Update, August 18th at 6:22 p.m.: Erin didn’t even make it to the central Atlantic – it’s now just a remnant low, and the NHC issued their last forecast discussion on it this evening.
At the moment, and per this amateur’s understanding of the GFS graphic tonight, there is no candidate for the next storm, Fernand, looming over the next several days. Of course, the atmosphere is in constant motion, we’re getting into the season’s peak weeks, and that could change in a hurry.
Update, August 16th at 12:42 p.m.: Erin has weakened, and this morning the NHC downgraded it to a tropical depression. They say the system will remain pretty much the same for the forecast period, but of note, they didn’t take the “Erin” name off it.
TDs are usually identified by numbers, but maybe they just do that when a named storm weakens; I’m not sure of the protocol. Hhowever, this amateur prefers to think they remember Dorian’s on-again-off-again style and also have an eye on the GFS, which currently shows Erin redeveloping and happily churning up mid-Atlantic waters in 180 hours:
Anything 180 hours out on a computer model is next-door to guessing. You just can’t rely on it. However, it’s interesting. Let’s not give up on Erin just yet (and let’s hope, if it strengthens again, it stays out to sea as shown!).
After watching things closely last night and this morning, the National Hurricane Center found Erin, the next tropical system in this year’s Atlantic hurricane season.
Here is the current NHC forecast discussion, with the basic gist (as this amateur understands it) highlighted:
WTNT45 KNHC 151440
TROPICAL STORM ERIN DISCUSSION NUMBER 3
NWS NATIONAL HURRICANE CENTER MIAMI FL AL052013
1100 AM AST THU AUG 15 2013
THE SATELLITE PRESENTATION OF THE CYCLONE HAS CONTINUED TO IMPROVE OVER THE PAST FEW HOURS. INFRARED IMAGERY SHOWS VERY COLD CLOUD TOPS SITUATED NEAR AND TO THE SOUTH OF THE ESTIMATED CENTER POSITION…WITH A SMALL BANDING FEATURE EXTENDING TO THE SOUTHWEST. THE INITIAL INTENSITY OF 35 KT IS SUPPORTED BY A BLEND OF THE LATEST OBJECTIVE AND SUBJECTIVE DVORAK ESTIMATES AND A 1102 UTC ASCAT-A PASS THAT SHOWED WINDS OF 32 KT. ERIN IS EXPECTED TO BE IN AN ENVIRONMENT THAT SUPPORTS SOME STRENGTHENING DURING THE NEXT COUPLE OF DAYS WITH SSTS OF 26-27C…LOW SHEAR…AND A MOIST ENVIRONMENT. BY DAY 3…THE SYSTEM WILL BE MOVING INTO A DRIER AND MORE STABLE ATMOSPHERIC ENVIRONMENT…WHICH SHOULD RESULT IN WEAKENING. THE GLOBAL MODELS AND THE HWRF SHOW A WEAK OR DISSIPATING SYSTEM BY DAY 5…HOWEVER THE SHIPS AND LGEM SHOW LITTLE CHANGE IN INTENSITY OR EVEN STRENGTHENING. THE OFFICIAL FORECAST LEANS A LITTLE TOWARD THE WEAKER SOLUTION AT DAYS 4 AND 5.
THE AFOREMENTIONED ASCAT PASS WAS ALSO HELPFUL IN LOCATING THE CENTER OF ERIN…WHICH IS A LITTLE SOUTH AND WEST OF PREVIOUS ESTIMATES. BASED ON A SOUTHWESTWARD ADJUSTMENT OF THE CENTER POSITION THE INITIAL MOTION ESTIMATE IS 285/13. ERIN IS CURRENTLY BEING STEERED BY A NARROW SUBTROPICAL RIDGE TO ITS NORTH…AND THE GUIDANCE IS IN GOOD AGREEMENT ON THIS MOTION CONTINUING FOR THE NEXT COUPLE OF DAYS. BY DAY 3…THE SPREAD IN THE GUIDANCE INCREASES. ON THE RIGHT SIDE OF THE GUIDANCE ENVELOPE THE GFDL… GFDL ENSEMBLE MEAN…ECMWF AND UKMET SHOW A NORTHWESTWARD OR WEST-NORTHWESTWARD MOTION. THE FIM…GFS…GFS ENSEMBLE MEAN AND HWRF ALL SHOW A WESTWARD TRACK…CONSISTENT WITH A SHALLOWER SYSTEM BEING STEERED BY THE LOW-LEVEL FLOW. THE NHC FORECAST AT DAYS 3 THROUGH 5 CONTINUES TO FOLLOW THIS SOUTHERN CAMP OF MODELS AND IS LARGELY AN UPDATE OF THE PREVIOUS NHC TRACK.
FORECAST POSITIONS AND MAX WINDS
INIT 15/1500Z 14.4N 26.5W 35 KT 40 MPH
12H 16/0000Z 15.0N 28.6W 40 KT 45 MPH
24H 16/1200Z 15.7N 31.2W 45 KT 50 MPH
36H 17/0000Z 16.7N 33.5W 45 KT 50 MPH
48H 17/1200Z 17.4N 35.8W 50 KT 60 MPH
72H 18/1200Z 18.0N 40.0W 50 KT 60 MPH
96H 19/1200Z 18.0N 44.5W 45 KT 50 MPH
120H 20/1200Z 18.0N 49.0W 35 KT 40 MPH