Levi Cowan has been tracking tropical systems since 2002, and is currently working on his bachelor's degree in physics at UAF.
By: Levi32, 6:40 PM GMT on July 29, 2009
Hi all. Sorry I couldn't give more of an explanation when I left. We were leaving out of town at the time. Thank you all for your kind comments and emails. I appreciate your concern. We are fine, it's just one of those crazy times when life throws you a bunch of curveballs.
Among other things, we may be moving within the next month, so needless to say, if that pans out we will be very busy packing and stuff like that. I doubt I will have much time for the blogs at least in the short term. The stress associated with things like that also tends to dampen my passions for such things as games, and even the weather. My brain gets overloaded I guess.
Anyway, it seems I always have to leave for one thing or another lol. Life is a rollercoaster. It doesn't look like it's going to be a big hurricane season which is good news. I may or may not find the time to pop in if a storm is threatening land or something. I'll try, but it's not exactly under my control lol.
You all promise to stay safe! Any season can throw a bad one at you. My thoughts and prayers are with you all. Till the next time!
By: Levi32, 6:32 AM GMT on July 09, 2009
Something has come up and I will be gone for at least a few days. Fortunately there is nothing in the tropics to worry about right now. Stay safe all!
By: Levi32, 4:06 PM GMT on July 06, 2009
Tropical Tidbit from 12:00pm EDT Monday, July 6th, 2009:
Turn up the volume and click HD if quality is too low:
We finally have a named storm in the world: TS Blanca in the eastern Pacific. This was former Invest 94-E, and should have been classified as a depression early yesterday afternoon, and I have no clue why the TPC didn't, but oh well. They waited too long and Blanca burned 'em. She skipped TD status all together and is now a 40kt TS officially but looks more like 50kts and strengthening fairly rapidly. There's even an eye-like feature on visible satellite imagery this morning. Blanca has about 12-24 hours before she moves over cold SSTs and into a stable airmass where she will steadily weaken after tomorrow. I wouldn't be surprised if she made a run at hurricane status before her time runs out, but I expect at least a strong TS out of her. Even if she had more time she would have a big cap on her intensification due to poleward outflow being cut off by the upper high west of Texas, which is the same thing that happened to Hurricane Andres in June. Blanca is moving WNW away from Mexico and is not a threat to land.
In the Atlantic there's not much to speak of. The only area of interest this week will be off the Carolinas starting around Wednesday. A front moving through will be slow to drag out and the models now all agree on some sort of cyclogenesis along the tail-end of the front during the next 6 days that will move NE. It will be interesting to see if we get a system that tries to go warm-core and follow a path similar to TD 1. If the upper ridge builds enough over the top of the system we may see it get trapped for a while off the SE coast before being pulled NE. This is the point where the models disagree, with some taking it out right away and others forming it further west and weaker, which traps it for longer. This is the classic setup that can result in home-brew development as upper troughs lift out over the northern Atlantic but leave the surface fronts behind. I will be keeping an eye on this as it evolves.
Elsewhere....a tropical wave along 72W in the central Caribbean is generating showers and thunderstorms over Puerto Rico and Hispaniola which are being enhanced by upper divergence on the east side of a TUTT that extends from NE of the Bahamas down through the NW Caribbean. This is shearing the convection to the north and east of the wave axis and development is not expected. Upper-level winds are not expected to become favorable for development over the next several days so if this wave is to have a chance it will be in the eastern Pacific.
We shall see what happens!
TS Blanca visible satellite: (click for loop)
Caribbean Visible Satellite: (click image for loop)
By: Levi32, 4:31 PM GMT on July 04, 2009
Yesterday I wrote about the effects that El Nino usually has on the Atlantic hurricane season. There have been a lot of questions about it this year, and I decided to make a video explaining El Nino's formation, and how it affects the weather pattern in a way that suppresses hurricane activity in our part of the world. There are many other factors but the ENSO is one of the big ones so it is worth understanding.
I had to fit this all into 15 minutes and I had so much I wanted to say, and I'm in a rush this morning so I couldn't revise it much, so I hope I made some sense lol. I know I mixed up my easts and wests again =/
Here's the link to the video. Since it was longer than 10 minutes I couldn't use YouTube so I had to use another site that WU won't let me embed here.
Tropical Tidbit from 12:30pm EDT Saturday, July 4th, 2009:
There's nothing going on in the tropics. Sure whatever we have Invest 94L but there's nobody out there to care about it. I don't have a problem with the NHC noticing these things and naming them and all that good stuff, but it makes me mad if they don't do it to systems right along our coastline! Like the 991mb low last year off the SE coast with an eye, and like 90L in late May this year. And yet they'll consider naming systems out in the middle of nowhere? It's insane.
Anyway if you want to talk about 94L fine. It's in waters less than 25C and embedded in an upper shortwave which means this is never going fully tropical. It tried very hard to go sub-tropical this morning when it tried to get a warm core with convection more over the center as wind shear lightened a little bit. Since then it decided it wanted to self-destruct so naturally the surface low turned tail and ran from the convection! It's now drifting towards the south, but should turn back onto its original course towards the ENE once it's convinced the convection isn't chasing it anymore. Due to its position under the shortwave getting sheared and the old fronts still attached to it, I don't think this will be able to go warm-core, although it's worth monitoring over the next few days before it moves over waters too cold to support STS development. A ship in the area is reporting SW winds of 36mph, so TS-force winds are possible near the center of this system.
Heat continues to pile up in the east Pacific and there is now a surface low out near 105W that may try to develop but it has a small window of opportunity before it moves over significantly colder SSTs within 48 hours. There is more stuff behind it that will probably try to develop during the next 10 days.
I will still be watching off the Carolinas in 4-7 days for a low forming on the tail-end of a front that will be stalling in that area. Any low that does form will likely be swept out to sea fairly quickly but it will be interesting to see if we can get a system to try to go warm-core along a similar path that TD 1 took.
We shall see what happens! Happy Independence Day!
Invest 94L model tracks:
Invest 94L Visible Satellite: (click image for loop)
Caribbean Visible Satellite: (click image for loop)
Updated: 4:32 PM GMT on July 04, 2009
By: Levi32, 4:05 PM GMT on July 03, 2009
Tropical Tidbit from 12:00pm EDT Friday, July 3rd, 2009:
There are no areas of imminent threat to develop through the end of this week.
However, there is one item of interest which the NHC has mentioned in its tropical outlook. A non-tropical area of low pressure in the NE Atlantic WSW of the Azores has become non-frontal, and has the potential to try to become a sub-tropical system. This low is embedded in the base of an upper shortwave trough that has become cut-off from the main westerly flow on the east side of an upper ridge in the SW Atlantic. This is imparting strong NW shear on the system, which is pushing its convection to the east of the center. If the low is to become sub-tropical it needs to become warm-core at the low-levels, and it can only do that if convection is allowed to build near and over the center. The system is over SSTs of between 25C and 26C, which is well above the 23C threshold for sub-tropical development. The models are hesitant to take this warm-core, but they keep it moving slowly eastward over waters greater than 23C for about 3 days before they become too cold for sub-tropical development. This system is not particularly likely to become sub-tropical but it will be monitored for any changes.
The GFS and ECMWF are still hinting at mischief off the Carolina coasts in 4-8 days. An upper shortwave trough is forecast to lag behind the main westerly flow over the southern states and help keep a front stalled off the SE coast in 4-5 days. With the upper pattern a little more zonal than it has been, the troughs off the eastern seaboard become more positively tilted (oriented SW to NE) and tend to be slow to drag out, especially the surface fronts that accompany them. In this situation you can get home-brew mischief from lows that form along the tail-end of the front between the SW side of the upper trough and the ridge over the Gulf of Mexico. The latest run of the GFS shows a weak closed low forming off the SE coast in 7 days. I will be continuing to keep an eye on this situation as it evolves.
There continues to be a massive build-up of heat in the eastern Pacific, evidenced by the very large area of convection that continues envelope the entire area. There is a broad area of low-level vorticity between 100W and 90W at around 10N. Somewhere in this area, likely further west than east, a surface low is forecast to form during the next couple days, and may end up developing into a tropical storm if the energy can bundle enough. If a storm does form it will most likely be steered NW and away from the Mexican coastline.
We shall see what happens! And Happy Independence Day to all!
Caribbean Visible Satellite: (click image for loop)
Below I have written up a presentation about the analog years for this year's hurricane season. My goal here is to provide some insight into what this season may have in store for us. If you find this kind of stuff interesting, you may want to stay tuned for a video I intend to make tomorrow about El Nino, how it works, and how it affects the Atlantic hurricane season. I hope you enjoy.
Tropical Tidbit Topic: 2009 Analog Years
I haven’t yet taken the time to do an extensive analysis of what this year’s hurricane season may have in store for us in terms of where the storms may go and how many there will be, although I have voiced my thoughts. While things are still quiet, now seemed like a good time to do more research and find evidence to back up my forecast.
My main focus here will be historic analog years, which are one of the greatest tools at our disposal for long-range and climate forecasting. Analogs are past years that had similar conditions to the present. Looking at what happened in the past often gives extremely valuable insight into the future. With all the talk about El Nino’s potential impact on the season, I decided to use the SOI (Southern Oscillation Index) as my base parameter for finding analogs. There are many other factors to consider, but the ENSO has one of if not the most influential impacts on Atlantic hurricane seasons. I looked for years with similar SOI patterns to this year (going negative in May and June, with predominantly positive values in all the prior months January-April). This particular pattern of monthly values doesn’t happen as often as you may think, especially in the last 60 years. Keep in mind that weather data starts becoming rapidly more sparse and unreliable the further back you go before the 1940s. I would have stuck to analogs for the past 60 years but as I said there are very few of them in this time period so I included older years as well.
The analog years I found were 1894, 1898, 1899, 1908, 1911, 1925, 1928, 1935, 1939, 1949, 1963, 1972, 1982, 1984, 2001, and 2006. 1963, 1982, and 2001 are less-than-perfect analogs, but they are still worth putting in. Instead of cluttering up the blog with a big map and description of every year, which are non-essential details, I’m going to put them all in a smaller wall so you can see the "big picture". They’re too small to see the dates but they start with the oldest year at the top left and the latest year at the bottom right. You can view the best track data here, courtesy of Unisys Weather.
Figure 1. Historical hurricane tracks in 2009 analog years based on January-June SOI behavior.
Notice where the greatest concentration of tracks is. In most of these years there is a congregation of tracks passing through or near to the north and east of what I like to call the "Bermuda Box". This box is formed off the SE US by connecting the points of Cape Hatteras, Bermuda, Turks/Caicos Islands, and south Florida.
Figure 2. The Bermuda Box.
The pattern in these analog years sticks out to me, with tracks focused more north and east and a lot of hurricanes affecting the US east coast, New England, Canada, and Bermuda. Also notice the considerable lack of tracks in the tropical Atlantic east of 55W, and even in the Caribbean. There are a couple of the years that were exceptions to this, but even most of those storms were very weak and didn’t ramp up until they reached 55-60W. This supports my thinking that this year will see a less active Cape Verde season due to low SSTs in the MDR (Main Development Region), anomalous downward air motion, and dry air. This is when you look for tropical waves coming off Africa to remain mostly weak in the eastern Atlantic but then try to develop out west closer to the Caribbean and SW Atlantic.
Not surprisingly, most of these analogs are either El Nino or neutral years (although there are only 6 years after 1950 when SST monitoring began). This is a good example of what El Nino does to the Atlantic hurricane tracks. It creates more downward motion, low SSTs, and higher wind shear in the deep tropics which limits storm activity south of 20N. This moves the bulk of the storm tracks north of 20N and closer to land, which makes home-brew systems more common and true deep tropical-born systems less of a majority.
The currently developing El Nino is already enforcing most of these factors with the MJO tending to focus downward motion in the tropical Atlantic, and wind shear has been mostly higher than normal since May. SSTs have been running below normal in the MDR this year, although they are starting to warm up and may recover to normal levels due to a weaker Azores high in the NE Atlantic, which causes weaker trade winds over the eastern/central Atlantic and therefore less upwelling of cooler water. There is a significant area of cold anomalies in the SW Atlantic as well, but the Gulf Stream and New England waters are starting to get above normal.
Figure 3. SST anomalies for the Atlantic and equatorial Pacific on July 2nd.
The upper pattern across North America and northern Atlantic also plays a big role in where storms will go. The CFS is forecasting an upper trough to stay locked off the eastern seaboard of the United States throughout the late summer and early fall, and a predominantly negative NAO (North Atlantic Oscillation) would support this in keeping the Bermuda High weaker than normal. This pattern would tend to steer most approaching hurricanes to the north and east, protecting the Gulf of Mexico from getting a lot of storms crossing over Florida. That doesn't necessarily mean it won't happen, as a short-term change in this pattern could easily steer a storm more towards the west.
Figure 4. The CFS 500mb height forecast for September, 2009.
Due to all these factors I expect the bulk of the storm tracks this year to be further north and east than last year, and less activity in the deep tropics and eastern Atlantic. That would put the areas of Bermuda, SE canada, the Bahamas, and the SE US coastline at higher risk this year. I expect several storms to recurve well east of the US, but the SE coast and New England has a good chance of being threatened when the Bermuda High extends far enough west to steer storms towards the eastern seaboard. This doesn't mean I think ALL the tracks will be in this area. There will likely be a few through the Caribbean and Gulf of Mexico as well, and everyone, as always, should be prepared to get hit.
So how many storms am I forecasting? Well, the average number of named storms each season for this set of analog years was about 9 storms. There were a few "non-seasons" in there with 5 years not making it past 6 named storms. This is what El Nino is usually expected to do to our hurricane season, however, there were also 4 years of 11-15 named storms. This proves that the ENSO is not a magic wand that makes years active or inactive, and there are many other factors that determine what the season is like. Any year can have a large number of storms, and even years with a low number can have a high impact season on the coastline. The slogan around here is "it only takes one". I am still forecasting 12 named storms for this hurricane season, which is on the high end of most of the forecasts out there. This is no different than my June 1st forecast, and the same goes for the tracks forecast.
Please keep in mind that I am not a certified Meteorologist and this forecast is unofficial. I hope everyone is prepared for the hurricane season!
We shall see what happens!
Updated: 5:52 PM GMT on July 03, 2009
By: Levi32, 3:58 PM GMT on July 01, 2009
Tropical Tidbit from 12:00pm EDT Wednesday, July 1, 2009:
Still no video. I'd like to keep them on deck for when they're needed.
We've made it through June with no officially named storms, and this is very normal for the Atlantic hurricane season, which only sees a named storm once in every 3 Junes. July will be starting off much the same, with very little going on in the deep tropics, and I expect everything south of 20N and east of 70W will be pretty much shut down for at least the first half of the month.
As I discussed in my tropical outlook a couple days ago, there will be areas to watch for trouble, and one of them was off the Carolinas and SE US coast between the 6th and the 13th. There is now a little model support for this idea, with the ECMWF and GFS forecasting a front to get stalled off the Carolinas in 6-8 days as an upper trough drags out of the east coast leaving a tail behind. Both models form lows along the front, taking most of them immediately NE as cold-core entities, but they both also still leave something behind in the form of an upper shortwave or a weak surface low. The CMC only goes out to 144 hours but it also shows the front setting up with areas of low pressure. I will be monitoring this situation as it gets closer.
Turning our attention to the east Pacific, there may be something to watch there as well. In the outlook I said they had a good chance of seeing a named storm in 5-10 days, which is 3-8 days today. This is due to the area of building energy south of Central America, which you can see culminating in a broad area of scattered moderate convection associated with a tropical wave along 98W. The ECMWF and CMC develop a tropical cyclone out of this area in 3-4 days, and the GFS, UKMET, and NOGAPS show low pressure areas. The later this develops the better chance it will have of becoming a hurricane. Right now the upper pattern is similar to that of when Andres was around, with the big upper high over Texas cutting off poleward outflow to any developing system in the east Pacific. After 6 days or so this high will break down into more of a big upper ridge than a closed high, which will allow more favorable conditions for an EPAC system to intensify. I will be watching this area as well. Watch that tropical wave for bundling energy. Right now it's broad and spread out, but if you see energy getting consolidating into a more compact area that means it's likely trying to develop. This may be the start of a burst of activity in the east Pacific over the next couple weeks with maybe 2-3 named storms out of it.
We shall see what happens!
Caribbean Visible Satellite: (click image for loop)
Updated: 4:19 PM GMT on July 01, 2009
MesoWest NERRS METEOROLOGICAL SITE AT KAC AK US
Fritz Creek, AK
|Dew Point:||53.0 °F|
|Wind:||2.0 mph from the SW|
|Wind Gust:||3.0 mph|
Updated: 5:30 PM AKDT on July 25, 2014
Overlooking Peterson Bay
|Dew Point:||45.2 °F|
|Wind:||4.0 mph from the NW|
|Wind Gust:||5.0 mph|
Updated: 6:38 PM AKDT on July 25, 2014
RAWS HOMER AK US
|Dew Point:||50.0 °F|
|Wind:||2.0 mph from the SE|
|Wind Gust:||7.0 mph|
Updated: 5:54 PM AKDT on July 25, 2014