Category Archives: Eastern and Central Pacific

TCs between Mexico and Hawaii

Tropical Depression Four-E Forms South of Acapulco

Tropical Depression Four-E formed south of Acapulco, Mexico on Saturday.  At 11:00 p.m. EDT on Saturday the center of Tropical Depression Four-E was located at latitude 14.3°N and longitude 100.0°W which put it about 180 miles (290 km) south of Acapulco.  It was moving toward the west-northwest at 10 m.p.h. (16 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 1006 mb.

A distinct surface center of circulation developed within a larger area of thunderstorms south of Mexico on Saturday.  Showers and thunderstorms began to consolidate near the center.  Additional bands of showers and thunderstorms formed outside the core of the circulation.  The thunderstorms began to produce upper level divergence which pumped mass away from the core of the depression.

Tropical Depression Four-E will move through an environment favorable for intensification during the next several days.  It will move over water where the Sea Surface Temperature is near 30°C.  An upper low over the western Gulf of Mexico is enhancing the upper level divergence to the northeast of the tropical depression.  An upper level ridge over Mexico is producing easterly winds which are blowing toward the top of the circulation, but the vertical wind shear is minimal.  Tropical Depression Four-E could intensify in a tropical storm on Sunday.  It has a chance to become a hurricane early next week before it reaches cooler water south of Baja California.

A subtropical ridge over Mexico is steering Tropical Depression Four-E toward the west-northwest and that general motion is expected to continue for another two or three days.  On its anticipated track the center of Tropical Depression Four-E is expected to remain south of the coast of Mexico.  Rainbands in the northern portion of the circulation could produce locally heavy rain over parts of southern Mexico.  The greatest risk would be for flash floods in those areas.

TD 03E Strengthens Into Tropical Storm Calvin

Tropical Depression 03E strengthened into Tropical Storm Calvin on Monday as it lingered south of Mexico.  At 5:00 p.m. EDT on Monday the center of Tropical Storm Calvin was located at latitude 15.5°N and longitude 95.5°W which put it about 70 miles (110 km) east-southeast of Puerto Angel, Mexico.  Calvin was moving toward the west-northwest at 2 m.p.h. (3 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 1005 mb.  A Tropical Storm Warning remains in effect for the portion of the coast from Boca De Pijijiapan to Punta Maldonado.

A band of thunderstorms wrapped tightly around the southern side of the center of circulation of former Tropical Depression 03E and the National Hurricane Center upgraded the system to Tropical Storm Calvin in its 5:00 p.m. EDT advisory on Monday.  Calvin is a small tropical storm and winds to tropical storm force only extend out about 60 miles (95 km) from the center of circulation.  Additional bands of showers and thunderstorms are occurring in the outer portions of the circulation which are over the Pacific Ocean.

Tropical Storm Calvin is in an environment that is marginally favorable for intensification.  It is over water where the Sea Surface Temperature is near 30°C.  However, Calvin is also very near the coast of Mexico and it could start to pull drier air into the western part of the circulation at any time.  Calvin is under the eastern end of an upper level ridge which is producing northerly winds which are blowing toward the top of the tropical storm.  The northerly winds are producing moderate vertical wind shear and the shear may be contributing to the location of the main band thunderstorms south of the center of circulation.

The future intensity of Tropical Storm Calvin will depend on whether or not it remains over the Pacific Ocean.  If Calvin stays over the open water, then further intensification is possible.  If Calvin moves closer to the coast, then further intensification is much less likely.  If Calvin moves inland, it will dissipate quickly.

Tropical Storm Calvin is in an area where the steering currents are weak and it moved very slowly toward the west-northwest during the past 18 hours.  A subtropical ridge north of Calvin is forecast to begin to steer the tropical storm more quickly toward the west-northwest.  If that happens, Calvin could make landfall on the coast of Mexico near Puerto Angel in 12 to 24 hours.  Locally heavy rainfall remain the biggest risks with Tropical Storm Calvin.

Formation of Tropical Depression 03E Prompts Mexico to Issue Warning for Coast

Tropical Depression 03E formed out of the cluster of thunderstorms formerly known as Invest 92E and the government of Mexico issued a Tropical Storm Warning for a portion of the south coast.  At 5:00 p.m. EDT on Sunday the center of Tropical Depression 03E was located at latitude 14.5°N and longitude 95.0°W which put it about 105 miles (170 km) southeast of Puerto Angel, Mexico.  The depression was moving toward the northwest at 5 m.p.h. (7 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 1007 mb.  A Tropical Storm Warning is in effect for the portion of the coast from Boca De Pijijiapan to Punta Maldonado, Mexico.

A distinct center of circulation developed within an area of thunderstorms that had been lingering over the Eastern North Pacific Ocean south of Mexico.  More thunderstorms formed closer to the center of circulation and the National  Hurricane Center determined that there was sufficient organization to designate the system as Tropical Depression 03E.  The stronger thunderstorms were occurring in a partial band close to the center of circulation.  Additional bands of showers and thunderstorms were forming in bands in other parts of the circulation.  The thunderstorms near the center have not yet begun to generate significant upper level divergence.

Tropical Depression 03E will be moving through an environment that is marginally favorable for intensification.  The depression will move over water where the Sea Surface Temperature is near 30°C.  It is moving under the western end of an upper level ridge.  The ridge is generating southeasterly winds which are blowing toward the top of the circulation.  Those winds are generating moderate vertical wind shear which is restricting upper level divergence to the east of the circulation.  The shear is inhibiting intensification.  Tropical Depression 03E will probably be able to extract enough energy to intensify into a tropical storm.

Tropical Depression 03E is moving around the western end of a subtropical ridge which is steering it toward the northwest.  A generally northwesterly motion is forecast for the next 24 to 48 hours.  On its anticipated track Tropical Depression 03E could approach the southern coast of Mexico in 24 to 36 hours.  It could be a tropical storm by that time.  Tropical Depression 03E is likely to bring gusty winds, locally heavy rain and the potential for flash floods to parts of southern Mexico.

Tropical Storm Beatriz Brings Heavy Rain to Southern Mexico

Tropical Depression Two-E intensified into Tropical Storm Beatriz on Thursday and Beatriz brought heavy rain to parts of southern Mexico.  At 5:00 p.m. EDT on Thursday the center of Tropical Storm Beatriz was located at latitude 15.5°N and longitude 96.8°W which put it about 25 miles (40 km) southwest of Puerto Angel, Mexico.  Beatriz was moving toward the north-northeast at 5 m.p.h. (8 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 1004 mb.  A Tropical Storm Warning was in effect for the portion of the coast from Salina Cruz to Puerto Escondido.

Tropical Depression Two-E intensified into Tropical Storm Beatriz on Thursday even though its structure evolved into a more asymmetrical system.  Tropical Storm Beatriz appeared to consist of a larger low pressure system which was centered just off the coast of Mexico.  The weather radar from Puerto Angel confirmed that the center of circulation was still offshore.  There were several smaller (mesoscale) counterclockwise rotating circulations that were revolving around the center of the larger low.  At least one of the smaller circulations was already over southern Mexico.  Many of the thunderstorms were occurring in a broad band that wrapped around the eastern and northern portions of the larger low pressure system.  The strongest winds were occurring within this primary rainband.  There were far fewer thunderstorms in the western half of the circulation.  It seemed that after air descended from mountains in Mexico then the air was drawn into the western side of Tropical Storm Beatriz.  The warmer drier air was inhibiting the formation of thunderstorms in the western half of Beatriz.

Although Tropical Storm Beatriz is over water where the Sea Surface Temperature is near 30°C, other environmental factors are unfavorable for intensification.  The proximity to land and the apparent ingestion of drier air are both negative factors.  A narrow upper level ridge oriented from the south-southwest to the north-northeast and a upper level trough to the west of Beatriz are producing brisk southerly winds that are blowing toward the top of the circulation.  Those upper level winds are causing moderate vertical wind shear.  Therefore, Tropical Storm Beatriz is unlike to intensify further during the next several days.

The future track of Tropical Storm Beatriz is uncertain.  If the circulation of Beatriz remains intact then the upper level trough and upper level ridge are likely to steer it toward the north-northeast.  Tropical Storm Beatriz would dissipate over the mountains of Mexico if that scenario occurs.  If the upper level winds are strong enough, the vertical shear could detach the upper portion of the circulation from the low level circulation.  That scenario sometimes occurs when slow moving storms approach the south coast of Mexico.  If that happens, the upper half of the circulation could be transported across Mexico and move over the southern Gulf of Mexico.  Some models are suggesting that a new surface low could form over the southern Gulf in several days, but the wind shear would have to decrease in order for that to occur.  The lower level circulation could be left behind near the coast of Mexico where it would drift slowly near the coast.

Tropical Storm Beatriz is bringing heavy rains to parts of southern Mexico and the heavy rain will continue to fall on Friday.  Locally heavy rain in the more mountainous portions of Oaxaca could create the potential for dangerous flash floods.

Tropical Depression 2E Prompts Tropical Storm Watch By Mexico

The National Hurricane Center designated former Invest 91E as Tropical Depression 2E and the government of Mexico issued a Tropical Storm Watch for the portion of the coast from Salina Cruz to Puerto Escondido.  At 11:00 a.m. EDT on Wednesday the center of Tropical Depression 2E was located at latitude 13.9°N and longitude 97.8°W which put it about 250 miles (400 km) southeast of Acapulco, Mexico.  The depression was moving toward the northeast at 3 m.p.h. (5 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 1007 mb.

Bands of showers and thunderstorms developed closer to the center of a broad area of low pressure previously designated as Invest 91E on Wednesday morning.  The improved organization prompted the National Hurricane Center to classify the system as Tropical Depression 2E.  Several bands of showers and thunderstorms were revolving around a tighter center of circulation.  Additional bands of showers and thunderstorms were strengthening in the outer portions of the circulation.  Thunderstorms in the inner part of the circulation were beginning to generate upper level divergence which was pumping out mass to the north and west of the depression.

Tropical Depression 2E will be moving through an environment that will be favorable for intensification.  It will be moving over water where the Sea Surface Temperature is 30°C to 31°C.  An upper level ridge centered east of the depression will generate southerly winds which will blow toward the top of the circulation.  Those winds will generate some vertical wind shear, but the shear will not be strong enough to prevent strengthening.  The circulation around the upper level ridge could actually enhance upper level divergence to the north of the depression.  Tropical Depression 2E is likely to intensify into a tropical storm during the next several days.

A subtropical high east of the depression is steering the system slowly toward the northeast.  A slow northerly motion is forecast for the next day or two.  Forecast guidance from the numerical models diverges when the system approaches Mexico.  Some models continue to move the depression inland over Mexico.  Other models suggest that the steering winds will weaken and that the system will stall before it reaches the coast.  The official forecast from the National Hurricane Center has the depression stalling very near the coast and then turning westward during the weekend.

Bands of rain in the outer part of the circulation are already moving over the coast.  Tropical Depression 2E will produce locally heavy rainfall over parts of southern Mexico and there is the potential for dangerous flash floods.

Invest 91E Slowly Organizing South of Mexico

A broad area of low pressure designated as Invest 91E slowly organized south of Mexico on Tuesday.  At 8:00 p.m. EDT on Tuesday the center of Invest 91E was located at latitude 13.7°N and longitude 97.9°W which put it about 220 miles (350 km) south-southeast of Acapulco, Mexico.  Invest 91E was moving toward the north-northeast at 6 m.p.h. (10 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 1007 mb.

Invest 91E consisted of a broad area of low pressure located south of Mexico.  The Invest did not have a well organized center of circulation.  Instead there was a broad area of counterclockwise rotation.  Many of the thunderstorms were in bands in the outer periphery of the circulation.  A few thunderstorms were beginning to form closer to the center and there were signs that some bands of showers were beginning to organize nearer to the core of the system.

Invest 91E will be moving through an area that will be favorable for development of a tropical cyclone.  It will move over water where the Sea Surface Temperature is near 30°C.  Invest 91E will be moving underneath the western portion of an upper level ridge.  The ridge will produce southerly winds which will blow toward the top of the circulation.  The southerly winds will cause some vertical wind shear.  However, the effects of the shear could be offset by upper level divergence created by the upper level ridge.  Invest 91E has a good chance to develop into a tropical depression and the National Hurricane Center is indicating that there is a 70% probability of a depression forming during the next 48 hours.

A subtropical ridge east of Invest 91E is steering the system slowly toward the north-northeast.  A general northerly motion is expected to continue for another 24 to 48 hours.  On its anticipated track Invest 91E will approach the southern coast of Mexico.  It could bring locally heavy rain when the outer bands on the northern side of the circulation move over land.

Strong Shear Weakens Adrian to a Tropical Depression

Strong vertical wind shear weakened Tropical Storm Adrian to a tropical depression on Wednesday.  At 11:00 p.m. EDT on Wednesday the center of Tropical Depression Adrian was located at latitude 10.5°N and longitude 93.1°W which put it about 420 miles (675 km) south-southeast of Salina Cruz, Mexico.  Adrian was moving toward the northwest at 5 m.p.h. (7 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 1007 mb.

An upper level ridge east of Adrian generated strong southeasterly winds which produced strong vertical wind shear and literally blew the top off of the tropical storm.  The upper half of the circulation was carried well to the northwest of low level circulation.  The low level circulation consists low clouds and weak showers.  No new thunderstorms have formed in the low level circulation since it decoupled from the upper half of the circulation.

Strong upper level winds are likely to continue to create strong vertical wind shear on Thursday.  Tropical Depression Adrian is likely to remain weak on Thursday.  If the low level circulation persists for several more days, then the upper level winds could weaken.  The Sea Surface Temperature is near 30°C.  So, if there is still a low level circulation, some strengthening could occur when the upper level winds diminish.

Tropical Storm Adrian Develops South of Guatemala

Tropical Storm Adrian developed south of Guatemala on Tuesday.  Adrian became the earliest tropical storm to form over the Eastern North Pacific Ocean during the satellite era.  At 11:00 p.m. EDT on Tuesday the center of Tropical Storm Adrian was located at latitude 9.5°N and longitude 92.3°W which put it about 360 miles (575 km) southwest of San Salvador, El Salvador.  Adrian was moving toward the west-northwest at 7 m.p.h. (11 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 1005 mb.

A well defined low level center of circulation developed within a large area of thunderstorms over the Eastern North Pacific Ocean on Tuesday and the National Hurricane Center classified the system as Tropical Storm Adrian.  A primary rainband wrapped about half way around the western side of the center of circulation.  Additional bands of showers and thunderstorms formed farther away from the center.  There were more thunderstorms west of the center, but bands were forming in all quadrants of Tropical Storm Adrian.  The strongest winds were occurring close to the center of circulation, which is the typical structure of a tropical cyclone.  Thunderstorms near the core of Adrian were beginning to generate upper level divergence which was pumping away mass.

Tropical Storm Adrian will be moving through an environment that will be favorable for intensification.  Adrian will move over water where the Sea Surface Temperature will be about 30.5°C.  An upper level ridge east of Adrian is producing southeasterly winds which are blowing toward the top of the circulation.  Those winds are causing some vertical wind shear, but the shear should not be great enough to prevent intensification.  Tropical Storm Adrian is likely to intensify during the next several days and it could become a hurricane later this week.

Adrian is moving around the southwestern part of a subtropical ridge, which is steering the tropical storm toward the west-northwest.  A general west-northwesterly motion is expected to continue for several more days.  When Adrian reaches the western end of the ridge later this week, the tropical storm will turn toward the north and it will move closer toward the coast.

Possible Tropical Development South of El Salvador

A broad area of low pressure has formed over the Eastern North Pacific Ocean south of El Salvador.  The environment is favorable for the development of a tropical cyclone.  The National Hurricane Center (NHC) has designated the low pressure system as Invest 90E.  NHC is indicating that there is a 50% probability of the formation of a tropical depression during the next 48 hours and an 80% probability of formation during the next five days.

At 2:00 p.m. EDT on Monday the center of Invest 90E was located at latitude 7.9°N and longitude 89.5°W which put it about 370 miles (595 km) south of San Salvador, El Salvador.  Invest 90E was stationary.  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.

More thunderstorms formed on Monday around a broad area of low pressure south of El Salvador.  Visible satellite imagery suggested a broad counterclockwise rotation of the area of thunderstorms, but there were no indications of a well developed core of the circulation.  Several smaller centers of rotation were visible within the broad low pressure system, but these may be transient features.  The broad area of thunderstorms was producing upper level divergence.  The divergence is pumping out mass and if that continues, then the surface pressure will decrease.

The area of low pressure is in an environment favorable for tropical development.  It is moving over water where the Sea Surface Temperature is near 30°C.  The low is sitting underneath an upper level ridge and the winds in the upper level are weak.  There is little vertical wind shear and there is nothing to inhibit upper level divergence.  The circulation should continue to organize, which is why the probability of formation of a tropical cyclone is high.

The area of low pressure is in an area where the steering currents are weak and Invest 90E was nearly stationary on Monday.  A high pressure system northeast of the broad area of low pressure system is expected to strengthen.  When that happens, the high is likely to steer the area of low pressure toward the northwest.

Tropical Storm Tina Forms West of Manzanillo

More thunderstorms formed near the center of a low pressure system west of Mexico on Sunday and the National Hurricane Center classified the system as Tropical Storm Tina.  At 10:00 p.m. EDT on Sunday the center of Tropical Storm Tina was located at latitude 18.5°N and longitude 107.1°W which put it about 185 miles (300 km) west of Manzanillo, Mexico.  Tina was moving toward the north 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 1005 mb.

The circulation of Tropical Storm Tina is not well organized.  Although there is a definite center of circulation in the lower levels, most of the thunderstorms are developing north and east of the center of circulation.  An upper level trough southwest of California is generating southwesterly winds which are blowing across the top of Tropical Storm Tina.  The strong vertical wind shear is tilting the circulation and it is causing the thunderstorms to be concentrated in the northeastern quadrant of the circulation.  The upper level winds are also inhibiting upper level divergence.

Although Tropical Storm Tina is moving over water where the Sea Surface Temperature is near 30°C, the atmospheric environment is unfavorable for intensification.  The strong vertical wind shear will prevent any significant intensification.  In fact, if the upper level winds get much stronger, the shear could blow the top half of the circulation northeast of the bottom half.  In that case the low level circulation will quickly spin down and dissipate.

If the vertical integrity of the circulation is maintained, then the upper level trough will steer Tropical Storm Tina toward the northeast and into Mexico.  However, if the circulation shears apart, a surface high pressure system could steer it slowly toward the west.  In either case the upper level winds could transport some moist air over Jalisco and Colima, where it could enhance rainfall.