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Hurricane Igor closes in on Bermuda

Posted by Sheena Parveen under Daily updates

Hurricane Igor, a category one hurricane with maximum sustained winds of 75mph as of the 8pm advisory, is closing in on Bermuda Sunday evening, possibly being a direct hit on the tiny island.  Earlier Sunday evening, sustained winds of 50 to 60mph were present, and wind gusts were up to 76 mph.  High surf has already erroded the beaches, mainly on the South side.  Igor is a very large hurricane, and as it passes over the island, rainfall totals of 6 to 9 inches are expected.  A hurricane warning has been in effect for Bermuda already.  Igor should be leaving the Island Monday morning, thereafter moving farther North into the cooler Atlantic waters, possibly becoming extratropical.

Radar imagery shows rain bands moving toward the island from the South as the eye nears, very closely to the SW of the island.  Igor is turning to the NE, and this turn could cause a direct hit.

Igor will continue N/NE, then more NE as a trough exits the U.S.  This will help push Igor farther into the Atlantic Ocean.

Computer models are agreeing on this path, but some are taking more of a loop around.   That is unlikely; Igor should be staying on a N/NE track.

On Florida’s East coast, Igor has produced wave heights of around 6 to 10 feet.  Closer to the center and closer to the island of Bermuda, Igor is causing seas to be as high as 20 to 30 feet.  These high waves are causing dangerous surf conditions along the East coast of the U.S., and it will be causing more beach erosion in Bermuda, mainly the South side.

Besides Igor, Julia is still hanging on to tropical storm strength.  Julia is getting caught in Hurricane Igor’s high wind shear, so this tropical storm may soon be a remnant low.  Julia is not expected to last that much longer as it moves NE and into cooler waters.

A tropical wave, Invest 94L, has become better organized this evening.  It is very close to becoming a tropical depression as it moves slowly in a north-westerly direction.  It’s about 400 miles West of the Cape Verde Islands.  Computer models are struggling to get a hold on this system, as some are tracking it moving West, and some are taking more NW across the Atlantic Ocean.

In all, we have 2 named systems still on the map, and one which may possibly be named soon.  The next name on the list is Lisa.  There is also an area of disturbed weather in the SW Caribbean–nothing of significance now–but it will continue to be watched over the next several days.

The CMC model is showing Invest 94L as a stronger system by Tuesday. . . possibly a tropical depression or tropical storm.  This model also keeps Igor and Julia on track.

Bermuda braces for Igor

Posted by Andy Johnson under Daily updates

Igor weakened to a Category 1 at 2:00 AM Sunday morning, September 18, 2010 but it is still a large and very dangerous hurricane. Fortunately, for Bermuda, Igor is no longer at the Category 4 strength that it was a few days ago.  Even though the maximum sustained winds have decreased, the size of the circulation itself have increased significantly. Hurricane force winds extended out 90 miles for the center and tropical storm force winds extended out 345 miles for the center. That is really incredible!

Bermuda residents use Hurricane Fabian as a benchmark reference for hurricanes. The center of the eye of Fabian passed 14 miles west of Bermuda on September 5, 2003 as a 120 MPH Category 3 storm. Since the eastern part of the eyewall affected Bermuda, Fabian is considered to have had a direct hit on the island. The maximum sustained 10-minute average winds were 120 MPH with a gust to 164 MPH at Bermuda Harbor. Since Hurricane Igor has weakened to a category 1 storm, Igor will not bring winds as strong as Fabian did.  Fabian was smaller than Igor, though, and was moving faster than Igor is moving. As a result, Bermuda could experience tropical storm winds for well over 24 hours or more as the lumbering circulation of Igor moves northward. At 7AM EDT,  Sunday, September 19, 2010, Bermuda radar shown below was already picking up squalls moving across the island. Compare that with the second image below taken Saturday evening. Also by 7AM EDT, winds were already gusting to 51 MPH at Kindley Field Airport, Bermuda.

The rain image overlaid on the cloud image below was taken by the Tropical Rainfall Measuring Mission (TRMM) Satellite’s TRMM Micorwave Imager (TMI) sensor.  Igor completed an eyewall replacement Saturday. This means that even though maximum winds are lower they are spread out over a larger area. The end result is that areas in the path of the hurricane will experience a longer period of squalls. The eye is still visible in the TMI image although it is not visible in IR satellite images.

 Igor’s eye  (the storm on the left) is no longer visible in the enhanced satellite image below. Small Julia (on the right) will eventually become absorbed into Igor in 2to 3 days.

 Waves are very high even along the east coast of the U.S., including Florida. Dangerous rip currents will be a problem for several days. Waves on Sunday morning were already almost 10′ offshore of Cape Canaveral, FL and 23′ west of Bermuda.

 The GFS model shown below is valid for 1AM, Monday, September 20, 2010.  Look at the huge wind field of Igor and compare that with the smaller size of Julia. A tropical wave moving off of Africa may eventually develop into a depression or even a tropical storm this week. The next name on the list is Lisa.

The GFS model below valid Friday at 8PM shows the possible new tropical depression or storm in the eastern Atlantic. The pattern will be changing to a large east-west high pressure ridge in the Atlantic. This may allow storms that develop next week to be steered further into the Gulf and Caribbean instead of recurving into the open Atlantic. This may cause a threat to the Gulf states, SE U.S. or even mid-Atlantic states by the first week in October.

Invest 94L shown below could be the incipient disturbance that becomes Lisa. The large area of convection in the western Gulf appears to have moved inland over NE Mexico and  SE Texas. A new tropical wave is emerging off of Africa behind Invest 94L. Also, a tropical wave in the eastern Caribbean will have to be watched closely next week as it moves into the western Caribbean and possibly into the Gulf of Mexico.

Even though the disturbance in the western Gulf has been causing torrential rains in south Texax, the area of intense convection (red areas) has shrunk considerably since Saturday.

Big Igor bears down on Bermuda

Posted by Andy Johnson under Daily updates

Igor has weakened to a Category 2 Saturday afternoon, September 18, 2010 but it is still a large and very dangerous hurricane. Fortunately, for Bermuda, Igor is no longer at the Category 4 strength that it was a few days ago.  Even though the maximum sustained winds have decreased, the size of the circulation itself have increased significantly. Hurricane force winds extended out 90 miles for the center and tropical storm force winds extended out 345 miles for the center. That is really incredible! As a result, Bermuda could experience tropical storm winds for up to 40 hours or more as the lumbering circulation of Igor moves northward. At 8PM EDT, September 18, 2010, Bermuda radar shown below was already picking up the outer squalls moving across the island.

The rain image overlaid on the cloud image below is actually taken from a satellite (not a radar) which measures rainfall.  The larger outer eyewall is becoming the dominant eyewall instead of the dissipating inner eyewall. This means that even though maximum winds are lower they are spread out over a larger area. The end result is that areas in the path of the hurricane will experience a longer period of squalls.

 The eye of Igor (the storm on the left) is still visible in the enhanced satellite image below. Small Julia (on the right) will eventually become absorbed into Igor in 3 to 4 days. Compare the size of the heavy convection (red area) with the size of Florida. The core of the hurricane is about the size of our state.

Waves are very high even along the east coast of the U.S., including Florida. Dangerous rip currents will be a problem for several days.

 The GFS model shown below is valid for Midnight on Monday.  Look at the huge wind field of Igor and compare that with the smaller size of Julia.

The GFS model below valid Friday shows a possible new tropical depression or storm in the eastern Atlantic. The pattern will be changing to a large east-west high pressure ridge in the Atlantic. This may allow storms that develop next week to be steered further into the Gulf and Caribbean instead of recurving into the open Atlantic.

Invest 94L shown below could be the incipient disturbance that becomes Lisa. We are also watching a large area of convection in the western Gulf.

The convection in the western Gulf is close to land and does not have a long period of time to develop before moving inland. We have seen rapid development, however, of storms close to land this year.

Karl dissipates, Igor and Julia move NW, and a new tropical wave forms

Posted by Sheena Parveen under Daily updates

Karl–which was a category 3 hurricane as it made landfall 10 miles North of Veracruz, Mexico on Friday–dissipated over the mountainous terrain at 4am Saturday morning.  Rain and high waves still exist in the wake of Karl, and mudslides through the country may become an issue.

Hurricane Igor is still a large and powerful hurricane, but was a category 2 as of Saturday morning.  It’s expected to reach major hurricane strength again (briefly) before it moves by Bermuda on Sunday.   To the East of Igor is Tropical Storm Julia.  High wind shear blowing off Igor is causing Julia to weaken and become unorganized.  This trend will continue as Julia moves closer to Igor.  Hurricane force winds extend out 105 miles from the center, and tropical storm force winds extend out 345 miles from the center. 

Igor is on a track toward Bermuda, and should be near the small island on Sunday.  The track has shifted to the East slightly, and if Igor stays far enough to the East of Bermuda, conditions will be better than expected.  High winds and seas will still occur on Sunday.  A hurricane warning is in effect for the island.

Most of the computer models are taking Igor near Bermuda, then on a NE path afterwards, sending the hurricane into cooler waters where it will weaken.  The BAMS and BAMM models are now suggesting Igor looping around, but that is highly unlikely.

Tropical Storm Julia, once a category 4 hurricane, is feeling the effects of Hurricane Igor not too far away.  Igor’s upper level wind flow is destroying Julia, and will continue to do so as both systems move through the Atlantic.  Julia will continue NW until it reaches close to Igor, then will be forced to the NE, following in Igor’s track.  At that time, it won’t be long for Julia to dissipate.

There is another tropical wave moving off the coast of Africa, which may have some good potential to develop.  As of Saturday morning, it was about 200 miles SW of the Cape Verde Islands.  Satellite imagery suggests a cyclonic spin developing in this tropical wave, which would indicate an area of low pressure.

This new tropical wave has now been labeled Invest 94L.

Computer models mainly take this system to the NW over the next few days.

Next week, the GFS model develops a new tropical wave as it moves West across the Atlantic Ocean.  At that time, Igor and Julia will have been long gone.

Major hurricane Karl makes landfall near Veracruz, Mexico

Posted by Sheena Parveen under Daily updates

Karl, which was a category 3 hurricane as of the 11am advisory from the NHC, is moving onto Mexico’s coast by Veracruz.  Wind speeds were measured to be near 115mph at landfall, and actual landfall was 10 miles North of Veracruz.  The center of Karl is less visible now, and that is expected as it makes land interaction.  This storm will cause a lot of flooding in parts of Mexico, even inland as it tracks across the country, possibly emerging in the Pacific.  It will weaken rapidly as it interacts with Mexico’s mountainous terrain.

Karl will continue West across Mexico, weakening rapidly from the rugged terrain.  If it hold together across the country, it could emerge in the Pacific Ocean, where it may once again intensify.

Some computer models are holding onto Karl all the way into the Pacific.

Two more hurricanes are spinning in the Atlantic Ocean.  Hurricane Igor is a very large category 3 hurricane, and just to its East is Hurricane Julia, a much smaller category 1 hurricane.  Julia is becoming very sheared. . . upper level winds flowing off Igor is taking a toll on Julia, causing weakening.  Conditions are staying favorable for Igor to keep major hurricane strength over the weekend, and possibly as it nears Bermuda by Sunday.

Igor’s path hasn’t changed much, and it’ll be taking a turn to the N/NW into the weekend.  At that point it will turn more to the NE, causing the center of the track to go right over Bermuda.  Without a doubt, Igor will impact Bermuda with high winds, high seas, and lots of rainfall, but the question is how much of an impact will it have?  That all depends on if the eye of Igor passes through, or if it stays to the right or left of the Island.  Strongest winds are around the eye, and the worst part of a hurricane is the right side in the direction of motion.  The best scenario for Bermuda will be for Igor to pass East of the Island.

Computer models are keeping Igor on the same path, but some are taking the storm a little more to the NE as it turns near Bermuda.

Julia (track below), weakening as it gets caught in Igor’s wind shear, will continue to feel the effects of stronger upper level winds as it nears Igor.  This closer interaction will push Julia to the NE into cooler waters of the Atlantic Ocean.

Wave heights are around 5 to 6 feet on Florida’s East coast because of Hurricane Igor.  Closer to the center of the hurricane, wave heights are around 20-30 feet!  Rip current risks will be high along the East coast all weekend.

The GFS model is on track, and hasn’t changed too much over the past few days.  There is a strong agreement that these storms will all continue on their predicted paths.  By Tuesday we could see another tropical wave make its way across the Atlantic Ocean from the coast of Africa.

Now 3 Hurricanes Spin in the Tropics

Posted by Sheena Parveen under Daily updates

Karl, in the Bay of Campeche, has been upgraded to a category 1 hurricane.   Although it is a weak hurricane, it has potential to become stronger before making landfall along Mexico’s East coast.  Ahead of Karl, wind shear is low, and water temperatures are well into the mid 80’s, making for very favorable coditions.

Karl will continue West, with no turn in its future, making landfall in Mexico over the weekend.  At that point, it may be a category 2 hurricane, or a strong category 1 hurricane.  Thereafter making landfall, Karl will rapidly weaken as it interacts with land.

Computer models are agreeing on Karl keeping a westerly track.

Aside from Karl, we are still tracking Igor and Julia.  Igor is keeping its category 4 status, and weakening will occur as it tracks NW, but it will most likely not weaken too much until it reaches cooler waters.  Igor has a very well defined eye, as well as large spiral bands extending from it.  This is a large and ferocious hurricane.  The bright pink colors around the hurricane eye tell where very strong thunderstorms are present.  Hurricane force winds extend 70 miles out from the center of the storm and tropical storm force winds extend 275 miles out from the storm. 

Currently there are no watches or warnings in effect for Bermuda, which is in the path of Igor, but watches and warnings will be issued soon for the island.  Not much is expected to change for Igor’s path, and unfortunately Bermuda is in the center of the path as of now.  By the time Igor reaches Bermuda, it may be a category 2 or 3 hurricane with winds near 130 to 120mph.

Computer models all head for Bermuda by Sunday, and as we get farther out in time, these models become tighter, showing more agreement in the track.  Afterwards, the models spread out a little more, but keep a N/NE path.  As Igor moves farther North, weakening will occur as it encounters cooler waters.

Julia, which was a category 4 hurricane Wednesday, was the strongest hurricane in history that far in the East Atlantic Ocean.  But that strength was short-lived, and now Julia is a category 2.  When being compared to Hurricane Igor, Hurricane Julia looks very pathetic.  It is a very small hurricane, with no clearly defined eye, and organization is becoming poor.  Despite the look of Julia, winds are still as high as 100 mph near the center.

Julia is on a W/NW path currently, at a very fast speed of 25 mph.  Since it is moving faster than Igor, it will run into Igor and be forced to turn to the NE.  At that time, it will continue to weaken as it runs encounters higher windshear and cooler waters.  This will keep  Julia far away from the United States. 

Computer models are on the same thought as Julia speeds to the W/NW, running into Igor and turning to the NE.

As Hurricane Igor continues up through the Atlantic Ocean, it will cause high waves and rough surf along Florida’s East coast, as well as the entire East coast of the U.S.  This will cause a higher risk of rip currents along beaches.  This storm will stay very far offshore, but seems to be on a direct path to Bermuda.

The GFS model shows that by Monday at 6pm, Igor will still be a very large system, moving into the North Atlantic, and Julia will be pushed alongside Igor as it runs into the system.

2010 Hurricane Season Superlatives

Posted by Andy Johnson under Daily updates

Earlier this year, Dr. Klotzbach, Dr. Gray, NOAA and many other national and international agencies were predicting an unusually active Atlantic hurricane season. For a while in July and early August, it seemed like those forecasts were not going to come to fruition. However, over the last two weeks an explosion of activity has occurred in the Atlantic basin and at least two more storms may develop by this time next week. For much of the early season, an unusually large dry Saharan Air Layer (SAL) covering much of the eastern and central Atlantic put a damper on activity. Also, the Madden-Julian Oscillation was not in a favorable phase for development, unlike now.

There were also large scale patterns that were locked in place. Remember the Russian heat wave and the Pakistan flood?  It seems as if the energy and moisture in the Indian Ocean monsoon kept training northward into the Indian subcontinent. As soon as the Russian heat wave broke and the Pakistan rains began to slow is when we noticed a increase in the Atlantic tropical activity. Even though we talk about African disturbances causing hurricanes, moisture can be traced all the way back in many of these disturbances to the Indian Ocean. It is more than co-incidence, I believe, that once the monsoon stopped continually flowing into Pakistan that we saw more incipient disturbances moving across Africa to the west instead of northward into Pakistan.

The two satellite images below (the first is in the visible channel and the second  is an enhanced IR image) are something you are not likely to see again in your lifetime! Two Category 4 hurricane at the same time in the same picture! The last time there were two Category 4 hurricanes present at the same time was in 1926. One of the those storms was the infamous 1926 Great Miami Hurricane which in today’s dollars (and accounting for population and wealth increase) would be the most expensive hurricane to hit the United States. Of course, Miami was much less populated in 1926. The two Category 4 hurricanes in 1926 only existed simultaneously at that strength for 6 hours. This year it looks like we may break that record.

Here are a few records or near record events:

1. Two Category 4 hurricane at the same time

2. Length of time that two Category 4 hurricanes existed

3. Hurricane Julia was the farthest east Category 4 hurricane

4. Hurricane Julia is the strongest hurricane so far east

5.  We have had  four Category 4 storms this year. If we end up with 5 we will tie 1999 and 2005 for the most number of Category 4 storms.

6. We have had four Category 4 or higher storms in 20 days. The previous record was four Caetegory 4 storms or higher in 24 days in 1999.

The structure of Igor still looks very impressive in the enhance satellite image below. However, there are some signs that drier air from the SAL to the north of Igor is eroding some of the convection that is distant from the center. The largest areal coverage of intense convection is in the southern semicircle. Usually, it is in the northern semicircle.

NHC has done a great job of forecasting locations of storms this year. Intensity forecasts continue to be more problematic. Tropical Storm Karl shown below intensified very rapidly before striking the Yucatan Peninsula at 8:45 EDT, September 15, 2010. In addition, none of the models suggested that Julia would strengthen to a Category 4 hurricane today. Even though Karl is over land there is a large envelope of circulation from the convection in the Florida Keys to rain bands in Honduras.

 The radar image below taken at 3:15 PM EDT from the Belize radar show that even though Karl has been over land for almost 7 hours there is still a well defined center (in the northwest part of the image).

The amazing image below shows that in addition to two Category 4 hurricanes, there is an additional tropical storm all at the same time. A new tropical wave coming off of Africa promises to develop over the next week into a tropical cyclone.

The water vapor image below shows that even though Igor has a lot of dry air to its north and west, it has been able to create its own moist environment.

The long range GFS model valid Tuesday at 8AM shows the enormous size of Igor near the southwest coast of Newfoundland, Julia being absorbed by Igor and two additional possible storms. If the one off of Africa were to be named first it would be Lisa and if the one in the Caribbean were to be named next it would be Matthew.

Igor begins to turn; Karl forms in Caribbean

Posted by Andy Johnson under Daily updates

Powerful Hurricane Igor, the strongest Atlantic hurricane in 3 years made a beeline to the west across the Atlantic from the Cape Verde Islands without much deviation from due west. We have been anticipating a gradual turn to the northwest and eventually north which would spare the United States from a direct hit. Finally, at 5AM Tuesday, September 14, 2010 the forward direction of Igor became west-northwesterly and that direction of movement has continued into the afternoon signaling the beginning of a broad turn to the north. As I mentioned in my blog yesterday, intensity changes over the next day or so will be due primarily to the phenomenon of eyewall replacement. Igor weakened since Monday due to eyewall replacement. Sometimes the double eyewall structure is masked on satellite images but it can be seen on radar images more distinctly. Since radar signals can not reach Igor due to the earth’s curvature, the next best thing is the use sensors on special satellites that detect rainfall. The WindSat satellite image shown below indicates a strong northern eyewall and a secondary weaker ring of rain at a further distance from the small distinct eye. After the eyewall replacement is complete, some intensification can be expected once again. Afterwards, as Igor gains latitude near Bermuda, slightly cooler water temperatures and some shear will cause weakening in the 3 to 5 day time frame, although Igor will likely still be a hurricane 5 days from now.

The high resolution McIDAS visible satellite image from FOX 13’s direct readout earth station continues to show a well defined hurricane with classic structures such as a symmetrical eye, good inflow in all quadrants and good outflow in all quadrants.

The image below is a magnification of the McIDAS image above. The eye is clearly visible and there are some breaks in the clouds where the sea surface can be seen. However, there are more low level fractocumulus clouds in the eye than there were yesterday.

The parade of storms can be seen in the basin-wide Mercator projection image shown below. Igor is the best defined, hurricane Julia has a circular structure but no clear eye at this magnification and Invest 92L is the least organized but is more circular in appearance than yesterday. 

The IR satellite image of Igor shown below shows a very well defined hurricane but with just a hint of slightly drier air in the northwestern quadrant. To the northwest of the eye, the red area of heaviest convection is not perfectly symmetrical further away from the eye.

Convection has increased in Invest 92L as can be seen in the enhanced IR satellite view below. A circular concentrated area of convection east of Belize is surrounded especially on the north by bands of curved convection.

One of the reasons that the NW edge of Igor’s eyewall looks slightly dented is the large SAL dry layer which Igor is moving into (shown below).

The long range GFS model valid Monday at 8:00 AM show Igor in the Atlantic east of the mid-Atlantic states and a smaller and weaker Julia to the east of Igor. By then, another tropical storm appears to be coming off of Africa and Karl has already moved into mainland Mexico. The next name on the list is Lisa.

Category 4 Igor remains strong

Posted by Andy Johnson under Daily updates

Category 5 storms with sustained winds of 156 MPH and higher are very rare. Hurricane Igor developed rapidly Sunday from a Category 2 to a Category 4 storm and has continued to intensify almost to the top  of the Category 4 scale Monday. Igor is a classically defined hurricane with a well-defined clear eye and a stadium effect appearance to the eye. When hurricanes reach intensities as high as Igor eventually they go through structural changes such as eyewall replacements. Over time the intense eyewall becomes more tightly wound and decreases in diameter. At some point in time a secondary maximum ring of winds that are concentric with the inner eyewall develops. During the eyewall replacement cycle the diameter of maximum winds increases even though the absolute maximum may decrease somewhat. Remember that winds are determined by the difference in pressure not the absolute value of pressure. So as the pressure structure changes the diameter of wind speeds change even though the total amount of energy many be quasi-constant. As eyewall replacements occur over the next few days, the maximum wind speeds in Igor will fluctuate. The last Category 5 hurricane in the Atlantic basin occurred in 2007 with Hurricane Felix. It is possible that Igor could briefly become a Category 5 storm.

The visible image below was taken from our exclusive McIDAS satellite earth station at FOX 13. Igor has a symetrical shape with banded counterclockwise inflow at low levels and cirrus clouds rotating clockwise above the storm. In order to maintain intensity, a hurricane must have both new energy being supplied from below and an effective way of exhausting the energy above. High pressure high above the storm evacuates the air and spins it out to the periphery of the storm.

The visible image below is a wider view of the image above showing the outer structure of the hurricane.

The enhanced IR satellite image below clearly shows the well defined eye in the temperature structure, as well.

 This hurricane season we have continued to be in a pattern where troughs move across the Atlantic breaking down the Azores-Bermuda high at regular intervals. Fortunately, this pattern allows hurricane to move poleward through weaknesses in the ridge which spares the United States. Most of the models continue this patter with Hurricane Igor. The outliers to the west at the respected UKMET (United Kingdom) and CMC (Canadian) models. Both the UKMET and CMC take Igor further west initially but still end up recurving him. There are always anxious moments, however, until the actual recurvature begins. As of Monday afternoon, Igor was still on a dead west course with no recurvature yet.

 The long range GFS model shown below valid for Sunday at 8:00 AM shows the large circulation of Igor recurving between a weakness in the ridge with two centers. One of the high pressure centers is near the Azores and one is over the eastern seaboard.

Invest 92L in the Caribbean has not shown any signs of circulation today although large areas of convection continue to move westward causing heavy in Jamaica and eastern Cuba.

The path of a NOAA plane is indicated below. The plane only found flight level winds of 16 MPH south of Jamaica.

Oddly enough, tropical storm warnings are still in effect for the southern Cape Verde Islands due to strengthening Tropical Storm Julia. It is very rare to see tropical storm warnings so far east.

The basin-wide view shown below pinpoints yet another tropical wave getting ready to emerge off of the African continent.

Tropical Trio

Posted by Andy Johnson under Daily updates

Major Category 4 Hurricane Igor dominates the satellite picture in the tropical Atlantic. Tropical Depression #12, which became Julia at 11PM Sunday was very strong even upon emerging off the coast of Africa. In fact, tropical storm warnings are in effect for the southern Cape Verde Islands, which is extremely rare. Igor caused the issuance of tropical storm watches for the southern Cape Verde Islands just a few days ago. It is unusual to see immediate development so far east in the Atlantic Ocean right off of the coast of Africa.

Igor stregthened rapidly on the afternoon of Sunday, September 12, 2010 increasing from a Category 2 to a Category 4 storm in about 6 hours.  The official NHC forecast keeps Igor as a Category 4 storm or greater for the next 5 days. It is very unusual to see a hurricane remain at category 4 intensity that long. It is possible that Igor could even reach Category 5 status at some point. The only feature working against Igor strengthening is the large area of dry SAL in the central Atlantic. Otherwise, near record water temperatures and low shear should allow Igor to maintain its major hurricane status for a long period of time. All of the models gradually turn Igor to the NW and eventually N, but exactly when that turn will occur is not known at this time. Igor does not appear to be a threat to Florida. It is too early to say whether or not Igor will affect the east coast of the U.S., Bermuda or Canada.

The enhanced satellite image below shows a classic hurricane structure with a very well defined circular eye feature.  There is banding in all quadrants and no effects of shear to be seen in the high level cirrus clouds. The cirrus outflow pattern is very symmetrical.

Convection (red areas) has increased with Invest 92L today. It is not circular in appearance but it stretched more in a northeast-southwest direction.

San Juan radar (shown below) shows large areas of showers and thunderstorms but they do no appear organized in a circular fashion at this range.

Tropical Storm Julia has caused the rare issuance of tropical storm warnings for the southern Cape Verde Islands identified below. Winds have been sustained at 35 MPH already today on some of the islands.

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Water vapor imagery below still shows large areas of dry air in the central Atlantic. Igor is headed towards more dry air and there is a slight chance the dry air could sap some of his strength. Other factors, however, support a major hurricane for the next 5 days.

The long range GFS model below is valid for Saturday at 8:00 AM. It shows Igor east of the mid-Atlantic states and Julia farther out in the Atlantic.

There are still more convective clusters in equatorial Africa that are threatening to develop into tropical cyclones next week.