Major Hurricane Hernan

[Somerset Squall]

Tropical Depression 09E has formed in the East Pacific, and has an initial intensity of 30kts. Convection is very deep over the well defined centre, and the depression is expected to strengthen into Tropical Storm Hernan soon. The new cyclone has about three days over warm waters to strengthen, and the NHC currently have 09E peaking at 60kts, so this one may become a hurricane before it hits those cooler waters on the west-northwestward track. With the favourable conditions including low shear, this definitely isn't out of the question.

[Cookie]

thanks for the updates

[Somerset Squall]

TD09E has become better organised overnight and has been upgraded to Tropical Storm Hernan. Hernan is being affected by northeasterly shear, which is leaving the centre slightly displaced east of the deep convection. However, shear is expected to ease and Hernan is now forecast by the NHC to briefly become a hurricane before reaching those cooler waters beyond 72hrs. The track forecast has not changed.

[Cookie]

thanks for the updates

Edited August 7, 2008 by cookie

[Somerset Squall]

Hernan has strengthened this afternoon in the face of northeasterly shear. The LLC remains partially exposed but in the southwestern quadrant of the storm is some very deep and persistant convection. Intensity has been increased to 50kts, and Hernan could become a hurricane later tomorrow before moving over cooler waters.

Image of Hernan on right (also shows TS Kika on left):

[Cookie]

looks very cool seeing both storms at once

[kold weather]

Hernan looks pretty good right now, T-numbers now upto 4.0 which does suggest an upgrade should be soon, though given the slightly lop-sided nature of the deepest convection they may hold back for another 6hrs but this has got some very impressive convection right now with some really cold cloud tops.

[Somerset Squall]

Hernan looks pretty good right now, T-numbers now upto 4.0 which does suggest an upgrade should be soon, though given the slightly lop-sided nature of the deepest convection they may hold back for another 6hrs but this has got some very impressive convection right now with some really cold cloud tops.

Indeed, the upgrade has now been made and Hernan is a 65kt hurricane. Favourable conditions will persist over the next 36hrs and therefore further strengthening is predicted. Beyond this time period, cooler waters await Hernan which will induce slow weakening.

[Somerset Squall]

Hernan has strengthened further, and is now at 75kts. The eye continues to get better defined. Hernan is moving generally westwards and should remain over warm waters for another 36hrs, so further strengthening is predicted. The NHC expect Hernan to peak at 85kts, though it is plausible for Hernan to get a little stronger than that as the environment remains favourable for the next day or so.

[James M]

Big increase in strength since I last checked, now a 105 knot Cat 3 Hurricane!

THE EYE OF HERNAN HAS BECOME DRAMATICALLY MORE DISTINCT IN GOES

INFRARED IMAGERY DURING THE PAST SEVERAL HOURS...AND IT IS NOW

SURROUNDED BY A SOLID RING OF CLOUD TOPS COLDER THAN -70C. AMSR-E

MICROWAVE IMAGERY AT 0937 UTC DEPICTED A SINGLE COMPLETE EYEWALL

AND AN EYE DIAMETER OF 20-25 N MI. THERE SEEMS LITTLE DOUBT THAT

HERNAN HAS BECOME A MAJOR HURRICANE... HAVING UNDERGONE RAPID

INTENSIFICATION SINCE YESTERDAY. THIS PROVIDES YET ANOTHER EXAMPLE

OF THE INABILITY OF MODEL GUIDANCE...AND THEREFORE THE HUMAN

FORECASTER...TO CAPTURE AND CONVEY THE TIMING AND MAGNITUDE OF THESE

EPISODES WITH A DETERMINISTIC INTENSITY FORECAST. THE EXACT

INITIAL INTENSITY IS A LITTLE UNCERTAIN. SUBJECTIVE DVORAK

ESTIMATES AT 12Z FROM TAFB AND SAB WERE BOTH 102 KT...WHILE

OBJECTIVE ESTIMATES ARE ABOUT 115 KT. THE ADVISORY INTENSITY

COMPROMISES AT 105 KT...BUT WITHOUT ACTUAL WIND DATA TO KNOW ANY

BETTER...IT IS POSSIBLE HERNAN IS A LITTLE STRONGER THAN THIS

ESTIMATE. UNDERLYING SEA-SURFACE TEMPERATURES ARE ABOUT 27 CELSIUS

NOW...AND ALONG THE FORECAST TRACK THE HURRICANE WILL CROSS THE 26

CELSIUS ISOTHERM IN ROUGHLY 24 HOURS...SO A GRADUAL WEAKENING TREND

IS FORECAST TO BEGIN AROUND THAT TIME. A FASTER DECLINE IS

FORECAST IN A COUPLE OF DAYS ONCE THE CYCLONE REACHES SUBSTANTIALLY

COOLER WATERS. THE OFFICIAL FORECAST IS ABOVE THE OBJECTIVE

GUIDANCE FOR THE NEXT DAY OR TWO...THEN SHOWS A FASTER WEAKENING

THAN THE MODELS DUE TO THE SMALL SIZE OF THE CYCLONE.

HERNAN HAS TURNED A LITTLE MORE TO THE RIGHT...AND ONE MUST GIVE

SOME OF THE MODELS CREDIT FOR CORRECTLY FORECASTING THIS BEND

YESTERDAY. THE INITIAL MOTION ESTIMATE IS 295/8...BUT A GRADUAL

TURN BACK TO THE LEFT IS FORECAST BY ALL OF THE DYNAMICAL MODELS AS

THE SUBTROPICAL RIDGE BUILDS WESTWARD OVER THE EASTERN PACIFIC

DURING THE NEXT COUPLE OF DAYS. BEYOND THAT TIME...A WEAKENING

HERNAN IS EXPECTED TO BECOME A MORE SHALLOW SYSTEM AND TURN

WESTWARD AND EVENTUALLY WEST-SOUTHWESTWARD IN THE LOW- TO MID-LEVEL

FLOW. THE NEW OFFICIAL TRACK FORECAST IS ALMOST IDENTICAL TO THE

PREVIOUS ONE AND IS CLOSE TO THE MODEL CONSENSUS.

FORECASTER KNABB

Edited August 9, 2008 by James M

[Somerset Squall]

Yes, Hernan has become the first major hurricane of the East Pacific season. I didn't foresee it getting quite this strong but I always though the NHC was punting a little low with the intensity, as shear was low and Hernan still has a while over very warm waters. Still has potential to get a little stronger, it's a case of wait and see to see just how high Hernan goes.

[Cookie]

what a jump since I last checked my word.

thanks everyone for the updates

[Somerset Squall]

Hernan has weakened to 85kts, and the eye has become more rugged overnight. Hernan is moving over cooler waters below 27C which is being held accountable for the weakening. Even cooler waters lie in the forecast track so Hernan will continue to weaken, the NHC say Hernan may lose hurricane status in the next 24hrs. Interestingly, around 120hrs time, waters are expected to warm up again, but it's too early to tell whether Hernan will make a comeback from it's expected tropical depression status by then.

[Somerset Squall]

Hernan has continued to weaken over cool waters, and is now a 60kt tropical storm. Further weakening will occur as waters remain too cool for development. However, beyond 96hrs, sea temps are expected to increase again on the westwards track which may prolong the life of the cyclone, if it survives that long.

[Cookie]

thanks good updates :lol:

[Somerset Squall]

Hernan now consists of a small, tight circulation with patchy, shallow convection flaring near the centre. Intensity is decreased to 55kts simply because there are still some pretty strong winds in the tight core. However, given Hernan's convectional state, the cyclone may not be around for much longer, and probably won't be by the time it finds warmer waters to the west. NHC expect degeneration into a remnant low by 72hrs.

[Somerset Squall]

Hernan continues to spin down over cool waters. Intensity is now at 35kts and very little convection remains near the still well defined centre.

[Cookie]

nice image that

[MAF]

and there are still tornadoes to deal with http://www.spc.noaa.gov/products/watch/ww0823.html

although Hernan now seems to be weakening