My 2013 Seasonal Forecast calls for 15 named storms, 4 Hurricanes and 2 Majors.

Background:

First my data set will be from a time frame of 1960 to 2012.  This will keep most of my data confined to a time within the “satellite era” of weather forecasting.  Secondly, there are a few atmospheric signals that I will use within those years to narrow down the data set even further.  Those “signals” in my research will be

1. Negative Analog Winter Temps (cold AO)
2. Sustained (or back-to-back) Neutral ENSO Years
3. Similar ENSO Anomaly Years
4. Equivalent Sunspot Years

Data Sets:

AO years are the simplest data set to pull, and includes the cold winter seasons of 1963, 1985, 1996, 2000, and 2010

There are numerous back-to-back neutral ENSO events over the last 50 years, including lengthy blocks from the 70′s, 80′s and 90′s.  Specifically, the data set features 1977, 1978, 1979, 1980, 1981, 1983, 1984, 1985, 1993, 1994, 1995, 2004, 2005 and 2006.

Current forecast anomaly for this year’s neutral ENSO is around -.3º.  This helps narrow down the ENSO events even more for my study.  Those years include 1961, 1966, 1978, 1983, 1984, 2001.

Finally, I introduced a new piece of theory into the science of hurricane forecasting, sunspots.  We find ourselves currently in a sunspot minimum year, but we have seen a cyclical pattern develop over time.  Sunspot research is relatively new, so my data set is not quite as deep as I would like, but does include similar sunspot minimum years of 1974, 1977, 1985, 1994, 1997, 2003 and 2004.

Linkage:

I used three different methods to narrow down all of the data in hand.  First, I took every year separately and analyzed those hurricane seasons individually.  Next, I re-classified the yearly data sets into their categories of either negative AO winters, ENSO neutral years and/or sunspot years.  Some of the years fell into multiple categories, while others stood independently.   Doing this enables me to fine tune which years I want to analyze closer for the 2013 Seasonal Forecast.

Field Narrowing:

For my study, I narrowed the data down to the years of 1977, 1981, 1985, 1994, 1996, 2004, and 2006.  Each of these years had multiple listings within an ENSO, sunspot or negative AO category.   From this point, the research is simple:  average out the number of named storms and hurricanes from this 7 year sample.

Conclusions:

The 7-year sample yields an average of 10.4 named storms, 6.5 hurricanes and 2.85 major hurricanes per year.  You may note that this sample is lower than my seasonal forecast of 15 named storms, 4 hurricanes and 2 major hurricanes.  Why the contrast?  Simple!  We are still in a period of increased hurricane activity (multidecadal variability) as well a period of enhanced satellite detection.  I have essentially attributed 2 extra named storms to the multidecadal variability and 2 more named storms for our advances in remote sensing and studying open-ocean cyclones.

To contrast, I am forecasting lower hurricane and major hurricane activity right now due to the near or below normal water temperatures in tropical breeding grounds of the western Atlantic Ocean.   The eastern Atlantic remains very warm into early April, but is not considered a true tropical breeding zone until August and September.   Because of this, I am “subjectively” lowering hurricane estimates by 2 and cutting the major hurricane forecast by 1.

Limitations:

My research is essentially a data set pull and is not proven to be a statistically significant way to forecast tropical weather.  I also do not incorporate any new data from the Atlantic thermohaline circulation theory the research team at Colorado State uses. I also do not incorporate any African monsoon “predictors” into my research nor do I use any hindcasting validation.

Regardless, I hope I have provided some insight into just “some” of the data analysis that goes into a seasonal forecast.  This is a unique challenge to actually come up with, and stay firm with specific numbers.  Maybe years from now our forecast skill will become even better that we can pinpoint specific areas of coastline that may be at high risk.

Let me lay out my case for you with four exhibits:

1. Sea Surface Temps are lower and lowering as a result of recent upwelling from Hurricane Isaac and the massive amounts of rain falling over the Gulf last week.
   

   Gulf of Mexico SSTs

2. The cyclonic spin with the ghost of Isaac, at this point, is all mid-level rotation.  There is absolutely nothing surface based this morning.
   

   500mb Analysis Chart

3. SHIPS model guidance first “initialized” a location and wind speeds for Invest 90L.  It has winds initialized at almost 30 mph, but on the surface charts, no area readings are above 20.  The end-result is a chart that is skewed to higher wind speeds over time as the storm moves out over the Gulf.  This is called a bias.
4. Climatology says little to anything in recent history has formed this close to the Gulf coastline in the month of September.  2007 was the most recent, AND ONLY example in the 2000′s,  of a depression forming.
   

   September Tropical Cyclone Climatology for Invest 90L

Given all the data I have shown you, and the impending weather change on Friday with an approaching cold front, I see little reason to believe Invest 90L will attain tropical cyclone status.  It will certainly bring some rain, some surf and a gusty breeze…but nothing for us to be concerned about at this juncture.

The two global models we look at to provide some insight into a possible landfall zone are the GFS and the ECMWF.  Both indicate the threat to the panhandle around Tuesday or Wednesday.

Euro / GFS Comparison for Isaac

But, that is still 5 days away and a lot will change in the atmosphere between now and then.  The basic feature we are waiting on is a larger upper trough to steer Isaac away.  That trough comes in early next week, which would unfortunately steer the storm into Florida.

300mb (Jet Stream) steering currents

Until then, look around the house and check your normal food and emergency supplies.  Make sure you are up to speed on evacuation routes and medications and the like.  It is  never a bad idea to go through this routine once a month anyway.  Call it “good practice” in hopes we don’t do this for real early next week.

Rainy weather is all about “patterns”.  The pattern we are stuck in now is known as “troughing”, and by its nature is a dynamical rain-maker.  In effect, it causes a vertical (rising) motion in the atmosphere, which in turns make clouds and then rain.  Add in some Florida humidity, and you have created yourself an efficient rain machine!

This pattern was put into motion about 3 weeks ago, as the big heat dome was building across the Central Plains.  Now that heat dome has pushed even further west, putting us in the dead base of the troughing pattern — the most efficient rain making area of a trough!

500mb Analysis Chart

Oddly enough, July and August is our rainy season along the Florida panhandle.  Check out the climatology chart from the National Weather Service.  In these two months alone, we can see as much as 15 inches of rain on average!

Panama City Rainfall Climatology

Over the last week, we have seen 8 inches of rain, or double what we should see for the entire month of August!  Below is the radar estimates of rainfall since August 1st.  It’s been a gully-washer!!

Radar Rainfall Estimates

As of Friday, August 10th, there are no flood watches or warnings in place.   But, that could change if the heavy rain continues to invade the “Sunshine State”.  Oh, and as for this pattern we are in, they typically last 4 to 6 weeks.  So, we expect another couple of weeks of off-and-on rainy weather!

However, an interesting graphic developed over the weekend by NOAA Scientist Corey Pieper (@Geostrophic) reveals, in fact, the National Hurricane track guidance will go down as a complete success. Although the actual track of Ernesto hugged the southern region on the original “cone of uncertainty”, it never meandered out of that highlighted yellow region.

Ernesto Forecast Track Verification

An average 5-day forecast from the National Hurricane Center can range over 230 nautical miles.  So, while it may “seem” that Ernesto’s track was a whiff, indeed it turns out that possibly the tropical guidance was a whiff.   The GFDL and the HWRF both had strong turns northwest into the Gulf of Mexico –  a theory that never played out.

As we have said before, it never really has been a problem with forecasting WHERE tropical cyclones go, rather how STRONG they become.   There are so many micro variables that have to go just right to get strengthening in a tropical cyclones.  Those micro variables, right now, are nearly impossible to simulate in forecast models on that run on a regional or global scale.  It is likely we will never see a model(s) that ever forecasts tropical cyclone strength with any skill in our lifetime.

1. a developing East Coast trough will turn the storm northwest towards the central Gulf of Mexico
2. developing East Coast trough is too shallow, and southern plains ridge returns to steer Ernesto towards Texas

Right now, the tropical models (GFDL and HWRF) depict this approaching trough on the stronger side, while the global models (ECMWF and GFS) show a shallower and faster trough forming.   The two forecasts are shown below for comparison:

GFS Forecast, valid Aug 8

HWRF Forecast, valid August 7th

As of today, I am leaning towards the global solution, based solely on persistence.  Ernesto is steamrolling westward, and the mean layer wind analysis shows no sign of that pattern fading.

Mean Layer Wind Analysis, August 3rd

As always, with any tropical cyclone, we will watch the storm and the models on a daily basis and do our best to not draw any immediate conclusions.  Ernesto will be more worth watching come Sunday evening.

Depression 5 will have quite a battle on its hands the next few days with some dry air and wind shear.  Coupled with that it is moving extremely fast, little development is expected until early next week.

Today’s charts reveal a slight change in the overall steering flow next week, as an upper high over the central Atlantic retrogrades to the northeast.  This will allow a modest northwest turn into the Caribbean Sea and near the Gulf of Mexico around about Wednesday the 8th.  At which point, the steering winds also relax and allow the depression to settle in over some very warm waters in the Caribbean.

Layer Wind Analysis

80º Water Temp and Depth

The very latest GFS forecast, which has been actually reliable this season, depicts a moderate tropical storm roaming the northern Gulf of Mexico around Aug 10-12.  The GFS latches onto an overall change in the steering pattern mentioned above.   To contrast, the ECMWF and the HWRF both keep a general strong west path with the depression and keep that large “heat dome” in place over the southern U.S. — this pattern would deflect tropical weather well south of the States.

GFS valid August 9th, 2012

As always, with tropical cyclones this far out, it will be IMPOSSIBLE to predict a landfall.  Only a general path can be outlined at this time.  And, with so many other atmospheric factors to overcome, Depression 5 will have to be watched day-by-day as it fluctuates in strength.

courtesy Univ. of Michigan

The past few weeks in the Florida panhandle have yielded very intense summer thunderstorms.  In some cases, we are talking thousands of strikes per hour!

An interesting question, though, was raised this past weekend to me: “what do you do if you are caught in a storm while out boating?”

I researched several articles from the weather service to private weather firms, and the prevailing safety rules are as follows

 The vast majority of lightning injuries and deaths on boats occur on small boats with NO cabin. It is crucial to listen to weather information when you are boating. If thunderstorms are forecast, do not go out. If you are out on the water and skies are threatening, get back to land and find a safe building or safe vehicle.

Boats with cabins offer a safer, but not perfect, environment. Safety is increased further if the boat has a properly installed lightning protection system. If you are inside the cabin, stay away from metal and all electrical components. STAY OFF THE RADIO UNLESS IT IS AN EMERGENCY!

If you are caught in a thunderstorm on a small boat, drop anchor and get as low as possible.  Large boats with cabins, especially those with lightning protection systems properly installed, or metal marine vessels are relatively safe. Remember to stay inside the cabin and away from any metal surfaces.

Atlantic Invest 94L

The GFS, typically a non-reliable tropical model, was the first to suggest a cyclone near Florida way back around May 10th.   Now that we have gotten closer to the event, a few other models are now hinting that a tropical system is indeed likely.

GFS Forecast from May 10th, valid May 22nd

The good news, from what I am seeing in the satellite loops and the upper-air data, is that steering currents will keep this storm away from the Florida panhandle.  And, as with most weak tropical systems, it will be heavily weighted on the eastern side.  That just means, the wind and rain will hold east of any circulation center.  The latest HWRF run brings this Invest up to tropical storm status quickly tonight, while the European mainly keeps it as an open wave, and the GFS still maintains some weak center.

Model Suite

WEBSITES:

U.S. Navy Tropical Weather Page

University of Albany Weather Page

Southwest Florida Water Management Tropical Page

Florida State Tropical Model Portal

NOAA Interactive Weather Satellite

SMARTPHONE APPS:

Hurricane Hound, for Android

Hurricane Software, for Apple

Hurricane Tracking, for Android

iMap Storm, for Apple