestor.

The ridge over North Africa will steer Tropical Depression Fifteen toward the northwest during the next several days.  On its anticipated track the center of the depression could reach the Cabo Verde Islands within 24 hours.  Since the depression is forecast to strengthen into a tropical storm watches and/or warnings could be issued.

Elsewhere over the Atlantic Ocean, Tropical Storm Melissa completed a transition to an extratropical cyclone on Monday.  At 11:00 a.m. EDT on Monday the center of Tropical Storm Melissa was located at latitude 41.0°N and longitude 51.4°W which put it about 405 miles (650 km) south-southeast of Cape Race, Newfoundland.  Melissa was moving toward the east at 23 m.p.h. (37 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 1004 mb.

Tropical Storm Ema Forms Southwest of Hawaii

Tropical Storm Ema formed southwest of Hawaii on Saturday.  At 5:00 p.m. EDT on Saturday the center of Tropical Storm Ema was located at latitude 21.1°N and longitude 163.9°W which put it about 245 miles (395 km) southeast of French Frigate Shoals.  Ema was moving toward the northwest at 13 m.p.h. (20 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 1003 mb.

A Tropical Storm Watch has been issued for the Papahanaumokuakea Marine National Monument from Nihoa to French Frigate Shoals to Maro Reef.

A distinct low level center of circulation formed in a small area of low pressure southwest of Hawaii on Saturday morning and the Central Pacific Hurricane Center designated the system as Tropical Storm Ema.  The circulation around Tropical Storm Ema was very small.  Winds to tropical storm force extended out 45 miles (75 km) from the center of circulation.  Several short bands of showers and thunderstorms developed around the center of Ema.  Storms near the center began to generate upper level divergence which pumped mass away from the tropical storm.

Tropical Storm Ema will move through an environment marginally favorable for intensification during the next 12 to 24 hours.  Ema will move over water where the Sea Surface Temperature is near 28°C.  An upper level trough west of Hawaii will produce southerly winds which will blow toward the top of the circulation.  Those winds will cause moderate vertical wind shear which inhibit the intensification of Tropical Storm Ema.  Ema could strengthen a little during the next 12 to 24 hours.  The upper level trough will produce stronger southwesterly winds on Sunday and the wind shear will increase.  Stronger wind shear will weaken Tropical Storm Ema in a day or so.  The upper level winds could blow the top half of Ema north of the low level circulation and the tropical storm could weaken very quickly if that happens.

The upper level trough will steer Tropical Storm Ema toward the north during the next 12 hours or so.  If the wind shear separates the upper and lower parts of the tropical storm, the low level center will be steered by winds closer to the surface.  Clockwise flow around a subtropical high pressure system centered northeast of Hawaii could steer Tropical Storm Ema more toward the northwest later on Sunday.

Typhoon Hagibis Brings Wind and Rain to Honshu

Typhoon Hagibis brought wind and rain to Honshu on Saturday.  At 11:00 a.m. EDT on Saturday the center of Typhoon Hagibis was located at latitude 36.6°N and longitude 140.8°E which put it about 50 miles south of Iwaki, Japan.  Hagibis was moving toward the north-northeast at 25 m.p.h. (40 km/h).  The maximum sustained wind speed was 85 m.p.h. (135 km/h) and there were wind gusts to 105 m.p.h. (165 km/h).  The minimum surface pressure was 969 mb.

The center of Typhoon Hagibis made landfall on the coast of Honshu on the Izu Peninsula southeast of Tokyo on Saturday.  The center of Hagibis moved quickly across the Tokyo metropolitan area toward Mito, Japan.  Typhoon Hagibis brought strong winds to coastal areas of Honshu.  A weather station at Tokyo International Airport in Haneda measured a sustained wind speed of 77 m.p.h. (124 km/h).  Rainbands on the northern side of Hagibis dropped heavy rain over the Tokyo metropolitan area.  Rainfall rates at some weather stations approached an inch (0.3 meters) per hour.  Flash floods occurred as the water from heavy rain ran off.  The rain also caused landslides on some steeper slopes.  Conditions will improve around Honshu as Typhoon Hagibis moves quickly away from Japan.  The heavy rain will end soon and the wind speed will gradually decrease.

Typhoon Hagibis Aims at Tokyo

Typhoon Hagibis was aimed at Tokyo on Friday afternoon.  At 5:00 p.m. EDT on Friday the center of Typhoon Hagibis was located at latitude 31.5°N and longitude 137.4°E which put it about 345 miles (555 km) south-southwest of Tokyo, Japan.  Hagibis was moving toward the north at 11 m.p.h. (17 km/h).  The maximum sustained wind speed was 120 m.p.h. (195 km/h) and there were wind gusts to 150 m.p.h. (240km/h).  The minimum surface pressure was 949 mb.

Typhoon Hagibis was weakening slowly as it shifted onto a course toward Tokyo.  An eye was no longer visible on satellites images.  The ring of strong thunderstorms around the center of Hagibis was weaker in the southern half of the ring.  Most of the stronger thunderstorms were occurring in bands in the northern half of Typhoon Hagibis.  Bands in the southern half of Hagibis consisted primarily of showers and lower clouds.  An upper level trough over eastern Asia was producing southwesterly winds which were causing moderate vertical wind shear.   In addition, Typhoon Hagibis appeared to be pulling drier air into the southern half of the circulation.  The combination of wind shear and drier seemed to have weakened the southern half of the typhoon.

Even though it had weakened, Typhoon Hagibis remained a dangerous typhoon.  Winds to typhoon force extended out 60 miles (95 km) from the center of circulation.  Winds to tropical storm force extended out about 190 miles (305 km) from the center.  The Hurricane Intensity Index (HII) for Hagibis was 22.1  The Hurricane Size Index (HSI) was 21.5 and the Hurricane Wind Intensity Size Index (HWISI) was 43.6.  Typhoon Hagibis was capable of causing major damage.

The upper level trough over eastern Asia will steer Typhoon Hagibis toward the northeast during the next several days.  On its anticipated track Typhoon Hagibis could approach the coast of Honshu southeast of Tokyo in 12 to 18 hours.  Hagibis will continue to weaken as it moves toward Tokyo, but it will still be a typhoon when it reaches the region around Tokyo  Typhoon Hagibis will bring damaging winds to the Tokyo metropolitan area.  Bands of showers and thunderstorms on the northern side of Hagibis are already dropping rain over portions of Honshu southeast of Tokyo.  The rain will continue for another 12 to 24 hours in many locations.  Locally heavy rain will cause flash floods in some parts of Honshu.

Subtropical Storm Melissa Develops off Northeast U.S. Coast

Subtropical Storm Melissa developed off the northeast coast of the U.S. on Friday.  At 11:00 a.m. EDT on Friday the center of Subtropical Storm Melissa was located at latitude 38.5°N and longitude 69.6°W which put it about 190 miles (300 km) south of Nantucket, Massachusetts.  Melissa was moving toward the south-southwest at 3 m.p.h. (5 km/h).  The maximum sustained wind speed was 65 m.p.h. (105 km/h) and there were wind gusts to 80 m.p.h. (130 km/h).  The minimum surface pressure was 995 mb.

More thunderstorms developed near the center of a large low pressure system off the northeast coast of the U.S. on Friday morning and the National Hurricane Center designated the system as Subtropical Storm Melissa.  Melissa initially began as an extratropical cyclone along a slow moving cold front off the east coast of the U.S earlier this week.  The cold front moved east of the surface low pressure system and the surface low stalled underneath an upper level trough.  More showers and thunderstorms began to develop in bands and the low pressure system started to look more subtropical.

The circulation around Melissa was characteristic of a subtropical storm.  There was a well defined center of circulation visible on satellite images.  However, many of the stronger thunderstorms were occurring in a band that wrapped around the northern portion of the circulation.  Bands in the other parts of the circulation consisted primarily of showers and lower clouds.  The circulation was drawing cooler, drier air into the western and southern parts of the subtropical storm.  The wind field around Subtropical Storm Melissa was large and asymmetrical.  Winds to tropical storm force extended out 350 miles (565 km) from the center in the northeastern part of Melissa.  Tropical storm force winds only extended out 100 miles (160 km) to the southeast of the center of circulation.

The intensity of Subtropical Storm Melissa may not change much during the next 12 to 24 hours.  Melissa will remain under the middle of the upper level trough during the rest of Friday.  The winds are weak in the middle of the trough and there will not be much vertical wind shear.  Subtropical Storm Melissa will be over water where the Sea Surface Temperature is near 24°C.  So, there will not be a lot of energy in the upper ocean to support intensification.  The upper level trough will move eastward on Saturday and westerly winds will blow toward the top of Melissa.  The westerly winds will cause significant vertical wind shear, which will start to weaken Subtropical Storm Melissa.

Since the winds are weak in the middle of the upper level trough, Subtropical Storm Melissa is unlikely to move much during the rest of Friday.  Stronger westerly winds will steer Melissa to the east during the weekend.  On its anticipated track Subtropical Storm Melissa is forecast to move away from the U.S. during the weekend.  The large circulation around Melissa will generate large waves which will affect the south coast of New England and the Mid-Atlantic states.  Coastal flooding could occur in some locations.