Miscellaneous/General

Miscellaneous/General

Hurricane Season 2016 Officially Ends, Higher ACE Index

From a record-breaking extremely strong El-Nino last hurricane season, the Atlantic, the EPAC and the Central Pacific this season all were above normal. This was pretty much forecast but Mother Nature fools forecasters all the time. A short summary of the season follows:

For the Atlantic,  2012 was the last time there was an above average season. The Atlantic saw 15 named storms during Hurricane season, 2016. Out of the 15 named storms, the Atlantic basin had 7 hurricanes Alex, Earl, Gaston, Hermine, Matthew, Nicole, and Otto. What surprised many is that out of those 7 hurricanes, 3 of which were major hurricanes – Gaston, Matthew, and Nicole.

Many were wondering would Florida be spared a hurricane this year. After all these years and true to form, Florida had two Tropical Storms – Colin and Julia, and finally, Hurricane Hermine made landfall in Florida, the first since Hurricane Wilma in 2005. The Eastern coast of the US also was battered with South Carolina having landfall with Tropical Storm Bonnie and Hurricane Matthew.

Speaking of Hurricane Matthew, it was the longest-lived storm in the Atlantic and it was also the strongest with maximum sustained winds of 160 MPH, a category 5. Hurricane Matthew made landfall at Haiti, Cuba, and the Bahamas but as a category 4 storm during  the trek of the Eastern Caribbean and the Atlantic.

Lest us not forget, there were other storms away from the US. Tropical Storm Danielle visited Mexico, Hurricane Earl in the Belize and lastly, very late in the season Hurricane Otto in Nicaragua.

So, how do we get a better feel of the hurricane season activity for this year? One method called Index. ACE Index is using a sum of the energy accumulated with all the cyclones (tropical storms, sub-tropical storms and hurricanes) that happened to form within the hurricane season. Calculating ACE is done by using the square of the the wind speed every six hours during the storm’s lifetime. Remember, a tropical depression is below 35 knots and it is not added. Hence, a cyclone that is longer lived will have a higher ACE indices verses a shorter lived cyclone which will have a lower ACE indices.  ACE indices of a single cyclone is windspeed (35 knots or higher) every six hour intervals  (0000, 0600, 1200, 1800 ) or ACE = 10kn2.

Total ACE:

\Sigma = \frac{Vmax^2}{10^4} \ \

* Vmax is estimated sustained wind speed in knots. *

An average seasonal ACE in the Atlantic is between 105 -115 or mean average of 110.

2016 Atlantic ACE
Tropical Cyclone Name
Max Wind Speed (in Knots)
ACE 10kn2
Alex *
75
4.1725
Bonnie *
40
0.1055
Colin
50
1.1350
Danielle *
40
0.4050
Earl
65
1.5450
Fiona *
45
3.0275
Gaston  105 24.2925
Hermine
70
3.0925
Ian
55
2.9575
Julia
35
1.2250
Karl
60
5.8150
Lisa
45
2.2600
Matthew
140
47.9950
Nicole
115
25.2075
Otto
95
6.1600
——–
ACE Total:
132.4350

Please note: Those with red asterisks have Tropical Cyclone Reports versus the Operational Advisories. The TCR’s are more comprehensive in detail. Those without the red asterisks will have the TCR’s in time. The ACE Index numbers may change with each TCR. I will try to update this post at that time.

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Hurricane Specialists (Updated)

Have you ever wondered who the hurricane specialists (forecasters) are at the National Hurricane Center (NHC) other than just their names you might see on the reports they produce during the hurricane season?

These people are the very best in their field. Not anyone can work as a specialist at the NHC. Only the best of the best were chosen. Although there will be those people who criticize every aspect of what the NHC does, thankfully those people are in the minority. These specialists do more than just view different satellite views and use some of the fantastic software they have (NAWIPS, ATCF, etc.) before they they write up the advisories, forecasts, warnings and other public products – there is a lot more behind the scenes. One thing the general public may not understand is that the specialist when writing up any of these advisory products, there are specific guidelines in how the report is written although there a few qualifiers that do allow some “freehand text” in a few of the reports. The forecaster will check on the latest model runs as this allows the specialist to help forecast where the storm might be heading. The data from the recon aircraft comes from the folks in the CARCAH (Chief Aerial Reconnaissance Coordination, All Hurricanes) office. The forecaster will have many conversations with whoever is staffing that office during the course of a recon mission – as that person is their link to the aircraft crew. The forecaster will also be checking with the TAFB (Tropical Analysis and Forecast Branch) as they provide a storm intensity estimate. The Hurricane Specialist uses the TAFB estimate as guidance but the Specialist will consider all available data in determining the intensity for the advisories.

A normal 6 hour forecast cycle;
The cycle begins, and 45 minutes later there is the reception of the fix data although that is the deadline time. The vast majority are in specialists hands 15 to 30 minutes after synoptic time. Aircraft fixes usually come right at synoptic time or even a bit earlier. An hour after the cycle started – the models are initialized. Again, that is the deadline time, usually the initialization of the models start a bit earlier. A few minutes later, the forecaster receives model guidance and starts the preparation for writing up the forecast. The primary text products in the forecast are the tropical advisory, forecast/advisory, and discussion. The second hour after the cycle started, the hotline call to both the (NWS) National Weather Service and the (DOD) Department of Defense is made. On the third hour, the forecaster has a deadline to release the tropical advisory products. Hours four and five are for possible media interviews. On hour six, the next cycle begins.

When storm watches or warnings are activated or during a landfall event the media is in the NHC building, but usually it’s the Director (Rick Knabb), Deputy Director (Ed Rappaport, PhD), or the Branch Chief (James Franklin) doing those interviews, not the Specialist on duty. There are a few times after the the advisory has been posted someone from the media may call and the forecaster on duty may answer any questions they may might have. When landfall is imminent within a stretch of shoreline, Federal and state level Emergency Managers, the NHC has someone who acts as a liaison between the EM’s and the NHC. Local EM’s are supposed to be in touch with their local WFO (Weather Forecast Office), who in turn relay their concerns to the NHC.

When hurricane season ends (officially) November 30th, the hurricane specialists remain busy outside the hurricane season. Occasionally, storms form before the official beginning of the hurricane season and also after the official end of the season, so specialists still have the responsibility with that storm too. They also have to attend some national and international hurricane conferences. The specialists do help the CPC (Climate Prediction Center), basically to prepare for the annual seasonal hurricane forecast. The specialists must also write seasonal summary articles and also participate in some applied research projects.

UPDATE: When Hurricane Sandy which become Post tropical and why the NHC and the Specialists no longer were issuing hurricane warnings as the very complex and extremely large weather system became a major issue. Basically, the NHC did not have the tools to be able to continue issuing those hurricane warnings. The old system would have caused known and unknown shutdowns within the different products and within the different vendors. Although the NHC would have loved to keep issuing the warnings, the risks were too great. For the 2013 hurricane season and beyond, the NHC now has those tools, recoding the different products and if another storm similar to Hurricane Sandy were to develop, the NHC and the Specialists now have the authority to keep issuing the warnings and other products.

So each hurricane season these specialists (and who get little recognition) are the ones that have to deal with criticism when their forecast might be off, but more times than not, they are very close in their forecast. With budget cuts and the economy the way it is, these specialists can only work with the tools they have available to them. Maybe it’s time for people to really thank the specialists for all the hard work they do.

Not Shown: US Navy Hurricane Specialist LCDR Dave Roberts
Photo credit – Dennis Feltgen

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Return of Sunspot AR1429

Earlier this month sunspot AR1429 which was the source of several strong solar flares and geomagnetic storms is beginning to reappear after a two week trip on the other (backside) of the sun. While on the backside there was a least one X class solar flare. Solar flares are ranked by strength using five categories: A, B, C, M and X. With the return of sunspot AR1429, this region seems to be very active. In the image below, magnetic loops towering over the sun’s NE limb signal the sunspot’s approach.

AR1429
Credit: Solar Dynamics Observatory

NASA’s Solar Dynamics Observatory (SDO) earlier today photographed huge plumes of plasma rising and falling over the limb of the sun (See the video below). Also, Two C category solar flares, a C5 and C7, also erupted creating an enormous magnetic canopy causing waves of ionization to ripple through the high atmosphere. If this continues, sunspot AR1429 may once again create havoc with satellites in orbit which may interfere with satellite communications or damage power grids on Earth but also allow the beautiful green aurora’s near the Earth’s poles.

Credit: Solar Dynamics Observatory

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Two Huge Solar Flares

Two major solar flares erupted March 6th, the most powerful solar eruption this year. Both of these flares are ranked as type X-class storms. X-class is the strongest type of solar flares that the sun can have. Solar flares are ranked by strength using five categories: A, B, C, M and X. The ranking system (similar to the Richter) so that category is 10 times stronger than the one before it. A B-class will be 10 times stronger than an A-class, a C-class would be 100 times stronger than A-class, etc. The categories are also broken down into subsets, ranging from 1 to 9, to pinpoint a solar flare’s strength. Only the X-class solar flares have subcategories that go higher than 9.

The first solar flare was an X5.4-class flare after erupting at 0002 March 7 GMT and the second one occurred about and hour later and was an X1.3. The X5.4 solar flare erupted from the giant active sunspot AR1429, which also was responsible for the major sun storm earlier this week. Earlier this week, several M-class and C-Class eruptions had been noted. Prior to this week’s eruptions, an X-class eruption occurred on January 27, 2012 with a ranking of X1.7.

x-class solar flare


CREDIT: NASA/SDO

In the image above, the solar flare is the brightest spot at the upper left.
Several of the sun-watching observatories noted the huge clouds of charged particles called coronal mass ejections (CME’s) erupting from the solar flares. Data from the Stereo-B spacecraft is not sufficient to determine if the cloud is heading directly for Earth but most likely not, but a glancing blow to the Earth’s Magnetosphere is possible on March 8th or 9th.

If any X-class solar flares were aimed directly at the Earth, the X-class solar flares can endanger astronauts in the International Space Station. They can create havoc with satellites in orbit which may interfere with satellite communications and major problem could be to damage with power grids on Earth.

The Sun is currently in an active phase of its 11-year weather cycle. The current cycle is known as Solar Cycle 24 and is expected to reach its peak level of activity in 2013.

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Tropical Storm Ophelia

Invest 98L has been upgraded to Tropical Storm Ophelia as of the 11PM advisory last night from the NHC. Due to strong westerly and southwesterly shear, Ophelia will struggle and any increase in intensity will be gradual. At the moment, the LLC is exposed and all the convection is to the east of the center due to the strong westerly shear. Ophelia is south of a subtropical high pressure ridge. For the next 36-48 hours Ophelia will be heading westward or just north of due west, after that the forecast is for a deep layer trough to dig down as it heads off the eastern coast of the US. Ophelia will be on the southwestern periphery of the ridge and the trough will turn west-northwest then northwest. Eventually, the trough will turn Ophelia north and then northeast.

Visible Satellite Image


 
Wind Shear


 
Steering Current

Before Ophelia gets close or near the northern Lesser Antilles, shear may relax a little and allow some strengthening. Once Ophelia begins to get close to 60°W longitude, shear is forecast to strengthen significantly and at that point, further intensity will be difficult, if not impossible. Once Ophelia begins the northern turn, the upper level winds may begin to ease and allow some more strengthening, but that is part of the long term forecast – so the dynamics may change.


 


 

12z GFS Model


 
00z Euro Model

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Invest 98L

The tropical wave tagged as Invest 98L about 1400 miles east of the Windward Islands has continued to develop and is much better organized than yesterday. Conditions are now much more favorable for the few days 98L may develop into a tropical depression possibly as soon as tomorrow. Most of the major players in the global models guidance are in agreement for Invest 98L to develop as a tropical storm as it continues to head westward and eventually into the eastern Caribbean. That said, both the European and the GFS models do want to weaken 98L possibly to just a tropical depression, mostly due to a ridge of high pressure that is forecast to strengthen along with increasing shear. This should cause 98L to accelerate it’s forward motion leaving the convection behind and eventually decoupling whatever is left of 98L back to just a tropical wave.

Dependent on what is left of 98L and also what the track guidance will be, regeneration may or may not occur. If 98L continues it’s westward track and can pass through the “graveyard” (an area near Hispaniola hostile for storms) somewhat intact, as it gets to 75°W longitude there is the slight chance, of regeneration, albeit very slim. More likely than not, 98L will not track westward but a more west-northwest and affecting the Leeward Islands and possibly Puerto Rico, although it would be more of a rain event than a wind event due to the shear.

 

 

 

Models

 

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Tropical Storm Maria Still Struggling

Tropical Storm Maria, a resilient storm with maximum sustained winds of 50 MPH (a decrease from yesterday of 60 MPH) continues to struggle despite all it going through. Again, the convection is to the east of the center of circulation and satellite presentation shows the “naked swirl”. Maria is again heading westward but at a turtles speed of about 1 or 2 MPH. Whether this is the beginning of the turn or not is to early to tell. Due to the westward movement, models tracks have been shifted slightly to the left of the original. An upper-level low to the northwest of the storm is creating 20-25 knots of westerly shear and not allowing Maria to better organized. The shear is forecast to decrease slightly in a few days which may allow some gradual strengthening but this is for a short window of time. A sharp increase of shear is forecast and along with some of the upwelling from where Hurricane Katia’s track was will keep Maria in an unfavorable environment and limit further intensification, if any.

IR Satellite Image

Wind Shear

The global models are in very good agreement as to what track Maria will take. A mid to upper level trough which is currently over the eastern US will slowly begin to turn Maria to the north in about 36-48 hours. Another trough, this one much deeper and stronger, later during the week will eventually turn Maria to the northeast along with an increase in the forward speed.

First Trough

Second Trough

Model Tracks

 


 

Elsewhere in the tropics, a few of the models (long term) are hinting that some tropical mischief may appear somewhere between 10 – 14 days most likely in the mid to western Caribbean or the Gulf of Mexico. The MJO does show upward motion (in green) in that area during those time frames. We will have to see if anything does develop.

Madden Julian Oscillation

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Tropical Storms Maria & Nate

Tropical Storm Maria is just barely hanging on enough to still be classified as a Tropical Storm. The center of circulation is well east of the convection and the entire storm is elongated. Maria started to make the more true WNW direction yesterday and now a NW direction. A few days ago, the forecast for the ridging of the subtropical high in the Atlantic was to strengthen and keep Maria a more WNW track. As of yesterday, it appeared that the ridging was not going to be as strong. Maria will soon be near the southwestern side of the ridge and due to an approaching trough to the southeast US coast, Maria will be heading NW and eventually a turn to the north is forecast. The track guidance confidence within the models seems to be very high and when that usually happens, 95 percent of the time it is correct.

At the moment, there an upper level low to the NNW of Maria and the flow from the ULL (SW shear) along with some flow from a high to the east of Maria. The combination of the two is inducing a hostile environment for further development for Maria. The ULL is slowly moving away to the northeast and the shear levels will be reduced allowing some strengthening within 24-48 hours and eventually enough for Maria to become a hurricane later on in the forecast . Although the track guidance is very clear, intensity will be a problem. Category one hurricane status seems to be foreseeable as long as Maria does develop but I don’t believe a category two storm is probable, but I don’t want to rule it out either.

Overall, the Leeward Islands and possibly Puerto Rico may have tropical force winds, but since all the winds are in the area with the convection which is east of the center, this most likely will not happen but those in that area should monitor just in case . The Bahamas this time seem to be spared but any westward movement could allow some higher winds to the the Bahamas and although it is highly unlikely, the Outer Banks of North Carolina.

 


 

Tropical Storm Nate which for days was somewhat adrift has finally been tracking almost due west toward Mexico. Tropical Storm Nate who was drifting for those days has had problems with both dry air intrusion and the depths of the ocean there is somewhat shallow, upwelling also seemed to keep Nate from strengthening. As Nate is heading away from the cooler waters, further strengthening should occur. Due to the bowl shape of Bay of Campeche, convergence may help Nate in strengthening for a short period of time before land interaction will stop further intensification.

Nate at the moment is in an environment of low shear and Nate may intensify enough to become a hurricane not to long before landfall. Once landfall begins, Nate will begin to lose it’s strength and identity as it heads into the mountains.

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Hurricane Katia, Tropical Storm Maria & Tropical Storm Nate

As Hurricane Katia traverse’s through cooler waters it appears that Katia is also having serious problems with dry air entrainment that is wrapping around from the southwest and into the inner eyewall along with moderate shearing. Katia is now a mid-category one storm and intensification is not indicated, in fact, the weakening process will continue for at least the next 24 hours. Due to the cooler SST’s any attempt to intensify with the shear decrease later in the forecast will be nullified by the SST’s. Once Katia begins the transformation to extra-tropical, Katia may slightly intensify, in 72- 96 hours during the transformation. Katia is heading NW at the moment but will be making the turn to the north within the next 24 hours and later turn to the NE while also accelerating and into the westerlies.

 


 

Tropical Depression Fourteen was upgraded to Tropical Storm Maria the 11am advisory from the NHC. As Hurricane Specialist Lixion Avila stated “…and yet another tropical storm in the Atlantic…” in the NHC Tropical Weather Outlook, it seems we are definitely in the peak of the hurricane season.
Tropical Storm Maria is heading just west of due west-northwest and the forward motion is currently at 23 MPH. If this continues, the Low-Level Circulation may out run the mid to upper levels of the convection. If so, Maria will have a very difficult time organizing and trying to intensify or at least it would be gradual. At the moment, the environment is not that conducive for further development as upper level winds in the 20-30 knot range may affect Maria but the overall pattern should allow for slow strengthening.

Although it is a little to early where Maria may head, the latest model runs with the exception of the BAMM (Shallow) tend to have Maria north of the Leeward Islands in several days. For what it’s worth, my own opinion is that the model are still a little biased to the north and although I believe the more turn to the WNW will happen, the more “western” track will happen before making the turn, thus this might be a much closer to the islands than forecast. As Katia leaves the scene, the sub-tropical ridge will want to build and keep Maria on that western track until finally heading on a more west-northwest track along the periphery of the southwestern edge of the ridge. A deep layered trough is forecasted by some of the models by 72 hours to be near the East coast of the US about the time Maria will be close or near the Leewards Islands. This trough should make Maria turn toward the NW and later to the north.

 


 

Invest 96L has been upgraded to Tropical Storm Nate as of the 5pm advisory from the NHC. Although Tropical Storm Nate had been “suggested” that it would develop to a at least a tropical depression, recon flew into the storm and found winds at flight level of 53 knots (un-flagged) or about 42 MPH at the surface, thus the storm was initiated as Tropical Storm Nate. As has been noted earlier, Nate has been drifting somewhat as the steering currents are quite weak. With the weak steering currents which may hang around for a few days, Nate will be in warm waters but there is vert dry air to the NW of Nate and this dry air (as been with many of the storms this year) may impact Nate later in the forecast period. Models at this time feel that Nate, in time, will be influenced by a developing ridge in the western Caribbean and making Nate turn to the west and into Mexico. Although this scenario may play out, if Nate moves further north, Nate will be north of the developing ridge and would then head toward the Gulf states or the Florida panhandle. It is just to early to say how this will play out with Nate.

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Hurricane Katia, Tropical Depression Fourteen, & Tropical Trouble in the Gulf – Invest 96L

Hurricane Katia, which last night had been upgraded to Category Four Storm has lost some of it’s intensity and decreased organization and in now down to a Category Two hurricane. Katia may be in the process again of going through an Eyewall Replacement Cycle but shear and dry air to from the northwest and west may have gotten into the outer core. Katia seems be reaching much cooler waters in the western Atlantic thus further intensification is not indicated. The good news is that Katia is forecast to be on a track that is optimum where the center of Katia will pass between and Bermuda as it makes a sharp turn to the northeast later in the forecast. There is a very good consensus within the models as far as the track is concerned.
No matter there Katia’s track will be, those along the east coast and Bermuda beware of rip tides and large swells!!


Invest 95L which continued to develop during the day has been upgraded to Tropical Depression Fourteen as of the 5PM advisory from the NHC. This no surprise as Tropical Depression Fourteen began to look very healthy and this is the peak of the hurricane season. Although the upper level winds are only marginal for TD 14 to develop, it is forecast to continue it’s development slowly. There is still a spread between the models as to the forecast track, but a WNW track should continue along with a decrease in it’s forward motion.


Invest 96L which was tagged late this afternoon is a system that was ready to start as that area has been near the monsoonal flow near the East Pacific. 96L is part of the energy left from the tail end of now remnants of Lee, now combining with the monsoonal flow. The MJO is in the upward motion in this area and 96L was forecasted to develop by some models. Most of the models at the moment want to take 96L into Mexico, which still may be the case but another possibility might be for it to be pulled up and head toward the Alabama/Florida Panhandle possibly as a tropical storm or low end category one hurricane.

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