Author Archives: jay_hobgood

Tropical Storm Ana Makes Landfall

The center of Tropical Storm Ana officially made landfall at 6:00 a.m. EDT on Sunday near Myrtle Beach, South Carolina.  Ana was officially a tropical storm at the time of landfall with maximum sustained winds of 45 m.p.h.  This is one of the earliest landfalls of a tropical storm in the U.S. in the historical record.  Ana moved inland slowly and it has weakened to a tropical depression.  At 2:00 p.m. EDT on Sunday the center of Tropical Depression Ana was located at latitude 34.1°N and longitude 78.9°W which put it about 30 miles north of Myrtle Beach, South Carolina.  Ana was moving toward the northeast at 5 m.p.h.  The maximum sustained wind speed was 35 m.p.h. and there were gusts to 45 m.p.h.  The minimum surface pressure was 1006 mb.  The Tropical Storm Warning for the portion of the coast from South Santee River, South Carolina to Cape Lookout, North Carolina has been discontinued.

The slow movement of Ana is creating the potential for locally heavy rain.  There has been some beach erosion as well, but generally the impacts have been minor.  An upper level trough approaching from the west is expected to steer Ana back out into the Atlantic.  However, strong vertical wind shear and cool Sea Surface Temperatures are expected to prevent significant redevelopment when Ana moves back over water.

Typhoon Noul Equivalent of Category 5 Hurricane

Typhoon Noul moved into an area with very little vertical wind shear and intensified into the equivalent of a Category 5 hurricane on the Saffir-Simpson Scale on Saturday.  At 11:00 p.m. EDT on Saturday Typhoon Noul was located at latitude 17.4°N and longitude 123.1°E which put it about 130 miles east of Tuguegarao and about 85 miles southeast of Escarpada Point on the northeastern tip of Luzon.  Noul was moving toward the north-northwest at 12 m.p.h.  The maximum sustained wind speed was 160 m.p.h. and there were gusts to 195 m.p.h.  The minimum surface pressure was 918 mb.

Noul is at the western end of the subtropical ridge that has been steering it toward the northwest.  It should gradually turn more toward the north on Sunday.  The anticipated track will take the center of Noul very close to the northeastern tip of Luzon in a few hours.  As it moves northward, it will start to be affected by westerly winds in a day or so.  Those winds will turn it more toward the northeast and it could affect some of the southern islands of Japan early next week.

As Noul moves toward the north it will move over cooler Sea Surface Temperatures  (SSTs).  In addition the upper level westerly winds will create more vertical wind shear over Noul.  The combination of cooler SSTs and more vertical wind shear will cause Noul to weaken throughout the next few days.  However, if could still be a typhoon when it passes by Okinawa in about 48 hours.

Noul could bring strong winds and heavy rain to the northeastern tip of Luzon on Sunday.  Mudslides could be a possibility in locations that receive heavy rain.

 

Ana Transitions to a Tropical Storm

As Subtropical Storm Ana sat over the relatively warm Sea Surface Temperatures of the Gulf Stream, it drew energy from the upper ocean.  More thunderstorms developed near the center of circulation and condensation released latent energy which warmed the middle and upper levels.  As a result, the circulation became more circularly symmetrical and eventually some upper level outflow developed at the top of the system. As a result of the structural changes, Ana made a transition from a subtropical storm to a tropical storm.

At 11:00 a.m. EDT on Saturday the center of Tropical Storm Ana was located at latitude 32.7°N and longitude 77.9°W which put it about 90 miles southeast of Myrtle Beach, South Carolina and about 105 miles south of Wilmington, North Carolina.  Ana was moving toward the northwest at 3 m.p.h.  The maximum sustained wind speed was 60 m.p.h. and there were gusts to 70 m.p.h.  The minimum surface pressure was 1001 mb.

A Tropical Storm Warning remains in effect from South Santee River, South Carolina to Cape Lookout, North Carolina.  A Tropical Storm Watch is in effect from Edisto Beach to South Santee River, South Carolina.

As the high pressure system that has been blocking the forward progress of Ana moves eastward, the tropical storm will move toward the coast.  It is likely to make landfall near the border of South Carolina and North Carolina on Sunday morning.  An upper level trough approaching from the west will turn Ana toward the northeast and sweep it out to sea after it makes landfall.

Ana is still over the relatively warm water of the Gulf Stream and it is likely to maintain its intensity on Saturday.  When Ana moves north of the Gulf Stream, it will cross over cooler water.  In addition, the approaching upper level trough will begin to generate some vertical wind shear over Ana.  The effects of cooler water and more wind shear mean that Ana will likely be weakening as it approaches the coast.  It will bring some wind, locally heavy rain and beach erosion, but the impacts should be minor in most locations.

Typhoon Noul Approaching the Philippines

Typhoon Noul continued to move steadily toward the west-northwest on Friday and it is approaching the northeastern Philippines.  At 3:00 pm. EDT on Friday the center of Typhoon Noul was located near latitude 13.9°N and longitude 127.0°E which put it about 300 miles east of Labo and about 480 miles east-southeast of Tuguegarao in the Philippines.  Noul was moving toward the west-northwest at 14 m.p.h.  The maximum sustained wind speed was 120 m.p.h. and there were gusts to 150 m.p.h.  The minimum surface pressure was 944 mb.  Noul is the equivalent of a Category 3 hurricane on the Saffir-Simpson Scale.

Noul is being steered to the west-northwest by a subtropical ridge located northeast of it.  As Noul nears the western end of the ridge, it is expected to begin to move more toward the northwest.  As Noul approaches the northeastern coast of Luzon, an upper level trough to the west is expected to turn it more toward the north.  The timing of the turn is still uncertain which makes the track forecast more difficult.  On its projected track Noul would approach northeastern Luzon in about 30 hours.

Noul is over Sea Surface Temperatures near 29°C and there is not much vertical wind shear.  However, there are fewer thunderstorms in the northwestern portion of the circulation and the could be some drier air in that region.  The environment is favorable for intensification but large changes in Noul’s intensity are not expected.  Noul is expected to be a significant typhoon when it approaches Luzon and it could bring strong winds and locally heavy rain to that region.  The heavy rain could lead to mudslides in areas where the slopes are steeper.

Tropical Storm Warning Issued for Ana

The National Hurricane Center has issued a Tropical Storm Warning for the portion of the coast from South Santee River, South Carolina to Surf City, North Carolina.  A Tropical Storm Watch remains in effect from Edisto Beach to South Santee River, South Carolina and from Surf City to Cape Lookout, North Carolina.

At 11:00 a.m. EDT on Friday the center of Subtropical Storm Ana was located at latitude 31.5°N north and longitude 77.3°W which put it about 250 miles east of Savannah, Georgia, about 190 miles east-southeast of Charleston, South Carolina and about 180 miles south-southeast of Wilmington, North Carolina.  Ana was nearly stationary.  The maximum sustained wind speed was 45 m.p.h. and there were gusts to 60 m.p.h.  The minimum surface pressure was 1001 mb.

Thunderstorms are forming on the southern and eastern sides of the circulation and Ana is beginning to look more like a tropical cyclone on satellite images.  It could slowly make a transition to a tropical storm during the next several days.

A high pressure system north of Ana is expected to move slowly eastward and steer Ana toward the coast during the next two or three days.  After that time an upper level trough approaching from the west is expected to steer Ana to the northeast and out to sea.

A combination of marginal Sea Surface Temperatures, drier air and some vertical wind shear is expected to limit the potential for intensification.  However, some modest intensification is possible and the surface pressure has decreased slightly in recent hours.

 

Subtropical Storm Ana Forms Off Southeast U.S. Coast

Thunderstorms developed closer to a broad area of low pressure off the southeast U.S. coast and the National Hurricane Center (NHC) classified it as Subtropical Storm Ana.  At 11:00 p.m. EDT on Thursday the center of Subtropical Storm Ana was located at latitude 31.5°N and longitude 77.6°E which put it about 250 miles east of Savannah, Georgia, about 180 miles southeast of Charleston, South Carolina and about 200 miles south of Wilmington, North Carolina.  Ana was moving toward the north at 2 m.p.h.  The maximum sustained wind speed was 45 m.p.h. and there were gusts to 60 m.p.h.  The minimum surface pressure was 1004 mb.  A Tropical Storm Watch has been issued for the portion of the coast from Edisto Beach, South Carolina to Cape Lookout, North Carolina.

More thunderstorms are being generated near the center of circulation, but the strongest winds are about 90 miles from the center.  So, the structure does not match a classical tropical cyclone where the strongest winds are closer to the center and NHC classified it as a subtropical storm.  The center of circulation is over Sea Surface Temperatures (SSTs) near 26°C which are warm enough to support the development of a tropical cyclone.  So, Ana could make a transition to a tropical storm during the next 24 to 48 hours.  The upper level winds are lighter and vertical wind shear has decreased.  However, because of the proximity to the coast some drier air is being pulled around the western side of the circulation.  Only modest intensification is expected due to marginal SSTs, some vertical wind shear and drier air.

A high pressure system north of Ana is likely to limit the motion of Ana for the next day or two.  Eventually, the high will shift eastward and an upper level trough approaching from the west will accelerate Ana toward the northeast.  Persistent northeasterly winds along the coast could create problems with beach erosion.  The slow movement also means some locations could receive locally heavy rainfall.

 

Typhoon Noul Intensfying North of Palau

Typhoon Noul continued to intensify on Wednesday as it passed north of Palau.  At 10:00 p.m. EDT on Wednesday the center of Typhoon Noul was located at latitude 10.7°N and longitude 133.7°E which put it about 270 miles north of Palau and about 550 miles east of the Philippines.  Noul was moving toward the west-northwest at 14 m.p.h.  The maximum sustained wind speed was 105 m.p.h. and there were gusts to 125 m.p.h.  The minimum surface pressure was 955 mb.

Noul is moving over water where the Sea Surface Temperatures are near 29°C.  It is moving close to the axis of an upper level ridge and so the vertical wind shear is low.  The environment is favorable for further intensification and Noul could eventually reach the equivalent of a major hurricane.

A subtropical ridge north of Noul is steering it toward the west-northwest and that motion is expected to continue for several days.   On its projected track Noul could approach the Philippines in two days and it could be near Luzon in three days.  As Noul nears Luzon it is expected to turn more toward the north.  If the circulation is intact after it crosses Luzon, it could head toward Taiwan.

Tropical Depression 07W Forms South of Pohnpei

The active period over the tropical Western North Pacific Ocean continues with the development of another tropical cyclone south of Pohnpei.  At 8:00 p.m. EDT on Wednesday the center of Tropical Depression 07W was located at latitude 4.4°N and longitude 156.8°E which put it about 160 miles south-southeast of Pohnpei.  The tropical depression was stationary.  The maximum sustained wind speed was 35 m.p.h. and there were gusts to 50 m.p.h.  The minimum surface pressure was 1004 mb.

A low level circulation center formed within a broad area of thunderstorms and the system was classified as Tropical Depression 07W.  The strongest thunderstorms are mainly located in the northwestern part of the circulation.  An upper level ridge located east of the depression is generating southeasterly winds over the top of it which is producing modest vertical wind shear.  The wind shear is the probably reason why most of the thunderstorms are northwest of the center of circulation.  The wind shear will also limit the rate of intensification during the next day or two.  Eventually the depression is expected to move farther west into an area with less wind shear and it could intensify more quickly.

Tropical Depression 07W is located near the western end of a subtropical ridge and the steering currents are relatively weak.  It may not move much for the next 12 to 24 hours.  Later this week the ridge is expected to strengthen and steer the depression toward the west-northwest.  On its projected track the depression could approach Pohnpei in two or three days.

Possible Development of Low Pressure East of Florida on Wednesday

A number of numerical models have been predicting the development of some type of low pressure system east of Florida this week.  The surface pressure has decreased by about 4 mb during the past 24 hours at several locations in the northern Bahamas, which could be an early sign that a surface low is in the formative stages.  When the low forms, it will likely be classified as either an extratropical cyclone (a typical mid-latitude low with a cold core) or a subtropical cyclone (a type of hybrid low with some tropical characteristics).  An upper level trough over the eastern Gulf of Mexico is generating strong southwesterly winds across the region.  At the same time a surface high pressure system north of the area is producing northeasterly winds in the lower levels.  The combination of southwesterly winds in the upper levels and northeasterly winds in the lower levels means the vertical wind shear over the likely development region is very high.  Since tropical cyclones form in regions of little vertical wind shear, the low is not likely to be a tropical cyclone when it develops.

However, the surface high north of the system is likely to inhibit the northward motion of the low.  If the low moves slowly while it is over warm Sea Surface Temperatures, the thunderstorms in the circulation could release enough latent energy to warm the upper levels of the circulation.  If, at the same time, an upper level ridge over the Central U.S. moves eastward and causes the upper level wind speed to diminish, then the wind shear over the low could be reduced.  Less shear and warmer temperatures in the upper levels could cause the structure of the low to taken on a more tropical form.  It is possible that it could make a transition to a tropical cyclone if the environment is just right.

The forecast track of the low is uncertain because it is unknown precisely where the low will form initially.  It does appear that after the low forms it will move northward slowly for several days.  The expected track could bring the low near the Mid-Atlantic Coast by the end of the week.  Given the Sea Surface Temperatures, the wind shear, and the time of year, the low is likely to be be of tropical storm strength by the end of the week.  However, both the track and intensity forecasts will be highly uncertain until the low pressure system organizes.  Even if the center of the low stays off the coast, northeasterly winds at the surface could generate some beach erosion.

Noul Intensified Into a Typhoon As It Passed Over Yap

Tropical Storm Noul intensified slowly on Tuesday and it attained typhoon status as it passed over Yap.  At 10:00 p.m. EDT on Tuesday the center of Typhoon Noul was located at latitude 9.5°N and longitude 137.5°E which put it about 20 miles west-southwest of Yap and about 230 miles east-northeast of Palau.  Noul was moving toward the west at 5 m.p.h.  The maximum sustained wind speed was 75 m.p.h. and there were gusts to 90 m.p.h.  The minimum surface pressure was 976 mb.  Noul brought wind and heavy rain to Yap on Tuesday.  The International Airport reported a wind gust of 68 m.p.h. as the center of Noul passed just south of it.

An upper level ridge located east of the center of circulation is causing light easterly winds to blow over the top of Noul, which is generating some vertical wind shear.  The shear could be the reason why most of the strongest thunderstorms are occurring in the southwestern quadrant of the circulation.  Noul remains over water where the Sea Surface Temperature is around 29°C.  The vertical wind shear is likely to slow the rate of intensification, but Noul is in an environment that favors further strengthening.

Noul is at the western end of a subtropical ridge and the steering pattern is relatively weak.  It is likely to continue to move slowly for another 12 to 24 hours.  Eventually a subtropical ridge is expected to build north of Noul and steering it toward the west-northwest at a faster speed.  On its projected path the center of Noul would pass several hundred miles north of Palau.  Noul could be approaching the northern Philippines by late in the week.