Monthly Archives: April 2020

One-E Becomes Earliest East Pacific Tropical Depression

Tropical Depression One-E became Saturday the earliest tropical depression for form over the Eastern North Pacific Ocean during the satellite era which began in 1966.  The previous date of the earliest formation over that region was May 9, 2017 when a depression formed that would ultimately strengthen into Tropical Storm Adrian.  At 11:00 a.m. EDT on Saturday the center of Tropical Depression One-E was located at latitude 14.1°N and longitude 116.1°E which put it about 730 miles (1175 km) southwest of the southern tip of Baja California.  The depression was moving toward the northwest at 7 m.p.h. (11 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.

More thunderstorms developed near the center of a low pressure system previously designated as Invest 90E southwest of Baja California on Saturday morning and National Hurricane Center designated the system as Tropical Depression One-E.  Tropical Depression One-E is the first tropical depression to form over the Eastern North Pacific Ocean during the month of April in the satellite era .  The distribution of thunderstorms around the depression was asymmetrical.  Many of the stronger thunderstorms were occurring in bands in the southern half of the circulation.  Bands in the northern half of the circulation consisted primarily of showers and lower clouds.  The southern half of the circulation was over warmer Sea Surface Temperatures, which may have contributed to the development of thunderstorms in that part of the tropical depression.

Tropical Depression One-E will move through an environment somewhat favorable for intensification during the next 24 hours.  The depression will move over water where the Sea Surface Temperature is near 26.5°C.  It will move under the western end of an upper level ridge over the Eastern North Pacific Ocean.  The ridge will produce southerly winds which will blow toward the top of the circulation.  Those winds will cause moderate vertical wind shear and they will inhibit intensification.  Conditions could be favorable enough to allow Tropical Depression One-E to strengthen into a tropical storm during the next 24 hours.  The depression will move over cooler Sea Surface Temperatures later on Sunday, which will cause it to weaken.

Tropical Depression One-E will move around the western end of a high pressure system over the Eastern North Pacific Ocean during the next 24 hours.  The high will steer the depression toward the northwest on Saturday.  A second high pressure system over the North Pacific Ocean will block the northward movement of the depression later on Sunday.  The second high will steer the depression more toward the west later in the weekend.

Possible Tropical Development

A tropical cyclone could possibly form south of Baja California during the next few days.  The system has been designated as Invest 90E.  At 2:00 p.m. EDT on Thursday the center of Invest 90E was located at latitude 10.2°N and longitude 111.7°W which put it about 870 miles (1405 km) south of the southern tip of Baja California.  It was moving toward the west at 9 mp.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 1008 mb.

An area of thunderstorms has persisted south of Baja California for the past several days.  More thunderstorms developed on Thursday.  Visible satellite images indicated that the thunderstorms were organizing into bands and there was some counterclockwise rotation of the bands around a center of circulation.  There appeared to be a low level center of circulation.  However, there were not enough thunderstorms around the center of circulation for the system to be classified as a tropical cyclone.

Invest 90E will move through an environment somewhat favorable for the formation of a tropical cyclone during the next 48 hours.  it will move over water where the Sea Surface Temperature is near 29°C.  Invest 90E will move under the western end of an upper level ridge over the Eastern North Pacific Ocean.  The ridge will produce southerly winds which will blow across the top of the system.  Those winds will cause moderate vertical wind shear and they will inhibit the formation of a tropical cyclone.   If the strength of the upper level wind diminishes slightly, then the environment will become more favorable for the formation of a tropical cyclone.  The National Hurricane Center indicated that the probability of formation of a tropical cyclone during the next two days was 40%.

Invest 90E will move around the western end of a high pressure system over the far Eastern North Pacific Ocean during the next several days.  The high will steer the system toward the northwest.  On its anticipated track Invest 90E will remain well to the southwest of Baja California during the weekend.

Tropical Cyclone Jeruto Develops Southeast of Diego Garcia

Tropical Cyclone Jeruto developed over the South Indian Ocean southeast of Diego Garcia on Wednesday.  At 5:00 p.m. EDT on Wednesday the center of Tropical Cyclone Jeruto was located at latitude 16.4°S and longitude 82.7°E which put it about 950 miles (1535 km) southeast of Diego Garcia.  Jeruto was moving toward the west-southwest 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 1003 mb.

The distribution of thunderstorms around Tropical Cyclone Jeruto was asymmetrical.  The strongest thunderstorms were occurring in bands southeast of the center of circulation.  An upper level trough east of Madagascar and an upper level ridge over the South Indian Ocean were interacting to produce strong northwesterly winds.  Those winds were blowing across the top of Tropical Cyclone Jeruto and they were causing strong vertical wind shear.  The strong shear was blowing the upper portion of the tropical cyclone to the southeast of the lower level circulation.  The strong wind shear was the reason for the asymmetrical distribution of thunderstorms.  Bands closer to the center of circulation consisted primarily of showers and lower clouds.

Tropical Cyclone Jeruto will move through an environment unfavorable for intensification during the next several days.  Jeruto will move over water where the Sea Surface Temperature is near 27°C.  So, there will be enough energy in the upper ocean to support intensification.   However, the upper level trough and ridge will continue to cause strong vertical wind shear.  The shear could be strong enough to blow the upper part of Tropical Cyclone Jeruto to the southeast of the lower level circulation.  Jeruto is likely to weaken during the next several days.

Since Tropical Cyclone Jeruto is likely to weaken and the circulation become more shallow, it will be steered by winds in the lower troposphere.  Those winds will steer Jeruto toward the west-southwest during the next several days.  On its anticipated track Tropical Cyclone Jeruto will pass well south of Diego Garcia.

Tropical Cyclone Harold Brings Wind and Rain to Tonga

Tropical Cyclone Harold brought wind and rain to Tonga on Wednesday.  At 11:00 p.m. EDT on Wednesday the center of Tropical Storm Harold was located at latitude 23.8°S and longitude 172.1°W which put it about 250 miles (400 km) southeast of Nuku Alofa, Tonga.  Harold was moving toward the east-southeast at 30 m.p.h. (50 km/h).  The maximum sustained wind speed was 125 m.p.h. (200 km/h) and there were wind gusts to 155 m.p.h. (250 km/h).  The minimum surface pressure was 945 mb.

After forming near the Solomon Islands and causing damage in Vanuatu and Fiji, Tropical Cyclone Harold brought gusty winds and locally heavy rain to portions of Tonga on Wednesday.  The core of Harold with the strongest winds passed about 60 miles (95 km)  southwest of Tongatapu.  However, winds to hurricane/typhoon force extended out 60 miles (95 km) from the center of Tropical Cyclone Harold.  Winds to tropical storm force extended out 200 miles (320 km) from the center of circulation.  An airport at Fua’amotu, Tonga reported a sustained wind speed of 58 m.p.h. (93 km/h) when Harold passed southwest of its location.  The airport also reported a wind gust of 89 m.p.h. (143 km/h).

Tropical Cyclone Harold moved quickly away from Tonga on Wednesday night.  Weather conditions were improving.  A high pressure system over the South Pacific Ocean will continue to steer Harold rapidly toward the east-southeast during the next several days.  On its anticipated track Tropical Cyclone Harold will pass well to the south of Niue.

Tropical Cyclone Harold will move into a less favorable environment.  Harold will move under the southwestern part of an upper level ridge over the South Pacific Ocean.  The ridge will produce northwesterly winds which will blow toward the top of the circulation.  Those winds will cause moderate vertical wind shear.  Harold will also move over cooler water.  Moderate vertical wind shear and cooler water will cause Tropical Cyclone Harold to weaken.  Harold could eventually make a transition to an extratropical cyclone when it moves out of the tropics.

Powerful Tropical Cyclone Harold Brings Wind and Rain to Fiji

Powerful Tropical Cyclone Harold brought strong wind and heavy rain to parts of Fiji on Tuesday night.  At 11:00 p.m. EDT on Tuesday the center of Tropical Cyclone Harold was located at latitude 19.4°S and longitude 178.7°E which put it about 30 miles (50 km) southeast of Tavuki, Fiji.  Harold was moving toward the east-southeast at 22 m.p.h (35 km/h).  The maximum sustained wind speed was 140 m.p.h. (225 km/h) and there were wind gusts to 165 m.p.h. (270 km/h).  The minimum surface pressure was 930 mb.

The eye of Tropical Cyclone Harold passed directly over Kadavu Island, Fiji on Tuesday night.  The Hurricane Intensity Index (HII) for Harold was 28.3.  The Hurricane Size Index (HSI) was 19.7 and the Hurricane Wind Intensity Size Index (HWISI) was 48.0.  Tropical Cyclone Harold probably caused significant damage to Kadavu.  Harold also brought gusty winds and heavy rain to Viti Levu.  Flash floods were likely to have occurred in areas that received heavy rain.

Tropical Cyclone Harold strengthened on Tuesday after it moved away from Vanuatu where it caused significant damage.  The eye became evident on satellite imagery again and a solid ring of thunderstorms formed a strong eyewall.  The strongest winds were occurring in that ring of storms.  Storms around the core of Harold generated strong upper level divergence which pumped mass away from the tropical cyclone.  The size of the circulation around Tropical Cyclone Harold continued to increase in size.  Winds to hurricane/typhoon force extended out 65 miles (105 km) from the center of circulation.  Winds to tropical storm force extended out 250 miles (400 km) from the center.

Tropical Cyclone Harold will move into an area less favorable for intensification during the next 24 hours.  Harold will move over water where the Sea Surface Temperature is near 28°C.  It will move under the southwestern part of an upper level ridge over the South Pacific Ocean.  The ridge will produce northwesterly winds which will blow toward the top of the circulation.  Those winds will increase in speed during the next 48 hours and the increased vertical wind shear will cause Tropical Cyclone Harold to weaken.  Harold could weaken slowly during the next 12 to 24 hours.

Tropical Cyclone Harold will move around the southwestern part of a high pressure system over the South Pacific Ocean.  The high will steer Harold quickly toward the east-southeast.  On its anticipated track the center of Tropical Cyclone Harold could reach Tonga within 12 to 18 hours.  Harold will be the equivalent of a major hurricane when it reaches Tonga.

Tropical Cyclone Harold Approaches Fiji

Tropical Cyclone Harold approached Fiji on Tuesday morning.  At 5:00 a.m. EDT on Tuesday the center of Tropical Cyclone Harold was located at latitude 17.4°S and longitude 173.4°E which put it about 270 miles (435 km) west of Nadi, Fiji.  Harold was moving toward the east-southeast at 17 m.p.h. (28 km/h).  The maximum sustained wind speed was 125 m.p.h. (200 km/h) and there were wind gusts to 155 m.p.h. (250 km/h).  The minimum surface pressure was 943 mb.

Although the maximum sustained wind speed in Tropical Cyclone Harold decreased, the area of stronger winds increased.  Winds to hurricane/typhoon force extended out 70 miles (110 km) from the center of Harold.  Winds to tropical storm force extended out 200 miles (320 km) from the center of circulation.  The Hurricane Intensity Index (HII) for Tropical Cyclone Harold was 23.6.  The Hurricane Size Index (HSI) was 22.1 and the Hurricane Wind Intensity Size Index (HWISI) was 45.7.  Tropical Cyclone Harold was capable of causing major damage.

The circulation around Tropical Cyclone Harold increased in size on Tuesday.  The previous small eye was no longer visible on satellite imagery, but the most recent images suggested that a larger eye could be developing that the center of circulation.  The newly forming eye was surround by a ring of strong thunderstorms and the strongest winds were occurring in that ring of storms.  Bands of showers and thunderstorms were revolving around the center of Harold.  Storms near the center were generating upper level divergence which was pumping mass away from the tropical cyclone.

Tropical Cyclone Harold will move through an environment favorable for intensification during the next 12 to 24 hours.  Harold will move over water where the Sea Surface Temperature is near 30°C.  It will move under the southwestern part of an upper level ridge over the South Pacific Ocean.  The ridge will produce northwesterly winds which will blow toward the top of the circulation.  Those winds will cause some vertical wind shear, but they will not be strong enough to prevent intensification.  Tropical Cyclone Harold could strengthen during the next 12 to 24 hours.

Tropical Cyclone Harold will move around the southwestern part of a high pressure system over the South Pacific Ocean.  The high will steer Harold toward the east-southeast during the next several days.  On its anticipated track Tropical Cyclone Harold could reach Fiji within 12 hours.  Harold will be capable of causing major wind damage.  It will drop heavy rain and flash floods are likely.  Tropical Cyclone Harold could reach Tonga within 36 hours.

Tropical Cyclone Harold Strengthens to Equivalent of Cat. 5 Hurricane

Tropical Cyclone Harold strengthened to the equivalent of a Category 5 hurricane on Monday.  After weakening while the eye crossed the southern end of Espiritu Santo, the core of Harold rapidly intensified and the tropical cyclone became even more powerful.  At 11:00 a.m. EDT on Monday the center of Tropical Cyclone Harold was located at latitude 16.2°S and longitude 169.4°E which put it about 120 miles (195 km) north-northeast of Port Vila, Vanuatu.  Harold was moving toward the east-southeast at 12 m.p.h. (19 km/h).  The maximum sustained wind speed was 165 m.p.h.  and there were wind gusts to 200 m.p.h. (320 km/h).  The minimum surface pressure was 912 mb.

The inner core of Tropical Cyclone Harold weakened when the eye moved across the southern end of Espiritu Santo.  For a time the eye was less distinct of satellite images.  However, the eye cleared out quickly after it moved back over water and the core of Harold strengthened further.  By Monday a small, well formed eye was evident infrared satellite images.  The eye had a diameter of 12 miles (19 km).  A ring of strong thunderstorms surrounded the eye and the strongest winds were occurring in that ring of storms.  Bands of showers and thunderstorms were revolving around the core of Tropical Cyclone Harold.  Storms near the core were generating strong upper level divergence which was pumping mass away from the tropical cyclone.

Winds to hurricane/typhoon force extended out 40 miles (65 km) from the center of Tropical Cyclone Harold.  Winds to tropical storm force extended out 190 miles (305 km) from the center of circulation.  The Hurricane Intensity Index (HII) for Tropical Cyclone Harold was 36.8.  The Hurricane Size Index (HSI) was 16.0 and the Hurricane Wind Intensity Size Index (HWISI) was 52.8.  Harold was capable of causing catastrophic damage.

The core of Tropical Cyclone Harold passed over the southern end of Espiritu Santo.  It then passed near the northern end of Malekula before battering Pentecost and Ambrym.  Harold likely caused catastrophic wind damage in those locations.  Tropical Cyclone Harold also dropped locally heavy rain over Espiritu Santo, Malekula, Pentecost, Maewo, and Ambrym.  Flash flooding probably occurred on those islands.

Tropical Cyclone Harold will move through an environment capable of support an intense tropical cyclone during the next several days.  Harold will move over water where the Sea Surface Temperature is near 30°C.  It will move under the southwestern part of an upper level ridge over the South Pacific Ocean.  The ridge will produce northwesterly winds which will blow toward the top of the circulation.  Those winds will cause some vertical wind shear.  If a rainband wraps around the existing eye and eyewall, then an eyewall replacement cycle could cause Tropical Cyclone Harold to weaken.  Tropical cyclones generally do not maintain Category 5 intensity for an extended period of time.  So, Tropical Cyclone Harold is likely to start to weaken within 24 hours.

Tropical Cyclone Harold will move around the southwestern part of a high pressure system over the South Pacific Ocean.  The high will steer Harold toward the east-southeast during the next few days.  On its anticipated track Tropical Cyclone Harold will move away from Vanuatu.  Harold could approach Fiji within 36 hours and it could still be the equivalent of a major hurricane at that time.

Tropical Cyclone Harold Batters Espiritu Santo

Tropical Cyclone Harold battered Espiritu Santo on Sunday.  The eye of Harold moved over the southwestern part of Espiritu Santo.  At 5:00 p.m. EDT on Sunday the center of Tropical Cyclone Harold was located at latitude 15.3°S and longitude 166.4°E which put it about 60 miles west-northwest of Luganville, Vanuatu.  Harold was moving toward the east at 7 m.p.h. (11 km/h).  The maximum sustained wind speed was 145 m.p.h. (230 km/h) and there were wind gusts to 175 m.p.h. (280 km/h).  The minimum surface pressure was 929 mb.

Tropical Cyclone Harold strengthened on Sunday as it slowly approached northern Vanuatu.  A circular eye with a diameter of 18 miles (29 km) was evident on satellite images.  The eye was surrounded by a ring of strong thunderstorms and the strongest winds were occurring in that ring of storms.  Bands of showers and thunderstorms were revolving around the core of Harold.  Storms near the core were generating strong upper level divergence which was pumping mass away from the tropical cyclone.

Winds to hurricane/typhoon force extended out 45 miles (75 km) from the center of Tropical Cyclone Harold.  Winds to tropical storm force extended out 120 miles (195 km) from the center of circulation.  The Hurricane Intensity Index (HII) for Tropical Cyclone Harold was 29.9.  The Hurricane Size Index (HSI) was 13.3 and the Hurricane Wind Intensity Size Index (HWISI) 43.2.  Harold was capable of causing significant damage.

Tropical Cyclone Harold will move around the southwestern part of a high pressure system over the South Pacific Ocean.  The high will steer Harold toward the east-southeast during the next few days.  On its anticipated track the center of Tropical Cyclone Harold will move across the southern end of Espiritu Santo.  The center will also pass near the northern end of Malekula, near the southern end of Pentecost and near Ambrym.  Tropical Cyclone Harold will drop heavy rain over Espiritu Santo, Malekula, Pentecost, Ambrym, Epi, Ambae and Maewo.  Harold will move slowly and the heavy rain is likely to cause flash floods.  Strong winds blowing toward the coast could produce significant storm surges on the eastern and northern coasts of some islands.

Tropical Cyclone Harold will move through an environment favorable for a strong tropical cyclone.  Harold will move over water where the Sea Surface Temperature is near 30°C.  It will move under the southwestern part of an upper level ridge over the South Pacific Ocean.  The ridge will produce northwesterly winds which will blow toward the top of the circulation.  Those winds will cause some vertical wind shear.  Since the core of Tropical Cyclone Harold will pass over the southern end of Espiritu Santo, increased friction will cause the circulation to weaken during the next 12 to 24 hours.

Major Tropical Cyclone Harold Nears Vanuatu

Major Tropical Cyclone Harold neared Vanuatu on Saturday night.  At 11:00 p.m. EDT on Saturday the center of Tropical Cyclone Vanuatu was located at latitude 15.5°S and longitude 166.0°E which put it about 80 miles (130 km) west-northwest of Unmet, Vanuatu.  Harold was moving toward the southeast at 7 m.p.h. (11 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. (240 km/h).  The minimum surface pressure was 949 mb.

Tropical Cyclone Harold intensified into the equivalent of a major hurricane.  The original small eye dissipated but a new larger eye developed on Saturday night.  The new eye was surround by a ring of strong thunderstorms and the strongest winds were occurring in that ring of storms.  Bands of showers and thunderstorms were revolving around the core of Tropical Cyclone Harold.  The strongest rainbands were in the eastern and southern parts of the circulation.  Storms near the core of Harold generated upper level divergence which pumped mass away from the center of the tropical cyclone.

Winds to hurricane/typhoon force extended out 30 miles (50 km) from the center of Tropical Cyclone Harold.  Winds to tropical storm force extended out 125 miles (200 km) from the center of circulation.  The Hurricane Intensity Index (HII) for Harold was 22.1.  The Hurricane Size Index (HSI) was 11.1 and the Hurricane Wind Intensity Size Index (HWISI) was 33.2.  Tropical Cyclone Harold was capable of causing major damage.

Tropical Cyclone Harold will move through an environment favorable for intensification during the next 24 hours.  Harold will move over water where the Sea Surface Temperature is near 30°C.  It will move around the southwestern part of an upper level ridge over the South Pacific Ocean.  The ridge will produce northwesterly winds which will blow toward the top of the circulation.  Those winds will cause some vertical wind shear and the wind shear could be strong enough to limit intensification.  Tropical Cyclone Harold could intensify further, but it may maintain its intensity on Sunday.

The ridge over the South Pacific Ocean will steer Tropical Cyclone Harold slowly toward the southeast during the next 24 hours.  On its anticipated track the core of Harold with the strongest winds will move slowly toward Malekula.  Tropical Cyclone Harold will drop heavy rain over central Vanuatu.  The slow movement of Harold could create the potential for very serious flooding on Espiritu Santo, Malekula, Ambrym and Epi.

Elsewhere in the tropics, Tropical Cyclone Irondro began to slowly weaken over the South Indian Ocean.  At 5:00 p.m. EDT on Saturday the center of Tropical Cyclone Irondro was located at latitude 23.3°S and longitude 81.5°E which put it about 1275 miles (2060 km) southwest of Cocos Island.  Irondro was moving toward the southeast at 18 m.p.h. (29 km/h).  The maximum sustained wind speed was 110 m.p.h. (175 km/h) and there were wind gusts to 130 m.p.h. (210 km/h).  The minimum surface pressure was 958 mb.

Tropical Cyclone Harold Rapidly Intensifies into Equivalent of Hurricane/Typhoon

Tropical Cyclone Harold rapidly intensified into the equivalent of a hurricane/typhoon west-northwest of Vanuatu on Friday.  At 11:00 p.m. EDT on Friday the center of Tropical Cyclone Harold was located at latitude 14.1°S and longitude 164.1°E which put it about 170 miles (275 km) west-northwest of Nokuku, Vanuatu.  Harold was moving toward the southeast at 5 m.p.h. (8 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 959 mb.

The circulation around Tropical Cyclone Harold organized quickly on Friday.  The inner end of a rainband wrapped around the center of circulation and a small eye formed.  A ring of strong thunderstorms surrounded the eye and the strongest winds were occurring in that ring of storms.  Bands of showers and thunderstorms were revolving around the core of Harold.  The strongest rainbands were in the eastern half of the circulation.  Bands in the western half of the circulation consisted primarily of showers and lower clouds.  Storms around the core of the circulation generated strong upper level divergence which pumped mass away to the east of the tropical cyclone.

Winds to hurricane/typhoon force extend out 35 miles (55 km) from the center of Tropical Cyclone Harold.  Winds to tropical storm force extended out 140 miles (225 km) from the center of circulation.  The Hurricane Intensity Index (HII) for Tropical Cyclone Harold was 17.8.  The Hurricane Size Index (HSI) was 12.0 and the Hurricane Wind Intensity Size Index (HWISI) was 29.8.  Harold was capable of causing serious damage.

Tropical Cyclone Harold will move through an environment favorable for intensification during the next 24 to 48 hours.  Harold will move over water where the Sea Surface Temperature is near 30°C.  It will move around the southwestern part of an upper level ridge over the South Pacific Ocean.  The ridge will produce northwesterly winds which will blow toward the top of the circulation.  Those winds will cause some vertical wind shear, but the shear will not be strong enough to prevent intensification.  Tropical Cyclone Harold will strengthen into the equivalent of a major hurricane during the next 12 hours.

The upper level ridge will steer Tropical Cyclone Harold slowly toward the southeast during the weekend.  On its anticipated track Harold will gradually approach Espiritu Santo and Malekula in Vanuatu.  The core of Tropical Cyclone Harold could move across the central part of Vanuatu in 48 to 72 hours.  Harold is likely to be the equivalent of a major hurricane at that time.

Elsewhere in the tropics, Tropical Cyclone Irondro intensified into the equivalent of a hurricane/typhoon over the South Indian Ocean.  At 5:00 p.m. EDT on Friday the center of Tropical Cyclone Irondro was located at latitude 19.9°S and longitude 76.4°E which put it about 885 miles (1425 km) south-southeast of Diego Garcia.  Irondro was moving toward the east-southeast at 21 m.p.h. (33 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. (170 km/h).  The minimum surface pressure was 973 mb.