Charles Fenwick: 2005 Hurricane Season

(Semi) random thought(s) re Ophelia

Thu, 15 Sep 2005 15:49:48 GMT

Daniel Drezner's unfortunately timed Hurricane porn post is appropriate at this time.

Despite all that is going on in the world, Ophelia has remained the big headline on cnn.com for the past day Websites of the blance of the MSM give the storm similar prominence.

All of them are in Carolina desperately searching for the money shot. Hitherto their efforts have been rewarded with a collapsed canopy (at Kure Beach) and the partial destruction of the fishing pier at Atlantic Beach.

A person unfamiliar with the history of hurricanes would assume from the media coverage that this is some sort of first for North Carolina. Of course, that is not the case. The stretch of coast from Little River Inlet to the Oregon Inlet is quite possibly the most storm battered in the country. Finding examples of recent storms to affect this area in a manner far more significant than Ophelia is an easy task.

- Isabel of 2003 "is considered to be one of the most significant tropical cyclones to affect portions of north-eastern North Carolina and east-central Virginia since Hurricane Hazel in 1954 and the Chesapeake-Potomac hurricane of 1933."

- The flooding caused by Floyd of '99 (enhanced by the passage of Tropical Storm Dennis over the same area only a couple of weeks earlier) was the seminal event in the history of many small towns along the rivers of northeast North Carolina and Virginia.

- Fran of 1996 made landfall as a category three hurricane and was responsible for 34 deaths in North Carolina, Virginia, West Virginia, and Pennsylvania.

The three storms were significant enough for each of their names to be retired.

Lest they feel forgotten, allow me to remind the reader of Bonnie of '98 (made landfall as a borderline category three in Wimington) and Bertha of '96 (made landfall as a category two in the vicinity of Wilimington).

The disparity between the amount of coverage being given to Ophelia and the signifcance of the event is staggering. Hurricane porn, indeed.

Tropics Watch 0915

Thu, 15 Sep 2005 13:42:40 GMT

Ophelia continues to crawl her way to the northeast parallel to the Outer Banks. Refer to the National Hurricane Center for the latest on her.

I haven't been able to shake the feeling that Ophelia is like Felix of '95 in that she is a storm existing between bursts of activity in the Atlantic. That is not to say that we will see three storms form on the day that she becomes extratropical (the way that Humberto, Iris, and Jerry all formed on August 22, 1995), but I do think that we will have some more activity as she pushes off to the open sea.

The prime suspect for the next storm is described in the Tropical Weather Discussion thusly:

CENTRAL ATLC TROPICAL WAVE IS ALONG 45W/46W S OF 15N MOVING
W 10-15 KT WITH A 1009 MB LOW ALONG THE WAVE NEAR 9N. BROAD 
CURVATURE IS OBSERVED ON INFRARED SATELLITE IMAGERY. WAVE IS 
ALSO EMBEDDED IN A COPIOUS AMOUNT OF TROPICAL MOISTURE PRODUCING 
A LARGE AREA OF SCATTERED MODERATE/ISOLATED STRONG CONVECTION 
WITHIN 150 NM OF LINE 7.5N46.5W TO 14N41.5W.

The global models are nearly unaminous in developing this wave into a tropical cyclone (the NOGAPS model hints at one but does not provide a clear depiction). They are also in good general agreement over the positioning of the high in the Atlantic; all suggest that it well be centered well to the east such that the storm would have a clear path to head north (and eventually recurve, rather than being 'trapped' by the high and steered towards Florida or the Carolinas).

The caveat to this is that the global models are sometimes over eager in developing systems and therefore have a tendency to turn them north prematurely (such a tendency was displayed with Emily, when the model runs from before she entered the Caribbean suggested that she was a Florida threat).

In contrast to the global models, the tropical models (such as BAMD and LBAR) suggest that that the system will manage to continue westward into the Caribbean . While on average, the performance of the global models is superior to that of the tropical models (as the global models are vastly more sophisticated), there are situations in which their performance is better, and this may very well be one of those cases.

Gone to backup site

Thu, 25 Aug 2005 16:15:43 GMT

As problems continue to plague my laptop, I've been forced to alternate means for posting for the near future. For the near future, posts will be at http://eotstorm.blogspot.com . Add to bookmarks and rss feeds as necessary.

Tropical Storm Katrina Update 242100Z

Wed, 24 Aug 2005 21:45:32 GMT

AT 5 PM EDT...2100Z...A TROPICAL STORM WARNING AND A HURRICANE
WATCH HAVE BEEN ISSUED FOR LAKE OKEECHOBEE. A TROPICAL STORM WARNING
AND A HURRICANE WATCH ARE NOW IN EFFECT FOR THE SOUTHEAST FLORIDA
COAST FROM VERO BEACH SOUTHWARD TO FLORIDA CITY...INCLUDING LAKE
OKEECHOBEE. A HURRICANE WATCH MEANS THAT HURRICANE CONDITIONS ARE
POSSIBLE WITHIN THE WATCH AREA...GENERALLY WITHIN 36 HOURS. A
HURRICANE WARNING WILL LIKELY BE ISSUED FOR PORTIONS OF THE
HURRICANE WATCH AREA LATER THIS EVENING

At 5 PM EDT, the center of Tropical Storm Katrina was at 25.6 North 77.2 West, 185 miles southeast of the east coast of Florida and moving to the northwest at 9 mph. Maximum sustained winds are 45 mph and minimum central pressure is 1002 millibars (29.59").

Tropical Storm Katrina Advisory Number Five

Initial intensity was set based on a combination of recon observations and satellite image analysis. There is uncertainty over the exact position of the center and the direction in which it is moving. Position given is a combination of recon, satellite, and radar observations. Other than that the short term forecast is fairly certain. Katrina will run into the southern edge of an upper level ridge of high pressure and be turned to the west. This will take her over south Florida in the next 36-48 hours. After that there is greater uncertainty as the models are split over Katrina's course in the Gulf of Mexico. The track forecast is similar to that of the consensus of the global models. Steady intensification is expected before the first landfall, with Katrina doing so as a category one hurricane (intensity forecast also has Katrina as a category one on second landfall). However, rapid intensification is a possibility, although dry air wrapping into the center is acting as an inhibiting factor. Due to the slow forward speed, the main threat from Katrina will be heavy rain and flooding across the Bahamas and south Florida.

Tropical Storm Katrina Discussion Number Five

Official forecast track

Katrina has been giving mixed signals today. Pressure fell by four millibars or so, but there hasn't been much of an increase in the wind speeds observed by the recon plane.

Here's the model guidance NHC had to work with for this forecast. NHC's forecast is along the lines of that indicated by the track labelled 'CONU', which as mentioned above, is a consensus of the global computer models. The GFS model continues to feature a sharper turn to the north and east. This may be skewing the consensus too far east. We'll have to watch and see how it reacts to the observations from the upper-air flight (which will be incorporated into the model runs tonight that will assist the 5 AM forecast tomorrow).

I continue to be concerned about a significant hurricane (stronger than that currently forecast by NHC) affecting the area between Mobile and St. Marks by early next week. Residents in those areas should be thinking about preparations for that possibility.

Tropical Storm Katrina

Wed, 24 Aug 2005 16:52:13 GMT

AT 11 AM EDT...1500Z...A TROPICAL STORM WARNING AND A HURRICANE
WATCH HAVE BEEN ISSUED FOR THE SOUTHEAST FLORIDA COAST FROM VERO
BEACH SOUTHWARD TO FLORIDA CITY. THIS REPLACES THE TROPICAL STORM
WATCH.  A HURRICANE WATCH MEANS THAT HURRICANE CONDITIONS ARE
POSSIBLE WITHIN THE WATCH AREA...GENERALLY WITHIN 36 HOURS.

At 11 AM EDT, the center of Tropical Storm Katrina was at 24.7 North 76.7 West, 50 miles east-southeast of Nassau, 230 miles east-southeast of southeast of Florida and moving to the north-northwest at 8 mph. Maximum sustained winds are 40 mph and minimum central pressure is1006 millibars (29.71").

Tropical Storm Katrina Advisory Number Four

All data indicate that the depression has become much better organized this morning and is now a tropical storm. The intensity estimate is based off observations from the recon plane and is in line with estimates derived from satellite imagery. Forecast track is unchanged from previous advisories. The storm is expected to turn to the west after 24 hours and emerge in the Gulf of Mexico in 72 hours. The ridge of high pressure that is expected to cause the turn to the west is then expected to weaken, allowing northward motion to resume. With Katrina showing good organization and enjoying favorable atmosopheric conditions, Katrina is forecast to become a minimal hurricane by time of landfall in south Florida.

Tropical Storm Katrina Discussion Number 4

Official track forecast with watches and warnings

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The season continues its streak of earliest named storms. The previous earliest eleventh named storm on record was Karen of 1995, which formed on August 28th. The earliest 12th named storm also formed on that date. While there exists a tropical wave that has the potential to continue the streak, dry air continues to keep it in check, so it looks like the streak will come to an end.

For south Florida there is not much new here. Everything is progressing as expected, with a strong tropical storm or a minimal hurricane expected to cross the peninsula on Friday. Shear being generated by the upper level high over the southeast should keep Katrina in that intensity range as she approaches the Florida coast.

Of greater concern is the threat that Katrina could pose to the Gulf coast. The degree of the threat increases with the westward component of movement that the storm has. If Katrina turns west relatively soon, she will enjoy a short time over land followed by a fairly long time over the Gulf of Mexico. Favorable conditions would allow it to intensify rather rapidly. Alternatively, if the turn occurs later than forecast, Katrina suffers by being over land longer and gets less time in the Gulf of Mexico. It is a bit soon to rate the probabilities of the scenarios, however, it is worthwhile for residents of the Gulf coast from Mobile, Alabama to St Mark's, Florida to be aware of the possibility of a singficant hurricane affecting their area in six days.

This is the computer model guidance the forecasters had to work with. The one significant outlier in earlier forecasts, the GFS (labeled AEMI in this graphic), has come more in line with the other models. As mentioned yesterday, the NOAA Gulfstream IV jet will be flying today to assist the computer models in their forecasts this evening (since the global models do not start calculating their forecasts until 11 PM or so EDT, any necessary changes to the NHC forecast would not be made until the 5 AM advisory package).

Unfortunately, I am experiencing problems with my primary computer, hence the late update. Am working on a backup, but at the moment, my timeliness in updates is by no means a guarantee. Check with the National Hurricane Center for the latest and greatest on Katrina.

Tropical Depression Twelve Update 240300Z

Wed, 24 Aug 2005 03:42:43 GMT

...TROPICAL STORM WATCH ISSUED FOR PORTIONS OF THE FLORIDA KEYS AND
FLORIDA EAST COAST...

At 11 PM EDT, the center of Tropical Depression Twelve was at 23.4 North 76.0 West, 140 miles southeast of Nassau, Bahamas and moving to the northwest at 7 mph. Maximum sustained winds are 35 mph and minimum central pressure is 1007 millibars (29.74").

Tropical Depression Twelve Advisory Number Two

Last observations from recon and current surface observations justify holding the intensity at 35 mph. However, there are indications that intensifcation is occurring now such that the depression would become a tropical storm in the next several hours.

The depression is currently in an area of weak steering currents, hence its slow motion. This motion is expected to persist through the forecast period with a bend to the west in 36 hours or so. This is the forecast offered by most of the global forecast models, with the exception of the GFS model, which more or less stalls the system over Florida.

Given the apparent organization trend, the depression could become a tropical storm by morning. Beyond that, there is much uncertainty. Intensity guidance is widely split, with one model not bringing the storm above tropical storm strength, and another insisting on a hurricane by time of landfall. The official forecast continues to be on the conservative side and brings a strong tropical storm ashore.

A tropical storm warning could be issued tomorrow for areas currently under the tropical storm watch. If intensification goes beyond what is currently forecast, a hurricane watch could be issued.

Forecast is highly uncertain, and that is reflected in an experimental forecast product, which shows equal probabilities of tropical storm force winds throughout the watch area (rather than being concentrated or centered on a particular area).

Tropical Depression Twelve Discussion Number Two

Official forecast with watch and warning areas

Well, a fair amount of the uncertainty from earlier is gone now. It appears that the multiple centers of circulation are consolidating, which certainly helps the forecast as it narrows the possibilities.

The downside to this consolidation is that does represent a significant improvement in organization, a necessary step for further intensification. With conditions at they are at the moment, poor organization was the only inhibiting factor in the near term. The storm may manage to get a fair bit in ahead of the National Hurricane Center's intensity forecast, although unfavorable upper-air conditions over Florida may be enough to keep it in check as it approaches the coast. Nonetheless, residents of south Florida should be prepared for high winds (60-80 mph) on Friday.

Uncertainty in the later forecast period will be reduced tomorrow evening when the Gulfstream-IV goes on its upper-air 'surveillance' mission. The data collected should help resolve the questions over the orientation and strength of the mid-upper level ridge of high pressure that will be key to the future movement of the storm.

Elsewhere in the tropics, the tropical wave west of the Cape Verdes Islands looked a little bit better on satellite tonight as it heads out of an area of unfavorable wind shear. Dry air, however, continues to inhibit its progression towards a tropical depression.

Tropical Depression Twelve

Tue, 23 Aug 2005 21:41:17 GMT

At 5 PM EDT, the center of newly formed Tropical Depression Twelve was at 23.2 North 75.5 West, 175 miles southeast of Nassau Bahamas and moving to the northwest at 8 mph. Maximum sustained winds are 35 mph and minimum central pressure is 1007 millibars (29.74"). The government of Bahamas has issued Tropical Storm Warnings for the central and northwest islands and a tropical storm or hurricane watch is possible for south Florida later this evening.

Tropical Depression Twelve Advisory Number One

Data from the reconnaisance plane as well as surface observations indicate that the area of low pressure over the Bahamas is sufficiently organized to warrant classification as a tropical depression.

Estimate of inital motion is to the northwest at 8 mph. The low level center is in a state of flux, and as such its exact position is uncertain. However, there is a broad low level circulation. The depression is forecast to move north through a gap in the high pressure ridge that exists over the southeast U.S. All of the global models fill in that gap, which cause their forecasts to feature a turn to the west , bringing the storm across south Florida in 72 hours and into the Gulf of Mexico in 96 hours.

The intensity forecast is challenging due to the uncertainty on how and when the storm will feature a well defined center. All factors are favorable for intensification and provided that the storm becomes organized within the next 24 hours, it would be a hurricane by the time it reached the coast. The official forecast keeps it just under hurricane strength as it crosses Florida, which is slightly more conservative than their model guidance.

Because a well defined feature from Tropical Depression Ten did not persist in a clear manner, NHC decided to classify this as a new storm. This differs from the case of Ivan last year, in which a feature clearly remained from the time it originally made landfall to the time it reentered the Gulf of Mexico and was classified a tropical storm once again.

Tropical Depression Twelve Discussion Number One

Official forecast track

A very challenging forecast due to the uncertainty over exactly where a dominant center of circulation will form at.

Here is the model guidance that NHC had to work with. The most reliable of the forecasts shown in the graphic is the one labled 'CONU', which is a consensus of particular dynamic models that produced a forecast.

Residents of south Florida will certainly want to keep a close eye on this, because if it were to become become organized, it could intensify fairly quickly (but not so much that it would be a dire threat). For most people, preparation will be limited to bringing inside stuff like lawn furniture that could get strewn about by 65-75 mph winds. Boat owners will want to be mindful of the possibility of hurricane warnings being posted on Wednesday night or Thursday if the storm becomes better organized.

There is far too much uncertainty tpresent for me to have much confidence in any comments beyond that. People along the gulf coast from Pensacola to the Texas border may need to start paying attention to this system after this weekend, but that is not necessarily a guarantee at this time.

Tropics Watch 0823

Tue, 23 Aug 2005 15:21:37 GMT

Tropical Storm Jose went ashore last night and is now dissipating over Mexico.

The Hurricane Hunters are in the air on their way to investigate the system that is currently located between the Bahamas and Cuba. If sufficient organization is found, the system will be declared a tropical depression (and probably will receive a new number as I stated yesterday).

Elsewhere, the tropical wave west of the Cape Verdes Islands continues to persevere in a somewhat unfavorable enviroment. Nevertheless, tropical depression formation is possible within the next two days.

Source: National Hurricane Center's Tropical Weather Outlook

Tropical Storm Jose Update 2215Z

Mon, 22 Aug 2005 23:07:23 GMT

At 6:15 PM EDT, the center of Tropical Storm Jose was at 19.6 North 95.4 West, 60 miles east-northeast of Veracruz Mexico and moving to the west at 6 mph. Maximum sustained winds are 50 mph and minimum central pressure is 1002 millibars (29.59").

Tropical Storm Jose Special Advisory Number Three

Recon plane recorded 54 knot winds, which suggest 45 knot winds at the surface. Also, the center fix given by the plane indicates that the storm is moving slower than previously supposed. The new forecast track assumes that this motion will continue and indicates landfall occurring tomorrow morning. Intensity forecast has some slight strenghtening happening before landfall. Due to the slow forward speed, the primary threat is flooding and mudslides once Jose goes ashore.

Tropical Storm Jose Discussion Number Three

Official track forecast

There's no mention of it in the discussion, but it is probable that the 60 knot surface ob was deemed to be unrepresentative of the storm, but was either a gust, or a downburst.

Some people are probably wondering why there was a significant difference between the intensity given in the 5 PM advisory and the intensity found by recon shortly thereafter, some people are probably asking why that happened.

The intensity given in the 5 PM advisory was based off satellite estimates. Those estimates are made before 2 PM EDT (and yes, there is a reason why they are not aligned with the advisory packages, but no, I won't go into it here). Jose certainly did not have the same appearance then that it does now (it was weaker). Also, the position of the center was highly uncertain. If the center is not placed in the right spot, then the intensity estimates will be off. The estimates provided were of reasonable quality given the limitations of the estimation method that are exposed when the exact position of the center is uncertain.

----------------------------------------------------------------------------------------------------

Now the clock starts ticking for the possibility of the 2005 season continuing its streak of earliest named storms. The record for the earliest 11th named storm belongs to 1995. Karen of that year formed at 06Z (2 AM EDT) on the 28th. The earliest 12th named storm, Luis, also of 1995, formed 18 hours later.

So, will the records be broken? Like the ESPN commercials used to say, 'It could happen, so you better watch'.

Tropical Storm Jose

Mon, 22 Aug 2005 21:30:05 GMT

ZCZC MIATCUAT1 ALL
TTAA00 KNHC DDHHMM
TROPICAL STORM JOSE TROPICAL CYCLONE UPDATE
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
425 PM CDT MON AUG 22 2005

...RECONNIASSANCE AIRCRAFT INDICATE THAT TROPICAL DEPRESSION ELEVEN
HAS BECOME TROPICAL STORM JOSE...

SHORTLY AFTER 400 PM CDT... RECONNAISSANCE AIRCRAFT REPORTED THAT
MAXIMUM SUSTAINED WINDS IN TROPICAL STORM JOSE WERE NEAR 45 MPH.
DETAILS WILL FOLLOW IN A SPECIAL ADVISORY TO BE ISSUED SHORTLY...
MAINLY TO UPDATE THE INTENSITY FORECAST.

FORECASTER KNABB

Tropical Depression Eleven Update 222100Z

Mon, 22 Aug 2005 21:08:20 GMT

At 5 PM EDT, the center of Tropical Depression Eleven was at 19.6 North 95.7 West, 45 miles northeast of Veracruz, Mexico and moving to the west at 8 mph. Maximum sustained winds are estimated to benear 35 mph and minimum central pressure is 1007 millibars (29.74").

Tropical Depression Eleven Advisory Number 2

Cutting this short because recon plane just found 35 knot winds at the surface... which suggest a tropical storm...

ok... continuing...

Recon plane is investigating the storm at this time. 30 knot estimate was based off satellite image analysis. The storm has an excellent appearance but has only another 12 hours or so over water. Should it become a tropical storm it would be the earliest 11th (sic) named storm on record. Rapid weakening will occur once the storm goes inland. While the GFDL model stalls the storm off-shore, the offical forecast is in line with that of the Beta and Advection models (BAMs), which do bring the storm ashore. If the storm were to deviate to the north, further intensification would occur. Primary threat is heavy rain and flooding.

Tropical Depression Eleven Discussion Number 2

This would not be the elventh named storm, it would be the tenth. The old record (for earliest tenth tropical storm observed in the Atlantic) ocurred in 1995 when Jerry formed on the afternoon of the 23rd.

And yes I said old... recon just found 60 knot winds at the surface... expect an update very soon...

Tropics Watch 0822

Mon, 22 Aug 2005 16:30:04 GMT

Other highlights in the Tropical Weather Outlook:

DISORGANIZED CLOUDINESS AND SHOWERS EXTEND FROM EASTERN CUBA AND
HISPANIOLA ACROSS THE SOUTHEASTERN BAHAMAS AND THE TURKS AND CAICOS
ISLANDS...AND INTO THE ATLANTIC FOR SEVERAL HUNDRED MILES. THIS
ACTIVITY IS POSSIBLY ASSOCIATED WITH THE REMNANTS OF TROPICAL
DEPRESSION TEN...AND DEVELOPMENT DURING THE NEXT DAY OR TWO SHOULD
BE SLOW TO OCCUR AS THE SYSTEM MOVES WESTWARD OR WEST-
NORTHWESTWARD.

Tropical Depression Ten was sufficiently enough destoryed by shear such that anything that forms from this will probably receive a new number. (Although this activity started in the general vicinity of the last position of the low level center of the ex-tropical depression, it is proabably more accurately described as being from the tropical wave that was behind it).

While there isn't anything organized, just a loose bunch of thunderstorms, a variety of forecast models are selling the idea of it becoming better organized, with it either heading north through the Bahamas, or west through the Florida Straits into the Gulf of Mexico. Because of the its relative proximity to land, the system will have to be watched closely. NHC has pencilled in recon flights to start early tomorrow afternoon if it looks like the system is developing.

A LARGE TROPICAL WAVE IS LOCATED OVER THE EASTERN ATLANTIC OCEAN
ABOUT 450 MILES WEST OF THE CAPE VERDE ISLANDS. WHILE THE
ASSOCIATED SHOWER ACTIVITY IS CURRENTLY LIMITED...THIS SYSTEM HAS
SOME POTENTIAL FOR SLOW DEVELOPMENT DURING THE NEXT DAY OR TWO AS
IT MOVES WESTWARD OR WEST-NORTHWESTWARD AT 10 TO 15 MPH.

The forecast models were very bullish on this system before it came off of Africa. Since then, however, they have been less enthusiastic. Very dry air to the north appears to be impeding development. This system looks to be a repeat of some combination of Irene and TD 10 as it underperforms against expectations.

In the eastern Pacific, Hurricane Hilary may be at her peak intensity at 105 mph. Her tropical storm force wind field is very large and caused tropical storm warnings to be posted for the Mexican coast despite her being well off-shore.

Tropical Depression Eleven Update

Mon, 22 Aug 2005 16:04:56 GMT

At 12 PM EDT, the center of Tropical Depression was near 19.5 North 95.0 West, 80 miles east-northeast of Veracruz, Mexico and moving to the west at 8 miles per hour. Maximum sustained winds are near 30 mph and minimum central pressure is estimated to be 1008 millibars (29.77").

Tropical Depression Eleven Advisory Number One

Satellite and radar observations indicated the formation of a tropical depression. Intensity estimate is based off satellite observation. Coniditions are favorable for development, however, the storm does not have much time to intensify before it will be over land. While model guidance does not suggest the system will become a tropical storm, the forecaster opts to be cautious and forecast the depression reaching tropical storm strength. A reconnaisance plane will be in the storm this afternoon to provide better information on the storm's strength.

Tropical Depression Eleven Discussion Number One

Forecast track

Certainly an impressive amount of convection present thanks to the warm waters, however, I'm not sure that it has enough organization to make tropical storm status. As always, the reconnaisance plane, which is scheduled to go into the storm by 5 PM EDT.

Tropical Depression Eleven forms

Mon, 22 Aug 2005 15:22:18 GMT

WONT41 KNHC 221436
DSAAT 
SPECIAL TROPICAL DISTURBANCE STATEMENT
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
935 AM CDT MON AUG 22 2005

...ELEVENTH TROPICAL DEPRESSION OF THE SEASON IS FORMING OVER THE
BAY OF CAMPECHE...

SATELLITE...RADAR...AND SURFACE DATA INDICATE A TROPICAL DEPRESSION
IS FORMING WITHIN THE DISTURBED WEATHER IN THE BAY OF CAMPECHE.  A
SPECIAL ADVISORY ON THIS SYSTEM WILL BE ISSUED WITHIN THE NEXT
HOUR.

TROPICAL STORM WATCHES AND/OR WARNINGS MAY BE REQUIRED FOR PORTIONS
OF THE EASTERN COAST OF MEXICO.

FORECASTER FRANKLIN

Yet another storm of the Bret and Gert variety. Forming over the Bay of Campeche and moving west it will barely have enough time to have a chance of reaching tropical storm status. At the moment conditions seem favorable enough for that to happen before it moves inland.

Tropical Storm Irene Update 130300Z

Sat, 13 Aug 2005 03:09:30 GMT

At 11 PM EDT, the center of Tropical Storm Irene was at 29.2 North 68.3 West, 300 miles southwest of Bermuda, 590 miles southeast of Cape Hatteras and moving to the northwest at 10 mph. Maximum sustained winds are 70 mph and minimum central pressure is 991 millibars (29.26").

Tropical Storm Irene Advisory Number 34

Irene is not as well organized as it was when the recon plane was in Irene. Because of that, intensity remains at 60 knots. However, due to a drop in pressure observed by a buoy near the center, the minimum central pressure was adjusted downward a few millibars. Best guess at current motion is nine knots on a heading of 310. Data from the Gulfstream-IV jet shows a ridge slightly stronger and more west than that depicted by any of the forecast models. This may cause more westward motion than was previously forecast. Models were in agreement with a turn to the north and then northeast. However, due to the observations from the Gulfstream, there may be a westward shift in the 00Z models. For now, however, the track forecast is essentially unchanged. Brief periods of intensification are expected to occur, however dry air will impede it. Current forecast makes Irene a hurricane in 12 hours, but keeps her as a category one throughout the period.

Tropical Storm Irene Discussion Number 34

Offiical forecast track

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I said this morning (121500Z update) that if the models were misrepresenting the high pressure ridge then their forecasts could all be wrong. Well, as the discussion states, they've been been depicting it weaker and further east then it actually is. It would not be surprising to see rather significantly different forecasts from the models this evening, possibly bringing Irene closer to land than currently forecast.

Elsewhere in the tropics, the disturbed area east of the Lesser Antilles that the National Hurricane Center has been mentioning in their Tropical Weather Outlook has not changed much in the past six hours (the Quickscat pass did not show a center any more closed than the previous pass). However, development into a tropical depression is still expected during the next day or so.

Next update probably won't be until 5 PM EDT tomorrow. I have drill with the Naval Reserves this weekend, so my availability to post will be limited. If there is no update from me on Saturday, then next will be on Sunday evening. As always, check with the National Hurricane Center for the latest and greatest on Irene and other tropical weather systems (Tropical Depression 10, perhaps).

Tropics Watch 0812 continued

Fri, 12 Aug 2005 21:42:25 GMT

Latest Tropical Weather Outlook :

SATELLITE DATA AND SURFACE OBSERVATIONS INDICATE THE WELL-DEFINED
LOW PRESSURE AREA CENTERED ABOUT 1150 MILES EAST OF THE WINDWARD
ISLANDS HAS CONTINUED TO BECOME BETTER ORGANIZED. THUNDERSTORM
ACTIVITY HAS BEEN GRADUALLY INCREASING AND ENVIRONMENTAL CONDITIONS
APPEAR FAVORABLE FOR A TROPICAL DEPRESSION TO FORM DURING THE NEXT
DAY OR SO AS THE SYSTEM MOVES WEST-NORTHWESTWARD AT ABOUT 10 MPH.

Further comments in the Tropical Weather Discussion

1012 MB LOW HAS DEVELOPED FROM THE TROPICAL WAVE PREVIOUSLY 
ALONG 39W.  THE BROAD CENTER OF THE LOW IS NEAR 11N41W AND IS 
MOVING WNW 10-15.  THIS IS A COMPLEX DISTURBANCE WITH A LOW/MID- 
LEVEL CENTER SEEN ON VISIBLE SATELLITE NEAR 12N42W WITH ANOTHER 
LOBE OF ENERGY ROTATING AROUND THE E SIDE NEAR 12N39W.  SURFACE 
OBSERVATIONS INDICATE A LARGE CLOSED CIRCULATION WITH BUOYS 
REPORTING WINDS OF 20-25 KT.  THE LOW HAS FAVORABLE CONDITIONS 
FOR FURTHER DEVELOPMENT WITH WARM WATER NEAR 83F... LIGHT 
SHEAR... AND IT SEEMS TO BE FAR ENOUGH SOUTH TO AVOID 
SIGNIFICANT DRY AIR IN THE MID-LEVELS.  THERE IS SOME EVIDENCE 
OF BANDING THOUGH CONVECTION HAS FADED A BIT THIS AFTERNOON.  
ISOLATED MODERATE FROM 10N-13N BETWEEN 40W-45W.

The Quikscat pass just ocurred, but the data has not been put out yet. If it indicates a closed circulation, then we could see a Tropical Depression Advisory package at 11 PM. Otherwise, provided that the organizing trend continues, we'll see the first advisory tomorrow. Something people with interests in the Leeward Islands will want to pay attention to.

Tropical Storm Irene Update 122100Z

Fri, 12 Aug 2005 21:05:00 GMT

At 5 PM EDT, the center of Tropical Storm Irene was at 28.7 North 67.5 West, 295 miles southwest of Bermuda, 650 miles southeast of Cape Hatteras and moving to the northwest at 10 mph. Maximum sustained winds are 70 mph and minimum central pressure is 997 millibars (29.44").

Tropical Storm Irene Advisory Number 33

Shear and Sea Surface Temperatures are favorable for strengthening, but since guidance does not bring Irene above category one strength, not much intensification is forecast. Movement is to the northwest (310) at 9 knots. Irene has been steered by a strong mid-level ridge. As the ridge shifts eastward, Irene is expected to turn to the north-northwest and then north into an area of light steering currents. She could meander for awhile before westerly flow takes Irene away from the U.S. "The official track forecast has been gradually shifting eastward in agrement with guidance. This lessens the potential threat to the United States East Coast".

Tropical Storm Irene Discussion Number 33

Official track forecast

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Not much to say here as things are playing out as expected so far.

Irene Recon Update 3

Fri, 12 Aug 2005 20:48:53 GMT

Just after I sent out the last update, recon recorded flight level winds of 75 knots... reduces to approximately 70 mph at the surface. Pressure unchanged at 997 millibars.

Irene Recon Update 2

Fri, 12 Aug 2005 20:24:50 GMT

Well, it's decision time for the NHC forecaster. Flight level winds of 60 knots suggest surface winds of 55-60 mph. However, the flight meteorologist seems to be observing sea state that suggests 65 knot winds , (which would make Irene a hurricane). Given that the two intensity estimates that are public (from AFWA and SSD) are under hurricane strength, it is doubtful that NHC would go with 75 mph winds this advisory. 70 is a possibility... 65 more likely. We'll find out soon.

Irene Recon Update 1

Fri, 12 Aug 2005 18:49:05 GMT

First VORTEX message was just sent out by the hurricane hunter. It indicates a minimum central pressure of 997 millibars and places the center at 28.4 North 67.1 West. It hasn't sampled the northeast quadrant yet, but (presumably on the basis of sea-state observation) they are estimting surface winds of 60 knots (70 mph).

Tropics Watch 0812

Fri, 12 Aug 2005 16:35:21 GMT

From the morning Tropical Weather Outlook:

SURFACE OBSERVATIONS INDICATE THAT A LOW PRESSURE AREA ASSOCIATED
WITH A TROPICAL WAVE HAS FORMED ABOUT 1200 MILES EAST OF THE
WINDWARD ISLANDS...AND SATELLITE IMAGES SUGGEST THAT THE SHOWER
ACTIVITY IS GRADUALLY BECOMING BETTER ORGANIZED. THIS SYSTEM HAS
THE POTENTIAL TO BECOME A TROPICAL DEPRESSION DURING THE NEXT DAY
OR TWO AS IT MOVES TOWARD THE WEST OR WEST-NORTHWEST.

System is about 3-5 days west of the Islands depending on how its forward motion varies. It had been moving at a 15-20 knots clip, but it appears to be slowing now. Latest Quikscat indicates that there is a rather broad closed circulation (Later: Not quite completely closed... looking at it again and a high-resolution graophic, I don't see a northerly wind.)

From the morning Tropical Weather Outlook:

SURFACE OBSERVATIONS INDICATE THAT A LOW PRESSURE AREA ASSOCIATED
WITH A TROPICAL WAVE HAS FORMED ABOUT 1200 MILES EAST OF THE
WINDWARD ISLANDS...AND SATELLITE IMAGES SUGGEST THAT THE SHOWER
ACTIVITY IS GRADUALLY BECOMING BETTER ORGANIZED. THIS SYSTEM HAS
THE POTENTIAL TO BECOME A TROPICAL DEPRESSION DURING THE NEXT DAY
OR TWO AS IT MOVES TOWARD THE WEST OR WEST-NORTHWEST.

Tropical Storm Irene Update 121500Z

Fri, 12 Aug 2005 15:50:51 GMT

At 11 AM EDT, the center of Tropical Storm Ireen was at 28.3 North 66.8 West, 300 miles of south-southwest of Bermuda and moving to the northwest at 13 mph. Maximum sustained winds are 65 mph and minimum central pressure is estimated to be 994 millibars (29.35").

Tropical Storm Irene Advisory Number 32

Cloud pattern is better organized then yesterday. There is a low level center in the deep convection . All three agencies (Air Force Weather Agency, Satellite Services Division , and Tropical Analysis and Forecasting Branch) agreed on an intensity of 55 knots. However, a recon plane is scheduled to enter the storm this afternoon so that NHC is no longer relying solely upon satellite-based estimates. Upper-air enviroment is favorable for development, however, with Irene passing over the waters recently occupied by Tropical Storms Franklin and Harvey, intensification past a category one hurricane is not expected. Irene is currently moving around the edge of a mid-level ridge. As the ridge shifts east-ward Irene is expected to turn to the north-northwest and a decrease in forward speed is anticipated. Eventually, a westerly steering flow would become established that would send Irene to sea. "That is too far in the future to be certain".

Tropical Storm Irene Discussion Number 32

Official track forecast

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As mentioned yesterday, today's big event is the recon flight and the upper-air flight. One will let us know what Irene's true intensity is and the other will help the computer models with their forecast. If the computer models do not shift much in their runs this evening (after taking in the observations from the upper-air flight) then confidence in the current forecast will be significantly higher. As it is now there is almost unaminouts support for the 'turn to sea' forecast. However, if they are all mis-representing the size and placement of the high pressure ridge, then their forecasts are all wrong and Irene could come in closer to land than currently forecast. That is why the upper-air flight is so important: it will take the observations that will give the models accurate data. In the case of Hurricane Isabel, the accuracy of the GFS model increased by as much as 40% after it started receiving observations from the Gulfstream-IV.

Observations from the hurricane hunter will start coming in after 1 PM EDT. The upper-air observations will be taken late this afternoon and evening and will be fed into the models when they start their 'runs' at 11 PM or so this evening.

Tropical Storm Irene Update 120300Z

Fri, 12 Aug 2005 03:28:44 GMT

At 11 PM EDT, the center of was near 26.4 North 64.9 West, 410 miles south of Bermuda, 875 miles southeast of Cape Hatteras and moving to the west-northwest at 15 mph. Maximum sustained winds are 50 mph and minimum central pressure is estimated to be 1000 millibars (29.53").

Tropical Storm Irene Advisory Number 30

Satellite imagery suggests that Irene's organization has not changed much in the past few hours. Intensity estimates from two of the three agencies are unchanged, so the intensity estimate for the advisory package is the same as before. The enviroment along Irene's path is favorable for development and the intensity forecast, which is a blend of model guidance, brings Irene to hurricane strength in 48 hours and maxxes out intensity at 90 mph. Locating the center continues to be a challenge, which makes the estimate of motion difficult as well. Best guess is a heading of 300 at a speed of 13 knots. Forecast millibars show a mid-level center of high pressure developing over Bermuda and then moving to the west late in the period. It is expected that Irene's forward speed will decrease as the storm approaches it. Beyond 36 hours, the models diverge significantly. Track forecast is similar to the previous one and shows slowing in the forward speed after day three, It is "in reasonable agreement with the FSU Super-Ensemble".

Tropical Storm Irene Discussion Number 30

Official track forecast

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Up through sunset today, it looked like Irene's organization was improving in a way that would justify higher intensity estimates. Since then however, she hasn't looked quite so good.   The Air Force Weather Agency intensity was slightly higher than the other two agencies, but as tends to be the norm, if two of the three are agreeing, then NHC goes with the majority (assuming of course that there are no other observations to go by).

There are several unanswered questions that cloud the track forecast. First and foremost is the position of the center. There is nothing clear-cut about its location in the satellite imagery as the three agencies continue to produce estimates that are significantly different. The second one is the position and strength of the Bermuda High. Tomorrow afternoon will bring some answers as a reconnaisance flight is scheduled to enter Irene at about 1 PM tomorrow afternoon. That will help answer the first question. Some help in the second question will come from a flight of NOAA's Gulf-Stream IV jet, which will sample the upper-air enviroment in front of Irene. Those observations will be fed into the evening runs of the forecast models. In the past, the observations have helped the models significantly in generating an accurate forecast.

At the moment there is no change in my thinking for landfall potential that was detailed in my previous post.

Via comments, Brendan Loy asks what chances I think Irene has of affecting New England. The scenario is what my Virginia-centric state of mind has thought of as the 'overshoot' scenario. The storm makes an approach to the Outer Banks but turns parallel to the coast and runs north until it finds land. The most recent example of it in pure form is Bob of 1991, (which affect my family since we were living in Brunswick, Maine at the time). Gloria of 1985 is another.

Due to the uncertainties of a five day forecast, it is a bit hard to have high confidence in rating the probability of such a scenario, but here goes anyway. I'm a bit too young to be familiar with the atmospheric setup that caused those tracks, however, one can reckon the positioning of high pressure that would have caused such a track (The NHC report on Bob offers merely a sentence or two on the matter). It seems like it would take the center to be positioned to be either a little bit further north than is normal (or elongated north-south), and somewhat off the coast. One thing noticable about these types of storms is that they are very much under the influence of a well-defined steering current, as their forward progress increases tremendously as they pass the Outer Banks.

Looking at what setup appears to be, I don't see such a scenario ocurring. Right now the options plausible to me are a quick turn out to sea, or a stall/near-stall off the coast that leaves the storm spinning until the next front passes through (carrying the storm off to the east).   I don't think there are any examples of storms approaching the coast slowly (in the fashion that some models are creeping Irene forward in the mid-late term of their forecasts)and then lurching to the north.

As always, the thoughts below the tear line are my own and do not reflect an official forecast by any organization.

Tropical Storm Irene Update 112100Z

Thu, 11 Aug 2005 21:31:58 GMT

At 5 PM EDT, the center of Tropical Storm Irene was at 25.7 North 63.9 West, 460 miles south of Bermuda, 950 miles southeast of Cape Hatteras North Carolina, and moving to the west-northwest at 15 mph. Maximum sustained winds are 50 mph and minimum central pressure is 1000 millibars (29.53 ").

Tropical Storm Irene Advisory Number 29

Convective pattern has not changed much today. Best estimate of the position of the center is that it is on the western edge of the clouds, not in the deep convection. Intensity estimates from the three agencies varied, NHC took the average of the three for the initial intensity, but notes it could be a bit higher. Initial motion estimate is 300 degrees at a speed of 13 knots. Models have not changed their forecasts much today. NOGAPS and UKMET models are to the right because they have Irene being a larger feature than the high pressure ridge, a scenario that the forecaster finds unlikely. Official forecast is close to the GFDL and GFDN models, which bring Irene closer to the Outer Banks and feature a decrease in forward speed late in the period. Official forecast is essentially unchanged and is on the left edge of the guidance envelope. Convection is expected to increase in intensity tonight as the source of dry mid-level air that has been inhibiting it is dissipating. Irene is expected to become a hurricane by this time tomorrow. The current intensity forecast maxxes Irene out at 85 mph.

Tropical Storm Irene Discussion Number 29

Official track forecast

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Obiously, someone forgot to tell Irene that dry air was supposed to inhibit her today. Looking at the infrared loop , we see a large amount of convection, with some intense areas sprouting up in the past hour or two. However, the convection is not particularly organized at the moment as it doesn't seem to be right on top of the circulation center. That holds down the satellite estimates. Regardless, the expansion of it does indicate intensification, and I would not be surprised to the the 11 PM advisory featuring 55-60 mph winds. As mentioned in the previous update, dry air was the only inhibiting factor. Everything else is favorable.

As far landfall potential possibilities go, history shows the probability of a storm affecting the U.S. mainland from Irene's current position is low. The closest is a storm that I mentioned in my 5 AM update: Emily of '93 , which brushed the Outer Banks, but still managed to cause significant damage to the southern parts of that area. Carol of '53 is another plausible analog. While not extremely close to Irene's current position, the possibility of a collapse in steering currents is reminiscent of Felix of '95.

Here is the 18Z model guidance. The track labeled NGPI is the NOGAPS referenced by the forecast; GFDI and GFNI are two of the other models that were referenced by the NHC discussion. One other forecast track worth mentioning from that graphic is CONU, which is a consensus of several of the models.

Irene as a weak tropical depression gave the model fits as they just could not handle her well. They tended to either over-estimate her and take her on a more northerly track than warrented or they wanted to kill her off. With Irene intensifying, she is fitting into a mold that the models are more familiar with. Their overall performance from here on out should be significantly better than that of the past five days or so.

As has been the case for the past day or so, my only concern for land being affected by Irene is the Outer Banks and as long as Irene persists on a more northerly track, that concern is reduced. Worst case scenario seems to be a situation like Emily where the southern Outer Banks were hit fairly hard and beach erosion was significant, but other nearby areas were much less affected as she turned quickly to sea. Residents of those area and people planning to be on vacation there during the next week should continue to monitor Irene's progress.

All remarks below the tear line are my personal thoughts and by no means reflect an official forecast by any organization.

Tropical Storm Irene Update 111500Z

Thu, 11 Aug 2005 15:58:15 GMT

At 11 AM EDT, the center of was at 25.1 North 62.6 West, 515 miles east-southeast of Cape Hatteras North Carolina and moving to the west-northwest at 17 mph. Maximum sustained winds are 50 mph and minimum central pressure is estimated to be 1000 millibars (29.53").

Tropical Storm Advisory Number 28

Convection has continued to increase and become better organized . Difficulties in locating a low low level center continue, the latest position estimate essentially placed the center on a well defined mid-level circulation. Two of the three agencies agreed on an intensity of 45 knots (based on Irene's appearance on satellite). Estimate of motion is 15 knots on a heading of 300. Forecast models are in excellent agreement through 48 hours and the agreement ends there. The UKMET and NOGAPS models turn Irene to sea at around 70 West, while GFDL and GFDN bring Irene very close to the North Carolina coast and the GFS persists in wanting to kill off Irene. Official forecast track favors the GFDL/N solution. Warm sea surface temperatures and low shear favor intensification of Irene, however dry air does lie in front of her. Intensity forecast brings Irene to hurricane strength in 36 hours and holds her maximum intensity at 85 mph.

Tropical Storm Irene Discussion Number 28

Official track forecast

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References for the intensification factors mentioned in the discussion: This Saharan Air Layer graphic shows the dry air that Irene will have to contend with in the near term. Sea Surface Temperatures are warm along Irene's path though if she deviates too far north. there is a drop off. The shear analysis shows a favorable upper-air enviroment. SHIPS guidance has not done well in these dry air situations, so it wouldn't surprise me if Irene doesn't make hurricane strength when forecast.

As mentioned in the center placing the center continues to be an issue. It may not be clarified until the first reconnaisance plane investigates Irene tomorrow afternoon.

My track forecast thoughts are unchanged, see previous post for details. As such residents of the Outer Banks and those planning to visit next week should monitor the progress of Irene.