Author Archives: jay_hobgood

Eugene Becomes a Hurricane Southwest of Baja California

Tropical Storm Eugene strengthened rapidly into a hurricane on Saturday as it moved southwest of Baja California.  At 11:00 p.m. EDT on Saturday the center of Hurricane Eugene was located at latitude 14.4°N and longitude 113.5°W which put it about 630 miles (1020 km) south-southwest of the southern tip of Baja California.  Eugene was moving toward the northwest at 8 m.p.h. (13 km/h).  The maximum sustained wind speed was 80 m.p.h. (130 km/h) and there were wind gusts to 95 m.p.h. (155 km/h).  The minimum surface pressure was 990 mb.

A primary raindband wrapped around the center of Hurricane Eugene on Saturday and an eye formed at the center of circulation.  The eye had a diameter of 30 miles (50 km).  Additional bands of showers and thunderstorms were revolving around the core of the circulation.  Thunderstorms were generating well developed upper level divergence which was pumping mass away in all directions.  The circulation of Hurricane Eugene was symmetrical and well organized.

Hurricane Eugene was moving over water where the Sea Surface Temperature (SST) was near 29°C.  Eugene was underneath the western end of an upper level ridge.  The ridge was producing southerly winds which were blowing toward the top of the hurricane, but the vertical wind shear was not very strong.  Eugene is likely to intensify on Sunday.  It will gradually move over cooler SSTs and Hurricane Eugene will move over water where the water is cooler than 26°C on Monday.  When Eugene reaches the cooler SSTs, it will begin a steady weakening trend.

Hurricane Eugene is moving around the western end of a subtropical ridge which is steering it toward the northwest.  Eugene is expected to continue to move toward the northwest during the next several days.  On its anticipated track Hurricane Eugene will move parallel to the west coast of Baja California.

Tropical Storm Eugene Forms South of Baja California

A distinct center of circulation consolidated within a broader area of low pressure south of Baja California on Friday and the National Hurricane Center classified the system as Tropical Storm Eugene.  At 5:00 p.m. EDT on Friday the center of Tropical Storm Eugene was located at latitude 11.9°N and longitude 111.2°W which put it about 765 miles (1230 km) south of the southern tip of Baja California.  Eugene was moving toward the northwest at 8 m.p.h. (13 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.

The circulation of Tropical Storm Eugene is large and there are numerous bands of showers and thunderstorms rotating around the center of circulation.  A primary rainband is wrapping around the southern and eastern sides of the center and the strongest winds are occurring northeast of the center of circulation.  The circulation is circular and symmetrical.  Thunderstorms around the core of Eugene are beginning to generate upper level divergence which is pumping out mass in all directions.

Tropical Storm Eugene will move through an environment that is favorable for intensification.  Eugene will move over water where the Sea Surface Temperature is near 29°C.  The upper level winds over Tropical Storm Eugene are relatively weak and there is not a lot of vertical wind shear.  The circulation of Tropical Storm Eugene will continue to consolidate and it is likely to intensify during the weekend.  It is likely to become a hurricane and it could intensify rapidly if an eye forms.

Tropical Storm Eugene is moving near the western end of a subtropical ridge which is steering it toward the northwest.  A generally northwesterly motion is expected to continue during the next few days.  On its anticipated track Tropical Storm Eugene would move parallel to the west coast of Baja California and the center would remain west of the coast.

Tropical Depression Four Develops East of the Lesser Antilles

Tropical Depression Four developed east of the Lesser Antilles on Wednesday night.  At 11:00 p.m. EDT on Wednesday the center of Tropical Depression Four was located at latitude 12.8°N and longitude 38.4°W which put it about 1545 (2485 km) east of the Lesser Antilles.  The depression was moving toward the west-northwest at 14 m.p.h. (22 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.

A larger area of thunderstorms formed and persisted on the western side of a tropical disturbance formerly designated as Invest 94L on Wednesday and the National Hurricane Center classified the system as Tropical Depression Four.  The distribution of thunderstorms is still asymmetrical.  Most of the stronger storms are developing in the western half of the circulation.  The thunderstorms in the western part of the circulation were beginning to generate upper level divergence.  There were few thunderstorms in the eastern half of the depression and the vertical structure of the circulation could be tilted to the west with height.

Tropical Depression Four will be moving through an environment that contains both positive and negative factors for intensification.  The depression will move over water where the Sea Surface Temperature is near 27°C.  So, there is sufficient energy in the upper ocean to support intensification.  An upper level ridge is producing easterly winds which are blowing toward the top of the circulation.  Those winds could be causing the circulation to tilt toward the west with height.  Moderate vertical wind shear could inhibit intensification.  Drier air is north of the tropical depression.  If the depression remains south of the drier air and if the vertical wind shear does not become too strong, then the depression could strengthen.  Alternatively, if the depression pulls in drier air and/or the vertical shear increases, then the depression could weaken back to a tropical wave.

The subtropical ridge over the Atlantic Ocean is steering Tropical Depression Four toward the west-northwest.  A general west-northwesterly motion is expected for the next several days.  The actual track will also have a significant effect on the future intensity of Tropical Depression Four. If the depression moves on a more southerly track, it will stay south of the drier air and it would have a greater opportunity to intensify.  If the depression moves farther to the north, it will move into the drier air and will be more likely to weaken,

Invest 94L Likely to Develop East of Lesser Antilles

A tropical disturbance currently designated as Invest 94L is likely to develop into a tropical cyclone east of the Lesser Antilles.  The National Hurricane Center’s probability of formation of a tropical cyclone from this system during the next five days is 70%.  At 2:00 p.m. EDT on Monday the center of Invest 94L was located at latitude 8.7°N and longitude 32.7°W which put it about 1830 miles (2950 km) east of the Lesser Antilles.  It was moving toward the west at 4 m.p.h. (6 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 1011 mb.

Invest 94L consists of a broad area of low pressure, but it has not developed a well organized inner core.  The initial area of low pressure consisted of a counterclockwise rotation associated with a tropical wave that moved over the eastern Atlantic Ocean.  The initial low slowed down as it was moving westward and a second tropical wave caught up to it.  The thunderstorms from the two waves appear to be merging into a single system.  An area of showers and thunderstorms on the northern and western sides of the surface low was part of the first tropical wave.  Other bands of showers and thunderstorms south and east of the low are associated with the second tropical wave.  If the broad low pressure system can collect the rotation from the two tropical waves, it could strengthen the surface low.

Invest 94L will move through an environment that will be favorable for the development of a tropical cyclone.  It will move over water where the Sea Surface Temperature (SST) is near 28°C.  There are easterly winds blowing at multiple levels in the atmosphere and there is little vertical winds shear.  The existence of a surface low pressure system, warm SSTs and little vertical wind shear are the primary ingredients for the development of a tropical cyclone.  That is the reason why there is strong probability that Invest 94L will develop into a tropical depression or a tropical storm.

Invest 94L will be steered by the subtropical high pressure system over the Atlantic Ocean.  A general westerly or west-northwesterly track is forecast during the next few days.  There is still significant uncertainty about the ultimate track and intensity of this system beyond that time frame.  It will need to be monitored closely as it moves west.

Tropical Storm Nanmadol Nearing Kyushu

Tropical Storm Nanmadol was quickly nearing Kyushu on Monday.  At 1:00 p.m. EDT on Monday the center of Tropical Storm Nanmadol was located at latitude 31.0°N and longitude 127.4°E which put it about 215 miles (345 km) southwest of Sasebo, Japan.  Nanmadol was moving toward the north-northeast at 24 m.p.h. (39 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. (135 km/h).  The minimum surface pressure was 986 mb.

The structure of Tropical Storm Nanmadol was still consistent with its designation of a tropical cyclone, but there were signs that it could be about to start the transition to an extratropical cyclone.  There was a core of thunderstorms around the center of circulation.  The strongest winds were occurring in the inner core which extended out about 25 miles (40 km) from the center.  Several rainbands were on the eastern side of the circulation.  There were far fewer showers and thunderstorms in the western half of the circulation.  There were some indications that Nanmadol could be pulling cooler, drier, more stable air into the western side of the tropical storm.

Tropical Storm Nanmadol has probably reached its maximum intensity and it is likely to weaken during the next two days.  Nanmadol is currently over water where the Sea Surface Temperature is near 27°C.  However, it has reached the upper level westerly in the middle latitudes and the vertical wind shear is increasing.  Nanmadol will weaken faster when it moves across Japan.

The westerly winds in the middle latitudes have turned Tropical Storm Nanmadol toward the north-northeast.  As Nanmadol moves farther north, the speed of the westerlies will increase and the tropical storm is forecast to move quickly toward the east-northeast across southern Japan.  On its anticipated track, Tropical Storm Nanmadol will reach Kyushu in a few hours.  Nanmadol will also move over Shikoku and Honshu.  Tropical Storm Nanmadol will bring a brief period of gusty winds and the potential for locally heavy rain when it moves across southern Japan.

Tropical Storm Nanmadol Brings Wind and Rain to Southern Ryukyu Islands

Tropical Storm Nanmadol brought wind and rain to the southern Ryukyu Islands on Sunday.  At 11:00 a.m. EDT on Sunday the center of Tropical Storm Nanmadol was located at latitude 24.4°N and longitude 124.7°E which put it about 40 miles (65 km) east of Ishigaki, Japan.  Nanmadol was moving toward the north-northwest at 21 m.p.h. (34 km/h).  The maximum sustained wind speed was 45 m.p.h. (75 km/h) and there were gusts to 60 m.p.h. (95 km/h).  The minimum surface pressure was 998 mb.

The core of Tropical Storm Nanmadol continued to organize on Sunday.  A ring of thunderstorms wrapped tightly around the center of circulation.  Additional bands of showers and thunderstorms formed outside the core.  Thunderstorms were beginning to generate more upper level divergence which was pumping out mass in all directions.  The circulation of Tropical Storm Nanmadol was fairly small.  Winds to tropical storm force only extend out about 70 miles (110 km) from the center.

Tropical Storm Nanmadol will be in an environment that is very favorable for intensification for about another 24 hours.  Nanmadol will be moving over water where the Sea Surface Temperature (SST) is near 29°C.  The circulation of Tropical Storm Nanmadol is underneath the center of an upper level ridge and the upper level winds are very weak.  Warm SSTs and almost no vertical wind shear will permit Tropical Storm Nanmadol to intensify during the next day and there could be a period of rapid intensification.  Nanmadol could strengthen into a typhoon before it reaches a less favorable environment.  The tropical storm will move over cooler SSTs and it will move into an area of stronger upper level westerly winds in a couple of days.  Nanmadol will begin to weaken when that happens.

Tropical Storm Nanmadol is moving around the western end of a subtropical ridge which is steering it toward the north.  A general northward motion is expected to continue for about another 24 hours.  Nanmadol will reach the westerly winds in the middle latitudes in about a day and those winds will turn it toward the northeast.  On its anticipated track the center of Tropical Storm Nanmadol will pass west of Okinawa.  Nanmadol could approach Kyushu in about 36 hours.  Tropical Storm Nanmadol will continue to cause gusty winds and locally heavy rain over the southern Ryukyu Islands for another 12 to 24 hours.

Tropical Storm Nanmadol Forms Southeast of Taiwan

Tropical Storm Nanmadol formed southeast of Taiwan on Saturday.  At 8:00 p.m. EDT on Saturday the center of Tropical Storm Nanmadol was located at latitude 20.7°N and longitude 127.1°E which put it about 475 miles (765 km) southeast of Taipei, Taiwan.  Nanmadol was moving toward the northwest at 24 m.p.h. (35 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 1002 mb.

A center of circulation consolidated rapidly on Saturday in an area of thunderstorms southeast of Taiwan.  A primary band of showers and thunderstorms wrapped around the northern and western side of the circulation.  Other bands of showers and thunderstorms developed in the northern half of the circulation.  The thunderstorms near the center began to generate upper level divergence which pumped out mass to the north of the tropical storm.

Tropical Storm Nanmadol will move through an area favorable for intensification during the next 24 hours.  Nanmadol will move over water where the Sea Surface Temperature is near 30°C.  An upper level ridge northeast of Nanmadol is producing southeasterly winds which are blowing toward the top of the tropical storm, but there is little vertical wind shear.  Tropical Storm Nanmadol is likely to intensify on Sunday.  When Nanmadol moves farther north, it will move over cooler water and it will be effected by the upper level westerly winds in the middle latitudes.  Cooler water and more vertical wind shear will cause Nanmadol to start to weaken at that time.

Tropical Storm Nanmadol is moving around the western end of a subtropical ridge which is steering it quickly toward the northwest.  Nanmadol will move in a general north-northwesterly direction on Sunday.  It will turn toward the northeast in 24 to 36 hours when it begins to be steered by the mid-latitude westerlies.  On its anticipated track Tropical Storm Nanmadol could approach the southernmost Ryukyu Islands including Ishigaki Jima in about 12 hours.  The center is expected to pass west of Okinawa.  Tropical Storm Nanmadol could approach Kyushu in a couple of days.  An intensifying Tropical Storm Nanmadol will bring gusty winds and locally heavy rain to the southernmost Ryukyu Islands.

Hurricane Dora Weakens South of Baja California

Hurricane Dora weakened as it moved over cooler water south of Baja California on Tuesday.  At 5:00 p.m. EDT on Tuesday the center of Tropical Storm Dora was located at latitude 19.6°N and longitude 111.4°W which put it about 245 miles (400 km) south-southwest of the southern tip of Baja California. Dora as moving toward the west-northwest at 13 m.p.h. (20 km/h).  The maximum sustained wind speed was 65 m.p.h. (105 km/h) and there were wind gusts to 75 m.p.h. (120 km/h).  The minimum surface pressure was 995 mb.

Tropical Storm Dora is moving over water where the Sea Surface Temperature (SST) is near 24°C.  The circulation of Tropical Storm Dora is still very well organized but it is unable to extract sufficient energy from the upper ocean to maintain its intensity.  As a result, the showers and thunderstorms are not rising as far into the atmosphere and the circulation is spinning down.  There is little vertical wind shear and so the circulation is still symmetrical, but it is not as vigorous.  The lack of wind shear will cause the weakening to occur more slowly than it would have if the upper level winds were stronger.

A subtropical ridge is steering Tropical Storm Dora toward the west-northwest and that general motion is expected to continue for anther day or two.  On its anticipated track, Tropical Storm Dora will move farther away from Baja California.  The forecast track would keep Dora over cooler SSTs and it should continue to weaken.

Dora Rapidly Intensifies Into First Eastern Pacific Hurricane of 2017

Tropical Storm Dora intensified rapidly into a hurricane during the overnight hours.  Dora is the first hurricane to develop over the Eastern North Pacific during 2017.  At 11:00 a.m. EDT on Monday the center of Hurricane Dora was located at latitude 17.3°N and longitude 106.3°W which put it about 220 miles (350 km) south of Cabo Corrientes, Mexico.  Dora was moving toward the west-northwest at 13 m.p.h. (20 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 985 mb.

The circulation of Hurricane Dora is very well organized.  A circular eye exists at the center of circulation.  A ring of strong thunderstorms surrounds the eye.  Additional bands of showers and thunderstorms are revolving around the core of the circulation.  Thunderstorms in Dora are generating well developed upper level divergence which is pumping large quantities of mass out in all directions.

Dora is a small hurricane.  Wind to hurricane force extend out about 25 miles (40 km) from the center of circulation.  Winds to tropical storm force extend out about 80 miles (130 km) from the center.  The Hurricane Intensity Index (HII) is 12.7.  The Hurricane Size Index (HSI) is 7.3.  The Hurricane Wind Intensity Size Index (HWISI) is 20.0.

Hurricane Dora will move through an environment favorable for intensification for another 12 to 18 hours.  It is currently over water where the Sea Surface Temperature (SST) is near 28°C.  Dora will move over SSTs that will gradually be cooler, but they should be warm enough to support further intensification for another 12 to 18 hours.  Hurricane Dora is moving through an area where upper level winds are weak and there is almost no vertical wind shear.  Hurricane Dora is likely to strengthen further during the next few hours.  Dora will move over much cooler SSTs when it passes south of Baja California and it will begin to weaken on Tuesday.

A subtropical ridge to the north of Dora is steering the hurricane toward the west-northwest and that general motion is expected to continue for another 24 to 48 hours.  On its anticipated track the center of Hurricane Dora will pass south of Baja California.

TD 04E Strengthens Rapidly Into Tropical Storm Dora

Tropical Depression Four-E strengthened rapidly into Tropical Storm Dora on Sunday.  At 11:00 p.m. EDT on Sunday the center of Tropical Storm Dora was located at latitude 16.4°N and longitude 104.3°W which put ti about 290 miles (470 km) south-southeast of Cabo Corrientes, Mexico.  Dora was moving toward the west-northwest at 14 m.p.h. (22 km/h).  The maximum sustained wind speed was 70 m.p.h. (110 km/h) and there were wind gusts to 80 m.p.h. (130 km/h).  The minimum surface pressure was 996 mb.

The circulation of Tropical Storm Dora organized quickly on Sunday.  A primary rainband wrapped tightly around the center of circulation.  An eyelike feature appeared to be forming on microwave and infrared satellite images.  Additional bands of showers and thunderstorms developed outside the core of Tropical Storm Dora.  Thunderstorms around the core generated upper level divergence which pumped out mass in all directions.

Tropical Storm Dora will be moving through an environment very favorable for intensification on Monday.  It will move over water where the Sea Surface Temperature (SST) is near 29°C.  An upper level ridge over Mexico is producing easterly winds that are blowing toward the top of the circulation, but there is little vertical wind shear.  A combination of warm water and little shear will allow Dora to intensify into a hurricane during the next 24 hours.  The rate of intensification could increase once the formation of the eye is complete.  Dora will move over cooler SSTs on Tuesday.  The cooler SSTs will initially halt the intensification.  When Dora is unable to extract sufficient energy from the upper ocean it will start to weaken.

A subtropical ridge northeast of Dora is steering the tropical storm toward the west-northwest and a general west-northwesterly motion is expected to continue for another day or two.  On its anticipated track the center of Tropical Storm Dora will remain southwest of Mexico.  Dora will pass south of Baja California on Tuesday.