Category Archives: forecast

interim Irma update

6 P.M. Thursday, Sept.7.2017

Trend highlighted in earlier post today is now showing up strongly in latest GFS output.

Idea of landfall Sunday morning over southwest Florida is looking more and more likely.  If trend continues, it’s VERY bad news for Florida.  Latest NHC update is starting to incorporate these ideas.

Hurricane Irma, part 3

Thursday, Sept.7, 2017

Models shift a bit…looking worse for Florida

Model solutions converge as U.S. landfall gets closer.  However, an old model idea is regaining favor and that, if it happens, could be really bad news for Florida.  More on that later.

First, The official National Hurricane Center’s forecast track has shifted a little westward from yesterday.  That’s in line with the model consensus which tracks Irma either along, or just east of Florida’s east coast.   A similar storm last fall followed this path and Florida fared pretty well.  Irma is stronger, however, so this path would create more problems this time around.

Following that path, landfall would occur somewhere around the GA/SC coast.  That area would have the highest risk of devastating winds/storm surge.

The current forecast follows the path described above with Irma either over Miami or just off the coast by about 7-8 P.M. Saturday, slowly moving north overnight and Sunday.  During this time it is expected to be either a strong Category 4 or Category 5. (winds 145 mph or higher).  Landfall would occur Sunday night near the GA/SC border.

New thoughts:

While the above remains the official forecast, I’ll wait awhile before I totally agree.  Tuesday, I mentioned that the forecast models fell into two camps.  One brought Irma up the Florida east coast; the other took it inland over the Gulf side.  That idea disappeared yesterday as the models shifted to a more easterly path.  Today, several models have brought back that idea, in what amounts to a very ugly way.

Hurricanes are purely tropical systems, but as they approach North America and recurve (turn) northward mid-latitude wind systems also get involved in the steering mechanism.  Our current cool weather has arrived do to an unseasonably strong upper level trough digging into eastern North America.  Apparently, yesterday the models felt the trough was stronger (and slower) than it actually is.  The result was to predict the storm path farther east.  Today, however, the models have corrected yesterday’s overreach.  That greatly reduces the trough’s ability to encourage Irma to turn northeast over the weekend as mid-latitude winds will become very weak.  How does that change things?

The models predicting the movement of Irma into the Gulf have also slowed her speed, probably due to the relaxing of the wind fields over the U.S.  They have also delayed the northward turn.  The result is Irma drifting between Florida and Cuba Saturday night, then turning northward Sunday into southwest Florida.  Furthermore, the delay will allow steering currents to weaken even more.  As a result, this model idea would allow a dying Irma to remain over Florida 24-36 hours!  You don’t even want to think about that scenario.

I’m hoping the models will present a clearer picture by tomorrow.  I’m also hoping that the current NHC prediction is very close to correct.  If it isn’t and the slower developing idea wins out, Irma will become a name we’ll remember for a long, long time.

Personally, I’m getting very worried about Florida.

Hurricane Irma, part 2

Wed. Sept. 6, 2017

 

Models change:  better prospects for Florida

Today’s model runs are shifting the path of Irma slightly north and the expected turn north a little sooner.  That adds up to slightly better news for residents of Florida.  Most models now have Irma hugging the Florida east coast Saturday night and Sunday.  That path would still create huge problems for the coast, but not as much as a direct hit would.

Florida’s slightly better news means worse news for Georgia and South Carolina.  Model consensus now puts landfall near the GA/SC border late Sunday.  Irma should still be a major hurricane so that area could well bear the brunt of the winds/storm surge.

Beyond that, a weakened Irma is expected to diminish while spreading tropical rains northward along the Atlantic Coast (mostly east of the Appalachians).

Other model ideas:

There is pretty good model agreement up to about 3-4 days.  After that, two models offer “outlier” solutions.

First, the Canadian model is much farther east than the consensus.  It keeps Irma far enough east of Florida’s east coast to ease the coastal erosion significantly.  Irma then brushes by the Outer Banks.  Later, a much weakened Irma could make landfall near Cape Cod.  At the moment, that’s the best case scenario for the U.S.

Second, the GFS continues to hang on to its ideas mentioned yesterday.  And, it is faster than the other models by 12-24 hours.  It is the only model to push the remnants of Irma northwest. It still pushes the dying storm over the lower Ohio Valley by Tue/Wed.

Those two model ideas sum up the frustrations facing forecasters every day.  The farther you try to look into the future, the more the uncertainty increases.   Two reliable models (for the short term), starting out with the same data, predicting the same major storm’s path.  At 6-7 days time, one has the parent system over western KY and the other has it near Cape Cod.  Go figure?

My ideas:

History has shown me that once a hurricane track forecast changes to a more easterly path, that trend usually continues.  And, very little forecast path change is likely in the 48 hours leading up to landfall or near miss.

With this in mind, I believe that by tomorrow morning (Thursday) the model consensus will continue to shift eastward.  Not as far as the Canadian, but in that direction.  By Friday, the forecast will be pretty well “locked in” with only minor adjustments after that.

Thus, I expect Irma will not make a direct hit on Florida.  East Florida will suffer from high surf and beach erosion, but problems will be minor to what a direct hit would create.

As Irma heads NNE, I expect the North Carolina coast to be hit hard.  It’s possible it could only be the Outer Banks area, not the whole coast.  After that, I don’t even want to speculate.

Stay tuned, by tomorrow we could have a whole set of new ideas!

 

Hurricane Irma

Irma’s a Category 5

 

Irma is a long way from the U.S., but some islands like the U.S. and British Virgin Islands will get hit hard soon.  After that the various models seem to fall into two central ideas – both bring Irma WNW staying just north of Puerto Rico and Cuba (while wiping out the Turks and Caicos) until things change while she’s just south of Florida.  About half the models bring the storm north either over Florida or just off the east coast.  Then a move inland anywhere between Georgia and Myrtle Beach. (Hilton Head ?)
   Second set of models brings Irma along the west coast of Florida with landfall over the panhandle to as far west as Mobile.
   It’s anybody’s guess at this time – a few minor changes over the next few days could alter the forecast significantly.
As to intensity, Irma’s a Category 5 now.  The strongest hurricane ever observed purely over the Atlantic Ocean.  Stronger hurricanes have formed over the Atlantic Basin, but they were in either the Gulf of Mexico or the Caribbean Sea.
     While hurricane position forecasting has steadily improved, the same cannot be said for intensity forecasts.  They are notoriously poor!  Just yesterday the forecast for Irma was to remain a Cat 3 through tomorrow, then slowly weaken; today she’s a Cat 5. Today’s prediction is for Irma to slowly weaken over the next five days, but remain a major hurricane.
P.S. Just a final thought…The morning run of the U.S. workhorse forecast model, the GFS, brings Irma northward along the Florida Coast this weekend with landfall near the Georgia/South Carolina border.  The GFS then weakens the storm as it drifts northwest.  Finally, the GFS has Irma’s remnants fading away over Kentucky next Wed/Thu.  Just something to think about.
(I think you should NEVER believe  a weather forecast that far in advance – let’s see what happens.)

 

Hits and Misses

Thursday, August 3, 2017

Quote of the day.

Yesterday, as part of my waking-up ritual, I turned on NOAA Weather Radio to get my daily morning update.  Within seconds, I burst out laughing.  I thought I must have mis-understood what I heard.  But, a second time around I heard the same thing.  from the Hazardous Weather Outlook came this statement:  Some Thunderstorms may produce lightning.

Your tax dollars at work.

And, speaking of our tax dollars…is it just me, or do others believe that our “official” forecasts have been pretty bad this summer?  I know as well as anyone about the frustrations of forecasting convective systems.  But, we’ve been bombarded with forecasts of “rainageddon”, severe storms and chaos several times with nothing to show for it.  In fact, the biggest rain we’ve had recently (July 23) was barely given any attention.  That situation was fun to watch while it unfolded – the NWS changed/updated their forecast 4-5 times over about 8 hours AND the only one that was correct came out about 3 hours after the rain ended!    NOTE:  The NWS had another case of “the cat chasing its tail” a few days back when they issued a spurious heavy thunderstorm forecast about three hours after the threat had ended.

El Nino/La Nina outlook

Most of the first half of the year, NOAA’s long term climate forecast model, Cfsv2, was predicting a climb  back into mild El Nino conditions for late fall and winter.  Over the past couple of months, the model has done a flip.  Now, it’s forecasting a mild La Nina to develop.

The consequences/forecast for North America has also flipped -early forecasts indicated a below normal temperature for our winter.  Now, they are strongly indicating a very mild winter.

And, by the way… the current NWS forecast for tomorrow is just plain not going to happen.  No way.  We have about a 30% chance for showers around 8-10 A.M.  Nothing close to the “numerous showers and thunderstorms” in the forecast.

Storm chances high late this afternoon

10:30 A.M. Wed., April 5, 2017

Atmosphere appears set up to do some damage later today – especially east of the I-65 corridor.  Strong upper air system is approaching and ample moisture is streaming northward.  That sets up a pretty high chance for thunderstorms as well as severe storms.  System will be slow to develop and will just be getting rolling about the time it hits central KY.  Strong/severe line of storms should pass Louisville area between 5 P.M. and 8 P.M.  Hail and high winds appear likely.   Storm line will intensify as it moves east of I-65 and heads toward I-75.  Also, higher risk for storms, some severe, over southern KY from I-65 eastward.

Much colder air arrives tomorrow.

Confusing weather…update #2

Thursday,March 30, 2017   5:15 P.M.

Severe storm threat has dropped to minimal, or less.

Situation is no longer “confusing” as the short term models continue to highlight the ideas presented earlier.  Some adjustments are needed to the timing, but the severe weather threat has moved to central Indiana eastward to central Ohio.  Severe storms are not expected locally.

Latest timing for Louisville metro area:

5 P.M. to 8 P.M.:  quite windy and warm, but only about a 5% -10% chance for a thunderstorm.

8 P.M. to 10 P.M.:  area of showers/thunderstorms (mostly moderate to strong)  moves from west to east across metro area.  No severe weather expected.

10 P.M. to 2 A.M.:  Rain with embedded weak to moderate thunderstorms continues.  Heavy rain briefly in thunderstorms.  Flash flooding is possible in a few areas.

2 A.M. to 4 A.M.:  Rain/thunder gradually fades away.

Confusing weather…3 P.M. update

Thursday, March 30, 2017  3 P.M.

Latest update based on short-term model and radar data…

1).  Most of the area (maybe all) should remain dry through at least 5 P.M.  Best chance for strong pop-up thunderstorms remains over Indiana.

2).  Between 5- 7 P.M.  Louisville area will see about a 40% chance for scattered thunderstorms.     Any storms that form could be strong, but any severe storms should be rare.  By 7 P.M. any chance for severe thunderstorms for the Louisville area will be over.

3).  By 7-9 P.M. a large area of strong-to-severe thunderstorms will break out over northern TN and southern KY and move rapidly northeast between I-65 and I-75.  Threat of severe storms will lie south and east of a line from Bowling Green to Cincinnati.

4). By 7 P.M. a weak cold front will be crossing the Wabash River (Indiana/Illinois border) and continue moving eastward.  At this time the front could be producing moderate to strong thunderstorms.  As the front moves eastward, its moisture will merge with the system mentioned in #3 (above) to create a large area of rain with weak to moderate thunderstorms mixed in.  This area should drop plenty of rain over our area between 8 P.M. and Midnight.  Some minor flash flooding will be possible.

A very confusing situation…

Thursday, March 30, 2017

The atmosphere may, or may not, be primed for severe storms later this afternoon/evening.  The confusion was apparent yesterday as the GFS and NAM far apart in their solutions for today’s weather/thunderstorm possibilities – the GFS wasn’t too keen on severe thunderstorms while the NAM jumped on severe weather big time.  Today, the GFS and NAM are closer, but still at odds.  Meanwhile the short term models, while agreeing in general about how things will evolve, are also divergent about the expected strength of any thunderstorms.

Going with the suspicion that each model has something good to add to the discussion, here’s how I believe the weather will evolve this afternoon/evening:                                                                First, the amount of cloud cover that remains this afternoon is very important.  Remains from storms to our west overnight have been hanging around this morning.  We should get enough brakes in the clouds this afternoon to allow some sunshine to build up heat (and energy) for some storms.  More sunshine is likely over KY than IN.  Lack of sunshine will diminish the severe storm threat.  Satellite data shows the clouds thinning as of Noon.

Second,  we have strong upper air dynamics over the midwest working their way slowly eastward, but surface conditions are a mishmash ( a highly technical term) of ill-defined air masses, outflow boundaries, and, so-far, ill-fated attempts to form a surface low pressure center and a cold front.  It looks as though it’ll take 4-8 hours or longer for things to get more organized.  By that time, the main threat for severe weather will shift east of the I-65 corridor.

Third, with lack of coordination between the upper and lower levels, things are just going to happen in a seeming random fashion this afternoon.  Quick-moving thunderstorms should pop up in a “hit ‘n’ miss” fashion over western and central KY and (mostly)  IN.  Most of these will be strong with gusty winds and hail possible.  Some could even reach “severe” limits, though these are likely to be few and far between.  By 6-7 P.M. the majority of these pop-up storms should be east of the I-65 corridor.  By this time, any severe weather threat should be over for the Louisville area.  Primary threat for severe storms this afternoon will be over central and northern Indiana.

Four,  by 7-8 P.M. the surface part of this system will be better organized and is expected to create a large area of rain and thunderstorms (non-severe)  over western KY and IN.  This will bring us a very wet evening.  Even a little flash flooding is possible.  Rain should diminish shortly after Midnight.

Comment

I see from this morning’s CJ  that  Rick and Cal are the two highest paid college basketball coaches in the land.  But, the educational ratings of the schools they coach are low.  We should gain an important bit of knowledge from the first two sentences.

Quick update – storms weakened quickly

Monday, March 27, 2017  5:50 P.M.

Storms are fading fast as they advance quickly northeast.  Louisville metro will see weak thunderstorms between 6 and 7 P.M.  There is no threat for severe weather – just some brief gusty winds and heavy downpours.

I suspect the NWS will drop the Watch for our area soon.  However, even if they let the WATCH linger, the threat for severe storms is already over.